Advertising Tunneling Capability in OSPF
draft-ietf-ospf-encapsulation-cap-03

Abstract

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 and itself. This document defines how to advertise egress tunnel capabilities 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 [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 November 20, 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. Encapsulation Sub-TLV
• 5.2. Protocol Type Sub-TLV
• 5.3. Endpoint Sub-TLV
• 5.4. Color Sub-TLV
• 6. IANA Considerations
• 6.1. OSPF Router Information
• 6.2. IGP Tunnel Encapsulation Types Registry
• 6.3. IGP Tunnel Encapsulation Attribute Types 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 MPLS-SPRING as described in [I-D.xu-mpls-unified-source-routing-instruction], where IP tunnels are used between MPLS-SPRING-enabled routers to traverse non-MPLS routers.
• Partial deployment of MPLS-BIER as described in [I-D.ietf-bier-architecture], where IP tunnels are used between MPLS-BIER-capable routers to traverse non MPLS-BIER [I-D.ietf-bier-mpls-encapsulation] routers.
• Partial deployment of IPv6 in IPv4 networks or IPv6 in IPv4 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 needs to select a type of tunnel which is supported by the egress and itself. This document describes how to use OSPF Router Information Link State Advertisements (LSAs) to advertise the egress tunneling capabilities of OSPF routers. In this document, OSPF refers to both OSPFv2 and OSPFv3.

2. Terminology

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

3. Advertising Encapsulation Capability

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 Encapsulation Capability TLV. This TLV is applicable to both OSPFv2 and OSPFv3. The Encapsulation Capability TLV SHOULD NOT appear more than once within a given OSPF Router Information (RI) Opaque LSA. If the Encapsulation Capability TLV appears more than once in an OSPF Router Information LSA, only the first occurrence MUST be processed and others MUST 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 Encapsulation Capability 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 (2 Octets)     |        Length (2 Octets)      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   |                            Sub-TLVs                           |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        

• Tunnel Type (2 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 (2 octets): Unsigned 16-bit 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 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 of the tunnel TLV that contains this Sub-TLV. The following are the types defined in this document:
  1. Encapsulation: Sub-TLV type = 1; (See Section 5.1)
  2. Protocol Type: Sub-TLV type = 2; (See Section 5.2)
  3. Endpoint: Sub-TLV type = 3; (See Section 5.3)
  4. Color: Sub-TLV type = 4; (See Section 5.4)
• Sub-TLV Length (1 octet): Unsigned 8-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 ignored and skipped upon receipt. 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 invalid, this specific Tunnel Encapsulation MUST be ignored and skipped. However, other Tunnel Encapsulations MUST be considered.

5.1. Encapsulation Sub-TLV

This Sub-TLV has its format defined in [RFC5512] and [I-D.ietf-idr-tunnel-encaps] under the name Encapsulation Sub-TLV.

5.2. Protocol Type Sub-TLV

This Sub-TLV has its format defined in [RFC5512] and [I-D.ietf-idr-tunnel-encaps] under the name Protocol Type.

5.3. Endpoint Sub-TLV

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

The valued 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.

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 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                             This document
      2    Protocol Type                             This document
      3    Endpoint                                  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 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.

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 detailed review of this document.

10. References

10.1. Normative References

10.2. Informative References

Authors' Addresses