--- 1/draft-ietf-dtn-tcpclv4-12.txt 2019-08-20 17:13:15.474712759 -0700 +++ 2/draft-ietf-dtn-tcpclv4-13.txt 2019-08-20 17:13:15.590715711 -0700 @@ -1,22 +1,22 @@ Delay Tolerant Networking B. Sipos Internet-Draft RKF Engineering Obsoletes: 7242 (if approved) M. Demmer Intended status: Standards Track UC Berkeley -Expires: October 2, 2019 J. Ott +Expires: February 21, 2020 J. Ott Aalto University S. Perreault - March 31, 2019 + August 20, 2019 Delay-Tolerant Networking TCP Convergence Layer Protocol Version 4 - draft-ietf-dtn-tcpclv4-12 + draft-ietf-dtn-tcpclv4-13 Abstract This document describes a revised protocol for the TCP-based convergence layer (TCPCL) for Delay-Tolerant Networking (DTN). The protocol revision is based on implementation issues in the original TCPCL Version 3 of RFC7242 and updates to the Bundle Protocol contents, encodings, and convergence layer requirements in Bundle Protocol Version 7. Specifically, the TCPCLv4 uses CBOR-encoded BPv7 bundles as its service data unit being transported and provides a @@ -32,89 +32,91 @@ Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." - This Internet-Draft will expire on October 2, 2019. + This Internet-Draft will expire on February 21, 2020. Copyright Notice Copyright (c) 2019 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 - 1.1. Convergence Layer Services . . . . . . . . . . . . . . . 4 - 2. Requirements Language . . . . . . . . . . . . . . . . . . . . 6 - 2.1. Definitions Specific to the TCPCL Protocol . . . . . . . 6 - 3. General Protocol Description . . . . . . . . . . . . . . . . 9 - 3.1. TCPCL Session Overview . . . . . . . . . . . . . . . . . 9 - 3.2. TCPCL States and Transitions . . . . . . . . . . . . . . 11 - 3.3. Transfer Segmentation Policies . . . . . . . . . . . . . 16 - 3.4. Example Message Exchange . . . . . . . . . . . . . . . . 17 - 4. Session Establishment . . . . . . . . . . . . . . . . . . . . 19 - 4.1. TCP Connection . . . . . . . . . . . . . . . . . . . . . 19 - 4.2. Contact Header . . . . . . . . . . . . . . . . . . . . . 19 - 4.3. Contact Validation and Negotiation . . . . . . . . . . . 20 - 4.4. Session Security . . . . . . . . . . . . . . . . . . . . 21 - 4.4.1. TLS Handshake Result . . . . . . . . . . . . . . . . 22 - 4.4.2. Example TLS Initiation . . . . . . . . . . . . . . . 22 - 4.5. Message Type Codes . . . . . . . . . . . . . . . . . . . 23 - 4.6. Session Initialization Message (SESS_INIT) . . . . . . . 24 - 4.7. Session Parameter Negotiation . . . . . . . . . . . . . . 26 - 4.8. Session Extension Items . . . . . . . . . . . . . . . . . 27 - 5. Established Session Operation . . . . . . . . . . . . . . . . 28 - 5.1. Upkeep and Status Messages . . . . . . . . . . . . . . . 28 - 5.1.1. Session Upkeep (KEEPALIVE) . . . . . . . . . . . . . 28 - 5.1.2. Message Rejection (MSG_REJECT) . . . . . . . . . . . 29 - 5.2. Bundle Transfer . . . . . . . . . . . . . . . . . . . . . 30 - 5.2.1. Bundle Transfer ID . . . . . . . . . . . . . . . . . 30 - 5.2.2. Data Transmission (XFER_SEGMENT) . . . . . . . . . . 31 - 5.2.3. Data Acknowledgments (XFER_ACK) . . . . . . . . . . . 33 - 5.2.4. Transfer Refusal (XFER_REFUSE) . . . . . . . . . . . 34 - 5.2.5. Transfer Extension Items . . . . . . . . . . . . . . 36 - 6. Session Termination . . . . . . . . . . . . . . . . . . . . . 38 - 6.1. Session Termination Message (SESS_TERM) . . . . . . . . . 38 - 6.2. Idle Session Shutdown . . . . . . . . . . . . . . . . . . 40 - 7. Implementation Status . . . . . . . . . . . . . . . . . . . . 40 - 8. Security Considerations . . . . . . . . . . . . . . . . . . . 41 - 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 42 - 9.1. Port Number . . . . . . . . . . . . . . . . . . . . . . . 42 - 9.2. Protocol Versions . . . . . . . . . . . . . . . . . . . . 43 - 9.3. Session Extension Types . . . . . . . . . . . . . . . . . 43 - 9.4. Transfer Extension Types . . . . . . . . . . . . . . . . 44 - 9.5. Message Types . . . . . . . . . . . . . . . . . . . . . . 45 - 9.6. XFER_REFUSE Reason Codes . . . . . . . . . . . . . . . . 45 - 9.7. SESS_TERM Reason Codes . . . . . . . . . . . . . . . . . 46 - 9.8. MSG_REJECT Reason Codes . . . . . . . . . . . . . . . . . 47 - 10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 48 - 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 48 - 11.1. Normative References . . . . . . . . . . . . . . . . . . 48 - 11.2. Informative References . . . . . . . . . . . . . . . . . 49 - Appendix A. Significant changes from RFC7242 . . . . . . . . . . 49 - Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 50 + 1.1. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . 4 + 2. Requirements Language . . . . . . . . . . . . . . . . . . . . 5 + 2.1. Definitions Specific to the TCPCL Protocol . . . . . . . 5 + 3. General Protocol Description . . . . . . . . . . . . . . . . 8 + 3.1. Convergence Layer Services . . . . . . . . . . . . . . . 8 + 3.2. TCPCL Session Overview . . . . . . . . . . . . . . . . . 10 + 3.3. TCPCL States and Transitions . . . . . . . . . . . . . . 12 + 3.4. Transfer Segmentation Policies . . . . . . . . . . . . . 18 + 3.5. Example Message Exchange . . . . . . . . . . . . . . . . 19 + 4. Session Establishment . . . . . . . . . . . . . . . . . . . . 21 + 4.1. TCP Connection . . . . . . . . . . . . . . . . . . . . . 21 + 4.2. Contact Header . . . . . . . . . . . . . . . . . . . . . 22 + 4.3. Contact Validation and Negotiation . . . . . . . . . . . 23 + 4.4. Session Security . . . . . . . . . . . . . . . . . . . . 24 + 4.4.1. TLS Handshake . . . . . . . . . . . . . . . . . . . . 24 + 4.4.2. TLS Authentication . . . . . . . . . . . . . . . . . 25 + 4.4.3. Example TLS Initiation . . . . . . . . . . . . . . . 26 + 4.5. Message Header . . . . . . . . . . . . . . . . . . . . . 27 + 4.6. Session Initialization Message (SESS_INIT) . . . . . . . 28 + 4.7. Session Parameter Negotiation . . . . . . . . . . . . . . 30 + 4.8. Session Extension Items . . . . . . . . . . . . . . . . . 31 + 5. Established Session Operation . . . . . . . . . . . . . . . . 32 + 5.1. Upkeep and Status Messages . . . . . . . . . . . . . . . 32 + 5.1.1. Session Upkeep (KEEPALIVE) . . . . . . . . . . . . . 32 + 5.1.2. Message Rejection (MSG_REJECT) . . . . . . . . . . . 33 + 5.2. Bundle Transfer . . . . . . . . . . . . . . . . . . . . . 34 + 5.2.1. Bundle Transfer ID . . . . . . . . . . . . . . . . . 35 + 5.2.2. Data Transmission (XFER_SEGMENT) . . . . . . . . . . 35 + 5.2.3. Data Acknowledgments (XFER_ACK) . . . . . . . . . . . 37 + 5.2.4. Transfer Refusal (XFER_REFUSE) . . . . . . . . . . . 38 + 5.2.5. Transfer Extension Items . . . . . . . . . . . . . . 41 + 6. Session Termination . . . . . . . . . . . . . . . . . . . . . 43 + 6.1. Session Termination Message (SESS_TERM) . . . . . . . . . 43 + 6.2. Idle Session Shutdown . . . . . . . . . . . . . . . . . . 45 + 7. Implementation Status . . . . . . . . . . . . . . . . . . . . 45 + 8. Security Considerations . . . . . . . . . . . . . . . . . . . 46 + 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 47 + 9.1. Port Number . . . . . . . . . . . . . . . . . . . . . . . 47 + 9.2. Protocol Versions . . . . . . . . . . . . . . . . . . . . 48 + 9.3. Session Extension Types . . . . . . . . . . . . . . . . . 48 + 9.4. Transfer Extension Types . . . . . . . . . . . . . . . . 49 + 9.5. Message Types . . . . . . . . . . . . . . . . . . . . . . 50 + 9.6. XFER_REFUSE Reason Codes . . . . . . . . . . . . . . . . 50 + 9.7. SESS_TERM Reason Codes . . . . . . . . . . . . . . . . . 51 + 9.8. MSG_REJECT Reason Codes . . . . . . . . . . . . . . . . . 52 + 10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 53 + 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 53 + 11.1. Normative References . . . . . . . . . . . . . . . . . . 53 + 11.2. Informative References . . . . . . . . . . . . . . . . . 54 + Appendix A. Significant changes from RFC7242 . . . . . . . . . . 55 + Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 56 1. Introduction This document describes the TCP-based convergence-layer protocol for Delay-Tolerant Networking. Delay-Tolerant Networking is an end-to- end architecture providing communications in and/or through highly stressed environments, including those with intermittent connectivity, long and/or variable delays, and high bit error rates. More detailed descriptions of the rationale and capabilities of these networks can be found in "Delay-Tolerant Network Architecture" @@ -153,129 +155,56 @@ | TCP | ---> Transport Layer +-------------------------+ | IPv4/IPv6 | ---> Network Layer +-------------------------+ | Link-Layer Protocol | ---> Link Layer +-------------------------+ Figure 1: The Locations of the Bundle Protocol and the TCP Convergence-Layer Protocol above the Internet Protocol Stack +1.1. Scope + This document describes the format of the protocol data units passed between entities participating in TCPCL communications. This document does not address: o The format of protocol data units of the Bundle Protocol, as those - are defined elsewhere in [RFC5050] and [I-D.ietf-dtn-bpbis]. This - includes the concept of bundle fragmentation or bundle - encapsulation. The TCPCL transfers bundles as opaque data blocks. + are defined elsewhere in [I-D.ietf-dtn-bpbis]. This includes the + concept of bundle fragmentation or bundle encapsulation. The + TCPCL transfers bundles as opaque data blocks. o Mechanisms for locating or identifying other bundle entities - within an internet. - -1.1. Convergence Layer Services - - This version of the TCPCL provides the following services to support - the overlaying Bundle Protocol agent. In all cases, this is not an - API defintion but a logical description of how the CL may interact - with the BP agent. Each of these interactions may be associated with - any number of additional metadata items as necessary to support the - operation of the CL or BP agent. - - Attempt Session The TCPCL allows a BP agent to pre-emptively attempt - to establish a TCPCL session with a peer entity. Each session - attempt can send a different set of session negotiation parameters - as directed by the BP agent. - - Terminate Session The TCPCL allows a BP agent to pre-emptively - terminate an established TCPCL session with a peer entity. The - terminate request is on a per-session basis. - - Session State Changed The TCPCL supports indication when the session - state changes. The top-level session states indicated are: - - Contact Negotating: A TCP connection has been made (as either - active or passive entity) and contact negotiation has begun. - - Session Negotiating: Contact negotation has been completed - (including possible TLS use) and session negotiation has begun. - - Established: The session has been fully established and is ready - for its first transfer. - - Closing: The entity received a SESS_TERM message and is in the - closing state. - - Terminated: The session has finished normal termination - sequencing.. - - Failed: The session ended without normal termination sequencing. - - Session Idle Changed The TCPCL supports indication when the live/ - idle sub-state changes. This occurs only when the top-level - session state is Established. Because TCPCL transmits serially - over a TCP connection, it suffers from "head of queue blocking" - this indication provides information about when a session is - available for immediate transfer start. - - Begin Transmission The principal purpose of the TCPCL is to allow a - BP agent to transmit bundle data over an established TCPCL - session. Transmission request is on a per-session basis, the CL - does not necessarily perform any per-session or inter-session - queueing. Any queueing of transmissions is the obligation of the - BP agent. - - Transmission Success The TCPCL supports positive indication when a - bundle has been fully transferred to a peer entity. - - Transmission Intermediate Progress The TCPCL supports positive - indication of intermediate progress of transferr to a peer entity. - This intermediate progress is at the granularity of each - transferred segment. - - Transmission Failure The TCPCL supports positive indication of - certain reasons for bundle transmission failure, notably when the - peer entity rejects the bundle or when a TCPCL session ends before - transferr success. The TCPCL itself does not have a notion of - transfer timeout. - - Reception Initialized The TCPCL supports indication to the reciver - just before any transmssion data is sent. This corresponds to - reception of the XFER_SEGMENT message with the START flag set. - - Interrupt Reception The TCPCL allows a BP agent to interrupt an - individual transfer before it has fully completed (successfully or - not). Interruption can occur any time after the reception is - initialized. + (peers) within a network or across an internet. The mapping of + Node ID to potential CL protocol and network address is left to + implementation and configuration of the BP Agent and its various + potential routing strategies. - Reception Success The TCPCL supports positive indication when a - bundle has been fully transferred from a peer entity. + o Logic for routing bundles along a path toward a bundle's endpoint. + This CL protocol is involved only in transporting bundles between + adjacent nodes in a routing sequence. - Reception Intermediate Progress The TCPCL supports positive - indication of intermediate progress of transfer from the peer - entity. This intermediate progress is at the granularity of each - transferred segment. Intermediate reception indication allows a - BP agent the chance to inspect bundle header contents before the - entire bundle is available, and thus supports the "Reception - Interruption" capability. + o Policies or mechanisms for assigning X.509 certificates, + provisioning or deploying certificates and private keys, or + configuring security parameters on an individual BP node or across + a network. - Reception Failure The TCPCL supports positive indication of certain - reasons for reception failure, notably when the local entity - rejects an attempted transfer for some local policy reason or when - a TCPCL session ends before transfer success. The TCPCL itself - does not have a notion of transfer timeout. + Any TCPCL implementation requires a BP agent to perform those above + listed functions in order to perform end-to-end bundle delivery. 2. Requirements Language The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", - "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this - document are to be interpreted as described in [RFC2119]. + "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and + "OPTIONAL" in this document are to be interpreted as described in BCP + 14 [RFC2119] [RFC8174] when, and only when, they appear in all + capitals, as shown here. 2.1. Definitions Specific to the TCPCL Protocol This section contains definitions specific to the TCPCL protocol. TCPCL Entity: This is the notional TCPCL application that initiates TCPCL sessions. This design, implementation, configuration, and specific behavior of such an entity is outside of the scope of this document. However, the concept of an entity has utility within the scope of this document as the container and initiator @@ -407,49 +336,151 @@ Figure 3: The relationship within a TCPCL Session of its two streams 3. General Protocol Description The service of this protocol is the transmission of DTN bundles via the Transmission Control Protocol (TCP). This document specifies the encapsulation of bundles, procedures for TCP setup and teardown, and a set of messages and node requirements. The general operation of the protocol is as follows. -3.1. TCPCL Session Overview +3.1. Convergence Layer Services + + This version of the TCPCL provides the following services to support + the overlaying Bundle Protocol agent. In all cases, this is not an + API defintion but a logical description of how the CL can interact + with the BP agent. Each of these interactions can be associated with + any number of additional metadata items as necessary to support the + operation of the CL or BP agent. + + Attempt Session: The TCPCL allows a BP agent to pre-emptively + attempt to establish a TCPCL session with a peer entity. Each + session attempt can send a different set of session negotiation + parameters as directed by the BP agent. + + Terminate Session: The TCPCL allows a BP agent to pre-emptively + terminate an established TCPCL session with a peer entity. The + terminate request is on a per-session basis. + + Session State Changed: The TCPCL supports indication when the + session state changes. The top-level session states indicated + are: + + Connecting: A TCP connection is being established. This state + only applies to the active entity. + + Contact Negotating: A TCP connection has been made (as either + active or passive entity) and contact negotiation has begun. + + Session Negotiating: Contact negotation has been completed + (including possible TLS use) and session negotiation has begun. + + Established: The session has been fully established and is ready + for its first transfer. + + Ending: The entity received a SESS_TERM message and is in the + ending state. + + Terminated: The session has finished normal termination + sequencing. + + Failed: The session ended without normal termination sequencing. + + Session Idle Changed: The TCPCL supports indication when the live/ + idle sub-state of the session changes. This occurs only when the + top-level session state is "Established". The session transitions + from Idle to Live at the at the start of a transfer in either + transfer stream; the session transitions from Live to Idle at the + end of a transfer when the other transfer stream does not have an + ongoing transfer. Because TCPCL transmits serially over a TCP + connection, it suffers from "head of queue blocking" this + indication provides information about when a session is available + for immediate transfer start. + + Begin Transmission: The principal purpose of the TCPCL is to allow a + BP agent to transmit bundle data over an established TCPCL + session. Transmission request is on a per-session basis, the CL + does not necessarily perform any per-session or inter-session + queueing. Any queueing of transmissions is the obligation of the + BP agent. + + Transmission Success: The TCPCL supports positive indication when a + bundle has been fully transferred to a peer entity. + + Transmission Intermediate Progress: The TCPCL supports positive + indication of intermediate progress of transferr to a peer entity. + This intermediate progress is at the granularity of each + transferred segment. + + Transmission Failure: The TCPCL supports positive indication of + certain reasons for bundle transmission failure, notably when the + peer entity rejects the bundle or when a TCPCL session ends before + transferr success. The TCPCL itself does not have a notion of + transfer timeout. + + Reception Initialized: The TCPCL supports indication to the reciver + just before any transmssion data is sent. This corresponds to + reception of the XFER_SEGMENT message with the START flag set. + + Interrupt Reception: The TCPCL allows a BP agent to interrupt an + individual transfer before it has fully completed (successfully or + not). Interruption can occur any time after the reception is + initialized. + + Reception Success: The TCPCL supports positive indication when a + bundle has been fully transferred from a peer entity. + + Reception Intermediate Progress: The TCPCL supports positive + indication of intermediate progress of transfer from the peer + entity. This intermediate progress is at the granularity of each + transferred segment. Intermediate reception indication allows a + BP agent the chance to inspect bundle header contents before the + entire bundle is available, and thus supports the "Reception + Interruption" capability. + + Reception Failure: The TCPCL supports positive indication of certain + reasons for reception failure, notably when the local entity + rejects an attempted transfer for some local policy reason or when + a TCPCL session ends before transfer success. The TCPCL itself + does not have a notion of transfer timeout. + +3.2. TCPCL Session Overview First, one node establishes a TCPCL session to the other by initiating a TCP connection in accordance with [RFC0793]. After setup of the TCP connection is complete, an initial contact header is exchanged in both directions to establish a shared TCPCL version and possibly initiate TLS security. Once contact negotiation is complete, TCPCL messaging is available and the session negotiation is used to set parameters of the TCPCL session. One of these parameters - is a singleton endpoint identifier for each node (not the singleton - Endpoint Identifier (EID) of any application running on the node) to - denote the bundle-layer identity of each DTN node. This is used to - assist in routing and forwarding messages (e.g. to prevent loops). + is a Node ID of each TCPCL Entity. This is used to assist in routing + and forwarding messages by the BP Agent and is part of the + authentication capability provided by TLS. Once negotiated, the parameters of a TCPCL session cannot change and if there is a desire by either peer to transfer data under different parameters then a new session must be established. This makes CL logic simpler but relies on the assumption that establishing a TCP connection is lightweight enough that TCP connection overhead is negligable compared to TCPCL data sizes. Once the TCPCL session is established and configured in this way, bundles can be transferred in either direction. Each transfer is performed by an sequence of logical segments of data within XFER_SEGMENT messages. Multiple bundles can be transmitted consecutively in a single direction on a single TCPCL connection. Segments from different bundles are never interleaved. Bundle interleaving can be accomplished by fragmentation at the BP layer or by establishing multiple TCPCL sessions between the same peers. + There is no fundamental limit on the number of TCPCL sessions which a + single node can establish beyond the limit imposed by the number of + available (ephemeral) TCP ports of the passive peer. A feature of this protocol is for the receiving node to send acknowledgment (XFER_ACK) messages as bundle data segments arrive. The rationale behind these acknowledgments is to enable the sender node to determine how much of the bundle has been received, so that in case the session is interrupted, it can perform reactive fragmentation to avoid re-sending the already transmitted part of the bundle. In addition, there is no explicit flow control on the TCPCL layer. @@ -459,38 +490,37 @@ hasn't already finished transmission) Note: This enables a cross- layer optimization in that it allows a receiver that detects that it already has received a certain bundle to interrupt transmission as early as possible and thus save transmission capacity for other bundles. For sessions that are idle, a KEEPALIVE message is sent at a negotiated interval. This is used to convey node live-ness information during otherwise message-less time intervals. - A SESS_TERM message is used to start the closing of a TCPCL session + A SESS_TERM message is used to start the ending of a TCPCL session (see Section 6.1). During shutdown sequencing, in-progress transfers can be completed but no new transfers can be initiated. A SESS_TERM message can also be used to refuse a session setup by a peer (see Section 4.3). It is an implementation matter to determine whether or not to close a TCPCL session while there are no transfers queued or in-progress. - Once a session is established established, TCPCL is a symmetric - protocol between the peers. Both sides can start sending data - segments in a session, and one side's bundle transfer does not have - to complete before the other side can start sending data segments on - its own. Hence, the protocol allows for a bi-directional mode of - communication. Note that in the case of concurrent bidirectional - transmission, acknowledgment segments MAY be interleaved with data - segments. + Once a session is established, TCPCL is a symmetric protocol between + the peers. Both sides can start sending data segments in a session, + and one side's bundle transfer does not have to complete before the + other side can start sending data segments on its own. Hence, the + protocol allows for a bi-directional mode of communication. Note + that in the case of concurrent bidirectional transmission, + acknowledgment segments MAY be interleaved with data segments. -3.2. TCPCL States and Transitions +3.3. TCPCL States and Transitions The states of a nominal TCPCL session (i.e. without session failures) are indicated in Figure 4. +-------+ | START | +-------+ | TCP Establishment | @@ -504,147 +534,163 @@ | Negotiated V +-------------+ +-------------+ | Established |----New Transfer---->| Established | | Session | | Session | | Idle |<---Transfers Done---| Live | +-------------+ +-------------+ | | +------------------------------------+ | - SESS_TERM Exchange + [SESSTERM] Exchange | V +-------------+ | Established | +-------------+ | Session |----Transfers------>| TCP | | Ending | Done | Terminating | +-------------+ +-------------+ | - +------------Close Message------------+ + +----------TCP Close Message----------+ | V +-------+ | END | +-------+ Figure 4: Top-level states of a TCPCL session Notes on Established Session states: Session "Live" means transmitting or reeiving over a transfer stream. Session "Idle" means no transmission/reception over a transfer stream. - Session "Closing" means no new transfers will be allowed. + Session "Ending" means no new transfers will be allowed. - The contact negotiation sequencing is performed either as the active - or passive peer, and is illustrated in Figure 5 and Figure 6 + Contact negotation involves exchanging a Contact Header (CH) in both + directions and deriving a negotiated state from the two headers. The + contact negotiation sequencing is performed either as the active or + passive peer, and is illustrated in Figure 5 and Figure 6 respectively which both share the data validation and analyze final - states of Figure 7. + states of the "[PCH]" activity of Figure 7 and the "[TCPCLOSE]" + activity which indicates TCP connection close. Successful + negotiation results in one of the Session Initiation "[SI]" + activities being performed. +-------+ - | START |-----TCP-----+ - +-------+ Connecting | + | START | + +-------+ + | + TCP Connecting V + +-----------+ + | TCP | +---------+ + | Connected |--Send CH-->| Waiting |--Timeout-->[TCPCLOSE] +-----------+ +---------+ - | Connected |--OK-->| Send CH |--OK-->[PCH] - +-----------+ +---------+ - | | - Error Error - | | - V | - [TCPTERM]<-------------+ + | + Recevied CH + V + [PCH] Figure 5: Contact Initiation as Active peer - +-------+ - | START |-----TCP----->[PCH] - +-------+ Connected + +-----------+ +---------+ + | TCP |--Wait for-->| Waiting |--Timeout-->[TCPCLOSE] + | Connected | CH +---------+ + +-----------+ | + Received CH + V + +-----------------+ + | Preparing reply |--Send CH-->[PSI] + +-----------------+ Figure 6: Contact Initiation as Passive peer - +-------->[TCPTERM]<----------+ - | | - Timeout Error - or Error | - | | - +-------+ +---------+ Contact +----------+ - | START |---->| Waiting |---- Header --->| Validate | - +-------+ +---------+ Received +----------+ - | - +---------------------------+ + + +-----------+ + | Peer CH | + | available | + +-----------+ | + Validate and + Negotiate V - +---------+ - +--Error--| Analyze |---No TLS---->[SI] - | | | ^ - | +---------+ | + +------------+ + | Negotiated |----Failure---->[TCPCLOSE] + +------------+ ^ | | | - V TLS | - [TCPTERM] Negotiated | - ^ | | - | V | - | +-----------+ | - | | Establish |---Success---+ - +--Error--| TLS | + No TLS +----Negotiate---+ | + V TLS | Failure + +-----------+ V | + | TCPCL | +---------------+ + | Messaging |<--Success--| TLS Finished | + | Available | +---------------+ +-----------+ - Figure 7: Processing of Contact Header (PCH) + Figure 7: Processing of Contact Header [PCH] - The session negotiation sequencing is performed either as the active - or passive peer, and is illustrated in Figure 8 and Figure 9 - respectively which both share the data validation and analyze final - states of Figure 10. + Session negotation involves exchanging a session initialization + (SESS_INIT) message in both directions and deriving a negotiated + state from the two messages. The session negotiation sequencing is + performed either as the active or passive peer, and is illustrated in + Figure 8 and Figure 9 respectively which both share the data + validation and analyze final states of Figure 10. The validation + here includes certificate validation and authentication when TLS is + used for the session. - +-------+ TCPCL - | START |--Messaging--+ - +-------+ Available | - V - +----------------+ - | Send SESS_INIT |--OK-->[PSI] - +----------------+ - | - Error + +-----------+ + | TCPCL | +---------+ + | Messaging |--Send SESS_INIT-->| Waiting |--Timeout-->[SESSTERM] + | Available | +---------+ + +-----------+ | + Recevied SESS_INIT | V - [SESSTERM] + [PSI] - Figure 8: Session Initiation as Active peer + Figure 8: Session Initiation [SI] as Active peer - +-------+ TCPCL - | START |---Messaging-->[PSI] - +-------+ Available + +-----------+ + | TCPCL | +---------+ + | Messaging |----Wait for ---->| Waiting |--Timeout-->[SESSTERM] + | Available | SESS_INIT +---------+ + +-----------+ | + Recevied SESS_INIT + | + +-----------------+ + | Preparing reply |--Send SESS_INIT-->[PSI] + +-----------------+ - Figure 9: Session Initiation as Passive peer + Figure 9: Session Initiation [SI] as Passive peer - +------->[SESSTERM]<--------+ - | | - Timeout Error - or Error | - | | - +-------+ +---------+ +----------+ - | START |---->| Waiting |---SESS_INIT--->| Validate | - +-------+ +---------+ Received +----------+ - | - +---------------------------+ + +----------------+ + | Peer SESS_INIT | + | available | + +----------------+ | + Validate and + Negotiate V - +---------+ +--------------+ - +--Error--| Analyze |---->| Established | - | | | | Session Idle | - | +---------+ +--------------+ + +------------+ + | Negotiated |---Failure--->[SESSTERM] + +------------+ + | + Success V - [SESSTERM] + +--------------+ + | Established | + | Session Idle | + +--------------+ - Figure 10: Processing of Session Initiation (PSI) + Figure 10: Processing of Session Initiation [PSI] Transfers can occur after a session is established and it's not in the ending state. Each transfer occurs within a single logical transfer stream between a sender and a receiver, as illustrated in Figure 11 and Figure 12 respectively. +--Send XFER_SEGMENT--+ +--------+ | | | Stream | +-------------+ | | Idle |---Send XFER_SEGMENT-->| In Progress |<------------+ @@ -661,81 +707,108 @@ Figure 11: Transfer sender states Notes on transfer sending: Pipelining of transfers can occur when the sending entity begins a new transfer while in the "Waiting for Ack" state. +-Receive XFER_SEGMENT-+ +--------+ | Send XFER_ACK | | Stream | +-------------+ | - | IDLE |--Receive XFER_SEGMENT-->| In Progress |<-------------+ + | Idle |--Receive XFER_SEGMENT-->| In Progress |<-------------+ +--------+ +-------------+ | +--------Sent Final XFER_ACK--------+ | V +--------+ | Stream | - | IDLE | + | Idle | +--------+ Figure 12: Transfer receiver states -3.3. Transfer Segmentation Policies + Session termination involves one entity initiating the termination of + the session and the other entity acknowledging the termination. For + either entity, it is the sending of the SESS_TERM message which + transitions the session to the ending substate. While a session is + being terminated only in-progress transfers can be completed and no + new transfers can be started. + + +-----------+ +---------+ + | Session |--Send SESS_TERM-->| Session | + | Live/Idle | | Ending | + +-----------+ +---------+ + + Figure 13: Session Termination [SESSTERM] from the Initiator + + +-----------+ +---------+ + | Session |--Send SESS_TERM-->| Session | + | Live/Idle | | Ending | + +-----------+<------+ +---------+ + | | + Receive SESS_TERM | + | | + +-------------+ + + Figure 14: Session Termination [SESSTERM] from the Responder + +3.4. Transfer Segmentation Policies Each TCPCL session allows a negotiated transfer segmentation polcy to be applied in each transfer direction. A receiving node can set the Segment MRU in its contact header to determine the largest acceptable segment size, and a transmitting node can segment a transfer into any sizes smaller than the receiver's Segment MRU. It is a network administration matter to determine an appropriate segmentation policy for entities operating TCPCL, but guidance given here can be used to steer policy toward performance goals. It is also advised to consider the Segment MRU in relation to chunking/packetization performed by TLS, TCP, and any intermediate network-layer nodes. - Minimum Overhead For a simple network expected to exchange + Minimum Overhead: For a simple network expected to exchange relatively small bundles, the Segment MRU can be set to be identical to the Transfer MRU which indicates that all transfers can be sent with a single data segment (i.e. no actual segmentation). If the network is closed and all transmitters are known to follow a single-segment transfer policy, then receivers can avoid the necessity of segment reassembly. Because this CL operates over a TCP stream, which suffers from a form of head-of- queue blocking between messages, while one node is transmitting a single XFER_SEGMENT message it is not able to transmit any XFER_ACK or XFER_REFUSE for any associated received transfers. - Predictable Message Sizing In situations where the maximum message + Predictable Message Sizing: In situations where the maximum message size is desired to be well-controlled, the Segment MRU can be set to the largest acceptable size (the message size less XFER_SEGMENT header size) and transmitters can always segment a transfer into maximum-size chunks no larger than the Segment MRU. This guarantees that any single XFER_SEGMENT will not monopolize the TCP stream for too long, which would prevent outgoing XFER_ACK and XFER_REFUSE associated with received transfers. - Dynamic Segmentation Even after negotiation of a Segment MRU for + Dynamic Segmentation: Even after negotiation of a Segment MRU for each receiving node, the actual transfer segmentation only needs to guarantee than any individual segment is no larger than that MRU. In a situation where network "goodput" is dynamic, the transfer segmentation size can also be dynamic in order to control message transmission duration. - Many other policies can be established in a TCPCL network between - these two extremes. Different policies can be applied to each - direction to/from any particular node. Additionally, future header - and transfer extension types can apply further nuance to transfer - policies and policy negotiation. + Many other policies can be established in a TCPCL network between the + two extremes of minimum overhead (large MRU, single-segment) and + predictable message sizing (small MRU, highly segmented). Different + policies can be applied to each transfer stream to and from from any + particular node. Additionally, future header and transfer extension + types can apply further nuance to transfer policies and policy + negotiation. -3.4. Example Message Exchange +3.5. Example Message Exchange The following figure depicts the protocol exchange for a simple session, showing the session establishment and the transmission of a single bundle split into three data segments (of lengths "L1", "L2", and "L3") from Entity A to Entity B. Note that the sending node can transmit multiple XFER_SEGMENT messages without waiting for the corresponding XFER_ACK responses. This enables pipelining of messages on a transfer stream. Although this example only demonstrates a single bundle transmission, it is @@ -780,21 +853,21 @@ <- | XFER_ACK (end) | | Transfer ID [I1] | | Length [L1+L2+L3] | +-------------------------+ +-------------------------+ | SESS_TERM | -> +-------------------------+ +-------------------------+ <- | SESS_TERM | +-------------------------+ - Figure 13: An example of the flow of protocol messages on a single + Figure 15: An example of the flow of protocol messages on a single TCP Session between two entities 4. Session Establishment For bundle transmissions to occur using the TCPCL, a TCPCL session MUST first be established between communicating entities. It is up to the implementation to decide how and when session setup is triggered. For example, some sessions MAY be opened proactively and maintained for as long as is possible given the network conditions, while other sessions MAY be opened only when there is a bundle that @@ -813,26 +886,33 @@ the implementation. Any source port number MAY be used for TCPCL sessions. Typically an operating system assigned number in the TCP Ephemeral range (49152-65535) is used. If the entity is unable to establish a TCP connection for any reason, then it is an implementation matter to determine how to handle the connection failure. An entity MAY decide to re-attempt to establish the connection. If it does so, it MUST NOT overwhelm its target with repeated connection attempts. Therefore, the entity MUST retry the connection setup no earlier than some delay time from the last - attempt, and it SHOULD use a (binary) exponential backoff mechanism - to increase this delay in case of repeated failures. + attempt, and it SHOULD use a (binary) exponential back-off mechanism + to increase this delay in case of repeated failures. The upper limit + on a re-attempt back-off is implementation defined but SHOULD be no + longer than one minute before signaling to the BP agent that a + connection cannot be made. Once a TCP connection is established, each entity MUST immediately transmit a contact header over the TCP connection. The format of the - contact header is described in Section 4.2. + contact header is described in Section 4.2. Because the TCPCL + protocol version in use is part of the initial contact header, nodes + using TCPCL version 4 can coexist on a network with nodes using + earlier TCPCL versions (with some negotiation needed for + interoperation as described in Section 4.3). 4.2. Contact Header Once a TCP connection is established, both parties exchange a contact header. This section describes the format of the contact header and the meaning of its fields. Upon receipt of the contact header, both entities perform the validation and negotiation procedures defined in Section 4.3. After receiving the contact header from the other entity, either entity MAY @@ -842,36 +922,38 @@ The format for the Contact Header is as follows: 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +---------------+---------------+---------------+---------------+ | magic='dtn!' | +---------------+---------------+---------------+---------------+ | Version | Flags | +---------------+---------------+ - Figure 14: Contact Header Format + Figure 16: Contact Header Format See Section 4.3 for details on the use of each of these contact header fields. The fields of the contact header are: magic: A four-octet field that always contains the octet sequence 0x64 0x74 0x6E 0x21, i.e., the text string "dtn!" in US-ASCII (and UTF-8). Version: A one-octet field value containing the value 4 (current - version of the protocol). + version of the TCPCL). Flags: A one-octet field of single-bit flags, interpreted according - to the descriptions in Table 1. + to the descriptions in Table 1. All reserved header flag bits + SHALL be not set by the sender. All reserved header flag bits + SHALL be ignored by the receiver. +----------+--------+-----------------------------------------------+ | Name | Code | Description | +----------+--------+-----------------------------------------------+ | CAN_TLS | 0x01 | If bit is set, indicates that the sending | | | | peer is capable of TLS security. | | | | | | Reserved | others | +----------+--------+-----------------------------------------------+ @@ -882,133 +964,202 @@ Upon reception of the contact header, each node follows the following procedures to ensure the validity of the TCPCL session and to negotiate values for the session parameters. If the magic string is not present or is not valid, the connection MUST be terminated. The intent of the magic string is to provide some protection against an inadvertent TCP connection by a different protocol than the one described in this document. To prevent a flood of repeated connections from a misconfigured application, an entity MAY elect to hold an invalid connection open and idle for some time - before closing it. + before ending it. The first negotiation is on the TCPCL protocol version to use. The active node always sends its Contact Header first and waits for a response from the passive node. The active node can repeatedly attempt different protocol versions in descending order until the passive node accepts one with a corresponding Contact Header reply. Only upon response of a Contact Header from the passive node is the TCPCL protocol version established and parameter negotiation begun. During contact initiation, the active TCPCL node SHALL send the highest TCPCL protocol version on a first session attempt for a TCPCL peer. If the active node receives a Contact Header with a different protocol version than the one sent earlier on the TCP connection, the TCP connection SHALL be terminated. If the active node receives a SESS_TERM message with reason of "Version Mismatch", that node MAY attempt further TCPCL sessions with the peer using earlier protocol version numbers in decreasing order. Managing multi-TCPCL-session state such as this is an implementation matter. If the passive node receives a contact header containing a version - that is greater than the current version of the protocol that the - node implements, then the node SHALL shutdown the session with a - reason code of "Version mismatch". If the passive node receives a - contact header with a version that is lower than the version of the - protocol that the node implements, the node MAY either terminate the - session (with a reason code of "Version mismatch") or the node MAY - adapt its operation to conform to the older version of the protocol. - The decision of version fall-back is an implementation matter. + that is greater than the current version of the TCPCL that the node + implements, then the node SHALL shutdown the session with a reason + code of "Version mismatch". If the passive node receives a contact + header with a version that is lower than the version of the protocol + that the node implements, the node MAY either terminate the session + (with a reason code of "Version mismatch") or the node MAY adapt its + operation to conform to the older version of the protocol. The + decision of version fall-back is an implementation matter. 4.4. Session Security This version of the TCPCL supports establishing a Transport Layer Security (TLS) session within an existing TCP connection. When TLS is used within the TCPCL it affects the entire session. Once established, there is no mechanism available to downgrade a TCPCL session to non-TLS operation. If this is desired, the entire TCPCL session MUST be terminated and a new non-TLS-negotiated session established. +4.4.1. TLS Handshake + The use of TLS is negotated using the Contact Header as described in Section 4.3. After negotiating an Enable TLS parameter of true, and before any other TCPCL messages are sent within the session, the - session entities SHALL begin a TLS handshake in accordance with - [RFC5246]. The parameters within each TLS negotiation are - implementation dependent but any TCPCL node SHALL follow all - recommended practices of [BCP195], or any updates or successors that - become part of [BCP195]. By convention, this protocol uses the node - which initiated the underlying TCP connection as the "client" role of - the TLS handshake request. + session entities SHALL begin a TLS handshake in accordance with TLS + 1.2 [RFC5246] or any successors that are compatible with TLS 1.2. By + convention, this protocol uses the node which initiated the + underlying TCP connection as the "client" role of the TLS handshake + request. The TLS handshake, if it occurs, is considered to be part of the contact negotiation before the TCPCL session itself is established. Specifics about sensitive data exposure are discussed in Section 8. -4.4.1. TLS Handshake Result + The parameters within each TLS negotiation are implementation + dependent but any TCPCL node SHALL follow all recommended practices + of BCP 195 [RFC7525], or any updates or successors that become part + of BCP 195. The TLS handshake SHOULD include a Server Name + Indication from the active peer. The TLS handshake SHALL request a + client-side certificate to allow authentication of the active peer. + The passive peer SHOULD supply a certificate within the TLS handshake + to allow authentication of its side of the session. The active peer + SHOULD supply a certificate within the TLS handshake to allow + authentication of its side of the session. All certificates supplied + during TLS handshake SHALL conform with the profile of [RFC5280]. + When a certificate is supplied during TLS handshake, the full + certification chain SHOULD be included unless security policy + indicates that is unnecessary. If a TLS handshake cannot negotiate a TLS session, both entities of - the TCPCL session SHALL terminate the TCP connection. At this point - the TCPCL session has not yet been established so there is no TCPCL + the TCPCL session SHALL close the TCP connection. At this point the + TCPCL session has not yet been established so there is no TCPCL session to terminate. This also avoids any potential security issues assoicated with further TCP communication with an untrusted peer. After a TLS session is successfully established, the active peer SHALL send a SESS_INIT message to begin session negotiation. This session negotation and all subsequent messaging are secured. -4.4.2. Example TLS Initiation +4.4.2. TLS Authentication - A summary of a typical CAN_TLS usage is shown in the sequence in - Figure 15 below. + Using X.509 certificates exchanged during the TLS handshake, each of + the entities can attempt to authenticate its peer at the network + layer (host name and address) and at the application layer (BP Node + ID). The Node ID exchanged in the Session Initialization is likely + to be used by the BP agent for making transfer and routing decisions, + so attempting host name validation is optional while attempting Node + ID validation is required. The logic for attempting validation is + separate from the logic for handling the result of validation, which + is based on local security policy. + + Any certificate received during TLS handshake SHALL be validated up + to one or more trusted certificate authority (CA) certificates. If + certificate validation fails or if security policy disallows a + certificate for any reason, the entity SHOULD terminate the session + (with a reason code of "Contact Failure"). + + Immediately after the TLS handshake, each side of the TCP connection + SHOULD perform host name validation of its peer in accordance with + [RFC6125] unless it is not needed by security policy. The active + peer SHALL attempt to authenticate the host name (of the passive + peer) used to initiate the TCP connection. The active peer MAY + attempt to authenticate the IP address of the other side of the TCP + connection. The passive peer SHALL attempt to authenticate the IP + address of the other side of the TCP connection. The passive peer + MAY use the IP address to resolve one or more host names of the + active peer and attempt to authenticate those. If host name + validation fails (including failure because the certificate does not + contain any DNS-ID), the entity SHOULD terminate the session (with a + reason code of "Contact Failure") unless security policy allows an + unauthticated host. + + Immediately before Session Parameter Negotiation, each side of the + session SHALL perform Node ID validation of its peer as described + below. Node ID validation SHALL succeed if the associated + certificate contains a subjectAltName entry of type + uniformResourceIdentifier whose value matches the Node ID of the + TCPCL entity. URI matching of Node IDs SHALL use the URI comparison + logic of [RFC3986] and scheme-based normalization of those schemes + specified in [I-D.ietf-dtn-bpbis]. This is similar to the URI-ID of + + [RFC6125] but does not require any structure to the scheme-specific- + part of the URI. If Node ID validation fails (including failure + because the certificate does not contain any subjectAltName URI), the + entity SHOULD terminate the session (with a reason code of "Contact + Failure") unless security policy allows an unauthticated node. + +4.4.3. Example TLS Initiation + + A summary of a typical TLS use is shown in the sequence in Figure 17 + below. Entity A Entity B - ======== ======== + active peer passive peer +-------------------------+ | Open TCP Connnection | -> +-------------------------+ +-------------------------+ <- | Accept Connection | +-------------------------+ +-------------------------+ | Contact Header | -> +-------------------------+ +-------------------------+ <- | Contact Header | +-------------------------+ +-------------------------+ +-------------------------+ | TLS Negotiation | -> <- | TLS Negotiation | | (as client) | | (as server) | +-------------------------+ +-------------------------+ - ... secured TCPCL messaging, starting with SESS_INIT ... + Host name validation occurs. + Secured TCPCL messaging can begin. + + +-------------------------+ +-------------------------+ + | SESS_INIT | -> <- | SESS_INIT | + +-------------------------+ +-------------------------+ + + Node ID validation occurs. + Session is established, transfers can begin. +-------------------------+ +-------------------------+ | SESS_TERM | -> <- | SESS_TERM | +-------------------------+ +-------------------------+ - Figure 15: A simple visual example of TCPCL TLS Establishment between + Figure 17: A simple visual example of TCPCL TLS Establishment between two entities -4.5. Message Type Codes +4.5. Message Header After the initial exchange of a contact header, all messages transmitted over the session are identified by a one-octet header with the following structure: 0 1 2 3 4 5 6 7 +---------------+ | Message Type | +---------------+ - Figure 16: Format of the Message Header + Figure 18: Format of the Message Header The message header fields are as follows: Message Type: Indicates the type of the message as per Table 2 below. Encoded values are listed in Section 9.5. +--------------+------+---------------------------------------------+ | Name | Code | Description | +--------------+------+---------------------------------------------+ | SESS_INIT | 0x07 | Contains the session parameter inputs from | @@ -1040,21 +1191,21 @@ Table 2: TCPCL Message Types 4.6. Session Initialization Message (SESS_INIT) Before a session is established and ready to transfer bundles, the session parameters are negotiated between the connected entities. The SESS_INIT message is used to convey the per-entity parameters which are used together to negotiate the per-session parameters as described in Section 4.7. - The format of a SESS_INIT message is as follows in Figure 17. + The format of a SESS_INIT message is as follows in Figure 19. +-----------------------------+ | Message Header | +-----------------------------+ | Keepalive Interval (U16) | +-----------------------------+ | Segment MRU (U64) | +-----------------------------+ | Transfer MRU (U64) | +-----------------------------+ @@ -1062,21 +1213,21 @@ +-----------------------------+ | EID Data (variable) | +-----------------------------+ | Session Extension | | Items Length (U32) | +-----------------------------+ | Session Extension | | Items (var.) | +-----------------------------+ - Figure 17: SESS_INIT Format + Figure 19: SESS_INIT Format The fields of the SESS_INIT message are: Keepalive Interval: A 16-bit unsigned integer indicating the interval, in seconds, between any subsequent messages being transmitted by the peer. The peer receiving this contact header uses this interval to determine how long to wait after any last- message transmission and a necessary subsequent KEEPALIVE message transmission. @@ -1088,30 +1239,32 @@ relation between the two is required. Transfer MRU: A 64-bit unsigned integer indicating the largest allowable total-bundle data size to be received in this session. Any bundle transfer sent to this peer SHALL have a Total Bundle Length payload no longer than the peer's Transfer MRU. This value can be used to perform proactive bundle fragmentation. The two entities of a single session MAY have different Transfer MRUs, and no relation between the two is required. - EID Length and EID Data: Together these fields represent a variable- - length text string. The EID Length is a 16-bit unsigned integer - indicating the number of octets of EID Data to follow. A zero EID - Length SHALL be used to indicate the lack of EID rather than a - truly empty EID. This case allows an entity to avoid exposing EID - information on an untrusted network. A non-zero-length EID Data - SHALL contain the UTF-8 encoded EID of some singleton endpoint in - which the sending entity is a member, in the canonical format of - :. This EID encoding is - consistent with [I-D.ietf-dtn-bpbis]. + Node ID Length and Node ID Data: Together these fields represent a + variable-length text string. The Node ID Length is a 16-bit + unsigned integer indicating the number of octets of Node ID Data + to follow. A zero-length Node ID SHALL be used to indicate the + lack of Node ID rather than a truly empty Node ID. This case + allows an entity to avoid exposing Node ID information on an + untrusted network. A non-zero-length Node ID Data SHALL contain + the UTF-8 encoded Node ID of the Entity which sent the SESS_INIT + message. Every Node ID SHALL be a URI consistent with the + requirements of [RFC3986] and the URI schemes of + [I-D.ietf-dtn-bpbis]. The Node ID itself can be authenticated as + described in Section 4.4.2. Session Extension Length and Session Extension Items: Together these fields represent protocol extension data not defined by this specification. The Session Extension Length is the total number of octets to follow which are used to encode the Session Extension Item list. The encoding of each Session Extension Item is within a consistent data container as described in Section 4.8. The full set of Session Extension Items apply for the duration of the TCPCL session to follow. The order and mulitplicity of these Session Extension Items MAY be significant, as defined in the associated @@ -1137,44 +1290,48 @@ Session Keepalive: Negotiation of the Session Keepalive parameter is performed by taking the minimum of this two contact headers' Keepalive Interval. The Session Keepalive interval is a parameter for the behavior described in Section 5.1.1. Enable TLS: Negotiation of the Enable TLS parameter is performed by taking the logical AND of the two contact headers' CAN_TLS flags. A local security policy is then applied to determine of the negotated value of Enable TLS is acceptable. It can be a reasonable security policy to both require or disallow the use of - TLS depending upon the desired network flows. If the Enable TLS - state is unacceptable, the node SHALL terminate the session with a - reason code of "Contact Failure". Note that this contact failure - is different than a failure of TLS handshake after an agreed-upon - and acceptable Enable TLS state. If the negotiated Enable TLS - value is true and acceptable then TLS negotiation feature - (described in Section 4.4) begins immediately following the - contact header exchange. + TLS depending upon the desired network flows. Because this state + is negotiated over an unsecured medium, there is a risk of a TLS + Stripping as described in Section 8. If the Enable TLS state is + unacceptable, the node SHALL terminate the session with a reason + code of "Contact Failure". Note that this contact failure reason + is different than a failure of TLS handshake or TLS authentication + after an agreed-upon and acceptable Enable TLS state. If the + negotiated Enable TLS value is true and acceptable then TLS + negotiation feature (described in Section 4.4) begins immediately + following the contact header exchange. Once this process of parameter negotiation is completed (which includes a possible completed TLS handshake of the connection to use TLS), this protocol defines no additional mechanism to change the parameters of an established session; to effect such a change, the TCPCL session MUST be terminated and a new session established. 4.8. Session Extension Items Each of the Session Extension Items SHALL be encoded in an identical - Type-Length-Value (TLV) container form as indicated in Figure 18. + Type-Length-Value (TLV) container form as indicated in Figure 20. The fields of the Session Extension Item are: Flags: A one-octet field containing generic bit flags about the - Item, which are listed in Table 3. If a TCPCL entity receives a + Item, which are listed in Table 3. All reserved header flag bits + SHALL be not set by the sender. All reserved header flag bits + SHALL be ignored by the receiver. If a TCPCL entity receives a Session Extension Item with an unknown Item Type and the CRITICAL flag set, the entity SHALL close the TCPCL session with SESS_TERM reason code of "Contact Failure". If the CRITICAL flag is not set, an entity SHALL skip over and ignore any item with an unknown Item Type. Item Type: A 16-bit unsigned integer field containing the type of the extension item. This specification does not define any extension types directly, but does allocate an IANA registry for such codes (see Section 9.3). @@ -1190,21 +1347,21 @@ data is sent. 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +---------------+---------------+---------------+---------------+ | Item Flags | Item Type | Item Length...| +---------------+---------------+---------------+---------------+ | length contd. | Item Value... | +---------------+---------------+---------------+---------------+ - Figure 18: Session Extension Item Format + Figure 20: Session Extension Item Format +----------+--------+-----------------------------------------------+ | Name | Code | Description | +----------+--------+-----------------------------------------------+ | CRITICAL | 0x01 | If bit is set, indicates that the receiving | | | | peer must handle the extension item. | | | | | | Reserved | others | +----------+--------+-----------------------------------------------+ @@ -1258,31 +1415,31 @@ 5.1.2. Message Rejection (MSG_REJECT) If a TCPCL node receives a message which is unknown to it (possibly due to an unhandled protocol mismatch) or is inappropriate for the current session state (e.g. a KEEPALIVE message received after contact header negotiation has disabled that feature), there is a protocol-level message to signal this condition in the form of a MSG_REJECT reply. - The format of a MSG_REJECT message is as follows in Figure 19. + The format of a MSG_REJECT message is as follows in Figure 21. +-----------------------------+ | Message Header | +-----------------------------+ | Reason Code (U8) | +-----------------------------+ | Rejected Message Header | +-----------------------------+ - Figure 19: Format of MSG_REJECT Messages + Figure 21: Format of MSG_REJECT Messages The fields of the MSG_REJECT message are: Reason Code: A one-octet refusal reason code interpreted according to the descriptions in Table 4. Rejected Message Header: The Rejected Message Header is a copy of the Message Header to which the MSG_REJECT message is sent as a response. @@ -1347,21 +1504,21 @@ Transfer ID space, the sending node SHALL terminate the session with SESS_TERM reason code "Resource Exhaustion". For bidirectional bundle transfers, a TCPCL node SHOULD NOT rely on any relation between Transfer IDs originating from each side of the TCPCL session. 5.2.2. Data Transmission (XFER_SEGMENT) Each bundle is transmitted in one or more data segments. The format - of a XFER_SEGMENT message follows in Figure 20. + of a XFER_SEGMENT message follows in Figure 22. +------------------------------+ | Message Header | +------------------------------+ | Message Flags (U8) | +------------------------------+ | Transfer ID (U64) | +------------------------------+ | Transfer Extension | | Items Length (U32) | @@ -1369,26 +1526,28 @@ +------------------------------+ | Transfer Extension | | Items (var.) | | (only for START segment) | +------------------------------+ | Data length (U64) | +------------------------------+ | Data contents (octet string) | +------------------------------+ - Figure 20: Format of XFER_SEGMENT Messages + Figure 22: Format of XFER_SEGMENT Messages The fields of the XFER_SEGMENT message are: Message Flags: A one-octet field of single-bit flags, interpreted - according to the descriptions in Table 5. + according to the descriptions in Table 5. All reserved header + flag bits SHALL be not set by the sender. All reserved header + flag bits SHALL be ignored by the receiver. Transfer ID: A 64-bit unsigned integer identifying the transfer being made. Transfer Extension Length and Transfer Extension Items: Together these fields represent protocol extension data for this specification. The Transfer Extension Length and Transfer Extension Item fields SHALL only be present when the 'START' flag is set on the message. The Transfer Extension Length is the total number of octets to follow which are used to encode the Transfer @@ -1438,38 +1597,40 @@ Although the TCP transport provides reliable transfer of data between transport peers, the typical BSD sockets interface provides no means to inform a sending application of when the receiving application has processed some amount of transmitted data. Thus, after transmitting some data, the TCPCL needs an additional mechanism to determine whether the receiving agent has successfully received the segment. To this end, the TCPCL protocol provides feedback messaging whereby a receiving node transmits acknowledgments of reception of data segments. - The format of an XFER_ACK message follows in Figure 21. + The format of an XFER_ACK message follows in Figure 23. +-----------------------------+ | Message Header | +-----------------------------+ | Message Flags (U8) | +-----------------------------+ | Transfer ID (U64) | +-----------------------------+ | Acknowledged length (U64) | +-----------------------------+ - Figure 21: Format of XFER_ACK Messages + Figure 23: Format of XFER_ACK Messages The fields of the XFER_ACK message are: Message Flags: A one-octet field of single-bit flags, interpreted - according to the descriptions in Table 5. + according to the descriptions in Table 5. All reserved header + flag bits SHALL be not set by the sender. All reserved header + flag bits SHALL be ignored by the receiver. Transfer ID: A 64-bit unsigned integer identifying the transfer being acknowledged. Acknowledged length: A 64-bit unsigned integer indicating the total number of octets in the transfer which are being acknowledged. A receiving TCPCL node SHALL send an XFER_ACK message in response to each received XFER_SEGMENT message. The flags portion of the XFER_ACK header SHALL be set to match the corresponding DATA_SEGMENT @@ -1502,31 +1663,31 @@ XFER_REFUSE can be used in cases where the agent's bundle storage is temporarily depleted or somehow constrained. A XFER_REFUSE can also be used after the bundle header or any bundle data is inspected by an agent and determined to be unacceptable. A receiver MAY send an XFER_REFUSE message as soon as it receives any XFER_SEGMENT message. The sender MUST be prepared for this and MUST associate the refusal with the correct bundle via the Transfer ID fields. - The format of the XFER_REFUSE message is as follows in Figure 22. + The format of the XFER_REFUSE message is as follows in Figure 24. +-----------------------------+ | Message Header | +-----------------------------+ | Reason Code (U8) | +-----------------------------+ | Transfer ID (U64) | +-----------------------------+ - Figure 22: Format of XFER_REFUSE Messages + Figure 24: Format of XFER_REFUSE Messages The fields of the XFER_REFUSE message are: Reason Code: A one-octet refusal reason code interpreted according to the descriptions in Table 6. Transfer ID: A 64-bit unsigned integer identifying the transfer being refused. +------------+------+-----------------------------------------------+ @@ -1571,26 +1732,28 @@ Note: If a bundle transmission is aborted in this way, the receiver MAY not receive a segment with the 'END' flag set to '1' for the aborted bundle. The beginning of the next bundle is identified by the 'START' bit set to '1', indicating the start of a new transfer, and with a distinct Transfer ID value. 5.2.5. Transfer Extension Items Each of the Transfer Extension Items SHALL be encoded in an identical - Type-Length-Value (TLV) container form as indicated in Figure 23. + Type-Length-Value (TLV) container form as indicated in Figure 25. The fields of the Transfer Extension Item are: Flags: A one-octet field containing generic bit flags about the - Item, which are listed in Table 7. If a TCPCL node receives a + Item, which are listed in Table 7. All reserved header flag bits + SHALL be not set by the sender. All reserved header flag bits + SHALL be ignored by the receiver. If a TCPCL node receives a Transfer Extension Item with an unknown Item Type and the CRITICAL flag set, the node SHALL refuse the transfer with an XFER_REFUSE reason code of "Extension Failure". If the CRITICAL flag is not set, an entity SHALL skip over and ignore any item with an unknown Item Type. Item Type: A 16-bit unsigned integer field containing the type of the extension item. This specification allocates an IANA registry for such codes (see Section 9.4). @@ -1605,21 +1768,21 @@ extension data is sent. 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +---------------+---------------+---------------+---------------+ | Item Flags | Item Type | Item Length...| +---------------+---------------+---------------+---------------+ | length contd. | Item Value... | +---------------+---------------+---------------+---------------+ - Figure 23: Transfer Extension Item Format + Figure 25: Transfer Extension Item Format +----------+--------+-----------------------------------------------+ | Name | Code | Description | +----------+--------+-----------------------------------------------+ | CRITICAL | 0x01 | If bit is set, indicates that the receiving | | | | peer must handle the extension item. | | | | | | Reserved | others | +----------+--------+-----------------------------------------------+ @@ -1635,27 +1798,27 @@ same transfer. The lack of a Transfer Length extension item in any transfer SHALL NOT imply anything about the potential length of the transfer. The Transfer Length extension SHALL be assigned transfer extension type ID 0x0001. If a transfer occupies exactly one segment (i.e. both START and END bits are set) the Transfer Length extension SHOULD NOT be present. The extension does not provide any additional information for single- segment transfers. - The format of the Transfer Length data is as follows in Figure 24. + The format of the Transfer Length data is as follows in Figure 26. +----------------------+ | Total Length (U64) | +----------------------+ - Figure 24: Format of Transfer Length data + Figure 26: Format of Transfer Length data The fields of the Transfer Length extension are: Total Length: A 64-bit unsigned integer indicating the size of the data-to-be-transferred. The Total Length field SHALL be treated as authoritative by the receiver. If, for whatever reason, the actual total length of bundle data received differs from the value indicated by the Total Length value, the receiver SHALL treat the transmitted data as invalid. @@ -1671,53 +1834,55 @@ termination, the REPLY bit of a SESS_TERM message SHALL NOT be set. Upon receiving a SESS_TERM message after not sending a SESS_TERM message in the same session, an entity SHALL send an acknowledging SESS_TERM message. When sent to acknowledge a termination, a SESS_TERM message SHALL have identical data content from the message being acknowledged except for the REPLY bit, which is set to indicate acknowledgement. After sending a SESS_TERM message, an entity MAY continue a possible in-progress transfer in either direction. After sending a SESS_TERM - message, an entity SHALL NOT begin any new outgoing transfer (i.e. - send an XFER_SEGMENT message) for the remainder of the session. - After receving a SESS_TERM message, an entity SHALL NOT accept any - new incoming transfer for the remainder of the session. + message, an entity SHALL NOT begin any new outgoing transfer for the + remainder of the session. After receving a SESS_TERM message, an + entity SHALL NOT accept any new incoming transfer for the remainder + of the session. Instead of following a clean shutdown sequence, after transmitting a SESS_TERM message an entity MAY immediately close the associated TCP connection. When performing an unclean shutdown, a receiving node SHOULD acknowledge all received data segments before closing the TCP connection. Not acknowledging received segments can result in unnecessary retransmission. When performing an unclean shutodwn, a transmitting node SHALL treat either sending or receiving a SESS_TERM message (i.e. before the final acknowledgment) as a failure of the transfer. Any delay between request to terminate the TCP connection and actual closing of the connection (a "half-closed" state) MAY be ignored by the TCPCL node. - The format of the SESS_TERM message is as follows in Figure 25. + The format of the SESS_TERM message is as follows in Figure 27. +-----------------------------+ | Message Header | +-----------------------------+ | Message Flags (U8) | +-----------------------------+ | Reason Code (U8) | +-----------------------------+ - Figure 25: Format of SESS_TERM Messages + Figure 27: Format of SESS_TERM Messages The fields of the SESS_TERM message are: Message Flags: A one-octet field of single-bit flags, interpreted - according to the descriptions in Table 8. + according to the descriptions in Table 8. All reserved header + flag bits SHALL be not set by the sender. All reserved header + flag bits SHALL be ignored by the receiver. Reason Code: A one-octet refusal reason code interpreted according to the descriptions in Table 9. +----------+--------+-----------------------------------------------+ | Name | Code | Description | +----------+--------+-----------------------------------------------+ | REPLY | 0x01 | If bit is set, indicates that this message is | | | | an acknowledgement of an earlier SESS_TERM | | | | message. | @@ -1769,21 +1934,21 @@ message but still SHALL close the TCP connection. Each TCPCL message is contiguous in the octet stream and has no ability to be cut short and/or preempted by an other message. This is particularly important when large segment sizes are being transmitted; either entire XFER_SEGMENT is sent before a SESS_TERM message or the connection is simply terminated mid-XFER_SEGMENT. 6.2. Idle Session Shutdown The protocol includes a provision for clean shutdown of idle - sessions. Determining the length of time to wait before closing idle + sessions. Determining the length of time to wait before ending idle sessions, if they are to be closed at all, is an implementation and configuration matter. If there is a configured time to close idle links and if no TCPCL messages (other than KEEPALIVE messages) has been received for at least that amount of time, then either node MAY terminate the session by transmitting a SESS_TERM message indicating the reason code of "Idle timeout" (as described in Table 9). 7. Implementation Status @@ -1795,99 +1960,101 @@ This section records the status of known implementations of the protocol defined by this specification at the time of posting of this Internet-Draft, and is based on a proposal described in [RFC7942]. The description of implementations in this section is intended to assist the IETF in its decision processes in progressing drafts to RFCs. Please note that the listing of any individual implementation here does not imply endorsement by the IETF. Furthermore, no effort has been spent to verify the information presented here that was supplied by IETF contributors. This is not intended as, and must not be construed to be, a catalog of available implementations or their - features. Readers are advised to note that other implementations may + features. Readers are advised to note that other implementations can exist. An example implementation of the this draft of TCPCLv4 has been created as a GitHub project [github-dtn-bpbis-tcpcl] and is intented to use as a proof-of-concept and as a possible source of interoperability testing. This example implementation uses D-Bus as the CL-BP Agent interface, so it only runs on hosts which provide the Python "dbus" library. 8. Security Considerations - One security consideration for this protocol relates to the fact that - entities present their endpoint identifier as part of the contact - header exchange. It would be possible for an entity to fake this - value and present the identity of a singleton endpoint in which the - node is not a member, essentially masquerading as another DTN node. - If this identifier is used outside of a TLS-secured session or - without further verification as a means to determine which bundles - are transmitted over the session, then the node that has falsified - its identity would be able to obtain bundles that it otherwise would - not have. Therefore, an entity SHALL NOT use the EID value of an - unsecured contact header to derive a peer node's identity unless it - can corroborate it via other means. When TCPCL session security is - mandated by a TCPCL peer, that peer SHALL transmit initial unsecured - contact header values indicated in Table 10 in order. These values - avoid unnecessarily leaking session parameters and will be ignored - when secure contact header re-exchange occurs. - - +--------------------+---------------------------------------------+ - | Parameter | Value | - +--------------------+---------------------------------------------+ - | Flags | The USE_TLS flag is set. | - | | | - | Keepalive Interval | Zero, indicating no keepalive. | - | | | - | Segment MRU | Zero, indicating all segments are refused. | - | | | - | Transfer MRU | Zero, indicating all transfers are refused. | - | | | - | EID | Empty, indicating lack of EID. | - +--------------------+---------------------------------------------+ - - Table 10: Recommended Unsecured Contact Header - TCPCL can be used to provide point-to-point transport security, but does not provide security of data-at-rest and does not guarantee end- - to-end bundle security. The mechanisms defined in [RFC6257] and + to-end bundle security. The bundle security mechanisms defined in [I-D.ietf-dtn-bpsec] are to be used instead. + When negotating whether to use TLS security as part of the contact + header exchange, it is possible for a man-in-the-middle attacker to + unset the CAN_TLS flag on either side of the exchange. This leads to + the "SSL Stripping" attack described in [RFC7457]. If TLS is desired + for use on any TCPCL network, it is strongly encouraged that the + security policy disallow use of TCPCL when "Enable TLS" is negotiated + to false. This requires that the TLS handshake occurs, regardless of + the policy-driven parameters of the handshake and policy-driven + handling of the handshake outcome. + Even when using TLS to secure the TCPCL session, the actual ciphersuite negotiated between the TLS peers MAY be insecure. TLS can be used to perform authentication without data confidentiality, for example. It is up to security policies within each TCPCL node to ensure that the negotiated TLS ciphersuite meets transport security requirements. This is identical behavior to STARTTLS use in [RFC2595]. + The certificates exchanged by TLS enable authentication of peer host + name and Node ID, but it is possible that a peer either not provide a + valid certificate or that the certificate does not validate either + the host name or Node ID of the peer. Having a CA-validated + certificate does not alone guarantee the identity of the network host + or BP node from which the certificate is provided; additional + validation procedures bind the host name or node ID based on the + contents of the certificate. The host name validation is a weaker + form of authentication, because even if a peer is operating on an + authenticated network host name it can provide an invalid Node ID and + cause bundles to be "leaked" to an invalid node. Especially in DTN + environments, network names and addresses of nodes can be time- + variable so binding a certificate to a Node ID is a more stable + identity. Node ID validation ensures that the peer to which a bundle + is transferred is in fact the node which the BP Agent expects it to + be. It is a reasonable policy to skip host name validation if + certificates can be guaranteed to validate the peer's Node ID. In + circumstances where certificates can only be issued to network host + names, Node ID validation is not possible but it could be reasonable + to assume that a trusted host is not going to present an invalid Node + ID. Trusting an authenticated host name can be feasable on a network + secured by a private CA but is not advisable on the Internet when + using a variety of public CAs. + Another consideration for this protocol relates to denial-of-service attacks. An entity MAY send a large amount of data over a TCPCL session, requiring the receiving entity to handle the data, attempt to stop the flood of data by sending a XFER_REFUSE message, or forcibly terminate the session. This burden could cause denial of service on other, well-behaving sessions. There is also nothing to prevent a malicious entity from continually establishing sessions and repeatedly trying to send copious amounts of bundle data. A listening entity MAY take countermeasures such as ignoring TCP SYN messages, closing TCP connections as soon as they are established, waiting before sending the contact header, sending a SESS_TERM message quickly or with a delay, etc. 9. IANA Considerations - In this section, registration procedures are as defined in [RFC8126]. + Registration procedures referred to in this section are defined in + [RFC8126]. - Some of the registries below are created new for TCPCLv4 but share - code values with TCPCLv3. This was done to disambiguate the use of - these values between TCPCLv3 and TCPCLv4 while preserving the - semantics of some values. + Some of the registries have been defined as version specific to + TCPCLv4, and imports some or all codepoints from TCPCLv3. This was + done to disambiguate the use of these codepoints between TCPCLv3 and + TCPCLv4 while preserving the semantics of some of the codepoints. 9.1. Port Number Port number 4556 has been previously assigned as the default port for the TCP convergence layer in [RFC7242]. This assignment is unchanged by protocol version 4. Each TCPCL entity identifies its TCPCL protocol version in its initial contact (see Section 9.2), so there is no ambiguity about what protocol is being used. +------------------------+-------------------------------------+ @@ -1932,303 +2099,345 @@ +-------+-------------+---------------------+ 9.3. Session Extension Types EDITOR NOTE: sub-registry to-be-created upon publication of this specification. IANA will create, under the "Bundle Protocol" registry, a sub- registry titled "Bundle Protocol TCP Convergence-Layer Version 4 Session Extension Types" and initialize it with the contents of - Table 11. The registration procedure is RFC Required within the + Table 10. The registration procedure is Expert Review within the lower range 0x0001--0x7FFF. Values in the range 0x8000--0xFFFF are reserved for use on private networks for functions not published to the IANA. +----------------+--------------------------+ | Code | Session Extension Type | +----------------+--------------------------+ | 0x0000 | Reserved | | | | | 0x0001--0x7FFF | Unassigned | | | | | 0x8000--0xFFFF | Private/Experimental Use | +----------------+--------------------------+ - Table 11: Session Extension Type Codes + Table 10: Session Extension Type Codes 9.4. Transfer Extension Types EDITOR NOTE: sub-registry to-be-created upon publication of this specification. IANA will create, under the "Bundle Protocol" registry, a sub- registry titled "Bundle Protocol TCP Convergence-Layer Version 4 Transfer Extension Types" and initialize it with the contents of - Table 12. The registration procedure is RFC Required within the + Table 11. The registration procedure is Expert Review within the lower range 0x0001--0x7FFF. Values in the range 0x8000--0xFFFF are reserved for use on private networks for functions not published to the IANA. +----------------+---------------------------+ | Code | Transfer Extension Type | +----------------+---------------------------+ | 0x0000 | Reserved | | | | | 0x0001 | Transfer Length Extension | | | | | 0x0002--0x7FFF | Unassigned | | | | | 0x8000--0xFFFF | Private/Experimental Use | +----------------+---------------------------+ - Table 12: Transfer Extension Type Codes + Table 11: Transfer Extension Type Codes 9.5. Message Types EDITOR NOTE: sub-registry to-be-created upon publication of this specification. IANA will create, under the "Bundle Protocol" registry, a sub- registry titled "Bundle Protocol TCP Convergence-Layer Version 4 - Message Types" and initialize it with the contents of Table 13. The - registration procedure is RFC Required. + Message Types" and initialize it with the contents of Table 12. The + registration procedure is RFC Required within the lower range 0x01-- + 0xEF. Values in the range 0xF0--0xFF are reserved for use on private + networks for functions not published to the IANA. - +-----------+--------------+ + +------------+--------------------------+ | Code | Message Type | - +-----------+--------------+ + +------------+--------------------------+ | 0x00 | Reserved | | | | | 0x01 | XFER_SEGMENT | | | | | 0x02 | XFER_ACK | | | | | 0x03 | XFER_REFUSE | | | | | 0x04 | KEEPALIVE | | | | | 0x05 | SESS_TERM | | | | | 0x06 | MSG_REJECT | | | | | 0x07 | SESS_INIT | | | | - | 0x08--0xf | Unassigned | - +-----------+--------------+ + | 0x08--0xEF | Unassigned | + | | | + | 0xF0--0xFF | Private/Experimental Use | + +------------+--------------------------+ - Table 13: Message Type Codes + Table 12: Message Type Codes 9.6. XFER_REFUSE Reason Codes EDITOR NOTE: sub-registry to-be-created upon publication of this specification. IANA will create, under the "Bundle Protocol" registry, a sub- registry titled "Bundle Protocol TCP Convergence-Layer Version 4 XFER_REFUSE Reason Codes" and initialize it with the contents of - Table 14. The registration procedure is RFC Required. + Table 13. The registration procedure is Specification Required + within the lower range 0x00--0xEF. Values in the range 0xF0--0xFF + are reserved for use on private networks for functions not published + to the IANA. - +------------+---------------------------+ + +------------+--------------------------+ | Code | Refusal Reason | - +------------+---------------------------+ + +------------+--------------------------+ | 0x00 | Unknown | | | | | 0x01 | Extension Failure | | | | | 0x02 | Completed | | | | | 0x03 | No Resources | | | | | 0x04 | Retransmit | | | | - | 0x05--0x07 | Unassigned | + | 0x05--0xEF | Unassigned | | | | - | 0x08--0xFF | Reserved for future usage | - +------------+---------------------------+ + | 0xF0--0xFF | Private/Experimental Use | + +------------+--------------------------+ - Table 14: XFER_REFUSE Reason Codes + Table 13: XFER_REFUSE Reason Codes 9.7. SESS_TERM Reason Codes EDITOR NOTE: sub-registry to-be-created upon publication of this specification. IANA will create, under the "Bundle Protocol" registry, a sub- registry titled "Bundle Protocol TCP Convergence-Layer Version 4 SESS_TERM Reason Codes" and initialize it with the contents of - Table 15. The registration procedure is RFC Required. + Table 14. The registration procedure is Specification Required + within the lower range 0x00--0xEF. Values in the range 0xF0--0xFF + are reserved for use on private networks for functions not published + to the IANA. - +------------+---------------------+ + +------------+--------------------------+ | Code | Termination Reason | - +------------+---------------------+ + +------------+--------------------------+ | 0x00 | Unknown | | | | | 0x01 | Idle timeout | | | | | 0x02 | Version mismatch | | | | | 0x03 | Busy | | | | | 0x04 | Contact Failure | | | | | 0x05 | Resource Exhaustion | | | | - | 0x06--0xFF | Unassigned | - +------------+---------------------+ + | 0x06--0xEF | Unassigned | + | | | + | 0xF0--0xFF | Private/Experimental Use | + +------------+--------------------------+ - Table 15: SESS_TERM Reason Codes + Table 14: SESS_TERM Reason Codes 9.8. MSG_REJECT Reason Codes EDITOR NOTE: sub-registry to-be-created upon publication of this specification. IANA will create, under the "Bundle Protocol" registry, a sub- registry titled "Bundle Protocol TCP Convergence-Layer Version 4 MSG_REJECT Reason Codes" and initialize it with the contents of - Table 16. The registration procedure is RFC Required. + Table 15. The registration procedure is Specification Required + within the lower range 0x01--0xEF. Values in the range 0xF0--0xFF + are reserved for use on private networks for functions not published + to the IANA. - +-----------+----------------------+ + +------------+--------------------------+ | Code | Rejection Reason | - +-----------+----------------------+ + +------------+--------------------------+ | 0x00 | reserved | | | | | 0x01 | Message Type Unknown | | | | | 0x02 | Message Unsupported | | | | | 0x03 | Message Unexpected | | | | - | 0x04-0xFF | Unassigned | - +-----------+----------------------+ + | 0x04--0xEF | Unassigned | + | | | + | 0xF0--0xFF | Private/Experimental Use | + +------------+--------------------------+ - Table 16: MSG_REJECT Reason Codes + Table 15: MSG_REJECT Reason Codes 10. Acknowledgments This specification is based on comments on implementation of [RFC7242] provided from Scott Burleigh. 11. References 11.1. Normative References - [BCP195] Sheffer, Y., Holz, R., and P. Saint-Andre, - "Recommendations for Secure Use of Transport Layer - Security (TLS) and Datagram Transport Layer Security - (DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May - 2015. - [I-D.ietf-dtn-bpbis] Burleigh, S., Fall, K., and E. Birrane, "Bundle Protocol - Version 7", draft-ietf-dtn-bpbis-12 (work in progress), - November 2018. + Version 7", draft-ietf-dtn-bpbis-14 (work in progress), + August 2019. [RFC0793] Postel, J., "Transmission Control Protocol", STD 7, RFC 793, DOI 10.17487/RFC0793, September 1981, . [RFC1122] Braden, R., Ed., "Requirements for Internet Hosts - Communication Layers", STD 3, RFC 1122, DOI 10.17487/RFC1122, October 1989, . [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . + [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform + Resource Identifier (URI): Generic Syntax", STD 66, + RFC 3986, DOI 10.17487/RFC3986, January 2005, + . + [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security (TLS) Protocol Version 1.2", RFC 5246, DOI 10.17487/RFC5246, August 2008, . + [RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S., + Housley, R., and W. Polk, "Internet X.509 Public Key + Infrastructure Certificate and Certificate Revocation List + (CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008, + . + + [RFC6125] Saint-Andre, P. and J. Hodges, "Representation and + Verification of Domain-Based Application Service Identity + within Internet Public Key Infrastructure Using X.509 + (PKIX) Certificates in the Context of Transport Layer + Security (TLS)", RFC 6125, DOI 10.17487/RFC6125, March + 2011, . + + [RFC7525] Sheffer, Y., Holz, R., and P. Saint-Andre, + "Recommendations for Secure Use of Transport Layer + Security (TLS) and Datagram Transport Layer Security + (DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May + 2015, . + [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 8126, DOI 10.17487/RFC8126, June 2017, . + [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC + 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, + May 2017, . + 11.2. Informative References [github-dtn-bpbis-tcpcl] Sipos, B., "TCPCL Example Implementation", . [I-D.ietf-dtn-bpsec] Birrane, E. and K. McKeever, "Bundle Protocol Security - Specification", draft-ietf-dtn-bpsec-09 (work in - progress), February 2019. + Specification", draft-ietf-dtn-bpsec-10 (work in + progress), April 2019. [RFC2595] Newman, C., "Using TLS with IMAP, POP3 and ACAP", RFC 2595, DOI 10.17487/RFC2595, June 1999, . [RFC4838] Cerf, V., Burleigh, S., Hooke, A., Torgerson, L., Durst, R., Scott, K., Fall, K., and H. Weiss, "Delay-Tolerant Networking Architecture", RFC 4838, DOI 10.17487/RFC4838, April 2007, . - [RFC5050] Scott, K. and S. Burleigh, "Bundle Protocol - Specification", RFC 5050, DOI 10.17487/RFC5050, November - 2007, . - - [RFC6257] Symington, S., Farrell, S., Weiss, H., and P. Lovell, - "Bundle Security Protocol Specification", RFC 6257, - DOI 10.17487/RFC6257, May 2011, - . - [RFC7242] Demmer, M., Ott, J., and S. Perreault, "Delay-Tolerant Networking TCP Convergence-Layer Protocol", RFC 7242, DOI 10.17487/RFC7242, June 2014, . + [RFC7457] Sheffer, Y., Holz, R., and P. Saint-Andre, "Summarizing + Known Attacks on Transport Layer Security (TLS) and + Datagram TLS (DTLS)", RFC 7457, DOI 10.17487/RFC7457, + February 2015, . + [RFC7942] Sheffer, Y. and A. Farrel, "Improving Awareness of Running Code: The Implementation Status Section", BCP 205, RFC 7942, DOI 10.17487/RFC7942, July 2016, . Appendix A. Significant changes from RFC7242 The areas in which changes from [RFC7242] have been made to existing headers and messages are: o Split contact header into pre-TLS protocol negotiation and SESS_INIT parameter negotiation. The contact header is now fixed- length. o Changed contact header content to limit number of negotiated options. - o Added contact option to negotiate maximum segment size (per each + o Added session option to negotiate maximum segment size (per each direction). + o Renamed "Endpoint ID" to "Node ID" to conform with BPv7 + terminology. + o Added session extension capability. o Added transfer extension capability. Moved transfer total length into an extension item. o Defined new IANA registries for message / type / reason codes to allow renaming some codes for clarity. + o Segments of all new IANA registries are reserved for private/ + experimental use. + o Expanded Message Header to octet-aligned fields instead of bit- packing. o Added a bundle transfer identification number to all bundle- related messages (XFER_SEGMENT, XFER_ACK, XFER_REFUSE). o Use flags in XFER_ACK to mirror flags from XFER_SEGMENT. o Removed all uses of SDNV fields and replaced with fixed-bit-length fields. - o Renamed SHUTDOWN to SESS_TERM to deconflict term "shutdown". + o Renamed SHUTDOWN to SESS_TERM to deconflict term "shutdown" + related to TCP connections. o Removed the notion of a re-connection delay parameter. The areas in which extensions from [RFC7242] have been made as new messages and codes are: o Added contact negotiation failure SESS_TERM reason code. o Added MSG_REJECT message to indicate an unknown or unhandled message was received.