draft-ietf-hip-rfc4423-bis-06.txt   draft-ietf-hip-rfc4423-bis-07.txt 
Network Working Group R. Moskowitz, Ed. Network Working Group R. Moskowitz, Ed.
Internet-Draft Verizon Internet-Draft Verizon
Obsoletes: 4423 (if approved) M. Komu Obsoletes: 4423 (if approved) M. Komu
Intended status: Informational Aalto Intended status: Informational Aalto
Expires: May 11, 2014 November 7, 2013 Expires: June 21, 2014 December 18, 2013
Host Identity Protocol Architecture Host Identity Protocol Architecture
draft-ietf-hip-rfc4423-bis-06 draft-ietf-hip-rfc4423-bis-07
Abstract Abstract
This memo describes a new namespace, the Host Identity namespace, and This memo describes a new namespace, the Host Identity namespace, and
a new protocol layer, the Host Identity Protocol, between the a new protocol layer, the Host Identity Protocol, between the
internetworking and transport layers. Herein are presented the internetworking and transport layers. Herein are presented the
basics of the current namespaces, their strengths and weaknesses, and basics of the current namespaces, their strengths and weaknesses, and
how a new namespace will add completeness to them. The roles of this how a new namespace will add completeness to them. The roles of this
new namespace in the protocols are defined. new namespace in the protocols are defined.
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on May 11, 2014. This Internet-Draft will expire on June 21, 2014.
Copyright Notice Copyright Notice
Copyright (c) 2013 IETF Trust and the persons identified as the Copyright (c) 2013 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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6. Control plane . . . . . . . . . . . . . . . . . . . . . . 15 6. Control plane . . . . . . . . . . . . . . . . . . . . . . 15
6.1. Base exchange . . . . . . . . . . . . . . . . . . . . . . 15 6.1. Base exchange . . . . . . . . . . . . . . . . . . . . . . 15
6.2. End-host mobility and multi-homing . . . . . . . . . . . 16 6.2. End-host mobility and multi-homing . . . . . . . . . . . 16
6.3. Rendezvous mechanism . . . . . . . . . . . . . . . . . . 16 6.3. Rendezvous mechanism . . . . . . . . . . . . . . . . . . 16
6.4. Relay mechanism . . . . . . . . . . . . . . . . . . . . . 17 6.4. Relay mechanism . . . . . . . . . . . . . . . . . . . . . 17
6.5. Termination of the control plane . . . . . . . . . . . . 17 6.5. Termination of the control plane . . . . . . . . . . . . 17
7. Data plane . . . . . . . . . . . . . . . . . . . . . . . 17 7. Data plane . . . . . . . . . . . . . . . . . . . . . . . 17
8. HIP and NATs . . . . . . . . . . . . . . . . . . . . . . 18 8. HIP and NATs . . . . . . . . . . . . . . . . . . . . . . 18
8.1. HIP and Upper-layer checksums . . . . . . . . . . . . . . 19 8.1. HIP and Upper-layer checksums . . . . . . . . . . . . . . 19
9. Multicast . . . . . . . . . . . . . . . . . . . . . . . . 19 9. Multicast . . . . . . . . . . . . . . . . . . . . . . . . 19
10. HIP policies . . . . . . . . . . . . . . . . . . . . . . 20 10. HIP policies . . . . . . . . . . . . . . . . . . . . . . 19
11. Design considerations . . . . . . . . . . . . . . . . . . 20 11. Design considerations . . . . . . . . . . . . . . . . . . 20
11.1. Benefits of HIP . . . . . . . . . . . . . . . . . . . . . 20 11.1. Benefits of HIP . . . . . . . . . . . . . . . . . . . . . 20
11.2. Drawbacks of HIP . . . . . . . . . . . . . . . . . . . . 23 11.2. Drawbacks of HIP . . . . . . . . . . . . . . . . . . . . 23
11.3. Deployment and adoption considerations . . . . . . . . . 24 11.3. Deployment and adoption considerations . . . . . . . . . 24
11.3.1. Deployment analysis . . . . . . . . . . . . . . . . . . . 25 11.3.1. Deployment analysis . . . . . . . . . . . . . . . . . . . 24
11.3.2. HIP in 802.15.4 networks . . . . . . . . . . . . . . . . 26 11.3.2. HIP in 802.15.4 networks . . . . . . . . . . . . . . . . 25
11.4. Answers to NSRG questions . . . . . . . . . . . . . . . . 26 11.4. Answers to NSRG questions . . . . . . . . . . . . . . . . 26
12. Security considerations . . . . . . . . . . . . . . . . . 28 12. Security considerations . . . . . . . . . . . . . . . . . 28
12.1. MiTM Attacks . . . . . . . . . . . . . . . . . . . . . . 28 12.1. MiTM Attacks . . . . . . . . . . . . . . . . . . . . . . 28
12.2. Protection against flooding attacks . . . . . . . . . . . 29 12.2. Protection against flooding attacks . . . . . . . . . . . 29
12.3. HITs used in ACLs . . . . . . . . . . . . . . . . . . . . 30 12.3. HITs used in ACLs . . . . . . . . . . . . . . . . . . . . 30
12.4. Alternative HI considerations . . . . . . . . . . . . . . 31 12.4. Alternative HI considerations . . . . . . . . . . . . . . 31
13. IANA considerations . . . . . . . . . . . . . . . . . . . 32 13. IANA considerations . . . . . . . . . . . . . . . . . . . 32
14. Acknowledgments . . . . . . . . . . . . . . . . . . . . . 32 14. Acknowledgments . . . . . . . . . . . . . . . . . . . . . 32
15. Changes from RFC 4423 . . . . . . . . . . . . . . . . . . 33 15. Changes from RFC 4423 . . . . . . . . . . . . . . . . . . 32
16. References . . . . . . . . . . . . . . . . . . . . . . . 33 16. References . . . . . . . . . . . . . . . . . . . . . . . 33
16.1. Normative References . . . . . . . . . . . . . . . . . . 33 16.1. Normative References . . . . . . . . . . . . . . . . . . 33
16.2. Informative references . . . . . . . . . . . . . . . . . 34 16.2. Informative references . . . . . . . . . . . . . . . . . 34
Authors' Addresses . . . . . . . . . . . . . . . . . . . 40 Authors' Addresses . . . . . . . . . . . . . . . . . . . 40
1. Introduction 1. Introduction
The Internet has two important global namespaces: Internet Protocol The Internet has two important global namespaces: Internet Protocol
(IP) addresses and Domain Name Service (DNS) names. These two (IP) addresses and Domain Name Service (DNS) names. These two
namespaces have a set of features and abstractions that have powered namespaces have a set of features and abstractions that have powered
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Architecturally, HIP provides for a different binding of transport- Architecturally, HIP provides for a different binding of transport-
layer protocols. That is, the transport-layer associations, i.e., layer protocols. That is, the transport-layer associations, i.e.,
TCP connections and UDP associations, are no longer bound to IP TCP connections and UDP associations, are no longer bound to IP
addresses but rather to Host Identities. In practice, the Host addresses but rather to Host Identities. In practice, the Host
Identities are exposed as LSIs and HITs for legacy applications and Identities are exposed as LSIs and HITs for legacy applications and
the transport layer to facilitate backward compatibility with the transport layer to facilitate backward compatibility with
existing networking APIs and stacks. existing networking APIs and stacks.
5.1. On the multiplicity of identities 5.1. On the multiplicity of identities
A host may have multiple identities both at the client and server
side. This raises some additional concerns that are addressed in
this section.
For security reasons, it may be a bad idea to duplicate the same Host For security reasons, it may be a bad idea to duplicate the same Host
Identity on multiple hosts because the compromise of a single host Identity on multiple hosts because the compromise of a single host
taints the identities of the other hosts. Management of machines taints the identities of the other hosts. Management of machines
with identical Host Identities may also present other challenges and, with identical Host Identities may also present other challenges and,
therefore, it is advisable to have a unique identity for each host. therefore, it is advisable to have a unique identity for each host.
Instead of duplicating identities, HIP opportunistic mode can be Instead of duplicating identities, HIP opportunistic mode can be
employed, where the initiator leaves out the identifier of the employed, where the initiator leaves out the identifier of the
responder when initiating the key exchange and learns it upon the responder when initiating the key exchange and learns it upon the
completion of the exchange. The tradeoffs are related to lowered completion of the exchange. The tradeoffs are related to lowered
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name, but also the Host Identity could be used for this purpose. name, but also the Host Identity could be used for this purpose.
However, a more compelling reason to employ multiple identities are However, a more compelling reason to employ multiple identities are
HIP-aware firewalls that are unable see the HTTP traffic inside the HIP-aware firewalls that are unable see the HTTP traffic inside the
encrypted IPsec tunnel. In such a case, each service could be encrypted IPsec tunnel. In such a case, each service could be
configured with a separate identity, thus allowing the firewall to configured with a separate identity, thus allowing the firewall to
segregate the different services of the single web server from each segregate the different services of the single web server from each
other [lindqvist-enterprise]. other [lindqvist-enterprise].
6. Control plane 6. Control plane
HIP decouples control and data plane from each other. The control HIP decouples control and data plane from each other. Two end-hosts
plane between two end-hosts is initialized using a key exchange initialize the control plane using a key exchange procedure called
procedure called the base exchange. The procedure can be assisted by the base exchange. The procedure can be assisted by new
new infrastructural intermediaries called rendezvous or relay infrastructural intermediaries called rendezvous or relay servers.
servers. In the event of IP address changes, the end-hosts sustain In the event of IP address changes, the end-hosts sustain control
control plane connectivity with mobility and multihoming extensions. plane connectivity with mobility and multihoming extensions.
Eventually, the end-hosts terminate the control plane and remove the Eventually, the end-hosts terminate the control plane and remove the
associated state. associated state.
6.1. Base exchange 6.1. Base exchange
The base exchange is key exchange procedure that authenticates the The base exchange is a key exchange procedure that authenticates the
initiator and responder to each other using their public keys. initiator and responder to each other using their public keys.
Typically, the initiator is the client-side host and the responder is Typically, the initiator is the client-side host and the responder is
the server-side host. The roles are used by the state machine of a the server-side host. The roles are used by the state machine of a
HIP implementation, but discarded upon successful completion. HIP implementation, but discarded upon successful completion.
The exchange consists of four messages during which the hosts also The exchange consists of four messages during which the hosts also
create symmetric keys to protect the control plane with Hash-based create symmetric keys to protect the control plane with Hash-based
message authentication codes (HMACs). The keys can be also used to message authentication codes (HMACs). The keys can be also used to
protect the data plane, and IPsec ESP [I-D.ietf-hip-rfc5202-bis] is protect the data plane, and IPsec ESP [I-D.ietf-hip-rfc5202-bis] is
typically used as the data-plane protocol, albeit HIP can also typically used as the data-plane protocol, albeit HIP can also
accommodate others. Both the control and data plane are terminated accommodate others. Both the control and data plane are terminated
using a closing procedure consisting of two messages. using a closing procedure consisting of two messages.
The base exchange also includes a computational puzzle In addition, the base exchange also includes a computational puzzle
[I-D.ietf-hip-rfc5201-bis] that the initiator must solve. The [I-D.ietf-hip-rfc5201-bis] that the initiator must solve. The
responder chooses the difficulty of the puzzle which allows the responder chooses the difficulty of the puzzle which permits the
responder to delay new incoming initiators according to local responder to delay new incoming initiators according to local
policies, for instance, when the responder is under heavy load. The policies, for instance, when the responder is under heavy load. The
puzzle can offer some resiliency against DoS attacks because the puzzle can offer some resiliency against DoS attacks because the
design of the puzzle mechanism allows the responder to remain design of the puzzle mechanism allows the responder to remain
stateless until the very end of the base exchange [aura-dos]. HIP stateless until the very end of the base exchange [aura-dos]. HIP
puzzles have also been researched under steady-state DDoS attacks puzzles have also been studied under steady-state DDoS attacks
[beal-dos], multiple adversary models with varying puzzle [beal-dos], on multiple adversary models with varying puzzle
difficulties [tritilanunt-dos] and ephemeral Host Identities difficulties [tritilanunt-dos] and with ephemeral Host Identities
[komu-mitigation]. [komu-mitigation].
6.2. End-host mobility and multi-homing 6.2. End-host mobility and multi-homing
HIP decouples the transport from the internetworking layer, and binds HIP decouples the transport from the internetworking layer, and binds
the transport associations to the Host Identities (through actually the transport associations to the Host Identities (actually through
either the HIT or LSI). After the initial key exchange, the HIP either the HIT or LSI). After the initial key exchange, the HIP
layer maintains transport-layer connectivity and data flows using its layer maintains transport-layer connectivity and data flows using its
mobility [I-D.ietf-hip-rfc5206-bis] and multihoming mobility [I-D.ietf-hip-rfc5206-bis] and multihoming
[I-D.ietf-hip-multihoming] extensions. Consequently, HIP can provide [I-D.ietf-hip-multihoming] extensions. Consequently, HIP can provide
for a degree of internetworking mobility and multi-homing at a low for a degree of internetworking mobility and multi-homing at a low
infrastructure cost. HIP mobility includes IP address changes (via infrastructure cost. HIP mobility includes IP address changes (via
any method) to either party. Thus, a system is considered mobile if any method) to either party. Thus, a system is considered mobile if
its IP address can change dynamically for any reason like PPP, DHCP, its IP address can change dynamically for any reason like PPP, DHCP,
IPv6 prefix reassignments, or a NAT device remapping its translation. IPv6 prefix reassignments, or a NAT device remapping its translation.
Likewise, a system is considered multi-homed if it has more than one Likewise, a system is considered multi-homed if it has more than one
globally routable IP address at the same time. HIP links IP globally routable IP address at the same time. HIP links IP
addresses together, when multiple IP addresses correspond to the same addresses together, when multiple IP addresses correspond to the same
Host Identity, and if one address becomes unusable, or a more Host Identity. If one address becomes unusable, or a more preferred
preferred address becomes available, existing transport associations address becomes available, existing transport associations can easily
can easily be moved to another address. be moved to another address.
When a node moves while communication is already on-going, address When a node moves while communication is already on-going, address
changes are rather straightforward. The peer of the mobile node can changes are rather straightforward. The peer of the mobile node can
just accept a HIP or an integrity protected ESP packet from any just accept a HIP or an integrity protected ESP packet from any
address and ignore the source address. However, as discussed in address and ignore the source address. However, as discussed in
Section 12.2 below, a mobile node must send a HIP UPDATE packet to Section 12.2 below, a mobile node must send a HIP UPDATE packet to
inform the peer of the new address(es), and the peer must verify that inform the peer of the new address(es), and the peer must verify that
the mobile node is reachable through these addresses. This is the mobile node is reachable through these addresses. This is
especially helpful for those situations where the peer node is especially helpful for those situations where the peer node is
sending data periodically to the mobile node (that is re-starting a sending data periodically to the mobile node (that is, re-starting a
connection after the initial connection). connection after the initial connection).
6.3. Rendezvous mechanism 6.3. Rendezvous mechanism
Making a contact to a mobile node is slightly more involved. In Establishing a contact to a mobile, moving node is slightly more
order to start the HIP exchange, the initiator node has to know how involved. In order to start the HIP exchange, the initiator node has
to reach the mobile node. Although infrequently moving HIP nodes to know how to reach the mobile node. For instance, the mobile node
could use Dynamic DNS [RFC2136] to update their reachability can employ Dynamic DNS [RFC2136] to update its reachability
information in the DNS, an alternative to using DNS in this fashion information in the DNS. To avoid the dependency to DNS, HIP provides
is to use a piece of new static infrastructure to facilitate its own HIP-specific alternative: the HIP rendezvous mechanism as
rendezvous between HIP nodes. defined in HIP Rendezvous specifications [I-D.ietf-hip-rfc5204-bis].
The mobile node keeps the rendezvous infrastructure continuously
updated with its current IP address(es). The mobile nodes must trust
the rendezvous mechanism to properly maintain their HIT and IP
address mappings.
The rendezvous mechanism is also needed if both of the nodes happen Using the HIP rendezvous extensions, the mobile node keeps the
to change their address at the same time, either because they are rendezvous infrastructure continuously updated with its current IP
mobile and happen to move at the same time, because one of them is address(es). The mobile nodes trusts the rendezvous mechanism in
off-line for a while, or because of some other reason. In such a order to properly maintain their HIT and IP address mappings.
case, the HIP UPDATE packets will cross each other in the network and
never reach the peer node.
The HIP rendezvous mechanism is defined in HIP Rendezvous The rendezvous mechanism is especially useful in scenarios where both
specifications [I-D.ietf-hip-rfc5204-bis]. of the nodes are expected to change their address at the same time.
In such a case, the HIP UPDATE packets will cross each other in the
network and never reach the peer node.
6.4. Relay mechanism 6.4. Relay mechanism
The HIP relay mechanism [I-D.ietf-hip-native-nat-traversal] is an The HIP relay mechanism [I-D.ietf-hip-native-nat-traversal] is an
alternative to the HIP rendezvous mechanism. The HIP relay mechanism alternative to the HIP rendezvous mechanism. The HIP relay mechanism
is more suitable for IPv4 networks with NATs because a HIP relay can is more suitable for IPv4 networks with NATs because a HIP relay can
forward all control and data plane communications in order to forward all control and data plane communications in order to
guarantee successful NAT traversal. guarantee successful NAT traversal.
6.5. Termination of the control plane 6.5. Termination of the control plane
The control plane between two hosts can be terminated using a secure The control plane between two hosts is terminated using a secure two
two message procotol as specified in (XX FIXME). The related state message exchange as specified in base exchange specification
(i.e. host associations) should be removed upon successful [I-D.ietf-hip-rfc5201-bis]. The related state (i.e. host
termination. associations) should be removed upon successful termination.
7. Data plane 7. Data plane
The control and data plane are decoupled in the HIP architecture. The encapsulation format for the data plane used for carrying the
This means that the encapsulation format for data plane used for application-layer traffic can be dynamically negotiated during the
carrying the application-layer traffic is changeable and can is key exchange. For instance, HICCUPS extensions [RFC6078] define one
dynamically negotiated during the key exchange. For instance, way to transport application-layer datagrams directly over the HIP
HICCUPS extensions [RFC6078] define a way to transport application- control plane, protected by asymmetric key cryptography. Also, S-RTP
layer datagrams directly over the HIP control plane, protected by has been considered as the data encapsulation protocol [hip-srtp].
asymmetric key cryptography. Also, S-RTP has been considered as the However, the most widely implemented method is the Encapsulated
data encapsulation protocol [hip-srtp]. However, the most widely Security Payload (ESP) [I-D.ietf-hip-rfc5202-bis] that is protected
implemented method is the Encapsulated Security Payload (ESP) by symmetric keys derived during the key exchange. ESP Security
[I-D.ietf-hip-rfc5202-bis] that is protected by symmetric keys Associations (SAs) offer both confidentiality and integrity
derived during the key exchange. ESP Security Associations (SAs) protection, of which the former can be disabled during the key
offer both confidentiality and integrity protection, of which the exchange. In the future, other ways of transporting application-
former can be disabled during the key exchange. In the future, other layer data may be defined.
ways of transporting application-layer data may be defined.
The ESP SAs are established and terminated between the initiator and The ESP SAs are established and terminated between the initiator and
the responder hosts. Usually, the hosts create at least two SAs, one the responder hosts. Usually, the hosts create at least two SAs, one
in each direction (initiator-to-responder SA and responder-to- in each direction (initiator-to-responder SA and responder-to-
initiator SA). If the IP addresses of either host are changed, the initiator SA). If the IP addresses of either host changes, the HIP
HIP mobility extensions can be used to re-negotiate the corresponding mobility extensions can be used to re-negotiate the corresponding
SAs. SAs.
On the wire, the difference in the use of identifiers between the HIP On the wire, the difference in the use of identifiers between the HIP
control and data plane is that the HITs are included in all control control and data plane is that the HITs are included in all control
packets, but not in the data plane when ESP is employed. Instead, packets, but not in the data plane when ESP is employed. Instead,
the ESP employs SPI numbers that act as compressed HITs. Any HIP- the ESP employs SPI numbers that act as compressed HITs. Any HIP-
aware middlebox (for instance, a HIP-aware firewall) interested in aware middlebox (for instance, a HIP-aware firewall) interested in
the ESP based data plane should keep track between the control and the ESP based data plane should keep track between the control and
data plane identifiers in order to associate them with each other. data plane identifiers in order to associate them with each other.
Since HIP does not negotiate any SA lifetimes, all lifetimes are Since HIP does not negotiate any SA lifetimes, all lifetimes are
local policy. The only lifetimes a HIP implementation must support subject to local policy. The only lifetimes a HIP implementation
are sequence number rollover (for replay protection), and SA timeout. must support are sequence number rollover (for replay protection),
An SA times out if no packets are received using that SA. and SA timeout. An SA times out if no packets are received using
Implementations may support lifetimes for the various ESP transforms that SA. Implementations may support lifetimes for the various ESP
and other data-plane protocols. transforms and other data-plane protocols.
8. HIP and NATs 8. HIP and NATs
Passing packets between different IP addressing realms requires Passing packets between different IP addressing realms requires
changing IP addresses in the packet header. This may occur, for changing IP addresses in the packet header. This may occur, for
example, when a packet is passed between the public Internet and a example, when a packet is passed between the public Internet and a
private address space, or between IPv4 and IPv6 networks. The private address space, or between IPv4 and IPv6 networks. The
address translation is usually implemented as Network Address address translation is usually implemented as Network Address
Translation (NAT) [RFC3022] or NAT Protocol translation (NAT-PT) Translation (NAT) [RFC3022] or NAT Protocol translation (NAT-PT)
[RFC2766]. [RFC2766].
In a network environment where identification is based on the IP In a network environment where identification is based on the IP
addresses, identifying the communicating nodes is difficult when NATs addresses, identifying the communicating nodes is difficult when NATs
are employed because the private address spaces introduced by NATs are employed because private address spaces are overlapping. In
are overlapping. In other words, two hosts cannot distinguished from other words, two hosts cannot distinguished from each other solely
each other solely based on their IP address. With HIP, the based on their IP address. With HIP, the transport-layer end-points
transport-layer end-points (i.e. applications) are bound to unique (i.e. applications) are bound to unique Host Identities rather than
Host Identities rather than overlapping private addresses. This overlapping private addresses. This allows two end-points to
makes it possible for two end-points to distinguish one other even distinguish one other even when they are located in different private
when they are located in private address realms. Thus, the IP address realms. Thus, the IP addresses are used only for routing
addresses used only for routing purposes; they may be changed freely purposes and can be changed freely by NATs when a packet between two
during when a packet between two hosts traverses possibly multiple HIP capable hosts traverses through multiple private address realms.
addressing realm boundaries.
NAT traversal extensions for HIP [I-D.ietf-hip-native-nat-traversal] NAT traversal extensions for HIP [I-D.ietf-hip-native-nat-traversal]
can be used to realize the actual end-to-end connectivity through NAT can be used to realize the actual end-to-end connectivity through NAT
devices. To support basic backward compatibility with legacy NATs, devices. To support basic backward compatibility with legacy NATs,
the extensions encapsulated both HIP control and data plane in UDP. the extensions encapsulate both HIP control and data plane in UDP.
The extensions define mechanisms for forwarding the two planes The extensions define mechanisms for forwarding the two planes
through an intermediary host called HIP relay and procedures to through an intermediary host called HIP relay and procedures to
establish direct end-to-end connectivity by penetrating NATs. establish direct end-to-end connectivity by penetrating NATs.
Besides this "native" NAT traversal mode for HIP, other NAT traversal Besides this "native" NAT traversal mode for HIP, other NAT traversal
mechanisms have been successfully utilized, such as Teredo mechanisms have been successfully utilized, such as Teredo
[varjonen-split]. [varjonen-split].
Besides legacy NATs, a HIP-aware NAT has been designed and Besides legacy NATs, a HIP-aware NAT has been designed and
implemented [ylitalo-spinat]. For a HIP-based flow, a HIP-aware NAT implemented [ylitalo-spinat]. For a HIP-based flow, a HIP-aware NAT
or NAT-PT system tracks the mapping of HITs, and the corresponding or NAT-PT system tracks the mapping of HITs, and the corresponding
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incoming packet are not necessarily the same as they were on the incoming packet are not necessarily the same as they were on the
sending host. Furthermore, it is not possible to recompute the sending host. Furthermore, it is not possible to recompute the
upper-layer checksums in the NAT/NAT-PT system, since the traffic is upper-layer checksums in the NAT/NAT-PT system, since the traffic is
ESP protected. Consequently, the TCP and UDP checksums are ESP protected. Consequently, the TCP and UDP checksums are
calculated using the HITs in the place of the IP addresses in the calculated using the HITs in the place of the IP addresses in the
pseudo header. Furthermore, only the IPv6 pseudo header format is pseudo header. Furthermore, only the IPv6 pseudo header format is
used. This provides for IPv4 / IPv6 protocol translation. used. This provides for IPv4 / IPv6 protocol translation.
9. Multicast 9. Multicast
A number of studies have intestigating HIP-based multicast have been A number of studies intestigating HIP-based multicast have been
published (including [shields-hip], [xueyong-hip], [xueyong-hip], published (including [shields-hip], [xueyong-hip], [xueyong-hip],
[amir-hip], [kovacshazi-host] and [xueyong-secure]). Particularly, [amir-hip], [kovacshazi-host] and [xueyong-secure]). Particularly,
so called bloom filters, that allow to compressing of multiple labels so called bloom filters, that allow compressing of multiple labels
into small datastructures, may be a promising way forward into small datastructures, may be a promising way forward
[sarela-bloom]. However, the different schemes have not been adopted [sarela-bloom]. However, the different schemes have not been adopted
by HIP working group (nor the HIP research group in IRTF), so the by HIP working group (nor the HIP research group in IRTF), so the
details are not further elaborated here. details are not further elaborated here.
10. HIP policies 10. HIP policies
There are a number of variables that will influence the HIP exchanges There are a number of variables that influence the HIP exchange that
that each host must support. All HIP implementations should support each host must support. All HIP implementations should support at
at least 2 HIs, one to publish in DNS or similar directory service least 2 HIs, one to publish in DNS or similar directory service and
and an unpublished one for anonymous usage. Although unpublished HIs an unpublished one for anonymous usage. Although unpublished HIs
will be rarely used as responder HIs, they are likely be common for will be rarely used as responder HIs, they are likely to be common
initiators. Support for multiple HIs is recommended. This provides for initiators. Support for multiple HIs is recommended. This
new challenges for systems or users to decide which type of HI to provides new challenges for systems or users to decide which type of
expose when they start a new session. HI to expose when they start a new session.
Opportunistic mode (where the initiator starts a HIP exchange without Opportunistic mode (where the initiator starts a HIP exchange without
prior knowledge of the responder's HI) presents a security tradeoff. prior knowledge of the responder's HI) presents a security tradeoff.
At the expense of being subject to MITM attacks, the opportunistic At the expense of being subject to MITM attacks, the opportunistic
mode allows the initiator learn the the identity of the responder mode allows the initiator to learn the identity of the responder
during communications rather than from an external directory. during communication rather than from an external directory.
Opportunistic mode can be used for registering to HIP-based services Opportunistic mode can be used for registration to HIP-based services
[I-D.ietf-hip-rfc5203-bis] (i.e. utilized by HIP for its own internal [I-D.ietf-hip-rfc5203-bis] (i.e. utilized by HIP for its own internal
purposes) or by the application layer [komu-leap]. For security purposes) or by the application layer [komu-leap]. For security
reasons, especially the latter requires some involvement from the reasons, especially the latter requires some involvement from the
user to accept the identity of the responder in a similar vain as SSH user to accept the identity of the responder in a similar vain as SSH
prompts the user when connecting to a server for the first time prompts the user when connecting to a server for the first time
[pham-leap]. In practice, this can be realized for with end-host [pham-leap]. In practice, this can be realized in end-host based
based firewalls in the case of legacy applications [karvonen-usable] firewalls in the case of legacy applications [karvonen-usable] or
or with native APIs for HIP APIs [RFC6317] in the case of HIP-aware with native APIs for HIP APIs [RFC6317] in the case of HIP-aware
applications. applications.
Many initiators would want to use a different HI for different Many initiators would want to use a different HI for different
responders. The implementations should provide for a policy of responders. The implementations should provide for a policy of
initiator HIT to responder HIT. This policy should also include initiator HIT to responder HIT. This policy should also include
preferred transforms and local lifetimes. preferred transforms and local lifetimes.
Responders would need a similar policy, describing the hosts allowed Responders would need a similar policy, describing the hosts allowed
to participate in HIP exchanges, and the preferred transforms and to participate in HIP exchanges, and the preferred transforms and
local lifetimes. local lifetimes.
skipping to change at page 21, line 12 skipping to change at page 21, line 9
2. Non-mobile: The address doesn't change during the course of an 2. Non-mobile: The address doesn't change during the course of an
"association". "association".
3. Reversible: A return header can always be formed by reversing the 3. Reversible: A return header can always be formed by reversing the
source and destination addresses. source and destination addresses.
4. Omniscient: Each host knows what address a partner host can use 4. Omniscient: Each host knows what address a partner host can use
to send packets to it. to send packets to it.
Actually, the fourth can be inferred from 1 and 3, but it is worth Actually, the fourth can be inferred from 1 and 3, but it is worth
mentioning for reasons that will be obvious soon if not already. mentioning explicitly for reasons that will be obvious soon if not
already.
In the current "post-classic" world, we are intentionally trying to In the current "post-classic" world, we are intentionally trying to
get rid of the second invariant (both for mobility and for multi- get rid of the second invariant (both for mobility and for multi-
homing), and we have been forced to give up the first and the fourth. homing), and we have been forced to give up the first and the fourth.
Realm Specific IP [RFC3102] is an attempt to reinstate the fourth Realm Specific IP [RFC3102] is an attempt to reinstate the fourth
invariant without the first invariant. IPv6 is an attempt to invariant without the first invariant. IPv6 is an attempt to
reinstate the first invariant. reinstate the first invariant.
Few client-side systems on the Internet have DNS names that are Few client-side systems on the Internet have DNS names that are
meaningful. That is, if they have a Fully Qualified Domain Name meaningful. That is, if they have a Fully Qualified Domain Name
(FQDN), that name typically belongs to a NAT device or a dial-up (FQDN), that name typically belongs to a NAT device or a dial-up
server, and does not really identify the system itself but its server, and does not really identify the system itself but its
current connectivity. FQDNs (and their extensions as email names) current connectivity. FQDNs (and their extensions as email names)
are application-layer names; more frequently naming services than a are application-layer names; more frequently naming services than
particular system. This is why many systems on the Internet are not particular systems. This is why many systems on the Internet are not
registered in the DNS; they do not have services of interest to other registered in the DNS; they do not have services of interest to other
Internet hosts. Internet hosts.
DNS names are references to IP addresses. This only demonstrates the DNS names are references to IP addresses. This only demonstrates the
interrelationship of the networking and application layers. DNS, as interrelationship of the networking and application layers. DNS, as
the Internet's only deployed, distributed database is also the the Internet's only deployed and distributed database, is also the
repository of other namespaces, due in part to DNSSEC and application repository of other namespaces, due in part to DNSSEC and application
specific key records. Although each namespace can be stretched (IP specific key records. Although each namespace can be stretched (IP
with v6, DNS with KEY records), neither can adequately provide for with v6, DNS with KEY records), neither can adequately provide for
host authentication or act as a separation between internetworking host authentication or act as a separation between internetworking
and transport layers. and transport layers.
The Host Identity (HI) namespace fills an important gap between the The Host Identity (HI) namespace fills an important gap between the
IP and DNS namespaces. An interesting thing about the HI is that it IP and DNS namespaces. An interesting thing about the HI is that it
actually allows one to give up all but the 3rd network-layer actually allows a host to give up all but the 3rd network-layer
invariant. That is to say, as long as the source and destination
addresses in the network-layer protocol are reversible, then things
work ok because HIP takes care of host identification, and
reversibility allows one to receive a packet back to one's partner
host. You do not care if the network-layer address changes in
transit (mutable) and you don't care what network-layer address the
partner is using (non-omniscient).
The Host Identity (HI) namespace fills an important gap between the
IP and DNS namespaces. An interesting thing about the HI is that it
actually allows one to give up all but the 3rd network-layer
invariant. That is to say, as long as the source and destination invariant. That is to say, as long as the source and destination
addresses in the network-layer protocol are reversible, then things addresses in the network-layer protocol are reversible, HIP takes
work ok because HIP takes care of host identification, and care of host identification, and reversibility allows a local host to
reversibility allows one to receive a packet back to one's partner receive a packet back from a remote host. The address changes
host. You do not care if the network-layer address changes in occurring during NAT transit (non-mutable) or host movement (non-
transit (mutable) and you don't care what network-layer address the omniscient or non-mobile) can be managed by the HIP layer.
partner is using (non-omniscient).
The Sockets API is the de-facto API for utilize the TCP/IP stack. With the exception High-Performance Computing applications, the
Application use the Sockets API either directly or indirectly through Sockets API is the most common way to develop network applications.
some libraries or frameworks. However, the Sockets API was based on Applications use the Sockets API either directly or indirectly
the assumption of static IP addresses and DNS with its lifetime through some libraries or frameworks. However, the Sockets API is
values was invented at later stages during the evolution of the based on the assumption of static IP addresses, and DNS with its
Internet. Hence, the Sockets API does not deal with the lifetime of lifetime values was invented at later stages during the evolution of
addresses [RFC6250]. As majority of the end-user equipment is mobile the Internet. Hence, the Sockets API does not deal with the lifetime
today, their addresses are effectively ephemeral, but the Sockets API of addresses [RFC6250]. As majority of the end-user equipment is
still gives a fallacious illusion of persistent IP addresses to the mobile today, their addresses are effectively ephemeral, but the
unwary developer. HIP can be used to solidify this illusion because Sockets API still gives a fallacious illusion of persistent IP
HIP provides persistent surrogate addresses to the application layer addresses to the unwary developer. HIP can be used to solidify this
in the form of LSIs and HITs. illusion because HIP provides persistent surrogate addresses to the
application layer in the form of LSIs and HITs.
The persistent identifiers as provided by HIP are useful in multiple The persistent identifiers as provided by HIP are useful in multiple
scenarios (as described in more detail in e.g. [ylitalo-diss] or scenarios (see, e.g., [ylitalo-diss] or [komu-diss], for a more
[komu-diss]): elaborate discussion):
o When a mobile host moves physically between two different WLAN o When a mobile host moves physically between two different WLAN
networks and obtains a new address, an application using the networks and obtains a new address, an application using the
identifiers remains isolated of the topology changes while the identifiers remains isolated regardless of the topology changes
underlying HIP layer re-establishes connectivity (i.e. a while the underlying HIP layer re-establishes connectivity (i.e. a
horizontal handoff). horizontal handoff).
o Similarly, the application utilizing the identifiers remains again o Similarly, the application utilizing the identifiers remains again
unaware of the topological changes when the underlying host unaware of the topological changes when the underlying host
equipped with WLAN and cellular network interfaces switches equipped with WLAN and cellular network interfaces switches
between the two different access technologies (i.e. a vertical between the two different access technologies (i.e. a vertical
handoff). handoff).
o Even when hosts are located in private address realms, o Even when hosts are located in private address realms,
applications can uniquely distinguish different hosts from each applications can uniquely distinguish different hosts from each
other based on their identifier. In other words, it can be stated other based on their identifiers. In other words, it can be
that HIP improves Internet transparency for the application layer stated that HIP improves Internet transparency for the application
[komu-diss]. layer [komu-diss].
o Site renumbering events for services can occur due to corporate o Site renumbering events for services can occur due to corporate
mergers or acquisitions, or by changes in Internet Service mergers or acquisitions, or by changes in Internet Service
Provider. They can involve changing the entire network prefix of Provider. They can involve changing the entire network prefix of
an organization, which is problematic due to hard-coded addresses an organization, which is problematic due to hard-coded addresses
in service configuration files or cached IP addresses at the in service configuration files or cached IP addresses at the
client side [RFC5887]. Considering such human errors, a site client side [RFC5887]. Considering such human errors, a site
employing location-independent identifiers as promoted by HIP may employing location-independent identifiers as promoted by HIP may
experience less problems while renumbering their network. experience less problems while renumbering their network.
o More agile IPv6 interoperability as discussed in section o More agile IPv6 interoperability as discussed in Section 4.4.
Section 4.4. IPv6-based applications can communicate using HITs IPv6-based applications can communicate using HITs with IPv4-based
with IPv4-based applications that are using LSIs. Also, the applications that are using LSIs. An addition, the underlying
underlying network type (IPv4 or IPv6) becomes independent of the network type (IPv4 or IPv6) becomes independent of the addressing
addressing family of the application. family of the application.
o HITs (or LSIs) can be used in IP-based access control lists as a o HITs (or LSIs) can be used in IP-based access control lists as a
more secure replacement for IPv6 addresses. Besides security, HIT more secure replacement for IPv6 addresses. Besides security, HIT
based access control has two other benefits. First, the use of based access control has two other benefits. First, the use of
HITs halves the size of access control lists as separate rules for HITs halves the size of access control lists because separate
IPv4 are not needed [komu-diss]. Second, HIT-based configuration rules for IPv4 are not needed [komu-diss]. Second, HIT-based
rules in HIP-aware middleboxes remain static and independent of configuration rules in HIP-aware middleboxes remain static and
topology changes, thus simplifying administrative efforts independent of topology changes, thus simplifying administrative
particularly for mobile environments. For instance, the benefits efforts particularly for mobile environments. For instance, the
of HIT based access control have been harnessed in the case of benefits of HIT based access control have been harnessed in the
HIP-aware firewalls, but can be utilized directly at the end-hosts case of HIP-aware firewalls, but can be utilized directly at the
as well [RFC6538]. end-hosts as well [RFC6538].
While some of these benefits could be and have been redundantly While some of these benefits could be and have been redundantly
implemented by individual applications, providing such generic implemented by individual applications, providing such generic
functionality at the lower layers is useful because it reduces functionality at the lower layers is useful because it reduces
software development efforts and networking software bugs (as the software development effort and networking software bugs (as the
layer is tested with multiple applications). It also allows the layer is tested with multiple applications). It also allows the
developer to focus on building the application itself rather than developer to focus on building the application itself rather than
delving into the intricacies of mobile networking, thus facilitating delving into the intricacies of mobile networking, thus facilitating
separation of concerns. separation of concerns.
HIP could also be realized by combining a number of different HIP could also be realized by combining a number of different
protocols, but the complexity of the resulting software may become protocols, but the complexity of the resulting software may become
substantially larger, and the interaction multiple possibly layered substantially larger, and the interaction between multiple possibly
protocols may have adverse effects on latency and throughput. It is layered protocols may have adverse effects on latency and throughput.
also worth noting that virtually nothing prevents realizing the HIP It is also worth noting that virtually nothing prevents realizing the
architecture, for instance, as an application-layer library, which HIP architecture, for instance, as an application-layer library,
has been actually implemented in the past [xin-hip-lib]. However, which has been actually implemented in the past [xin-hip-lib].
the tradeoff in moving the HIP layer to the application layer is that However, the tradeoff in moving the HIP layer to the application
legacy applications may not be supported. layer is that legacy applications may not be supported.
11.2. Drawbacks of HIP 11.2. Drawbacks of HIP
In computer science, many problems can be solved with an extra layer In computer science, many problems can be solved with an extra layer
of indirection. However, the indirection always involves some costs of indirection. However, the indirection always involves some costs
as there no such thing as "free lunch". In the case of HIP, the main as there is no such a thing as "free lunch". In the case of HIP, the
costs could be stated as follows: main costs could be stated as follows:
o In general, a new layer and a new namespace involves always some o In general, a new layer and a new namespace always involve some
initial effort in terms implementation, deployment and initial effort in terms of implementation, deployment and
maintenance. Some education of people may also be needed. maintenance. Some education of developers and administrators may
However, the HIP community at the IETF have spent years in also be needed. However, the HIP community at the IETF has spent
experimenting, exploring, testing, documenting and implementing years in experimenting, exploring, testing, documenting and
HIP curb the amount of efforts required. implementing HIP to ease the adoption costs.
o HIP decouples identifier and locator roles of IP addresses. o HIP decouples identifier and locator roles of IP addresses.
Consequently, a mapping mechanism is needed to associate them Consequently, a mapping mechanism is needed to associate them
together. A failure to map a HIT to its corresponding locator may together. A failure to map a HIT to its corresponding locator may
result in failed connectivity because a HIT is "flat" by its result in failed connectivity because a HIT is "flat" by its
nature and cannot be looked up from the hierarchically organized nature and cannot be looked up from the hierarchically organized
DNS. HITs are flat by design due to a security tradeoff. The DNS. HITs are flat by design due to a security tradeoff. The
more bits are allocated for the hash in the HIT, the less likely more bits are allocated for the hash in the HIT, the less likely
there will be (malicious) collisions. there will be (malicious) collisions.
o From performance viewpoint, HIP control and data plane processing o From performance viewpoint, HIP control and data plane processing
introduces some overhead in terms throughput and latency as introduces some overhead in terms of throughput and latency as
elaborated below. elaborated below.
The key exchange introduces some extra latency (two round trips) in The key exchange introduces some extra latency (two round trips) in
connection establishment. This can further affect TCP traffic the initial transport layer connection establishment between two
particularly when a TCP application triggers the key exchange and the hosts. With TCP, additional delay occurs if the underlying network
triggering SYN packet is dropped instead of being cached. Similarly stack implementation drops the triggering SYN packet during the key
as with the key exchange, a similar performance penalty may incur for exchange. The same cost may also occur during HIP handoff
TCP during HIP handoff procedures. The penalty can be constrained procedures. However, subsequent TCP sessions using the same HIP
with caching TCP packets. Also, TCP user timeout [RFC5482] is association will not bear this cost (within the key lifetime). Both
another way to optimize TCP behavior during handoffs the key exchange and handoff penalties can be minimized by caching
[scultz-intermittent]. TCP packets. The latter case can further be optimized with TCP user
timeout extensions [RFC5482] as described in further detail by
Schuetz et al [scultz-intermittent].
The most CPU-intensive operations involve the use of the asymmetric The most CPU-intensive operations involve the use of the asymmetric
keys and Diffie-Hellman key derivation at the control plane, but this keys and Diffie-Hellman key derivation at the control plane, but this
occurs only during the key exchange, its maintenance (handoffs, occurs only during the key exchange, its maintenance (handoffs,
refreshing of key material) and tear down procedures of HIP refreshing of key material) and tear down procedures of HIP
associations. The data plane is typically implemented with ESP has a associations. The data plane is typically implemented with ESP
smaller overhead due to symmetric key encryption. Naturally, even because it has a smaller overhead due to symmetric key encryption.
ESP involves some overhead in terms latency (processing costs) and Naturally, even ESP involves some overhead in terms of latency
throughput (tunneling) (see e.g. [ylitalo-diss] for a performance (processing costs) and throughput (tunneling) (see e.g.
evaluation). [ylitalo-diss] for a performance evaluation).
11.3. Deployment and adoption considerations 11.3. Deployment and adoption considerations
This section describes some deployment and adoption considerations This section describes some deployment and adoption considerations
related to HIP from a technical perspective. related to HIP from a technical perspective.
11.3.1. Deployment analysis 11.3.1. Deployment analysis
HIP has commercially been utilized at Boeing airplane factory for HIP has commercially been utilized at Boeing airplane factory for
their internal purposes[paine-hip]. It has been included in a their internal purposes [paine-hip]. It has been included in a
security product called Tofino to support layer-two Virtual Private security product called Tofino to support layer-two Virtual Private
Networks [henderson-vpls] to facilitate, e.g, supervisory control and Networks [henderson-vpls] to facilitate, e.g, supervisory control and
data acquisition (SCADA) security. However, HIP has not been a "wild data acquisition (SCADA) security. However, HIP has not been a "wild
success" [RFC5218] in the Internet as argued by Levae et al success" [RFC5218] in the Internet as argued by Levae et al
[leva-barriers]. Here, we briefly highligt some of their findings [leva-barriers]. Here, we briefly highlight some of their findings
based on interviews with 19 experts from the industry and academia. based on interviews with 19 experts from the industry and academia.
From a marketing perspective, the demand for HIP has been low and From a marketing perspective, the demand for HIP has been low and
substitute technologies have been favored. Another identified reason substitute technologies have been favored. Another identified reason
has been that some technical misconceptions related to the early has been that some technical misconceptions related to the early
stages of HIP specifications still persist. Two identified stages of HIP specifications still persist. Two identified
misconceptions are that HIP does not support NAT traversal, and HIP misconceptions are that HIP does not support NAT traversal, and that
must be implemented in the OS kernel. Both of these claims are HIP must be implemented in the OS kernel. Both of these claims are
untrue; HIP does have NAT traversal extensions untrue; HIP does have NAT traversal extensions
[I-D.ietf-hip-native-nat-traversal], and kernel modifications can be [I-D.ietf-hip-native-nat-traversal], and kernel modifications can be
avoided with modern operating systems by diverting packets for avoided with modern operating systems by diverting packets for
userspace processing. userspace processing.
The analysis clarifies infrastructural requirements for HIP. In a The analysis by Levae et al clarifies infrastructural requirements
minimal set up, a client and server machine have to run HIP software. for HIP. In a minimal set up, a client and server machine have to
However, to avoid manual configurations, usually DNS records for HIP run HIP software. However, to avoid manual configurations, usually
are set up. For instance, the popular DNS server software Bind9 does DNS records for HIP are set up. For instance, the popular DNS server
not require any changes to accomodate DNS records for HIP because software Bind9 does not require any changes to accomodate DNS records
they can be supported in binary format in its configuration files for HIP because they can be supported in binary format in its
[RFC6538]. HIP rendezvous servers and firewalls are optional. No configuration files [RFC6538]. HIP rendezvous servers and firewalls
changes are required to network address points, NATs, edge routers or are optional. No changes are required to network address points,
core networks. HIP may require holes in legacy firewalls. NATs, edge routers or core networks. HIP may require holes in legacy
firewalls.
The analysis also clarifies the requirements for the host components The analysis also clarifies the requirements for the host components
that consist of three parts. First, a HIP control plane component is that consist of three parts. First, a HIP control plane component is
required, typically implemented as as userspace daemon. Second, a required, typically implemented as a userspace daemon. Second, a
data plane component is needed. Most HIP implementations utilize the data plane component is needed. Most HIP implementations utilize the
so called BEET mode of ESP that has been available since Linux kernel so called BEET mode of ESP that has been available since Linux kernel
2.6.27, but is included also as a userspace component in HIPL and 2.6.27, but is included also as a userspace component in a few of the
OpenHIP implementations. Third, HIP systems usually provide a DNS implementations. Third, HIP systems usually provide a DNS proxy for
proxy for the local host that translates HIP DNS records to LSIs and the local host that translates HIP DNS records to LSIs and HITs, and
HITs, and communicates the corresponding locators to HIP userspace communicates the corresponding locators to HIP userspace daemon.
daemon. While the third component is not strictly speaking While the third component is not strictly speaking mandatory, it is
mandatory, it is very useful for avoiding manual configurations. The very useful for avoiding manual configurations. The three components
three components are further described in the HIP experiment report are further described in the HIP experiment report [RFC6538].
[RFC6538].
Based on the interviews, Levae et al suggest further directions to Based on the interviews, Levae et al suggest further directions to
facilitate HIP deployment. Transitioning the HIP specifications to facilitate HIP deployment. Transitioning the HIP specifications to
the standards track may help, but other measures could be taken. As the standards track may help, but other measures could be taken. As
a more radical measure, the authors suggest to implement HIP as a a more radical measure, the authors suggest to implement HIP as a
purely application-layer library [xin-hip-lib] or other kind of purely application-layer library [xin-hip-lib] or other kind of
middleware. On the other hand, more conservative measures include middleware. On the other hand, more conservative measures include
focusing on private deployments controlled by a single stakeholder. focusing on private deployments controlled by a single stakeholder.
As an a more concrete example of such a scenario, HIP could be used As a more concrete example of such a scenario, HIP could be used by a
by a single service provider to provide interconnectivity between its single service provider to facilitate secure connectivity between its
servers [komu-cloud]. servers [komu-cloud].
11.3.2. HIP in 802.15.4 networks 11.3.2. HIP in 802.15.4 networks
The IEEE 802 standards have been defining MAC layered security. Many The IEEE 802 standards have been defining MAC layered security. Many
of these standards use EAP [RFC3748] as a Key Management System (KMS) of these standards use EAP [RFC3748] as a Key Management System (KMS)
transport, but some like IEEE 802.15.4 [IEEE.802-15-4.2011] leave the transport, but some like IEEE 802.15.4 [IEEE.802-15-4.2011] leave the
KMS and its transport as "Out of Scope". KMS and its transport as "Out of Scope".
HIP is well suited as a KMS in these environments: HIP is well suited as a KMS in these environments:
o HIP is independent of IP addressing and can be directly o HIP is independent of IP addressing and can be directly
transported over any network protocol. transported over any network protocol.
o Master Keys in 802 protocols are strictly pair-based with group o Master Keys in 802 protocols are commonly pair-based with group
keys transported from the group controller using pair-wise keys. keys transported from the group controller using pair-wise keys.
o AdHoc 802 networks can be better served by a peer-to-peer KMS than o AdHoc 802 networks can be better served by a peer-to-peer KMS than
the EAP client/server model. the EAP client/server model.
o Some devices are very memory constrained and a common KMS for both o Some devices are very memory constrained and a common KMS for both
MAC and IP security represents a considerable code savings. MAC and IP security represents a considerable code savings.
11.4. Answers to NSRG questions 11.4. Answers to NSRG questions
skipping to change at page 30, line 29 skipping to change at page 30, line 14
hosts for sending data prior to completing the address tests. hosts for sending data prior to completing the address tests.
Otherwise, if HIP is used between two hosts that fully trust each Otherwise, if HIP is used between two hosts that fully trust each
other, the hosts may optionally decide to skip the address tests. other, the hosts may optionally decide to skip the address tests.
However, such performance optimization must be restricted to peers However, such performance optimization must be restricted to peers
that are known to be trustworthy and capable of protecting themselves that are known to be trustworthy and capable of protecting themselves
from malicious software. from malicious software.
12.3. HITs used in ACLs 12.3. HITs used in ACLs
At end-hosts, HITs can be used in IP-based access control lists at At end-hosts, HITs can be used in IP-based access control lists at
the application and network layers". At middleboxes, HIP-aware the application and network layers. At middleboxes, HIP-aware
firewalls [lindqvist-enterprise] can use HITs or public keys to firewalls [lindqvist-enterprise] can use HITs or public keys to
control both ingress and egress access to networks or individual control both ingress and egress access to networks or individual
hosts, even in the presence of mobile devices because the HITs and hosts, even in the presence of mobile devices because the HITs and
public keys are topologically independent. As discussed earlier in public keys are topologically independent. As discussed earlier in
Section 7, once a HIP session has been established, the SPI value in Section 7, once a HIP session has been established, the SPI value in
an ESP packet may be used as an index, indicating the HITs. In an ESP packet may be used as an index, indicating the HITs. In
practice, firewalls can inspect HIP packets to learn of the bindings practice, firewalls can inspect HIP packets to learn of the bindings
between HITs, SPI values, and IP addresses. They can even explicitly between HITs, SPI values, and IP addresses. They can even explicitly
control ESP usage, dynamically opening ESP only for specific SPI control ESP usage, dynamically opening ESP only for specific SPI
values and IP addresses. The signatures in HIP packets allow a values and IP addresses. The signatures in HIP packets allow a
skipping to change at page 31, line 26 skipping to change at page 31, line 12
Some of the HIP-aware middleboxes, such as firewalls Some of the HIP-aware middleboxes, such as firewalls
[lindqvist-enterprise] or NATs [ylitalo-spinat], may observe the on- [lindqvist-enterprise] or NATs [ylitalo-spinat], may observe the on-
path traffic passively. Such middleboxes are transparent by their path traffic passively. Such middleboxes are transparent by their
nature and may not get a notification when a host moves to a nature and may not get a notification when a host moves to a
different network. Thus, such middleboxes should maintain soft state different network. Thus, such middleboxes should maintain soft state
and timeout when the control and data plane between two HIP end-hosts and timeout when the control and data plane between two HIP end-hosts
has been idle too long. Correspondingly, the two end-hosts may send has been idle too long. Correspondingly, the two end-hosts may send
periodically keepalives, such as UPDATE packets or ICMP messages periodically keepalives, such as UPDATE packets or ICMP messages
inside the ESP tunnel, to sustain state at the on-path middleboxes. inside the ESP tunnel, to sustain state at the on-path middleboxes.
Another aspect related to HIP-aware middleboxes is that the One general limitation related to end-to-end encryption is that
association between the control and data plane, in the case of ESP, middleboxes may not be able to participate to the protection of
is weak and can be exploited under certain assumptions as described malign data flows. While the issue may affect also other protocols,
by Heer et al[heer-end-host]. In the scenario, the attacker has Heer at al [heer-end-host] have analyzed the problem in the context
already gained access to the target network protected by a HIP-aware of HIP. More specifically, when ESP is used as the data-plane
firewall, but wants to circumvent the HIP-based firewall. To achieve protocol for HIP, the association between the control and data plane
this, the attacker passively observes a base exchange between two HIP is weak and can be exploited under certain assumptions. In the
hosts and later replays it. This way, the attacker manages to scenario, the attacker has already gained access to the target
penetrate the firewall and can use a fake ESP tunnel to transport its network protected by a HIP-aware firewall, but wants to circumvent
own data. This is possible because the firewall cannot distinguish the HIP-based firewall. To achieve this, the attacker passively
when the ESP tunnel is valid. As a solution, HIP-aware middleboxes observes a base exchange between two HIP hosts and later replays it.
may participate to the control plane interaction by adding random This way, the attacker manages to penetrate the firewall and can use
nonce parameters to the control traffic, which the the end-hosts have a fake ESP tunnel to transport its own data. This is possible
to sign to guarantee the freshness of the control traffic because the firewall cannot distinguish when the ESP tunnel is valid.
[heer-midauth]. As an alternative, extensions for transporting data As a solution, HIP-aware middleboxes may participate to the control
plane directly over the control plane can be used [RFC6078]. plane interaction by adding random nonce parameters to the control
traffic, which the the end-hosts have to sign to guarantee the
freshness of the control traffic [heer-midauth]. As an alternative,
extensions for transporting data plane directly over the control
plane can be used [RFC6078].
12.4. Alternative HI considerations 12.4. Alternative HI considerations
The definition of the Host Identifier states that the HI need not be The definition of the Host Identifier states that the HI need not be
a public key. It implies that the HI could be any value; for example a public key. It implies that the HI could be any value; for example
a FQDN. This document does not describe how to support such a non- a FQDN. This document does not describe how to support such a non-
cryptographic HI, but examples of such protocol variants do exist cryptographic HI, but examples of such protocol variants do exist
([urien-rfid], [urien-rfid-draft]). A non-cryptographic HI would ([urien-rfid], [urien-rfid-draft]). A non-cryptographic HI would
still offer the services of the HIT or LSI for NAT traversal. It still offer the services of the HIT or LSI for NAT traversal. It
would be possible to carry HITs in HIP packets that had neither would be possible to carry HITs in HIP packets that had neither
skipping to change at page 33, line 42 skipping to change at page 33, line 33
[I-D.ietf-hip-rfc5201-bis] [I-D.ietf-hip-rfc5201-bis]
Moskowitz, R., Heer, T., Jokela, P., and T. Henderson, Moskowitz, R., Heer, T., Jokela, P., and T. Henderson,
"Host Identity Protocol Version 2 (HIPv2)", "Host Identity Protocol Version 2 (HIPv2)",
draft-ietf-hip-rfc5201-bis-14 (work in progress), draft-ietf-hip-rfc5201-bis-14 (work in progress),
October 2013. October 2013.
[I-D.ietf-hip-rfc5202-bis] [I-D.ietf-hip-rfc5202-bis]
Jokela, P., Moskowitz, R., and J. Melen, "Using the Jokela, P., Moskowitz, R., and J. Melen, "Using the
Encapsulating Security Payload (ESP) Transport Format with Encapsulating Security Payload (ESP) Transport Format with
the Host Identity Protocol (HIP)", the Host Identity Protocol (HIP)",
draft-ietf-hip-rfc5202-bis-04 (work in progress), draft-ietf-hip-rfc5202-bis-05 (work in progress),
September 2013. November 2013.
[I-D.ietf-hip-rfc5203-bis] [I-D.ietf-hip-rfc5203-bis]
Laganier, J. and L. Eggert, "Host Identity Protocol (HIP) Laganier, J. and L. Eggert, "Host Identity Protocol (HIP)
Registration Extension", draft-ietf-hip-rfc5203-bis-02 Registration Extension", draft-ietf-hip-rfc5203-bis-02
(work in progress), September 2012. (work in progress), September 2012.
[I-D.ietf-hip-rfc5204-bis] [I-D.ietf-hip-rfc5204-bis]
Laganier, J. and L. Eggert, "Host Identity Protocol (HIP) Laganier, J. and L. Eggert, "Host Identity Protocol (HIP)
Rendezvous Extension", draft-ietf-hip-rfc5204-bis-02 (work Rendezvous Extension", draft-ietf-hip-rfc5204-bis-02 (work
in progress), September 2012. in progress), September 2012.
 End of changes. 58 change blocks. 
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