OSPF Working Group X. Xu, Ed.
Internet-Draft Huawei
Intended status: Standards Track B. Decraene, Ed.
Expires: March 14, 2018 Orange
R. Raszuk
Bloomberg LP
L. Contreras
Telefonica I+D
L. Jalil
September 10, 2017

Advertising Tunnel Encapsulation Capabilities in OSPF


Networks use tunnels for a variety of reasons. A large variety of tunnel types are defined and the ingress tunnel router needs to select a type of tunnel which is supported by the egress tunnel router and itself. This document defines how to advertise the tunnel encapsulation capabilities of egress tunnel routers in OSPF Router Information Link State Advertisement (LSAs).

Requirements Language

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119.

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/.

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This Internet-Draft will expire on March 14, 2018.

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Table of Contents

1. Introduction

Networks use tunnels for a variety of reasons, such as:

The ingress tunnel router needs to select a type of tunnel which is supported by the egress tunnel router and itself. This document describes how to use OSPF Router Information Link State Advertisements (LSAs) to advertise the tunneling capabilities of OSPF routers acting as egress tunnel routers. In this document, OSPF refers to both OSPFv2 [RFC2328] and OSPFv3 [RFC5340].

2. Terminology

This memo makes use of the terms defined in [RFC7770].

3. Tunnel Encapsulation Capabilities TLV

Routers advertise their supported encapsulation type(s) by advertising a new TLV of the OSPF Router Information (RI) Opaque LSA [RFC7770], referred to as the Tunnel Encapsulation Capabilities TLV. This TLV is applicable to both OSPFv2 and OSPFv3. The Tunnel Encapsulation Capabilities TLV SHOULD NOT appear more than once within a given OSPF Router Information (RI) Opaque LSA. If the Tunnel Encapsulation Capabilities TLV appears more than once in an OSPF Router Information LSA, only the first occurrence MUST be processed and others SHOULD be ignored. The scope of the advertisement depends on the application but it is recommended that it SHOULD be domain-wide. The Type code of the Tunnel Encapsulation Capabilities TLV is TBD1, the Length value is variable, and the Value field contains one or more Tunnel Encapsulation Type Sub-TLVs (see Section 4). Each Encapsulation Type Sub-TLVs indicates a particular encapsulation format that the advertising router supports along with the parameters to be used for the tunnel.

4. Tunnel Encapsulation Type Sub-TLVs

The Tunnel Encapsulation Type Sub-TLV is structured as follows:

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   |    Tunnel Type (2 Octets)     |        Length (2 Octets)      |
   |                                                               |
   |         Tunnel Encapsulation Attribute Sub-TLVs               |
   |                                                               |

5. Tunnel Encapsulation Attribute Sub-TLVs

Tunnel Encapsulation Attribute Sub-TLV are structured as follows:

           |     Sub-TLV Type   (2 Octets)     |
           |     Sub-TLV Length (2 Octets)     |
           |     Sub-TLV Value  (Variable)     |
           |                                   |

Section 6.2) is seen in an LSA, it SHOULD be treated as an invalid Sub-TLV. If a Sub-TLV is invalid, its Tunnel Encapsulation Type TLV MUST be ignored and skipped. However, other Tunnel Encapsulation Type TLVs MUST be considered.

Any unknown Sub-TLVs MUST be deemed as invalid Sub-TLVs and therefore MUST be ignored and skipped upon receipt. When a reserved value (See

The advertisement of an Encapsulation Type Sub-TLV (See Section 5.1) indicates that the advertising router support a particular tunnel encapsulation along with the parameters to be used for the tunnel. The decision to use that tunnel is driven by the capability of the ingress router to support the encapsulation type and the policy on the ingress router. The Color Sub-TLV (See Section 5.4) may be used as an input to this policy. Note that some tunnel types may require the execution of an explicit tunnel setup protocol before they can be used to carry data. A tunnel MUST NOT be used if there is no route toward the IP address specified in the Endpoint Sub-TLV (See Section 5.3) or if the route is not advertised by the router advertising the Tunnel Encapsulation Attribute Sub-TLVs for the tunnel.

5.1. Encapsulation Sub-TLV

This Sub-TLV of type 1 is defined in Section 3.2 "Encapsulation Sub-TLVs for Particular Tunnel Types" of [I-D.ietf-idr-tunnel-encaps] from both a syntax and semantic standpoint.

5.2. Protocol Type Sub-TLV

This Sub-TLV of type 2 is defined in Section 3.4.1 "Protocol Type sub-TLV" of [I-D.ietf-idr-tunnel-encaps] from a syntactic, semantic, and usage standpoint.

5.3. Endpoint Sub-TLV

Type is 3. The value field carries the Network Address to be used as tunnel destination address.

If length is 4, the tunnel endpoint is an IPv4 address.

If length is 16, the tunnel endpoint is an IPv6 address.

5.4. Color Sub-TLV

Type is 4. The value field is a 4-octet opaque unsigned integer.

The color value is user-defined and configured locally on the advertising routers. It may be used by service providers to define policies on the ingress tunnel routers, for example, to control the selection of the tunnel to use.

This color value can be referenced by BGP routes carrying Color Extended Community [I-D.ietf-idr-tunnel-encaps]. If the tunnel is used to reach the BGP Next-Hop of BGP routes, then attaching a Color Extended Community attached to those routes express the willingness of the BGP speaker to use a tunnel of the same color.

5.5. Load-Balancing Block Sub-TLV

This Sub-TLV of type 5 is defined in [RFC5640] from a syntactic, semantic and usage standpoint.

5.6. IP QoS Field

This Sub-TLV of type 6 is defined in Section 3.3.1 "IPv4 DS Field" of [I-D.ietf-idr-tunnel-encaps] from a syntactic, semantic and usage standpoint.

5.7. UDP Destination Port

This Sub-TLV of type 7 is defined in Section 3.3.2 "UDP Destination Port" of [I-D.ietf-idr-tunnel-encaps] from a syntactic, semantic and usage standpoint.

6. IANA Considerations

6.1. OSPF Router Information

This document requests IANA to allocate a new code point from the OSPF Router Information (RI) registry.

    Value   TLV Name                               Reference
    -----   ---------------------------------      -------------
    TBD1    Tunnel Encapsulation Capabilities      This document

6.2. Tunnel Encapsulation Attribute Sub-TLVs Registry

This document requests IANA to create a new registry "Tunnel Encapsulation Attribute Sub-TLVs" with the following registration procedure:

  Registry Name: OSPF Tunnel Encapsulation Attribute Sub-TLVs

Value          Name                   Reference
-----------    --------------------   --------------------------------------------
          0    Reserved               This document 
          1    Encapsulation          This document & [I-D.ietf-idr-tunnel-encaps]
          2    Protocol Type          This document & [I-D.ietf-idr-tunnel-encaps]
          3    Endpoint               This document
          4    Color                  This document
          5    Load-Balancing Block   This document & [RFC5640]
          6    IP QoS                 This document & [I-D.ietf-idr-tunnel-encaps]
          7    UDP Destination Port   This document & [I-D.ietf-idr-tunnel-encaps]
    8-65499    Unassigned
65500-65534    Experimental           This document
      65535    Reserved               This document

7. Security Considerations

Security considerations applicable to softwires can be found in the mesh framework [RFC5565]. In general, security issues of the tunnel protocols signaled through this OSPF capability extension are inherited.

If a third-party is able to modify any of the information that is used to form encapsulation headers, to choose a tunnel type, or to choose a particular tunnel for a particular payload type, user data packets may end up getting misrouted, misdelivered, and/or dropped. However, since an OSPF routing domain is usually well-controlled and well-managed network, the possiblity of the above risk is very low.

Security considerations for the base OSPF protocol are covered in [RFC2328] and [RFC5340].

8. Contributors

Uma Chunduri
Email: uma.chunduri@gmail.com

9. Acknowledgements

This document is partially inspired by [RFC5512].

The authors would like to thank Greg Mirsky, John E Drake, Carlos Pignataro and Karsten Thomann for their valuable comments on this document. Special thanks should be given to Acee Lindem for his multiple detailed reviews of this document and help. The authors would like to thank Pete Resnick, Joe Touch, David Mandelberg, Sabrina Tanamal, Tim Wicinski, Amanda Baber for their Last Call reviews and thank Spencer Dawkins, Mirja Kühlewind, Ben Campbell, Benoit Claise, Alvaro Retana, Adam Roach and Suresh Krishnan for their AD reviews.

10. References

10.1. Normative References

[I-D.ietf-idr-tunnel-encaps] Rosen, E., Patel, K. and G. Velde, "The BGP Tunnel Encapsulation Attribute", Internet-Draft draft-ietf-idr-tunnel-encaps-07, July 2017.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs", RFC 5226, DOI 10.17487/RFC5226, May 2008.
[RFC5640] Filsfils, C., Mohapatra, P. and C. Pignataro, "Load-Balancing for Mesh Softwires", RFC 5640, DOI 10.17487/RFC5640, August 2009.
[RFC7770] Lindem, A., Shen, N., Vasseur, JP., Aggarwal, R. and S. Shaffer, "Extensions to OSPF for Advertising Optional Router Capabilities", RFC 7770, DOI 10.17487/RFC7770, February 2016.

10.2. Informative References

[RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, DOI 10.17487/RFC2328, April 1998.
[RFC5340] Coltun, R., Ferguson, D., Moy, J. and A. Lindem, "OSPF for IPv6", RFC 5340, DOI 10.17487/RFC5340, July 2008.
[RFC5512] Mohapatra, P. and E. Rosen, "The BGP Encapsulation Subsequent Address Family Identifier (SAFI) and the BGP Tunnel Encapsulation Attribute", RFC 5512, DOI 10.17487/RFC5512, April 2009.
[RFC5565] Wu, J., Cui, Y., Metz, C. and E. Rosen, "Softwire Mesh Framework", RFC 5565, DOI 10.17487/RFC5565, June 2009.
[RFC7490] Bryant, S., Filsfils, C., Previdi, S., Shand, M. and N. So, "Remote Loop-Free Alternate (LFA) Fast Reroute (FRR)", RFC 7490, DOI 10.17487/RFC7490, April 2015.

Authors' Addresses

Xiaohu Xu (editor) Huawei EMail: xuxiaohu@huawei.com
Bruno Decraene (editor) Orange EMail: bruno.decraene@orange.com
Robert Raszuk Bloomberg LP EMail: robert@raszuk.net
Luis M. Contreras Telefonica I+D EMail: luismiguel.contrerasmurillo@telefonica.com
Luay Jalil Verizon EMail: luay.jalil@verizon.com