Advertising Tunnelling Capability in IS-IS

Some networks use tunnels for a variety of reasons, such as: Partial deployment of MPLS-SPRING as described in , 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 , where IP tunnels are used between MPLS-BIER-capable routers so as to traverse non MPLS-BIER routers. Partial deployment of IPv6 (resp. IPv4) in IPv4 (resp. IPv6) networks as described in , 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 , 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.

This memo makes use of the terms defined in .

Routers advertises their supported encapsulation type(s) by advertising a new sub-TLV of the IS-IS Router CAPABILITY TLV , 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.

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

Tunnel Type (1 octets): identifies the type of tunneling technology being signaled. This document defines the following types: L2TPv3 over IP : Type code=1; GRE : Type code=2; Transmit tunnel endpoint : Type code=3; IPsec in Tunnel-mode : Type code=4; IP in IP tunnel with IPsec Transport Mode : Type code=5; MPLS-in-IP tunnel with IPsec Transport Mode : Type code=6; IP in IP : Type code=7; VXLAN : Type code=8; NVGRE : Type code=9; MPLS : Type code=10; MPLS-in-GRE : Type code=11; VXLAN GPE : Type code=12; MPLS-in-UDP : Type code=13; MPLS-in-UDP-with-DTLS : Type code=14; MPLS-in-L2TPv3 : Type code=15; 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.

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

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: Encapsulation Parameters: sub-TLV type = 1; (See Section 5.1) Encapsulated Protocol: sub-TLV type = 2; (See Section 5.2) End Point: sub-TLV type = 3; (See Section 5.3) 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.

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

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

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.

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.

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

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

Assignments of Encapsulation Types are via Standards Action .

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

Assignments of Encapsulation Attribute Types are via Standards Action .

Security considerations applicable to softwires can be found in the mesh framework . 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 .

This document is partially inspired by . The authors would like to thank Carlos Pignataro and Karsten Thomann for their valuable comments on this draft.