Advertising Tunnel Encapsulation Capabilities in OSPF
draft-ietf-ospf-encapsulation-cap-07

Abstract

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/.

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 March 14, 2018.

Copyright Notice

Copyright (c) 2017 IETF Trust and the persons identified as the document authors. All rights reserved.

This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License.

Table of Contents

• 1. Introduction
• 2. Terminology
• 3. Tunnel Encapsulation Capabilities TLV
• 4. Tunnel Encapsulation Type Sub-TLVs
• 5. Tunnel Encapsulation Attribute Sub-TLVs
• 5.1. Encapsulation Sub-TLV
• 5.2. Protocol Type Sub-TLV
• 5.3. Endpoint Sub-TLV
• 5.4. Color Sub-TLV
• 5.5. Load-Balancing Block Sub-TLV
• 5.6. IP QoS Field
• 5.7. UDP Destination Port
• 6. IANA Considerations
• 6.1. OSPF Router Information
• 6.2. Tunnel Encapsulation Attribute Sub-TLVs Registry
• 7. Security Considerations
• 8. Contributors
• 9. Acknowledgements
• 10. References
• 10.1. Normative References
• 10.2. Informative References
• Authors' Addresses

1. Introduction

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

• Partial deployment of IPv6 in IPv4 networks or IPv4 in IPv6 networks as described in [RFC5565], where IPvx tunnels are used between IPvx-enabled routers so as to traverse non-IPvx routers.
• Remote Loop-Free Alternate (RLFA) repair tunnels as described in [RFC7490], where tunnels are used between the Point of Local Repair and the selected PQ node.

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               |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        

• Tunnel Type (2 octets): Identifies the type of tunneling technology being signaled. Tunnel types are shared with the BGP extension [I-D.ietf-idr-tunnel-encaps] and hence are defined in the IANA registry "BGP Tunnel Encapsulation Attribute Tunnel Types". Unknown types are to be ignored and skipped upon receipt.
• Length (2 octets): Unsigned 16-bit integer indicating the total number of octets of the value field. Note that this is a padding to be ignored if the length field is longer than the field indicated by the sub-TLVs.
• Value (variable): Zero or more Tunnel Encapsulation Attribute Sub-TLVs as defined in Section 5.

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.

• Sub-TLV Type (2 octets): Each Sub-TLV type defines a certain property of the tunnel TLV that contains this Sub-TLV. Types are registered in the IANA registry "OSPF Tunnel Encapsulation Attribute Sub-TLVs" Section 6.2.
• Sub-TLV Length (2 octets): Unsigned 16-bit integer indicating the total number of octets of the Sub-TLV value field.
• Sub-TLV Value (variable): Encodings of the value field depend on the Sub-TLV type as enumerated above. The following sub-sections define the encoding in detail.

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:

• The values in the range 1-255 are to be allocated using the "Standards Action" registration procedure as defined in [RFC5226].
• The values in the range 256-65499 are to be allocated using the "First Come, First Served" 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
Huawei
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

10.2. Informative References

Authors' Addresses