Advertising Tunnelling Capability in IS-IS
draft-ietf-isis-encapsulation-cap-01

Abstract

Some networks use tunnels for a variety of reasons. A large variety of tunnel types are defined and the ingress needs to select a type of tunnel which is supported by the egress. This document defines how to advertise egress tunnel capabilities in IS-IS Router Capability TLV.

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 [RFC2119].

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 http://datatracker.ietf.org/drafts/current/.

Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress."

This Internet-Draft will expire on October 26, 2017.

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 (http://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. Advertising Encapsulation Capability
• 4. Tunnel Encapsulation Type
• 5. Tunnel Encapsulation Attribute
• 5.1. Tunnel Parameters sub-TLV
• 5.2. Encapsulated Protocol sub-TLV
• 5.3. End Point sub-TLV
• 5.4. Color sub-TLV
• 6. IANA Considerations
• 6.1. IS-IS Router Capability
• 6.2. IGP Tunnel Encapsulation Types Registry
• 6.3. IGP Tunnel Encapsulation Attribute Types Registry
• 7. Security Considerations
• 8. Acknowledgements
• 9. References
• 9.1. Normative References
• 9.2. Informative References
• Authors' Addresses

1. Introduction

Some networks use tunnels for a variety of reasons, such as:

• Partial deployment of MPLS-SPRING as described in [I-D.xu-mpls-unified-source-routing-instruction], where IP tunnels are used between MPLS-SPRING-enabled routers so as to traverse non- MPLS routers.
• Partial deployment of MPLS-BIER as described in Section 6.9 of [I-D.ietf-bier-architecture], where IP tunnels are used between MPLS-BIER-capable routers so as to traverse non MPLS-BIER [I-D.ietf-bier-mpls-encapsulation] routers.
• Partial deployment of IPv6 (resp. IPv4) in IPv4 (resp. 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 repair tunnels as described in [RFC7490], where tunnels are used between the Point of Local Repair and the selected PQ node.

The ingress needs to select a type of tunnel which is supported by the egress. This document describes how to use IS-IS Router Capability TLV to advertise the egress tunnelling capabilities of nodes.

2. Terminology

This memo makes use of the terms defined in [RFC4971].

3. Advertising Encapsulation Capability

Routers advertises their supported encapsulation type(s) by advertising a new sub-TLV of the IS-IS Router CAPABILITY TLV [RFC4971], referred to as Encapsulation Capability sub-TLV. This sub-TLV SHOULD NOT appear more than once within a given IS-IS Router CAPABILITY TLV. The scope of the advertisement depends on the application but it is recommended that it SHOULD be domain-wide. The Type code of the Encapsulation Capability sub-TLV is TBD1, the Length value is variable, and the Value field contains one or more Tunnel Encapsulation Type sub-TLVs. Each Encapsulation Type sub-TLVs indicates a particular encapsulation format that the advertising router supports.

4. Tunnel Encapsulation Type

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   |    Length     |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                                                               |
       |                             Value                             |
       |                                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

• Tunnel Type (1 octets): identifies the type of tunneling technology being signaled. This document defines the following types:
  1. L2TPv3 over IP [RFC3931] : Type code=1;
  2. GRE [RFC2784] : Type code=2;
  3. Transmit tunnel endpoint [RFC5566] : Type code=3;
  4. IPsec in Tunnel-mode [RFC5566] : Type code=4;
  5. IP in IP tunnel with IPsec Transport Mode [RFC5566] : Type code=5;
  6. MPLS-in-IP tunnel with IPsec Transport Mode [RFC5566] : Type code=6;
  7. IP in IP [RFC2003] [RFC4213]: Type code=7;
  8. VXLAN [RFC7348] : Type code=8;
  9. NVGRE [RFC7637] : Type code=9;
  10. MPLS [RFC3032] : Type code=10;
  11. MPLS-in-GRE [RFC4023] : Type code=11;
  12. VXLAN GPE [I-D.ietf-nvo3-vxlan-gpe] : Type code=12;
  13. MPLS-in-UDP [RFC7510] : Type code=13;
  14. MPLS-in-UDP-with-DTLS [RFC7510] : Type code=14;
  15. MPLS-in-L2TPv3 [RFC4817] : Type code=15;
  16. GTP: Type code=16;

  Unknown types are to be ignored and skipped upon receipt.

• Length (1 octets): unsigned integer indicating the total number of octets of the value field.
• Value (variable): zero or more Tunnel Encapsulation Attribute sub- TLVs as defined in Section 5.

5. Tunnel Encapsulation Attribute

The Tunnel Encapsulation Attribute sub-TLV is structured as as follows:

                        +-----------------------------------+
                        |      Sub-TLV Type (1 Octet)       |
                        +-----------------------------------+
                        |     Sub-TLV Length (1 Octet)      |
                        +-----------------------------------+
                        |     Sub-TLV Value (Variable)      |
                        |                                   |
                        +-----------------------------------+

• Sub-TLV Type (1 octet): each sub-TLV type defines a certain property about the tunnel TLV that contains this sub-TLV. The following are the types defined in this document:
  1. Encapsulation Parameters: sub-TLV type = 1; (See Section 5.1)
  2. Encapsulated Protocol: sub-TLV type = 2; (See Section 5.2)
  3. End Point: sub-TLV type = 3; (See Section 5.3)
  4. Color: sub-TLV type = 4; (See Section 5.4)
• Sub-TLV Length (1 octet): unsigned 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 ignored and skipped. However, if the TLV is understood, the entire TLV MUST NOT be ignored just because it contains an unknown sub-TLV.

If a sub-TLV is erroneous, this specific Tunnel Encapsulation MUST be ignored and skipped. However, others Tunnel Encapsulations MUST be considered.

5.1. Tunnel Parameters sub-TLV

This sub-TLV has its format defined in [RFC5512] under the name Encapsulation sub-TLV.

5.2. Encapsulated Protocol sub-TLV

This sub-TLV has its format defined in [RFC5512] under the name Protocol Type.

5.3. End Point sub-TLV

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

If length is 4, the Address Family (AFI) is IPv4.

If length is 16, the Address Family (AFI) is IPv6.

5.4. Color sub-TLV

The valued field is a 4 octets opaque unsigned integer.

The color value is user defined and configured locally on the routers. It may be used by the service providers to define policies.

6. IANA Considerations

6.1. IS-IS Router Capability

This document requests IANA to allocate a new code point from registry IS-IS Router CAPABILITY TLV.

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

6.2. IGP Tunnel Encapsulation Types Registry

              Registry Name: IGP Tunnel Encapsulation Type.

   Value      Name                                         Reference
   -------    ------------------------------------------   -------------
         0    Reserved                                     This document
         1    L2TPv3 over IP                               This document
         2    GRE                                          This document
         3    Transmit tunnel endpoint                     This document
         4    IPsec in Tunnel-mode                         This document
         5    IP in IP tunnel with IPsec Transport Mode    This document
         6    MPLS-in-IP tunnel with IPsec Transport Mode  This document
         7    IP in IP                                     This document
         8    VXLAN                                        This document
         9    NVGRE                                        This document
        10    MPLS                                         This document
        11    MPLS-in-GRE                                  This document
        12    VXLAN-GPE                                    This document
        13    MPLS-in-UDP                                  This document
        14    MPLS-in-UDP-with-DTLS                        This document
        15    MPLS-in-L2TPv3                               This document
        16    GTP                                          This document
    17-250    Unassigned
   251-254    Experimental                                 This document
       255    Reserved                                     This document

This document requests IANA to create a new registry "IGP Tunnel Encapsulation Types" with the following registration procedure: [RFC5226].

6.3. IGP Tunnel Encapsulation Attribute Types Registry

This document requests IANA to create a new registry "IGP Tunnel Encapsulation Attribute Types" with the following registration procedure:

           Registry Name: IGP Tunnel Encapsulation Attribute Types.

Value      Name                                      Reference
-------    ------------------------------------      -------------
      0    Reserved                                  This document
      1    Encapsulation parameters                  This document
      2    Protocol                                  This document
      3    End Point                                 This document
      4    Color                                     This document
  5-250    Unassigned
251-254    Experimental                              This document
    255    Reserved                                  This document

Assignments of Encapsulation Attribute Types are via Standards Action [RFC5226].

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 IGP 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.

Security considerations for the base IS-IS protocol are covered in [RFC1195].

8. Acknowledgements

This document is partially inspired by [RFC5512].

The authors would like to thank Carlos Pignataro and Karsten Thomann for their valuable comments on this draft.

9. References

9.1. Normative References

9.2. Informative References

Authors' Addresses