Extensions to IS-IS for Layer-2 Systems
Extracted elements (17)
Layer-2 routing technologies such as RBridges, 802.1aq, and OTV encapsulate classical Layer-2 packets with an outer header and route them using IS-IS link state PDUs carrying Layer-2 addresses. This document provides the common IS-IS TLV infrastructure these technologies share.
The TLVs defined in this document are intentionally generic Layer-2 additions; technology-specific extensions (e.g., for TRILL/RBridges, 802.1aq, OTV) are expected to define additional sub-TLVs or TLVs as needed. This document does not propose any new forwarding mechanisms.
The MAC-RI TLV is carried in LSPs (not IIH or SNP PDUs) and may be carried multiple times within a single LSP and across multiple LSPs.
The MT-PORT-CAP TLV may occur multiple times and is carried exclusively within IS-IS Hello (IIH) PDUs, not in LSPs or SNPs.
The 4-bit RESV field in the MAC-RI TLV MUST be sent as zero and ignored on receipt.
The 4 reserved bits (R) in the MT-PORT-CAP TLV MUST be sent as zero and ignored on receipt.
The Confidence field in the MAC-RI TLV, if not used by the specific protocol, MUST be set to zero on transmission and be ignored on receipt.
The MAC-RI TLV MUST contain only unicast MAC addresses.
The Confidence field in MAC-RI is an 8-bit quantity indicating the confidence level in the advertised MAC addresses. Its semantics are defined by the specific Layer-2 technology using this TLV.
The MAC-Reachability (MAC-RI) TLV is IS-IS TLV type 147. It carries a Topology-id/Nickname (2 bytes), a Confidence byte, a 4-bit RESV field, a 12-bit VLAN-ID, and one or more 48-bit unicast MAC addresses (6 bytes each). It is carried in IS-IS LSPs.
The Multi-Topology-aware Port Capability (MT-PORT-CAP) TLV is IS-IS TLV type 143. It carries a 12-bit Topology Identifier (MT ID) and a set of sub-TLVs formatted per RFC 5305, and is carried within IS-IS Hello (IIH) PDUs.
The Topology Identifier field in MT-PORT-CAP is 12 bits; when set to zero, it indicates the TLV carries base topology information. Similarly, a zero Topology-id/Nickname in MAC-RI implies MAC addresses are reachable across all topologies or nicknames of the originating IS.
The VLAN-ID field in MAC-RI is 12 bits and applies to all subsequent MAC addresses in the same TLV instance. A value of zero indicates no VLAN is specified.
This document registers two new IS-IS TLV codepoints in the IS-IS TLV codepoint registry: MT-Port-Cap-TLV (type 143), valid in IIH PDUs only, and MAC-RI TLV (type 147), valid in LSP PDUs only.
This document adds no additional security risks to IS-IS, nor does it provide any additional security for IS-IS. Implementors should rely on existing IS-IS security mechanisms.
MAC-RI TLV (type 147) value field encoding: 2-byte Topology-id/Nickname, 1-byte Confidence, 2-byte field with 4-bit RESV and 12-bit VLAN-ID, then N MAC addresses of 6 bytes each. Total length is 5 + 6*n bytes.
MT-PORT-CAP TLV (type 143) encoding: 1-byte Type, 1-byte Length, 2-byte field with 4 reserved bits (R) followed by a 12-bit Topology Identifier, then variable-length sub-TLVs. Total value field length includes sub-TLV bytes.