Standard TLVs

IS-IS uses Type-Length-Value (TLV) encoding. SPBM employs IS-IS as the interior gateway protocol and implements additional TLVs to support additional functionality. The switch also supports Sub-TLVs. TLVs exist inside IS-IS packets and Sub-TLVs exist as additional information in TLVs.

The switch supports and is in full compliance with standard 802.1 aq TLVs. The IEEE ratified the 802.1aq standard that defines SPBM and the Type-Length-Value (TLV) encoding that IS-IS uses to support SPBM services. The following table lists all the TLVs that the switch supports.

Table 1. Standard TLVs

TLV

Description

Usage

1

Area addresses — The Area Addresses TLV contains the area addresses to which the IS-IS is connected.

IS-IS area

22

Extended IS reachability — The Extended IS Reachability TLV contains information about adjacent neighbors.

IS-IS adjacencies

Sub-TLV 29: SPBM link metric is carried within this TLV.

129

Protocols supported — The Protocol supported TLV carries the Network Layer Protocol Identifiers (NLPID) for the Network Layer protocols where the IS-IS can be used.

SPBM in addition to existing NLPID (IPV4 0xCC, IPV6 0x*E..), IEEE 802.1aq defined SPBM NLPID as 0xC1.

135

Extended IP reachability — The Extended IP Reachability TLV 135 is used to distribution IP reachability between IS-IS peers.

SPBM uses this existing IS-IS TLV to carry IP Shortcut routes in the Global Routing Table (GRT).

143

Multi-topology port aware capability (MT-Port-Capability) TLV

This TLV carries the SPB instance ID in a multiple SPB instances environment. This TLV is carried within IS-IS Hello Packets (IIH), only when parallel links exist.

This TLV carries the following SPBM Sub TLV:

  • Sub-TLV 6: SPB B-VID Sub TLV indicates the mapping between a VLAN and its equal cost tree (ECT) algorithm. To form an adjacency, both nodes must have a matching primary (B-VLAN, ECT) pair, and secondary (B-VLAN, ECT) pair, the number of B-VLANs must be equal, B-VLAN values must match, ECT values for the B-VLANs must match. Used in IS-IS Hellos only.

  • MCID Sub TLV: The MCID is a digest of the VLANs and MSTI. Neighboring SPBM nodes must agree on the MCID to form an adjacency. The MCID is set to all zeros (0).

    After the switch receives a non-zero MCID Sub TLV, it reflects content back to the neighbor.

  • Link L1 Metric Sub-TLV 7: Contains L1 metric of the link

144

Multi-topology Capability (MT-Capability) TLV.

This TLV carries the SPB instance ID in a multiple SPB instance environment. This TLV is carried within LSPs.

In multicast over Fabric Connect, TLV 144 on the BEB bridge, where the sender is located, has the transmit (Tx) bit set. On the BEB bridge, where the receiver is located the receive (Rx) bit is set.

TLV 144 is the service identifier TLV. TLV 144 advertizes B-MAC and I-SID information.

This TLV carries the following Sub TLVs:

Sub-TLV 1: SPB instance Sub TLV contains a unique SPSourceID (nickname) to identify the SPBM node within this SPB topology.

Sub-TLV 3: SPB Service ID (I-SID) is stored in TLV 144 sub-TLV 3. Sub-TLV 3 carries service group membership (I-SIDs) for a particular SPBM B-VLAN.

184

SPBM IP VPN reachability — IS-IS TLV 184 is used to advertise SPBM L3 VSN route information across the SPBM cloud.

IP reachability for Layer 3 VSNs

185

IPVPN multicast TLV with IPMC sub TLV — The IPVPN multicast TLV contains information about the scope I-SID.

TLV 185 on the BEB bridge, where the source is located, displays the multicast source and group addresses and has the transmit (Tx) bit set. Each multicast group has its own data I-SID that maps to the source and group addresses.

As part of the IPVPN TLV, sub-TLVs define IPv4 unicast, IPv6 unicast and IPv4 multicast information.

Layer 2 VSN IP multicast over Fabric Connect and Layer 3 VSN IP multicast over Fabric Connect (using VRF) use TLV 185.

186

IP multicast TLV (GRT) — TLV 186 on the BEB bridge, where the source is located, displays the multicast source and group addresses and has the transmit (Tx) bit set. Each multicast group has its own data I-SID that maps to the source and group addresses.

IP Shortcuts with IP multicast over Fabric Connect use TLV 186.

All multicast streams are constrained within the level in which they originate, which is called the scope level.

236

IPv6 Reachability — The IPv6 reachability TLV 236 is used to distribute IPv6 network reachability between IS-IS peers.

SPBM uses the existing IS-IS TLV to carry IPv6 shortcut routes through the SPBM core.

For more information on IP multicast over Fabric Connect, see IP Multicast over Fabric Connect.