[Docs] [txt|pdf] [Tracker] [Email] [Diff1] [Diff2] [Nits]

Versions: (draft-zzhang-tsvwg-generic-transport-functions) 00

intarea                                                         Z. Zhang
Internet-Draft                                                 R. Bonica
Intended status: Standards Track                             K. Kompella
Expires: July 16, 2021                                  Juniper Networks
                                                        January 12, 2021


                       Generic Delivery Functions
           draft-zzhang-intarea-generic-delivery-functions-00

Abstract

   Some functionalities (e.g. fragmentation/reassembly and Encapsulating
   Security Payload) provided by IPv6 can be viewed as delivery
   functions independent of IPv6 or even IP entirely.  This document
   proposes to provide those functionalities at different layers (e.g.,
   MPLS, BIER or even Ethernet) independent of IP.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   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 July 16, 2021.

Copyright Notice

   Copyright (c) 2021 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




Zhang, et al.             Expires July 16, 2021                 [Page 1]


Internet-Draft         Generic Delivery Functions           January 2021


   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Specifications  . . . . . . . . . . . . . . . . . . . . . . .   4
     2.1.  Generic Delivery Function Header  . . . . . . . . . . . .   4
     2.2.  Generic Fragmentation Header  . . . . . . . . . . . . . .   5
     2.3.  Payload Type Header . . . . . . . . . . . . . . . . . . .   6
     2.4.  Generic ESP/Authentication Header . . . . . . . . . . . .   6
     2.5.  MPLS Signaling  . . . . . . . . . . . . . . . . . . . . .   6
       2.5.1.  BGP Signaling . . . . . . . . . . . . . . . . . . . .   6
       2.5.2.  IGP Signaling . . . . . . . . . . . . . . . . . . . .   7
   3.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
   5.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   9
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   9
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   9
     6.2.  Informative References  . . . . . . . . . . . . . . . . .   9
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  10

1.  Introduction

   Consider an operator providing Ethernet services such as pseudowires,
   VPLS or EVPN.  The Ethernet frames that a Provider Edge (PE) device
   receives from a Customer Edge (CE) device may have a larger size than
   the PE-PE path MTU (pMTU) in the provider network.  This could be
   because

   1.  the provider network is built upon virtual connections (e.g.
       pseudowires) provided by another infrastructure provider, or

   2.  the customer network uses jumbo frames while the provider network
       does not, or

   3.  the provider-side overhead for transporting customers packets
       across the network pushes past the pMTU.

   In any case, the provider cannot simply require its customers to
   change their MTU.

   To get those large frames across the provider network, currently the
   only workaround is to encapsulate the frames in IP (with or without
   GRE) and then fragment the IP packets.  Even if MPLS is used for
   service delimiting, IP is used for transporation (MPLS over IP/GRE).
   This may not be desirable in certain deployment scenarios, where MPLS




Zhang, et al.             Expires July 16, 2021                 [Page 2]


Internet-Draft         Generic Delivery Functions           January 2021


   is the preferred transport or IP encapsulation overhead is deemed
   excessive.

   IPv6 fragmentation and reassembly are based on the IPv6 Fragmentation
   header below [RFC8200]:

   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  Next Header  |   Reserved    |      Fragment Offset    |Res|M|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                         Identification                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                    Figure 1: IPv6 Fragmentation Header

   This document proposes adapting this header for use in non-IP
   contexts, since the fragmentation/reassembly function is actually
   independent of IPv6 except the following aspects:

   o  The fragment header is identified as such by the "previous"
      header.

   o  The "Next Header" value is from the "Internet Protocol Numbers"
      registry.

   o  The "Identification" value is unique in the (source, destination)
      context provided by the IPv6 header

   The "Identification" field, in conjunction with the IPv6 source and
   destination identifies fragments of the original packet, for the
   purpose of reassembly.

   Therefore, the fragmentation/reassembly function can be applied at
   other layers as long as a) the fragment header is identified as such;
   and b) the context for packet identification is provided.  Examples
   of such layers include MPLS, BIER, and Ethernet (if IEEE determines
   it is so desired).

   For the same consideration, the IP Encapsulating Security Payload
   (ESP) [RFC4303] could also be applied at other layers if ESP is
   desired there.  For example, if for whatever reason the Ethernet
   service provider wants to provide ESP between its PEs, it could do so
   without requiring IP encapsulation if ESP is applied at non-IP
   layers.

   We refer to these as Generic Delivery Functions (GDFs), which could
   be achieved at a shim layer between a source and destination delivery
   points, for example:




Zhang, et al.             Expires July 16, 2021                 [Page 3]


Internet-Draft         Generic Delivery Functions           January 2021


   o  Source and destination IP/Ethernet nodes

   o  Ingress and egress nodes of MPLS Label Switch Paths (LSPs)

   o  BIER Forwarding Ingress Routers (BFIRs) and BIER Forwarding Egress
      Routers (BFERs)

   It is not the intention to apply the GDFs hop by hop between the
   source and destination delivery points.

   The possibility of applying some other IP functions (e.g.
   Authentication Header [RFC4302]) is for further study.

2.  Specifications

2.1.  Generic Delivery Function Header

   The following Generic Delivery Function Header (GDFH) is defined:

   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0 0 0 0| Rsved |  This Header  | Header Length |  Next Header  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~              Variable field per "This header"                 ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                Figure 2: Generic Delivery Function Header

   0000 nibble:  Prevents the GDFH from being mistaken as an IP header
      by a router doing deep packet inspection for ECMP hashing purpose.

   This Header:  The type of this GDFH header.  For example, TBD1 for
      generic fragmentation, TBD2 for generic ESP.  The values are from
      a space independent of the "Next Header".

   Header Length:  The number of octets of the entire header.

   Next Header:  The type of next header.  For functions that IETF is
      concerned with, the "Next Header" values are from the "Internet
      Protocol Numbers" registry.  A next header could be another GDFH,
      so a value is to be assigned for GDFH from the registry.

   The outer header MUST identify that a GDFH follows.  Encoding "This
   Header" in the GDFH allows that a single outer header encoding can be
   used for different GDFHs.

   If the outer header is BIER, a TBD value for the "proto" field in the
   BIER header identifies that a GDFH follows.




Zhang, et al.             Expires July 16, 2021                 [Page 4]


Internet-Draft         Generic Delivery Functions           January 2021


   If the outer header is MPLS, the label preceding the GDFH indicates
   that a GDFH follows (see Section 2.5).

   If the outer header is Ethernet (if IEEE would decide to provide the
   generic delivery functions on top of Ethernet directly), then a new
   Ethertype would be assigned by IEEE.

2.2.  Generic Fragmentation Header

   For generic fragmentation/reassembly functionality, the GDFH takes
   the following Generic Fragmentation Header (GFH) format:

   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0 0 0 0| Rsved | Header Length |     TBD1      |  Next Header  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Fragment Offset    |R|S|M| Identification (variable)     ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                         Identification                        |
   |                           (continues)
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                  Figure 3: Generic Fragmentation Header

   The "Fragment Offset" and "M" flag bit fields are as in the IPv6
   Fragmentation Header.

   R: The "R" flag bit is reserved.  It MUST be 0 on transmitting and
      ignored on receiving.

   Identification:  at least 4-octet long. // would 2-octet be ok as
      minimum?

   S: If the "S" flag bit is clear, the context for the Identification
      field is provided by the outer header, and only the source-
      identifying information in the outer header is used.

      If the "S" flag bit is set, the variable Identification field
      encodes both source-identifying information (e.g. the IP address
      of the node adding the GFH) and an identification number unique
      within that source.

   When a GFH is used together with other GDFHs, the GFH SHOULD be the
   first GDFH.

   If the outer header is BIER and the "S" flag bit is clear, the "BFIR-
   id" field in the BIER header provides the context for the
   "Identification" field.




Zhang, et al.             Expires July 16, 2021                 [Page 5]


Internet-Draft         Generic Delivery Functions           January 2021


   If the outer header is MPLS, the "S" flag bit MAY be clear if the the
   label preceeding the GFH identifies the sending node in addition to
   indicating that a GFH follows (see Section 2.5).

2.3.  Payload Type Header

   While originally it is not the intention to provide a way to identify
   the payload type after an MPLS label stack, it has been pointed out
   that the GFH now provides the payload-identifying functionality as a
   by product - even when fragmentation is not needed, a GFH can be
   inserted, with the Fragmentation Offset, the M-bit and Identification
   fields set to 0, and the Next Header set appropriately.

   If the payload-identifying functionality is deemed as desired, a
   dedicated header type could be assigned for this purpose, with a
   smaller header compared to GFH.

   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0 0 0 0| Rsved |Header Length:4|     TBD3      |  Next Header  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                   Figure 4: Generic Payload Type Header

2.4.  Generic ESP/Authentication Header

   To be specified in future revisions.

2.5.  MPLS Signaling

   When GDFH is used with MPLS, the preceeding label needs to indicate
   that a GDFH follows, and optionally identify the node that does the
   fragmentation.  The label can be signaled via BGP or IGP as sepcified
   below.

2.5.1.  BGP Signaling

   This document defines a new transitive BGP "GDFH Labels" attribute,
   very similar to the "PE Distinguisher Labels" attribute defined in
   [RFC6514] (and the text below is adapted from Section 8 of
   [RFC6514]):











Zhang, et al.             Expires July 16, 2021                 [Page 6]


Internet-Draft         Generic Delivery Functions           January 2021


     +---------------------------------+
     |     Node Address                |
     +---------------------------------+
     |     Label (3 octets)            |
     +---------------------------------+
     .......
     +---------------------------------+
     |     Node Address                |
     +---------------------------------+
     |     Label (3 octets)            |
     +---------------------------------+

   The Label field contains an MPLS label encoded as 3 octets, where the
   high-order 20 bits contain the label value.  The Node Address MAY be
   0, meaning that the following label only indicates a GDFH follows
   when the label is used in the label stack of a data packet.

   The Node Address MAY also be a unicast address, indicating that the
   following label when used in the label stack of a data packet will
   both indicate that a GDFH follows and identify the sending node.

   If a node supports GDFH with MPLS, it attaches the attribute in the
   BGP routes for its local addresses.  A border router SHOULD remove
   the attribute if no node beyond the border will use GDFH with MPLS to
   send traffic to the corresponding addresses.

   A router that supports the attribute considers this attribute to be
   malformed if the Node Address field does not contain a unicast
   address or 0.  The attribute is also considered to be malformed if:
   (a) the Node Address field is expected to be an IPv4 address, and the
   length of the attribute is not a multiple of 7 or (b) the Node
   Address field is expected to be an IPv6 address, and the length of
   the attribute is not a multiple of 19.  The Address Family Indicator
   (AFI) of the BGP route that the attribute is attached to provides the
   information on whether the Node Address field contains an IPv4 or
   IPv6 address.  Each of the Node Addresses in the attribute MUST be of
   the same address family as the route that is carrying the attribute.

2.5.2.  IGP Signaling

   This document defines an OSPFv2 "GDFH Labels" sub-TLV of OSPFv2
   Extended Prefix TLV [RFC7684], with the value part being the same as
   BGP "GDFH Labels" attribute above.  If an OSPFv2 router surports GDFH
   with MPLS, it includes the GDFH Labels sub-TLV in the Extended Prefix
   TLV that is attached to its local addresses advertised in its OSPFv2
   Extended Prefix Opaque LSA.





Zhang, et al.             Expires July 16, 2021                 [Page 7]


Internet-Draft         Generic Delivery Functions           January 2021


   Similary, This document defines an OSPFv3 "GDFH Labels" sub-TLV of
   OSPFv3 Intra/Inter-Area-Prefix TLVs [RFC8362], with the value part
   being the same as BGP "GDFH Labels" attribute above.  If an OSPFv3
   router surports GDFH with MPLS, it includes the GDFH Labels sub-TLV
   in the Intra-Area-Prefix TLV for its local addresses.

   This document also defines an ISIS "GDFH Labels" sub-TLV of ISIS
   prefix-reachability TLV [RFC5120] [RFC5305] [RFC5308], with the value
   part being the same as BGP "GDFH Labels" attribute above.  If an ISIS
   router surports GDFH with MPLS, it includes the sub-TLV to the
   prefix-reachability TLV for its local addresses.

   For both OSPF and ISIS, when advertising a prefix from one area/level
   to another, if there is a "GDFH Labels TLV" attached in the source
   area/level, the TLV SHOULD be attached in the target area/level and
   the prefix SHOULD NOT be summarized.

3.  Security Considerations

   To be provided.

4.  IANA Considerations

   This document makes the following IANA requests:

   o  A new BGP Attribute type for "GDFH Labels" from the BGP Path
      Attributes registry

   o  A new OSPFv2 sub-TLV type for "GDFH Labels" from the OSPFv2
      Extended Prefix TLV Sub-TLVs registry

   o  A new OSPFv3 sub-TLV type for "GDFH Labels" from the OSPFv3
      Extended-LSA sub-TLV registry

   o  A new BIER Next Protocol Identifier value for GDFH from BIER Next
      Protocol Identifiers registry

   o  A new Internect Protocol Number for GDFH from the Internet
      Protocol Numbers registry

   This document requests IANA to set up a "Generic Deliver Function
   Header Types" registry with the following initial assigments:

   0: Reserved

   1: Generic Fragmentation

   2: Generic ESP



Zhang, et al.             Expires July 16, 2021                 [Page 8]


Internet-Draft         Generic Delivery Functions           January 2021


5.  Acknowledgements

   The authors thank Stewart Bryant and Tony Przygienda for their
   valuable comments and suggestions.

6.  References

6.1.  Normative References

   [RFC4303]  Kent, S., "IP Encapsulating Security Payload (ESP)",
              RFC 4303, DOI 10.17487/RFC4303, December 2005,
              <https://www.rfc-editor.org/info/rfc4303>.

   [RFC5120]  Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi
              Topology (MT) Routing in Intermediate System to
              Intermediate Systems (IS-ISs)", RFC 5120,
              DOI 10.17487/RFC5120, February 2008,
              <https://www.rfc-editor.org/info/rfc5120>.

   [RFC5305]  Li, T. and H. Smit, "IS-IS Extensions for Traffic
              Engineering", RFC 5305, DOI 10.17487/RFC5305, October
              2008, <https://www.rfc-editor.org/info/rfc5305>.

   [RFC5308]  Hopps, C., "Routing IPv6 with IS-IS", RFC 5308,
              DOI 10.17487/RFC5308, October 2008,
              <https://www.rfc-editor.org/info/rfc5308>.

   [RFC7684]  Psenak, P., Gredler, H., Shakir, R., Henderickx, W.,
              Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute
              Advertisement", RFC 7684, DOI 10.17487/RFC7684, November
              2015, <https://www.rfc-editor.org/info/rfc7684>.

   [RFC8200]  Deering, S. and R. Hinden, "Internet Protocol, Version 6
              (IPv6) Specification", STD 86, RFC 8200,
              DOI 10.17487/RFC8200, July 2017,
              <https://www.rfc-editor.org/info/rfc8200>.

   [RFC8362]  Lindem, A., Roy, A., Goethals, D., Reddy Vallem, V., and
              F. Baker, "OSPFv3 Link State Advertisement (LSA)
              Extensibility", RFC 8362, DOI 10.17487/RFC8362, April
              2018, <https://www.rfc-editor.org/info/rfc8362>.

6.2.  Informative References

   [RFC4302]  Kent, S., "IP Authentication Header", RFC 4302,
              DOI 10.17487/RFC4302, December 2005,
              <https://www.rfc-editor.org/info/rfc4302>.




Zhang, et al.             Expires July 16, 2021                 [Page 9]


Internet-Draft         Generic Delivery Functions           January 2021


   [RFC6514]  Aggarwal, R., Rosen, E., Morin, T., and Y. Rekhter, "BGP
              Encodings and Procedures for Multicast in MPLS/BGP IP
              VPNs", RFC 6514, DOI 10.17487/RFC6514, February 2012,
              <https://www.rfc-editor.org/info/rfc6514>.

Authors' Addresses

   Zhaohui Zhang
   Juniper Networks
   1133 Innovation Way
   Sunnyvale  94089
   USA

   Phone: +1 408 745 2000
   Email: zzhang@juniper.net


   Ron Bonica
   Juniper Networks
   1133 Innovation Way
   Sunnyvale  94089
   USA

   Phone: +1 408 745 2000
   Email: rbonica@juniper.net


   Kireeti Kompella
   Juniper Networks
   1133 Innovation Way
   Sunnyvale  94089
   USA

   Phone: +1 408 745 2000
   Email: kireeti@juniper.net
















Zhang, et al.             Expires July 16, 2021                [Page 10]


Html markup produced by rfcmarkup 1.129d, available from https://tools.ietf.org/tools/rfcmarkup/