LISP Generic Protocol Extension

LISP, as defined in and extended in , defines an encapsulation format that carries IPv4 or IPv6 (henceforth referred to as IP) packets in a LISP header and outer UDP/IP transport. The LISP header does not specify the protocol being encapsulated and therefore is currently limited to encapsulating only IP packet payloads. Other protocols, most notably VXLAN (which defines a similar header format to LISP), are used to encapsulate L2 protocols such as Ethernet. This document defines an extension for the LISP header, as defined in , to indicate the inner protocol, enabling the encapsulation of Ethernet, IP or any other desired protocol all the while ensuring compatibility with existing LISP deployments. A flag in the LISP header, called the P-bit, is used to signal the presence of the 8-bit Next Protocol field. The Next Protocol field, when present, uses 8 bits of the field allocated to the echo-noncing and map-versioning features. The two features are still available, albeit with a reduced length of Nonce and Map-Version.

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.

This document uses terms already defined in .

As described in the introduction, the LISP header has no protocol identifier that indicates the type of payload being carried. Because of this, LISP is limited to carry IP payloads. The LISP header contains a series of flags (some defined, some reserved), a Nonce/Map-version field and an instance ID/Locator-status-bit field. The flags provide flexibility to define how the various fields are encoded. Notably, Flag bit 5 is the last reserved bit in the LISP header.

This document defines the following changes to the LISP header in order to support multi-protocol encapsulation: Flag bit 5 is defined as the Next Protocol bit. The P bit MUST be set to 1 to indicate the presence of the 8 bit next protocol field. P = 0 indicates that the payload MUST conform to LISP as defined in . Flag bit 5 was chosen as the P bit because this flag bit is currently unallocated. The lower 8 bits of the first 32-bit word are used to carry a Next Protocol. This Next Protocol field contains the protocol of the encapsulated payload packet. LISP uses the lower 24 bits of the first word for either a nonce, an echo-nonce, or to support map-versioning . These are all optional capabilities that are indicated in the LISP header by setting the N, E, and the V bit respectively. When the P-bit and the N-bit are set to 1, the Nonce field is the middle 16 bits. When the P-bit and the V-bit are set to 1, the Version field is the middle 16 bits. When the P-bit is set to 1 and the N-bit and the V-bit are both 0, the middle 16-bits are set to 0. This draft defines the following Next Protocol values: IPv4 IPv6 Ethernet Network Service Header

LISP-GPE uses the same UDP destination port (4341) allocated to LISP. A LISP-GPE router MUST not encapsulate non-IP packets to a LISP router. A method for determining the capabilities of a LISP router (GPE or "legacy") is out of the scope of this draft. When encapsulating IP packets to a LISP "legacy" router the P bit MUST be set to 0.

When a LISP-GPE router performs Ethernet encapsulation, the inner 802.1Q [IEEE8021Q] priority code point (PCP) field MAY be mapped from the encapsulated frame to the Type of Service field in the outer IPv4 header, or in the case of IPv6 the 'Traffic Class' field.

When a LISP-GPE router performs Ethernet encapsulation, the inner header 802.1Q [IEEE8021Q] VLAN Identifier (VID) MAY be mapped to, or used to determine the LISP Instance ID field.

IANA is requested to set up a registry of LISP-GPE "Next Protocol". These are 8-bit values. Next Protocol values in the table below are defined in this draft. New values are assigned via Standards Action . Next Protocol Description Reference 0 Reserved This Document 1 IPv4 This Document 2 IPv6 This Document 3 Ethernet This Document 4 NSH This Document 5..255 Unassigned

LISP-GPE security considerations are similar to the LISP security considerations documented at length in . With LISP-GPE, issues such as dataplane spoofing, flooding, and traffic redirection may depend on the particular protocol payload encapsulated.

A special thank you goes to Dino Farinacci for his guidance and detailed review.