IS-IS Extensions Supporting IEEE 802.1aq Shortest Path Bridging
RFC 6329
| Document | Type | RFC - Proposed Standard (April 2012; Errata) | |
|---|---|---|---|
| Authors | Paul Unbehagen , Nigel Bragg , David Allan , Don Fedyk , Peter Ashwood-Smith | ||
| Last updated | 2020-01-21 | ||
| Stream | Internet Engineering Task Force (IETF) | ||
| Formats | plain text html pdf htmlized with errata bibtex | ||
| Reviews | |||
| Stream | WG state | WG Document | |
| Document shepherd | No shepherd assigned | ||
| IESG | IESG state | RFC 6329 (Proposed Standard) | |
| Action Holders |
(None)
|
||
| Consensus Boilerplate | Unknown | ||
| Telechat date | |||
| Responsible AD | Stewart Bryant | ||
| IESG note | David Ward (dward@juniper.net) is the document shepherd. | ||
| Send notices to | (None) | ||
Internet Engineering Task Force (IETF) D. Fedyk, Ed.
Request for Comments: 6329 Alcatel-Lucent
Category: Standards Track P. Ashwood-Smith, Ed.
ISSN: 2070-1721 Huawei
D. Allan
Ericsson
N. Bragg
Ciena Limited
P. Unbehagen
Avaya
April 2012
IS-IS Extensions Supporting IEEE 802.1aq Shortest Path Bridging
Abstract
802.1aq Shortest Path Bridging (SPB) has been standardized by the
IEEE as the next step in the evolution of the various spanning tree
and registration protocols. 802.1aq allows for true shortest path
forwarding in a mesh Ethernet network context utilizing multiple
equal cost paths. This permits it to support much larger Layer 2
topologies, with faster convergence, and vastly improved use of the
mesh topology. Combined with this is single point provisioning for
logical connectivity membership, which includes point-to-point,
point-to-multipoint, and multipoint-to-multipoint variations. This
memo documents the IS-IS changes required to support this IEEE
protocol and provides some context and examples.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc6329.
Fedyk, et al. Standards Track [Page 1]
RFC 6329 IS-IS Support of IEEE 802.1aq April 2012
Copyright Notice
Copyright (c) 2012 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.
Fedyk, et al. Standards Track [Page 2]
RFC 6329 IS-IS Support of IEEE 802.1aq April 2012
Table of Contents
1. Introduction ....................................................4
2. Terminology .....................................................4
3. Conventions Used in This Document ...............................5
4. 802.1aq Overview ................................................6
4.1. Multi-Topology Support .....................................8
4.2. Data Path SPBM - Unicast ...................................8
4.3. Data Path SPBM - Multicast (Head-End Replication) ..........9
4.4. Data Path SPBM - Multicast (Tandem Replication) ............9
4.5. Data Path SPBV Broadcast ..................................11
4.6. Data Path SPBV Unicast ....................................11
4.7. Data Path SPBV Multicast ..................................12
5. SPBM Example ...................................................12
6. SPBV Example ...................................................14
7. SPB Supported Adjacency types ..................................16
8. SPB IS-IS Adjacency Addressing .................................16
9. IS-IS Area Address and SYSID ...................................17
10. Level 1/2 Adjacency ...........................................17
11. Shortest Path Default Tie-Breaking ............................17
12. Shortest Path ECT .............................................18
13. Hello (IIH) Protocol Extensions ...............................19
13.1. SPB-MCID Sub-TLV .........................................20
13.2. SPB-Digest Sub-TLV .......................................21
13.3. SPB Base VLAN Identifiers (SPB-B-VID) Sub-TLV ............23
14. Node Information Extensions ...................................24
14.1. SPB Instance (SPB-Inst) Sub-TLV ..........................24
14.1.1. SPB Instance Opaque ECT-ALGORITHM
(SPB-I-OALG) Sub-TLV ..............................28
15. Adjacency Information Extensions ..............................29
15.1. SPB Link Metric (SPB-Metric) Sub-TLV .....................29
15.1.1. SPB Adjacency Opaque ECT-ALGORITHM
(SPB-A-OALG) Sub-TLV ..............................30
16. Service Information Extensions ................................30
16.1. SPBM Service Identifier and Unicast Address
(SPBM-SI) Sub-TLV ........................................30
16.2. SPBV MAC Address (SPBV-ADDR) Sub-TLV .....................32
17. Security Considerations .......................................34
18. IANA Considerations ...........................................34
19. References ....................................................35
19.1. Normative References .....................................35
19.2. Informative References ...................................36
20. Acknowledgments ...............................................36
Fedyk, et al. Standards Track [Page 3]
RFC 6329 IS-IS Support of IEEE 802.1aq April 2012
1. Introduction
802.1aq Shortest Path Bridging (SPB) [802.1aq] has been standardized
by the IEEE as the next step in the evolution of the various spanning
tree and registration protocols. 802.1aq allows for true shortest
path forwarding in an Ethernet mesh network context utilizing
multiple equal cost paths. This permits SPB to support much larger
Layer 2 topologies, with faster convergence, and vastly improved use
of the mesh topology. Combined with this is single point
provisioning for logical connectivity membership, which includes
point-to-point (E-LINE), point-to-multipoint (E-TREE), and
multipoint-to-multipoint (E-LAN) variations.
The control protocol for 802.1aq is IS-IS [IS-IS] augmented with a
small number of TLVs and sub-TLVs. This supports two Ethernet
encapsulating data paths, 802.1ad (Provider Bridges) [PB] and 802.1ah
(Provider Backbone Bridges) [PBB]. This memo documents those TLVs
while providing some overview.
Note that 802.1aq requires no state machine or other substantive
changes to [IS-IS]. 802.1aq simply requires a new Network Layer
Protocol Identifier (NLPID) and set of TLVs. In the event of
confusion between this document and [IS-IS], [IS-IS] should be taken
as authoritative.
2. Terminology
In addition to well-understood IS-IS terms, this memo uses
terminology from IEEE 802.1 and introduces a few terms:
802.1ad Provider Bridges (PBs) - Q-in-Q encapsulation
802.1ah Provider Backbone Bridges (PBBs), MAC-IN-MAC
encapsulation
802.1aq Shortest Path Bridging (SPB)
Base VID VID used to identify a VLAN in management operations
B-DA Backbone Destination Address 802.1ah PBB
B-MAC Backbone MAC Address
B-SA Backbone Source Address in 802.1ah PBB header
B-VID Backbone VLAN ID in 802.1ah PBB header
B-VLAN Backbone Virtual LAN
BPDU Bridge PDU
BridgeID 64-bit quantity = (Bridge Priority:16)<<48 | SYSID:48
BridgePriority 16-bit relative priority of a node for tie-breaking
C-MAC Customer MAC. Inner MAC in 802.1ah PBB header
C-VID Customer VLAN ID
ECT-ALGORITHM 32-bit unique ID of an SPF tie-breaking set of rules
ECT-MASK 64-bit mask XORed with BridgeID during tie-breaking
E-LAN Bidirectional Logical Connectivity between >2 UNIs
Fedyk, et al. Standards Track [Page 4]
RFC 6329 IS-IS Support of IEEE 802.1aq April 2012
E-LINE Bidirectional Logical Connectivity between two UNIs
E-TREE Asymmetric Logical Connectivity between UNIs
FDB Filtering Database: {DA/VID}->{next hops}
I-SID Ethernet Services Instance Identifier used for
Logical Grouping for E-LAN/LINE/TREE UNIs
LAN Local Area Network
LSDB Link State Database
LSP Link State PDU
MAC Media Access Control
MAC-IN-MAC Ethernet in Ethernet framing as per 802.1ah [PBB]
MDT Multicast Distribution Tree
MMRP Multiple MAC Registration Protocol 802.1ak [MMRP]
MT Multi-Topology. As used in [MT]
MT ID Multi-Topology Identifier (12 bits). As used in [MT]
NLPID Network Layer Protocol Identifier: IEEE 802.1aq= 0xC1
NNI Network-Network Interface
Q-in-Q Additional S-VID after a C-VID (802.1ad) [PB]
PBB Provider Backbone Bridge - forwards using PBB
Ingress Check Source Forwarding Check - drops misdirected frames
(S,G) Source & Group - identity of a source-specific tree
(*,G) Any Source & Group - identity of a shared tree
S-VID Service VLAN ID
SA Source Address
SPB Shortest Path Bridging - generally all of 802.1aq
SPB Shortest Path Bridge - device implementing 802.1aq
SPB-instance Logical SPB instance correlated by MT ID
SPBM Device implementing SPB MAC mode
SPBV Device implementing SPB VID mode
SPSourceID 20-bit identifier of the source of multicast frames
SPT Shortest Path Tree computed by one ECT-ALGORITHM
SPT Region A set of SPBs with identical VID usage on their NNIs
SPVID Shortest Path VLAN ID: a C-VID or S-VID that
identifies the source
STP Spanning Tree Protocol
UNI User-Network Interface: customer-to-SPB attach point
VID VLAN ID: 12-bit logical identifier after MAC header
VLAN Virtual LAN: a logical network in the control plane
3. Conventions Used in This Document
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 [RFC2119].
The lowercase forms with an initial capital "Must", "Must Not",
"Shall", "Shall Not", "Should", "Should Not", "May", and "Optional"
in this document are to be interpreted in the sense defined in
Fedyk, et al. Standards Track [Page 5]
RFC 6329 IS-IS Support of IEEE 802.1aq April 2012
[RFC2119], but are used where the normative behavior is defined in
documents published by SDOs other than the IETF.
4. 802.1aq Overview
This section provides an overview of the behavior of [802.1aq] and is
not intended to be interpreted as normative text. For the definitive
behavior, the reader should consult [802.1aq]. Nonetheless,
lowercase forms with initial capitalization of the conventions in RFC
2119 are used in this section to give the reader an indication of the
intended normative behaviors as above.
802.1aq utilizes 802.1Q-based Ethernet bridging. The filtering
database (FDB) is populated as a consequence of the topology computed
from the IS-IS database. For the reader unfamiliar with IEEE
terminology, the definition of Ethernet behavior is almost entirely
in terms of "filtering" (of broadcast traffic) rather than
"forwarding" (the explicit direction of unicast traffic). This
document uses the generic term "forwarding", and it has to be
understood that these two terms simply represent different ways of
expressing the same behaviors.
802.1aq supports multiple modes of operation depending on the type of
data plane and the desired behavior. For the initial two modes of
802.1aq (SPBV and SPBM), routes are shortest path, are forward- and
reverse-path symmetric with respect to any source/destination pair
within the SPB domain, and are congruent with respect to unicast and
multicast. Hence, the shortest path tree (SPT) to a given node is
congruent with the multicast distribution tree (MDT) from a given
node. The MDT for a given VLAN is a pruned subset of the complete
MDT for a given node that is identical to its SPT. Symmetry and
congruency preserve packet ordering and proper fate sharing of
Operations, Administration, and Maintenance (OAM) flows by the
forwarding path. Such modes are fully supported by existing
[802.1ag] and [Y.1731] OAM mechanisms.
VLANs provide a natural delineation of service instances. 802.1aq
supports two modes, SPB VID (SPBV) and SPB MAC (SPBM). In SPBV,
multiple VLANS can be used to distribute load on different shortest
path trees (each computed by a different tie-breaking rule) on a
service basis. In SPBM, service instances are delineated by I-SIDs
but VLANs again can be used to distribute load on different shortest
path trees.
There are two encapsulation methods supported. SPBM can be used in a
PBB network implementing PBB (802.1ah [PBB]) encapsulation. SPBV can
be used in PB networks implementing VLANs, PB (802.1aq [PB]), or PBB
Fedyk, et al. Standards Track [Page 6]
RFC 6329 IS-IS Support of IEEE 802.1aq April 2012
encapsulation. The two modes can co-exist simultaneously in an SPB
network.
The practical design goals for SPBV and SPBM in the current 802.1aq
specification are networks of size 100 nodes and 1000 nodes
respectively. However, since SPBV can be sparsely used in an SPB
region it can simply span a large SPB region with a small number of
SPVIDs.
In SPBM and SPBV each bridge has at least one unique "known" MAC
address which is advertised by IS-IS in the SYSID.
In the forwarding plane, SPBM uses the combination of one or more
B-VIDs and "known" Backbone-MAC (B-MAC) addresses that have been
advertised in IS-IS. The term Backbone simply implies an
encapsulation that is often used in the backbone networks, but the
encapsulation is useful in other types of networks where hiding
C-MACs is useful.
The SPBM filtering database (FDB) is computed and installed for
unicast and multicast MAC addresses, while the SPBV filtering
database is computed and installed for unidirectional VIDs (referred
to as SPVIDs), after which MAC reachability is learned (exactly as in
bridged Ethernet) for unicast MACs.
Both SPBV and SPBM use source-specific multicast trees. If they
share the same ECT-ALGORITHM (32-bit worldwide unique definition of
the computation), the tree is the same SPT. For SPBV, (S,G) is
encoded by a source-specific VID (the SPVID) and a standard Group MAC
address. For SPBM, (S,G) is encoded in the destination B-MAC address
as the concatenation of a 20-bit SPB wide unique nodal nickname
(referred to as the SPSourceID) and the 24-bit I-SID together with
the B-VID that corresponds to the ECT-ALGORITHM network wide.
802.1aq supports membership attributes that are advertised with the
I-SID (SPBM) or Group Address (SPBV) that defines the group.
Individual members can be transmitters (T) and/or receivers (R)
within the group, and the multicast state is appropriately sized to
these requests. Multicast group membership is possible even without
transmit membership by performing head-end replication to the
receivers thereby eliminating transit multicast state entirely.
Some highly connected mesh networks provide for path diversity by
offering multiple equal cost alternatives between nodes. Since
congruency and symmetry Must be honored, a single tree may leave some
links under-utilized. By using different deterministic tie-breakers,
up to 16 shortest paths of arbitrary diversity are possible between
any pair of nodes. This distributes the traffic on a VLAN basis.
Fedyk, et al. Standards Track [Page 7]
RFC 6329 IS-IS Support of IEEE 802.1aq April 2012
SPBV and SPBM May share a single SPT with a single ECT-ALGORITHM or
use any combination of the 16 ECT-ALGORITHMs. An extensible
framework permits additional or alternative algorithms with other
properties and parameters (e.g., ECMP, (*,G)) to also be supported
without any changes in this or the IEEE documents.
4.1. Multi-Topology Support
SPB incorporates the multi topology features of [MT] thereby allowing
multiple logical SPB instances within a single IS-IS instance.
To accomplish this, all SPB-related information is either explicitly
or implicitly associated with a Multi-Topology Identifier (MT ID).
SPB information related to a given MT ID thus forms a single logical
SPB instance.
Since SPB has its own adjacency metrics and those metrics are also
associated with an MT ID, it is possible to have different adjacency
metrics (or infinite metrics) for SPB adjacencies that are not only
distinct from IP or other NLPIDs riding in this IS-IS instance, but
also distinct from those used by other SPB instances in the same
IS-IS instance.
Data plane traffic for a given MT ID is intrinsically isolated by the
VLANs assigned to the SPB instance in question. Therefore, VLANs
(represented by VIDs in TLVs and in the data plane) Must Not overlap
between SPB instances (regardless of how the control planes are
isolated).
The [MT] mechanism when applied to SPB allows different routing
metrics and topology subsets for different classes of services.
The use of [MT] other than the default MT ID #0 is completely
OPTIONAL.
The use of [MT] to separate SPB from other NLPIDs is also OPTIONAL.
4.2. Data Path SPBM - Unicast
Unicast frames in SPBM are encapsulated as per 802.1ah [PBB]. A
Backbone Source Address (B-SA), Backbone Destination Address (B-DA),
Backbone VLAN ID (B-VID), and an I-Component Service Instance ID
(I-TAG) are used to encapsulate the Ethernet frame. The B-SA is a
B-MAC associated with the ingress 802.1aq bridge, usually the "known"
B-MAC of that entire bridge. The B-DA is one of the "known" B-MACs
associated with the egress 802.1aq bridge. The B-VID and I-TAG are
mapped based on the physical or logical UNI port (untagged, or tagged
either by S-TAG or C-TAG) being bridged. Normal learning and
Fedyk, et al. Standards Track [Page 8]
RFC 6329 IS-IS Support of IEEE 802.1aq April 2012
broadcast to unknown C-MACs is applied as per [PBB] at the
ingress/egress SPBs only.
Unlike [PBB] on a (*,G) tree, the B-DA forwarding on tandem nodes
(NNI to NNI) is performed without learning. Instead, the output of
802.1aq computations, based on the TLVs specified in this document,
is used to populate the filtering databases (FDBs). The FDB entries
map {B-DA, B-VID} to an outgoing interface and are only populated
from the IS-IS database and computations.
The B-SA/B-VID is checked on tandem nodes against the ingress port.
If the B-SA/B-VID (as a destination) entry in the FDB does not point
to the port on which the packet arrived, the packet is discarded.
This is referred to as an ingress check and serves as a very powerful
loop mitigation mechanism.
4.3. Data Path SPBM - Multicast (Head-End Replication)
Head-end replication is supported for instances where there is a
sparse community of interest or a low likelihood of multicast
traffic. Head-end replication requires no multicast state in the
core. A UNI port wishing to use head-end replication Must Not
advertise its I-SID membership with the Transmit (T) bit set but
instead Must locally and dynamically construct the appropriate
unicast serial replication to all the other receivers (Receive (R)
bit set) of the same I-SID.
When an unknown customer unicast or a multicast frame arrives at an
SPBM User-Network Interface (UNI) port that has been configured to
replicate only at the head end, the packet is replicated once for
each receiver, encapsulated, and sent as a unicast frame. The set of
receivers is determined by inspecting the IS-IS database for other
SPBs that have registered interest in the same I-SID with the R bit
set. This R bit / I-SID pair is found in the SPBM Service Identifier
and Unicast Address (SPBM-SI) sub-TLV. The packets are encapsulated
as per the SPBM unicast forwarding above.
4.4. Data Path SPBM - Multicast (Tandem Replication)
Tandem replication uses the shortest path tree to replicate frames
only where the tree forks and there is at least one receiver on each
branch. Tandem replication is bandwidth efficient but uses multicast
FDB entries (state) in core bridges, which might be unnecessary if
there is little multicast traffic demand. The head-end replication
mode is best suited for the case where there is little or no true
multicast traffic for an I-SID. Tandem replication is triggered on
transit nodes when the I-SID is advertised with the T bit set.
Fedyk, et al. Standards Track [Page 9]
RFC 6329 IS-IS Support of IEEE 802.1aq April 2012
Broadcast, unknown unicast, or multicast frames arriving at an SPBM
UNI port are encapsulated with a B-DA multicast address that uniquely
identifies the encapsulating node (the root of the Multicast
Distribution Tree) and the I-SID scoping this multicast.
This B-DA address is a well-formed multicast group address (as per
802.1Q and 802.1ah) that concatenates the SPSourceID A' with the
I-SID M (written as DA=<A',M> and uniquely identifying the (S,G)
tree). This exact format is given in Figure 1 below:
M L TYP
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1|1|0|0|SPSrcMS| SPSrc [8:15] | SPSrc [0:7] | I-SID [16:23] |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| I-SID [8:15] | I-SID [0:7] |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: SPBM Multicast Address Format
(SPSrcMS represents SPSrc [16:19])
Note: In Figure 1, the index numbering from less significant bit to
more significant bit within a byte or field within a byte gives
the wire order of the bits in the address consistent with the IETF
format in the rest of this document. (The IEEE convention for
number representation reverses the bits within an octet compared
with IETF practice.)
o M is the multicast bit, always set to 1 for a multicast DA. (It
is the lowest bit in the most significant byte.)
o L is the local bit, always set to 1 for an SPBM-constructed
multicast DA.
o TYP is the SPSourceID type. 00 is the only type supported at this
time.
o SPSrc (SPSourceID) is a 20-bit quantity that uniquely identifies a
SPBM node for all B-VIDs allocated to SPBM operation. This is
just the SPSourceID advertised in the SPB Instance (SPB-Inst) sub-
TLV. The value SPSourceID = 0 has special significance; it is
advertised by an SPBM node that has been configured to assign its
SPSourceID dynamically, which requires LSDB synchronization, but
where the SPSourceID assignment has not yet completed.
o I-SID is the 24-bit I-Component Service ID advertised in the SPBM
Service Identifier TLV. It occupies the lower 24 bits of the SPBM
multicast DA. The I-SID value 0xfff is reserved for SPBM control
traffic (refer to the default I-SID in [802.1aq]).
Fedyk, et al. Standards Track [Page 10]
RFC 6329 IS-IS Support of IEEE 802.1aq April 2012
This multicast address format is used as the DA on frames when they
are first encapsulated at ingress to the SPBM network. The DA is
also installed into the FDBs on all SPBM nodes that are on the
corresponding SPT between the source and other nodes that have
registered receiver interest in the same I-SID.
Just as with unicast forwarding, the B-SA/B-VID May be used to
perform an ingress check, but the SPSourceID encoded in the DA and
the "drop-on-unknown" functionality of the FDB in [PBB] achieve the
same effect.
The I-Component at the egress SPBM device has completely standard
[PBB] behavior and therefore will:
1) learn the remote C-SA to B-SA relationship and
2) bridge the original customer frame to the set of local UNI ports
that are associated with the I-SID.
4.5. Data Path SPBV Broadcast
When a packet for an unknown DA arrives at an SPBV UNI port, VID
translation (or VID encapsulation for untagged Frames) with the
corresponding SPVID for this VLAN and ingress SPB is performed.
SPVID forwarding is simply an SPT that follows normal VLAN forwarding
behavior, with the exception that the SPVID is unidirectional. As a
result, shared VLAN learning (SVL) is used between the forward- and
reverse-path SPVIDs associated with the same Base VID to allow SPBV
unicast forwarding to operate in the normal reverse learning fashion.
Ingress check is done by simply verifying that the bridge to which
the SPVID has been assigned is indeed "shortest path" reachable over
the link over which the packet tagged with that SPVID arrived. This
is computed from the IS-IS database and is implied when the SPVID is
associated with a specific incoming port.
4.6. Data Path SPBV Unicast
When a packet for a known DA arrives at an SPBV UNI port, VID
translation (or VID encapsulation for untagged Frames) with the
corresponding SPVID for this VLAN and ingress bridge is performed.
Since the SPVID will have been configured to follow a source-specific
SPT and the DA is known, the packet will follow the source-specific
path towards the destination C-MAC.
Ingress check is as per the previous SPBV section.
Fedyk, et al. Standards Track [Page 11]
RFC 6329 IS-IS Support of IEEE 802.1aq April 2012
4.7. Data Path SPBV Multicast
C-DA multicast addresses May be advertised from SPBV UNI ports.
These may be configured or learned through the Multiple MAC
Registration Protocol (MMRP). MMRP is terminated at the edge of the
SPBV network and IS-IS carries the multicast addresses. Tandem SPBV
devices will check to see if they are on the SPF tree between SPBV
UNI ports advertising the same C-DA multicast address, and if so will
install multicast state to follow the SPBV SPF trees.
Ingress check is as per the previous two SPBV sections.
5. SPBM Example
Consider the small example network shown in Figure 2. Nodes are
drawn in boxes with the last nibble of their B-MAC address :1..:7.
The rest of the B-MAC address nibbles are 4455-6677-00xx. Links are
drawn as "--" and "/", while the interface indexes are drawn as
numbers next to the links. UNI ports are shown as "<==>" with the
desired I-SID shown at the end of the UNI ports as "i1".
+----+ +----+
| :4 | 2 ------1 | :5 | <==> i1
+----+ +----+
1 3 3 2
/ \ / \
1 4 3 2
+----+ +----+ +----+
i1 <==> | :1 | 2----1 | :2 | 2------1 | :3 | <==> i1
+----+ +----+ +----+
3 6 5 3
\ / \ /
3 2 1 2
+----+ +----+
| :6 | 1-------3 | :7 | <==> i1
+----+ +----+
Figure 2: SPBM Example 7-Node Network
Using the default ECT-ALGORITHM (00-80-C2-01), which picks the equal
cost path with the lowest BridgeID, this ECT-ALGORITHM is assigned to
B-VID 100. When all links have the same cost, then the 1-hop
shortest paths are all direct and the 2-hop shortest paths (which are
of course symmetric) are as follows:
{ 1-2-3, 1-2-5, 1-2-7, 6-2-5,
4-2-7, 4-1-6, 5-2-7, 6-2-3, 4-2-3 }
Fedyk, et al. Standards Track [Page 12]
RFC 6329 IS-IS Support of IEEE 802.1aq April 2012
Node :1's unicast forwarding table therefore routes toward B-MACs :7,
:3, and :5 via interface/2, while its single-hop paths are all direct
as can be seen from its FDB given in Figure 3.
Node :1 originates multicast since it is at the head of the MDT to
nodes :3, :5, and :7 and is a transmitter of I-SID 1, which nodes :3,
:5, and :7 all wish to receive. Node :1 therefore produces a
multicast forwarding entry whose DA contains its SPSourceID (which is
the last 20 bits of the B-MAC in the example) and the I-SID 1. Node
:1 thereafter sends packets matching this entry to interface if/2
with B-VID=100. Node :1's full unicast (U) and multicast (M) table
is shown in Figure 3. Note that the IN/IF (incoming interface) field
is not specified for unicast traffic, and for multicast traffic has
to point back to the root of the tree, unless it is the head of the
tree -- in which case, we use the convention if/00. Since node :1 is
not transit for any multicast, it only has a single entry for the
root of its tree for I-SID=1.
+-------+-------------------+------+-----------------+
| IN/IF | DESTINATION ADDR | BVID | OUT/IF(s) |
+-------+-------------------+------+-----------------+
U| if/** | 4455-6677-0002 | 0100 | {if/2 }
U| if/** | 4455-6677-0003 | 0100 | {if/2 }
U| if/** | 4455-6677-0004 | 0100 | {if/1 }
U| if/** | 4455-6677-0005 | 0100 | {if/2 }
U| if/** | 4455-6677-0006 | 0100 | {if/3 }
U| if/** | 4455-6677-0007 | 0100 | {if/2 }
M| if/00 | 7300-0100-0001 | 0100 | {if/2 }
Figure 3: SPBM Node :1 FDB - Unicast (U) and Multicast (M)
Node :2, being at the center of the network, has direct 1-hop paths
to all other nodes; therefore, its unicast FDB simply sends packets
with the given B-MAC/B-VID=100 to the interface directly to the
addressed node. This can be seen by looking at the unicast entries
(the first 6) shown in Figure 4.
Fedyk, et al. Standards Track [Page 13]
RFC 6329 IS-IS Support of IEEE 802.1aq April 2012
+-------+-------------------+------+-----------------+
| IN/IF | DESTINATION ADDR | BVID | OUT/IF(s) |
+-------+-------------------+------+-----------------+
U| if/** | 4455-6677-0001 | 0100 | {if/1 }
U| if/** | 4455-6677-0003 | 0100 | {if/2 }
U| if/** | 4455-6677-0004 | 0100 | {if/4 }
U| if/** | 4455-6677-0005 | 0100 | {if/3 }
U| if/** | 4455-6677-0006 | 0100 | {if/6 }
U| if/** | 4455-6677-0007 | 0100 | {if/5 }
M| if/01 | 7300-0100-0001 | 0100 | {if/2,if/3,if/5 }
M| if/02 | 7300-0300-0001 | 0100 | {if/1 }
M| if/03 | 7300-0500-0001 | 0100 | {if/1,if/5 }
M| if/05 | 7300-0700-0001 | 0100 | {if/1,if/3 }
Figure 4: SPBM Node :2 FDB Unicast (U) and Multicast (M)
Node :2's multicast is more complicated since it is a transit node
for the 4 members of I-SID=1; therefore, it requires 4 multicast FDB
entries depending on which member it is forwarding/replicating on
behalf of. For example, node :2 is on the shortest path between each
of nodes {:3, :5, :7} and :1. So it must replicate from node :1
I-SID 1 out on interfaces { if/2, if/3 and if/5 } (to reach nodes :3,
:5, and :7). It therefore creates a multicast DA with the SPSourceID
of node :1 together with I-SID=1, which it expects to receive over
interface/1 and will replicate out interfaces { if/2, if/3 and if/5
}. This can be seen in the first multicast entry in Figure 4.
Note that node :2 is not on the shortest path between nodes :3 and :5
nor between nodes :3 and :7; however, it still has to forward packets
to node :1 from node :3 for this I-SID, which results in the second
multicast forwarding entry in Figure 4. Likewise, for packets
originating at nodes :5 or :7, node :2 only has to replicate twice,
which results in the last two multicast forwarding entries in Figure
4.
6. SPBV Example
Using the same example network as Figure 2, we will look at the FDBs
produced for SPBV mode forwarding. Nodes :1, :5, :3, and :7 wish to
transmit and receive the same multicast MAC traffic using multicast
address 0300-0000-000f and at the same time require congruent and
symmetric unicast forwarding. In SPBV mode, the only encapsulation
is the C-TAG or S-TAG, and the MAC addresses SA and DA are reverse-
path learned, as in traditional bridging.
Fedyk, et al. Standards Track [Page 14]
RFC 6329 IS-IS Support of IEEE 802.1aq April 2012
+----+ +----+
| :4 | 2 ------1 | :5 | <==> MMAC ..:f
+----+ +----+
1 3 3 2
/ \ / \
1 4 3 2
+----+ +----+ +----+
MMAC<==> | :1 | 2----1 | :2 | 2------1 | :3 | <==> MMAC ..:f
..:f +----+ +----+ +----+
3 6 5 3
\ / \ /
3 2 1 2
+----+ +----+
| :6 | 1-------3 | :7 | <==> MMAC ..:f
+----+ +----+
Figure 5: SPBV Example 7-Node Network
Assuming the same ECT-ALGORITHM (00-80-C2-01), which picks the equal
cost path with the lowest BridgeID, this ECT-ALGORITHM is assigned to
Base VID 100, and for each node the SPVID = Base VID + Node ID (i.e.,
101, 102..107). When all links have the same cost, then the 1-hop
shortest paths are all direct, and the 2-hop shortest paths (which
are of course symmetric) are as previously given for Figure 2.
Node :1's SPT for this ECT-ALGORITHM is therefore (described as a
sequence of unidirectional paths):
{ 1->4, 1->6, 1->2->3, 1->2->5, 1->2->7 }
The FDBs therefore must have entries for the SPVID reserved for
packets originating from node :1, which in this case is VID=101.
Node :2 therefore has an FDB that looks like Figure 6. In
particular, it takes packets from VID 101 on interface/01 and sends
to nodes :3, :5, and :7 via if/2, if/3, and if/5. It does not
replicate anywhere else because the other nodes (:4 and :6) are
reached by the SPT directly from node :1. The rest of the FDB
unicast entries follow a similar pattern; recall that the shortest
path between :4 and :6 is via node :1, which explains replication
onto only two interfaces from if/4 and if/6. Note that the
destination addresses are wild cards, and SVL exists between these
SPVIDs because they are all associated with Base VID = 100, which
defines the VLAN being bridged.
Fedyk, et al. Standards Track [Page 15]
RFC 6329 IS-IS Support of IEEE 802.1aq April 2012
+-------+-------------------+------+-----------------+
| IN/IF | DESTINATION ADDR | VID | OUT/IF(s) |
+-------+-------------------+------+-----------------+
U| if/01 | ************** | 0101 | {if/2,if/3,if/5 }
U| if/02 | ************** | 0103 | {if/1,if/4,if/6 }
U| if/04 | ************** | 0104 | {if/2,if/5 }
U| if/03 | ************** | 0105 | {if/1,if/5,if/6 }
U| if/06 | ************** | 0106 | {if/2,if/3 }
U| if/05 | ************** | 0107 | {if/1,if/3,if/4 }
Figure 6: SPBV Node :2 FDB Unicast
Now, since nodes :5, :3, :7 and :1 are advertising membership in the
same multicast group address :f, Node 2 requires additional entries
to replicate just to these specific nodes for the given multicast
group address. These additional multicast entries are given below in
Figure 7.
+-------+-------------------+------+-----------------+
| IN/IF | DESTINATION ADDR | VID | OUT/IF(s) |
+-------+-------------------+------+-----------------+
M| if/01 | 0300-0000-000f | 0101 | {if/2,if/3,if/5 }
M| if/02 | 0300-0000-000f | 0103 | {if/1 }
M| if/03 | 0300-0000-000f | 0105 | {if/1,if/5 }
M| if/05 | 0300-0000-000f | 0107 | {if/1,if/3 }
Figure 7: SPBV Node :2 FDB Multicast (M)
7. SPB Supported Adjacency types
IS-IS for SPB currently only supports peer-to-peer adjacencies.
Other link types are for future study. As a result, pseudonodes and
links to/from pseudonodes are not considered as part of the IS-IS SPF
computations and will be avoided if present in the physical topology.
Other NLPIDs MAY of course use them as per normal.
IS-IS for SPB Must use the IS-IS three-way handshake for IS-IS point-
to-point adjacencies described in RFC 5303.
8. SPB IS-IS Adjacency Addressing
The default behavior of 802.1aq is to use the normal IS-IS Ethernet
multicast addresses for IS-IS.
There are however additional Ethernet multicast addresses that have
been assigned for 802.1aq for special use cases. These do not in any
way change the state machinery or packet formats of IS-IS but simply
Fedyk, et al. Standards Track [Page 16]
RFC 6329 IS-IS Support of IEEE 802.1aq April 2012
recommend and reserve different multicast addresses. Refer to
[802.1aq] for additional details.
9. IS-IS Area Address and SYSID
A stand-alone implementation (supporting ONLY the single NLPID=0xC1)
of SPB Must use an IS-IS area address value of 0, and the SYSID Must
be the well-known MAC address of the SPB device.
Non-stand-alone implementations (supporting other NLPIDs) MUST use
the normal IS-IS rules for the establishment of a level 1 domain
(i.e., multiple area addresses are allowed only where immediate
adjacencies share a common area address). Level 2 operations of
course place no such restriction on adjacent area addresses.
10. Level 1/2 Adjacency
SPBV and SPBM will operate within either an IS-IS level 1 or level 2.
As a result, the TLVs specified here MAY propagate in either level 1
or level 2 LSPs. IS-IS SPB implementations Must support level 1 and
May support level 2 operations. Hierarchical SPB is for further
study; therefore, these TLVs Should Not be leaked between level 1 and
level 2.
11. Shortest Path Default Tie-Breaking
The default algorithm is ECT-Algorithm = 00-80-c2-01.
Two mechanisms are used to ensure symmetry and determinism in the
shortest path calculations.
The first mechanism addresses the problem when different ends (nodes)
of an adjacency advertise different values for the SPB-LINK-METRIC.
To solve this, SPB shortest path calculations Must use the maximum
value of the two nodes' advertised SPB-LINK-METRICs when accumulating
and minimizing the (sub)path costs.
The second mechanism addresses the problem when two equal sums of
link metrics (sub)paths are found. To solve this, the (sub)path with
the fewest hops between the fork/join points Must win the tie.
However, if both (sub)paths have the same number of hops between the
fork and join points, then the default tie-breaking Must pick the
path traversing the intermediate node with the lower BridgeID. The
BridgeID is an 8-byte quantity whose upper 2 bytes are the node's
BridgePriority and lower 6 bytes are the node's SYSID.
Fedyk, et al. Standards Track [Page 17]
RFC 6329 IS-IS Support of IEEE 802.1aq April 2012
For example, consider the network in Figure 2 when a shortest path
computation is being done from node :1. Upon reaching node :7, two
competing sub-paths fork at node :1 and join at node :7, the first
via :2 and the second via :6. Assuming that all the nodes advertise
a Bridge Priority of 0, the default tie-breaking rule causes the path
traversing node :2 to be selected since it has a lower BridgeID
{0...:2} than node :6 {0...:6}. Note that the operator may cause the
tie-breaking logic to pick the alternate path by raising the Bridge
Priority of node :2 above that of node :6.
The above algorithm guarantees symmetric and deterministic results in
addition to having the critical property of transitivity (shortest
path is made up of sub-shortest paths).
12. Shortest Path ECT
Standard ECT Algorithms initially have been proposed ranging from
00-80-c2-01 to 00-80-c2-10.
To create diversity in routing, SPB defines 16 variations on the
above default tie-breaking algorithm; these have worldwide unique
designations 00-80-C2-01 through 00-80-C2-10. These designations
consist of the IEEE 802.1 OUI (Organizationally Unique Identifier)
value 00-80-C2 concatenated with indexes 0X01..0X10. These
individual algorithms are implemented by selecting the (sub)path with
the lowest value of:
XOR BYTE BY BYTE(ECT-MASK{ECT-ALGORITHM.index},BridgeID)
Where:
ECT-MASK{17} = { 0x00, 0x00, 0xFF, 0x88,
0x77, 0x44, 0x33, 0xCC,
0xBB, 0x22, 0x11, 0x66,
0x55, 0xAA, 0x99, 0xDD,
0xEE };
XOR BYTE BY BYTE - XORs BridgeID bytes with ECT-MASK
ECT-MASK{1}, since it XORs with all zeros, yields the default
algorithm described above (00-80-C2-01); while ECT-MASK{2}, since it
XORs with a mask of all ones, will invert the BridgeID, essentially
picking the path traversing the largest Bridge ID. The other ECT-
MASKs produce diverse alternatives. In all cases, the
BridgePriority, since it is the most significant part of the
BridgeID, permits overriding the SYSID as the selection criteria and
gives the operator a degree of control on the chosen ECT paths.
Fedyk, et al. Standards Track [Page 18]
RFC 6329 IS-IS Support of IEEE 802.1aq April 2012
To support many other tie-breaking mechanisms in the future, two
opaque ECT TLVs are defined, which may be used to provide parameters
to ECT-ALGORITHMs outside of the currently defined space.
ECT-ALGORITHMs are mapped to VIDs, and then services can be assigned
to those VIDs. This permits a degree of traffic engineering since
service assignment to VID is consistent end to end through the
network.
13. Hello (IIH) Protocol Extensions
IEEE 802.1aq can run in parallel with other network layer protocols
such as IPv4 and IPv6; therefore, failure of two SPB nodes to
establish an adjacency MUST NOT cause rejection of an adjacency for
the purposes of other network layer protocols.
IEEE 802.1aq has been assigned the NLPID value 0xC1 [RFC6328], which
MUST be used by Shortest Path Bridges (SPBs) to indicate their
ability to run 802.1aq. This is done by including this NLPID value
in the IS-IS IIH PDU Protocols Supported TLV (type 129). 802.1aq
frames MUST only flow on adjacencies that advertise this NLPID in
both directions of the IIH PDUs. 802.1aq computations MUST consider
an adjacency that has not advertised 0xC1 NLPID in both directions as
non-existent (infinite link metric) and MUST ignore any IIH SPB TLVs
they receive over such adjacencies.
IEEE 802.1aq augments the normal IIH PDU with three new TLVs, which
like all other SPB TLVs, travel within Multi-Topology [MT] TLVs,
therefore allowing multiple logical instances of SPB within a single
IS-IS protocol instance.
Since SPB can use many VIDs and Must agree on which VIDs are used for
which purposes, the IIH PDUs carry a digest of all the used VIDs (on
the NNIs) referred to as the SPB-MCID TLV, which uses a common and
compact encoding reused from 802.1Q.
SPB neighbors May support a mechanism to verify that the contents of
their topology databases are synchronized (for the purposes of loop
prevention). This is done by exchanging a digest of SPB topology
information (computed over all MT IDs) and taking specific actions on
forwarding entries when the digests indicate a mismatch in topology.
This digest is carried in the Optional SPB-Digest sub-TLV.
Finally, SPB needs to know which SPT Sets (defined by ECT-ALGORITHMs)
are being used by which VIDs, and this is carried in the Base VLAN
Identifiers (SPB-B-VID) sub-TLV.
Fedyk, et al. Standards Track [Page 19]
RFC 6329 IS-IS Support of IEEE 802.1aq April 2012
13.1. SPB-MCID Sub-TLV
This sub-TLV is added to an IIH PDU to indicate the digest for the
multiple spanning tree configuration a.k.a. MCID. This TLV is a
digest of local configuration of which VIDs are running which
protocols. (The information is not to the level of a specific
algorithm in the case of SPB.) This information Must be the same on
all bridges in the SPT Region controlled by an IS-IS instance. The
data used to generate the MCID is populated by configuration and is a
digest of the VIDs allocated to various protocols. Two MCIDs are
carried to allow non-disruptive transitions between configurations
when the changes are non-critical.
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
+-+-+-+-+-+-+-+-+
|Type=SPB-MCID | = 4
+-+-+-+-+-+-+-+-+
| Length | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MCID (51 Bytes) |
| ............... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Aux MCID (51 Bytes) |
| ............... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
o Type: sub-TLV type 4.
o Length: The size of the value defined below (102).
o MCID (51 bytes): The complete MCID defined in IEEE 802.1Q, which
identifies an SPT Region on the basis of matching assignments of
VIDs to control regimes (xSTP, SPBV, SPBM, etc.). Briefly, the
MCID consists of a 1-byte format selector, a 32-byte configuration
name, a 2-byte revision level, and finally a 16-byte signature of
type HMAC-MD5 over an array of 4096 elements that contain
identifiers of the use of the corresponding VID. Refer to Section
13.8 of [802.1aq] for the exact format and procedure. Note that
the use of the VID does not include specification of a specific
SPB ECT-ALGORITHM; rather, it is coarser grain.
o Aux MCID (51 bytes): The complete MCID defined in IEEE 802.1Q,
which identifies an SPT Region. The aux MCID allows SPT Regions
to be migrated by the allocation of new VLAN to FDB Mappings
without interruption to existing traffic.
Fedyk, et al. Standards Track [Page 20]
RFC 6329 IS-IS Support of IEEE 802.1aq April 2012
The SPB-MCID sub-TLV is carried within the MT-Port-Cap TLV [RFC6165]
with the MT ID value of 0, which in turn is carried in an IIH PDU.
13.2. SPB-Digest Sub-TLV
This sub-TLV is Optionally added to an IIH PDU to indicate the
current SPB topology digest value. It is always carried in an
MT-Port-Cap TLV [RFC6165] with an MT ID value of 0. This information
should settle to be the same on all bridges in an unchanging
topology. Matching digests indicate (with extremely high
probability) that the topology view between two SPBs is synchronized;
this match (or lack of match) is used to control the updating of
forwarding information. The SPB Agreement Digest is computed based
on contributions derived from the current topologies of all SPB MT
instances and is designed to change when significant topology changes
occur within any SPB instance.
During the propagation of LSPs, the Agreement Digest may vary between
neighbors until the key topology information in the LSPs is common.
The digest is therefore a summarized means of determining agreement
between nodes on database commonality, and hence of inferring
agreement on the distance to all multicast roots. When present, it
is used for loop prevention as follows: for each shortest path tree
where it has been determined the distance to the root has changed,
"unsafe" multicast forwarding is blocked until the exchanged
Agreement Digests match, while "safe" multicast forwarding is allowed
to continue despite the disagreement in digests and hence topology
views. Section 28.2 of [802.1aq] defines in detail what constitutes
"safe" vs. "unsafe".
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
+-+-+-+-+-+-+-+-+
|Type=SPB-Digest| = 5
+-+-+-+-+-+-+-+-+
| Length | (1 byte)
+-----+-+---+---+
| Res |V| A | D | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Agreement Digest (Length - 1) |
| ............... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
o Type: sub-TLV type 5.
o Length: The size of the value.
o V bit: Agreed digest valid bit. See Section 28.2 of [802.1aq].
Fedyk, et al. Standards Track [Page 21]
RFC 6329 IS-IS Support of IEEE 802.1aq April 2012
o A (2 bits): The Agreement Number 0-3, which aligns with the BPDU's
Agreement Number concept [802.1aq]. When the Agreement Digest for
this node changes, this number is incremented. The node then
checks for Agreement Digest match (as below). The new local
Agreement Number and the updated local Discarded Agreement Number
are then transmitted with the new Agreement Digest to the node's
neighbors in the Hello PDU. Once an Agreement Number has been
sent, it is considered outstanding until a matching or more recent
Discarded Agreement Number is received from the neighbor.
o D (2 bits): The Discarded Agreement Number 0-3, which aligns with
BPDU's Agreement Number concept. When an Agreement Digest is
received from a neighbor, this number is set to the received
Agreement Number to signify that this node has received this new
agreement and discarded any previous ones. The node then checks
whether the local and received Agreement Digests match. If they
do, this node then sets:
the local Discarded Agreement Number = received Agreement Number +
1
If the Agreement Digests match, AND received Discarded Agreement
Number ==
local Agreement Number + N (N = 0 || 1)
then the node has a topology matched to its neighbor.
Whenever the local Discarded Agreement Number relating to a
neighbor changes, the local Agreement Digest, Agreement Number,
and Discarded Agreement Number are transmitted.
o Agreement Digest. This digest is used to determine when SPB is
synchronized between neighbors for all SPB instances. The
Agreement Digest is a hash computed over the set of all SPB
adjacencies in all SPB instances. In other words, the digest
includes all VIDs and all adjacencies for all MT instances of SPB
(but not other network layer protocols). This reflects the fact
that all SPB nodes in a region Must have identical VID allocations
(see Section 13.1), and so all SPB instances will contain the same
set of nodes. The exact procedure for computing the Agreement
Digest and its size are defined in Section 28.2 of [802.1aq].
The SPB-Digest sub-TLV is carried within the MT-Port-Cap TLV
[RFC6165] (with the MT ID value 0), which in turn is carried in an
IIH PDU.
When supported, this sub-TLV MUST be carried on every IIH between SPB
neighbors, not just when a Digest changes.
Fedyk, et al. Standards Track [Page 22]
RFC 6329 IS-IS Support of IEEE 802.1aq April 2012
When one peer supports this TLV and the other does not, loop
prevention by Agreement Digest Must Not be done by either side.
13.3. SPB Base VLAN Identifiers (SPB-B-VID) Sub-TLV
This sub-TLV is added to an IIH PDU to indicate the mappings between
ECT algorithms and Base VIDs (and by implication the VID(s) used on
the forwarding path for each SPT Set for a VLAN identified by a Base
VID) that are in use. Under stable operational conditions, this
information should be the same on all bridges in the topology
identified by the MT-Port-Cap TLV [RFC6165] it is being carried
within.
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
+-+-+-+-+-+-+-+-+
|Type= SPB-B-VID| = 68
+-+-+-+-+-+-+-+-+
| Length | (1 byte)
+-+-+-+-+-+-+-+-+-----------------------------------------------+
| ECT-VID Tuple (1) (6 bytes) |
+---------------------------------+-----------------------------+
| ... | ECT-VID Tuple(2) (6 bytes) |
+---------------------------------+-----------------------------+
| ..... |
+---------------------------------------------------------------+
| ..... |
| ..... |
+---------------------------------------------------------------+
o Type: sub-TLV type 6.
o Length: The size of the value is ECT-VID Tuples*6 bytes. Each
6-byte part of the ECT-VID tuple is formatted 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ECT-ALGORITHM (32 bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Base VID (12 bits) |U|M|RES|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
o ECT-ALGORITHM (4 bytes): The ECT-ALGORITHM is advertised when the
bridge supports a given ECT-ALGORITHM (by OUI/Index) on a given
Base VID. There are 17 predefined IEEE algorithms for SPB with
index values 0X00..0X10 occupying the low 8 bits and the IEEE
OUI=00-80-C2 occupying the top 24 bits of the ECT-ALGORITHM.
Fedyk, et al. Standards Track [Page 23]
RFC 6329 IS-IS Support of IEEE 802.1aq April 2012
o Base VID (12 bits): The Base VID that is associated with the SPT
Set.
o Use-Flag (1 bit): The Use-Flag is set if this bridge, or any
bridge in the LSDB, is currently using this ECT-ALGORITHM and Base
VID. Remote usage is discovered by inspection of the U bit in the
SPB-Inst sub-TLV of other SPB bridges (see Section 14.1)
o M bit (1 bit): The M bit indicates if this Base VID operates in
SPBM (M = 1) or SPBV (M = 0) mode.
The SPB-B-VID sub-TLV is carried within the MT-Port-Cap TLV
[RFC6165], which in turn is carried in an IIH PDU.
14. Node Information Extensions
All SPB nodal information extensions travel within a new multi-
topology capability TLV MT-Capability (type 144).
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
+-+-+-+-+-+-+-+-+
|Type = MT-CAP | = 144
+-+-+-+-+-+-+-+-+
| Length | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|O R R R| MT ID | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(sub-TLVs ... )
The format of this TLV is identical in its first 2 bytes to all
current MT TLVs and carries the MT ID as defined in [MT].
The O (overload) bit carried in bit 16 has the same semantics as
specified in [MT], but in the context of SPB adjacencies only.
There can be multiple MT-Capability TLVs present, depending on the
amount of information that needs to be carried.
14.1. SPB Instance (SPB-Inst) Sub-TLV
The SPB-Inst sub-TLV gives the SPSourceID for this node/topology
instance. This is the 20-bit value that is used in the formation of
multicast DAs for frames originating from this node/instance. The
SPSourceID occupies the upper 20 bits of the multicast DA together
with 4 other bits (see the SPBM 802.1ah multicast DA address format
section). This sub-TLV MUST be carried within the MT-Capability TLV
in the fragment ZERO LSP. If there is an additional SPB instance, it
Fedyk, et al. Standards Track [Page 24]
RFC 6329 IS-IS Support of IEEE 802.1aq April 2012
MUST be declared under a separate MT-Capability TLV and also carried
in the fragment ZERO LSP.
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
+-+-+-+-+-+-+-+-+
|Type = SPB-Inst| = 1
+-+-+-+-+-+-+-+-+
| Length | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| CIST Root Identifier (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| CIST Root Identifier (cont) (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| CIST External Root Path Cost (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Bridge Priority | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|R R R R R R R R R R R|V| SPSourceID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Num of Trees | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| VLAN-ID (1) Tuples (8 bytes) |
| ........................... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
...........................
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| VLAN-ID (N) Tuples (8 bytes) |
| ........................... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where VLAN-ID tuples have the format as:
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
+-+-+-+-+-+-+-+-+
|U|M|A| Res |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ECT-ALGORITHM (32 bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Base VID (12 bits) | SPVID (12 bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
o Type: sub-TLV type 1.
o Length: Total number of bytes contained in the value field.
Fedyk, et al. Standards Track [Page 25]
RFC 6329 IS-IS Support of IEEE 802.1aq April 2012
o CIST Root Identifier (64 bits): The CIST Root Identifier is for
SPB interworking with Rapid STP (RSTP) and Multiple STP (MSTP) at
SPT Region boundaries. This is an imported value from a spanning
tree.
o CIST External Root Path Cost (32 bits): The CIST External Root
Path Cost is the cost to root, derived from the spanning tree
algorithm.
o Bridge Priority (16 bits): Bridge priority is the 16 bits that
together with the 6 bytes of the System ID form the Bridge
Identifier. This allows SPB to build a compatible spanning tree
using link state by combining the Bridge Priority and the System
ID to form the 8-byte Bridge Identifier. The 8-byte Bridge
Identifier is also the input to the 16 predefined ECT tie-breaker
algorithms.
o V bit (1 bit): The V bit (SPBM) indicates this SPSourceID is auto-
allocated (Section 27.11 of [802.1aq]). If the V bit is clear,
the SPSourceID has been configured and Must be unique. Allocation
of SPSourceID is defined in IEEE [802.1aq]. Bridges running SPBM
will allocate an SPSourceID if they are not configured with an
explicit SPSourceID. The V bit allows neighbor bridges to
determine if the auto-allocation was enabled. In the rare chance
of a collision of SPsourceID allocation, the bridge with the
highest priority Bridge Identifier will win conflicts. The lower
priority bridge will be re-allocated; or, if the lower priority
bridge is configured, it will not be allowed to join the SPT
Region.
o SPSourceID: a 20-bit value used to construct multicast DAs as
described below for multicast frames originating from the origin
(SPB node) of the Link State Packet (LSP) that contains this TLV.
More details are in IEEE [802.1aq].
o Number of Trees (8 bits): The Number of Trees is set to the number
of {ECT-ALGORITHM, Base VID plus flags} tuples that follow. Each
ECT-ALGORITHM has a Base VID, an SPVID, and flags described below.
This Must contain at least the one ECT-ALGORITHM (00-80-C2-01).
Each VID Tuple consists of:
o U bit (1 bit): The U bit is set if this bridge is currently using
this ECT-ALGORITHM for I-SIDs it sources or sinks. This is a
strictly local indication; the semantics differ from the Use-Flag
found in the Hello, which will set the Use-Flag if it sees other
nodal U bits are set OR it sources or sinks itself.
Fedyk, et al. Standards Track [Page 26]
RFC 6329 IS-IS Support of IEEE 802.1aq April 2012
o M bit (1 bit): The M bit indicates if this is SPBM or SPBV mode.
When cleared, the mode is SPBV; when set, the mode is SPBM.
o A bit (1 bit): The A bit (SPB), when set, declares this is an
SPVID with auto-allocation. The VID allocation logic details are
in IEEE [802.1aq]. Since SPVIDs are allocated from a small pool
of 12-bit resources, the chances of collision are high. To
minimize collisions during auto-allocation, LSPs are initially
advertised with the originating bridge setting the SPVID to 0.
Only after learning the other bridges' SPVID allocations does this
bridge re-advertise this sub-TLV with a non-zero SPVID. This will
minimize but not eliminate the chance of a clash. In the event of
a clash, the highest Bridge Identifier is used to select the
winner, while the loser(s) with lower Bridge Identifier(s) Must
withdraw their SPVID allocation(s) and select an alternative
candidate for another trial. SPVID May also be configured. When
the A bit is set to not specify auto-allocation and the SPVID is
set to 0, this SPBV bridge is used for transit only within the SPB
region. If a port is configured with the Base VID as a neighbor
using RSTP or MSTP, the bridge will act as an ingress filter for
that VID.
o ECT-ALGORITHM (4 bytes): ECT-ALGORITHM is advertised when the
bridge supports a given ECT-ALGORITHM (by OUI/Index) on a given
VID. This declaration Must match the declaration in the Hello PDU
originating from the same bridge. The ECT-ALGORITHM and Base VID
Must match what is generated in the IIHs of the same node. The
ECT-ALGORITHM, Base VID tuples can come in any order, however.
There are currently 17 worldwide unique 802.1aq defined ECT-
ALGORITHMs given by values 00-80-C2-00 through 00-80-C2-10.
o Base VID (12 bits): The Base VID that associated the SPT Set via
the ECT-ALGORITHM.
o SPVID (12 bits): The SPVID is the Shortest Path VID assigned for
the Base VID to this node when using SPBV mode. It is not defined
for SPBM mode and Must be 0 for SPBM mode B-VIDs.
Fedyk, et al. Standards Track [Page 27]
RFC 6329 IS-IS Support of IEEE 802.1aq April 2012
14.1.1. SPB Instance Opaque ECT-ALGORITHM (SPB-I-OALG) Sub-TLV
There are multiple ECT algorithms defined for SPB; however, for the
future, additional algorithms may be defined including but not
limited to ECMP- or hash-based behaviors and (*,G) multicast trees.
These algorithms will use this Optional TLV to define new algorithm
parametric data. For tie-breaking parameters, there are two broad
classes of algorithm, one that uses nodal data to break ties and one
that uses link data to break ties. This sub-TLV is used to associate
opaque tie-breaking data with a node. This sub-TLV, when present,
MUST be carried within the MT-Capability TLV (along with a valid SPB-
Inst sub-TLV). Multiple copies of this sub-TLV MAY be carried for
different ECT-ALGORITHMs relating to this node.
There are of course many other uses of this opaque data that have yet
to be defined.
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
+-+-+-+-+-+-+-+-+
|Type=SPB-I-OALG| = 2
+-+-+-+-+-+-+-+-+
| Length | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Opaque ECT-ALGORITHM (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Opaque ECT Information (variable) |
| ....................... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
o Type: sub-TLV type 2.
o Length: Total number of bytes contained in the value field.
o ECT-ALGORITHM: ECT-ALGORITHM is advertised when the bridge
supports a given ECT-ALGORITHM (by OUI/Index) on a given VID.
o ECT Information: ECT-ALGORITHM Information of variable length
which SHOULD be in sub-TLV format with an IANA numbering space
where appropriate.
Fedyk, et al. Standards Track [Page 28]
RFC 6329 IS-IS Support of IEEE 802.1aq April 2012
15. Adjacency Information Extensions
15.1. SPB Link Metric (SPB-Metric) Sub-TLV
The SPB-Metric sub-TLV (type 29) occurs within the Multi-Topology
Intermediate System Neighbor (MT-ISN) TLV (type 222) or within the
Extended IS Reachability TLV (type 22). If this sub-TLV is not
present for an IS-IS adjacency, then that adjacency Must not carry
SPB traffic for the given topology instance.
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
+-+-+-+-+-+-+-+-+
|Type=SPB-Metric| = 29
+-+-+-+-+-+-+-+-+
| Length | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SPB-LINK-METRIC | (3 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Num of Ports | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Port Identifier | ( 2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
o Type: sub-TLV type 29.
o Length: Total number of bytes contained in the value field.
o SPB-LINK-METRIC: the administrative cost or weight of using this
link as a 24-bit unsigned number. This metric applies to the use
of this link for SPB traffic only. Smaller numbers indicate lower
weights and are more likely to carry SPB traffic. Only one metric
is allowed per SPB instance per link. If multiple metrics are
required, multiple SPB instances Must be used, either within IS-IS
or within several independent IS-IS instances. If this metric is
different at each end of a link, the maximum of the two values
Must be used in all SPB calculations for the weight of this link.
The maximum SPB-LINK-METRIC value 2^24 - 1 has a special
significance; this value indicates that although the IS-IS
adjacency has formed, incompatible values have been detected in
parameters configured within SPB itself (for example, different
regions), and the link Must Not be used for carrying SPB traffic.
Full details are found in [802.1aq].
o Num of Ports: the number of ports associated with this link.
o Port Identifier: the standard IEEE port identifier used to build a
spanning tree associated with this link.
Fedyk, et al. Standards Track [Page 29]
RFC 6329 IS-IS Support of IEEE 802.1aq April 2012
15.1.1. SPB Adjacency Opaque ECT-ALGORITHM (SPB-A-OALG) Sub-TLV
There are multiple ECT algorithms defined for SPB; however, for the
future, additional algorithms may be defined. The SPB-A-OALG sub-TLV
occurs within the Multi-Topology Intermediate System TLV (type 222)
or the Extended IS Reachability TLV (type 22). Multiple copies of
this sub-TLV MAY be carried for different ECT-ALGORITHMs related to
this adjacency.
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
+-+-+-+-+-+-+-+-+
|Type=SPB-A-OALG| = 30
+-+-+-+-+-+-+-+-+
| Length | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Opaque ECT Algorithm (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Opaque ECT Information (variable) |
| ......................... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
o Type: sub-TLV type 30.
o Length: Total number of bytes contained in the value field.
o ECT-ALGORITHM: ECT-ALGORITHM is advertised when the bridge
supports a given ECT-ALGORITHM (by OUI/Index) on a given VID.
o ECT Information: ECT-ALGORITHM Information of variable length in
sub-TLV format using new IANA type values as appropriate.
16. Service Information Extensions
16.1. SPBM Service Identifier and Unicast Address (SPBM-SI) Sub-TLV
The SPBM-SI sub-TLV (type 3) is used to introduce service group
membership on the originating node and/or to advertise an additional
B-MAC unicast address present on, or reachable by the node.
Fedyk, et al. Standards Track [Page 30]
RFC 6329 IS-IS Support of IEEE 802.1aq April 2012
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
+-+-+-+-+-+-+-+-+
|Type = SPBM-SI | = 3
+-+-+-+-+-+-+-+-+
| Length | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| B-MAC ADDRESS |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| B-MAC ADDRESS (6 bytes) | Res. | Base VID (12 bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|T|R| Reserved | I-SID #1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|T|R| Reserved | I-SID #2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
.................
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|T|R| Reserved | I-SID #n |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
o Type: sub-TLV type 3.
o Length: Total number of bytes contained in the value field.
o B-MAC ADDRESS: a unicast address of this node. It may be the
single nodal address, or it may address a port or any other level
of granularity relative to the node. In the case where the node
only has one B-MAC address, this Should be the same as the SYSID
of the node. To add multiple B-MACs this TLV MUST be repeated per
additional B-MAC.
o Base VID (12 bits): The Base VID associated with the B-BMAC allows
the linkage to the ECT-ALGORITHM and SPT Set defined in the SPB-
Inst sub-TLV.
o I-SID #1 .. #n: 24-bit service group membership identifiers. If
two nodes have an I-SID in common, intermediate nodes on the
unique shortest path between them will create forwarding state for
the related B-MAC addresses and will also construct multicast
forwarding state using the I-SID and the node's SPSourceID to
construct a multicast DA as described in IEEE 802.1aq LSB. Each
I-SID has a Transmit (T) and Receive (R) bit that indicates if the
membership is as a transmitter, a receiver, or both (with both
bits set). In the case where the Transmit (T) and Receive (R)
bits are both zero, the I-SID instance is ignored for the purposes
of distributed multicast computation, but the unicast B-MAC
address Must be processed and installed at nodes providing transit
to that address. If more I-SIDs are associated with a particular
Fedyk, et al. Standards Track [Page 31]
RFC 6329 IS-IS Support of IEEE 802.1aq April 2012
B-MAC than can fit in a single sub-TLV, this sub-TLV can be
repeated with the same B-MAC but with different I-SID values.
o Note: When the T bit is not set, an SPB May still multicast to all
the other receiving members of this I-SID (those advertising with
their R bits set), by configuring edge replication and serial
unicast to each member locally.
The SPBM-SI sub-TLV, when present, MUST be carried within the
MT-Capability TLV and can occur multiple times in any LSP fragment.
16.2. SPBV MAC Address (SPBV-ADDR) Sub-TLV
The SPBV-ADDR sub-TLV is IS-IS sub-TLV type 4. It Should be used for
advertisement of Group MAC addresses in SPBV mode. Unicast MAC
addresses will normally be distributed by reverse-path learning, but
carrying them in this TLV is not precluded. It has the following
format:
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
+-+-+-+-+-+-+-+-+
| Type=SPBV-ADDR| = 4 (1 byte)
+-+-+-+-+-+-+-+-+
| Length | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|R|R| SR| SPVID | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+...+-+-+-+-+-+-+-+-+-+-+-+
|T|R| Reserved | MAC 1 Address | (1+6 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+...+-+-+-+-+-+-+-+-+-+-+-+
...
+-+-+-+-+-+-+-+-+-+-+-+-+...+-+-+-+-+-+-+-+-+-+-+-+
|T|R| Reserved | MAC N Address | (1+6 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+...+-+-+-+-+-+-+-+-+-+-+-+
o Type: sub-TLV type 4.
o Length: Total number of bytes contained in the value field. The
number of MAC address associated with the SPVID is computed by
(Length - 2)/7.
o SR bits (2 bits): The SR bits are the service requirement
parameter from MMRP. The service requirement parameters have the
value 0 (Forward all Groups) and 1 (Forward All Unregistered
Groups) defined. However, this attribute May also be missing. So
the SR bits are defined as 0 not declared, 1 Forward all Groups,
and 2 Forward All Unregistered Groups. The two 'R' reserved bits
Fedyk, et al. Standards Track [Page 32]
RFC 6329 IS-IS Support of IEEE 802.1aq April 2012
immediately preceding these SR bits Shall be set to zero when
originating this sub-TLV and Shall be ignored on receipt.
o SPVID (12 bits): The SPVID and by association Base VID and the
ECT-ALGORITHM and SPT Set that the MAC addresses defined below
will use. If the SPVID is not allocated the SPVID Value is 0.
Note that if the ECT-ALGORITHM in use is spanning tree algorithm
this value Must be populated with the Base VID and the MAC Must be
populated.
o T bit (1 bit): This is the Transmit allowed bit for a following
group MAC address. This is an indication that the Group MAC
address in the context of the SPVID of the bridge advertising this
Group MAC Must be installed in the FDB of transit bridges, when
the bridge computing the trees is on the corresponding ECT-
ALGORITHM shortest path between the bridge advertising this MAC
with the T bit set and any receiver of this Group MAC address. A
bridge that does not advertise this bit set for a MAC address Must
Not cause multicast forwarding state to be installed on other
transit bridges in the network for traffic originating from that
bridge.
o R bit (1 bit): This is the Receive allowed bit for the following
MAC address. This is an indication that MAC addresses as the
receiver Must be populated and installed when the bridge computing
the trees lies on the corresponding shortest path for this ECT-
ALGORITHM between this receiver and any transmitter to this MAC
address. An entry that does not have this bit set for a Group MAC
address is prevented from receiving on this Group MAC address
because transit bridges Must Not install multicast forwarding
state towards it in their FDBs.
o MAC Address (48 bits): The MAC address declares this bridge as
part of the multicast interest for this destination MAC address.
Multicast trees can be efficiently constructed for destination by
populating FDB entries for the subset of the shortest path tree
that connects the bridges supporting the MAC address. This
replaces the function of MMRP for SPTs. The T and R bits above
have meaning as specified above.
The SPBV-ADDR sub-TLV, when present, MUST be carried within the
MT-Capability TLV and can occur multiple times in any LSP fragment.
Fedyk, et al. Standards Track [Page 33]
RFC 6329 IS-IS Support of IEEE 802.1aq April 2012
17. Security Considerations
This document adds no additional security risks to IS-IS, nor does it
provide any additional security for IS-IS when used in a configured
environment or a single-operator domain such as a data center.
However, this protocol may be used in a zero-configuration
environment. Zero configuration may apply to the automatic detection
and formation of an IS-IS adjacency (forming an NNI port). Likewise,
zero configuration may apply to the automatic detection of VLAN-
tagged traffic and the formation of a UNI port, with resultant I-SID
advertisements.
If zero configuration methods are used to autoconfigure NNIs or UNIs,
there are intrinsic security concerns that should be mitigated with
authentication procedures for the above cases. Such procedures are
beyond the scope of this document and are yet to be defined.
In addition, this protocol can create significant amounts of
multicast state when an I-SID is advertised with the T bit set.
Extra care should be taken to ensure that this cannot be used in a
denial-of-service attack [RFC4732] in a zero-configuration
environment.
18. IANA Considerations
Note that the NLPID value 0xC1 [RFC6328] used in the IIH PDUs has
already been assigned by IANA for the purpose of 802.1aq; therefore,
no further action is required for this code point.
Since 802.1aq operates within the IS-IS Multi-Topology framework,
every sub-TLV MUST occur in the context of the proper MT TLV (with
the exception of the SPB-Metric sub-TLV, which MAY travel in TLV 22
where its MT ID is unspecified but implied to be 0). IANA has
allocated sub-TLVs for three Multi-Topology TLVs per 802.1aq. These
are the MT-Port-Cap TLV [RFC6165] used in the IIH, the MT-Capability
TLV (new) used within the LSP, and finally the MT-ISN TLV [MT] used
to contain adjacency information within the LSP.
This document creates the following TLVs and sub-TLVs within the IIH
and LSP PDUs MT TLVs as described below. The '*' indicates new IANA
assignments (per this document). Other entries are shown to provide
context only.
The MT-Capability TLV is the only TLV that required a new sub-
registry. Type value 144 has been assigned, with a starting sub-TLV
value of 1, and managed by Expert Review.
Fedyk, et al. Standards Track [Page 34]
RFC 6329 IS-IS Support of IEEE 802.1aq April 2012
+-----+----+-----------------+--------+------+-------------+
| PDU |TLV | SUB-TLV | TYPE | TYPE | #OCCURRENCE |
+-----+----+-----------------+--------+------+-------------+
IIH
MT-Port-Cap 143
* SPB-MCID 4 1
* SPB-Digest 5 >=0
* SPB-B-VID 6 1
LSP
* MT-Capability 144 >=1
* SPB-Inst 1 1
* SPB-I-OALG 2 >=0
* SPBM-SI 3 >=0
* SPBV-ADDR 4 >=0
MT-ISN 222
or Extended IS Reachability 22
* SPB-Metric 29 1
* SPB-A-OALG 30 >=0
19. References
19.1. Normative References
[802.1aq] "Standard for Local and Metropolitan Area Networks:
Virtual Bridges and Virtual Bridged Local Area Networks -
Amendment 9: Shortest Path Bridging", IEEE P802.1aq, Draft
4.6, 2012.
[IS-IS] ISO/IEC 10589:2002, Second Edition, "Intermediate System
to Intermediate System Intra-Domain Routing Exchange
Protocol for use in Conjunction with the Protocol for
Providing the Connectionless-mode Network Service (ISO
8473)", 2002.
[MT] Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi
Topology (MT) Routing in Intermediate System to
Intermediate Systems (IS-ISs)", RFC 5120, February 2008.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC6165] Banerjee, A. and D. Ward, "Extensions to IS-IS for Layer-2
Systems", RFC 6165, April 2011.
[RFC6328] Eastlake 3rd, D., "IANA Considerations for Network Layer
Protocol Identifiers", BCP 164, RFC 6328, July 2011.
Fedyk, et al. Standards Track [Page 35]
RFC 6329 IS-IS Support of IEEE 802.1aq April 2012
19.2. Informative References
[802.1ag] "Standard for Local and Metropolitan Area Networks /
Virtual Bridged Local Area Networks / Amendment 5:
Connectivity Fault Management", IEEE STD 802.1ag, 2007.
[MMRP] "Standard for Local and Metropolitan Area Networks Virtual
Bridged Local Area Networks - Amendment 07: Multiple
Registration Protocol", IEEE STD 802.1ak, 2007.
[PB] "Standard for Local and Metropolitan Area Networks /
Virtual Bridged Local Area Networks / Amendment 4:
Provider Bridges", IEEE STD 802.1ad, 2005.
[PBB] "Standard for Local and Metropolitan Area Networks /
Virtual Bridged Local Area Networks / Amendment 7:
Provider Backbone Bridges", IEEE STD 802.1ah, 2008.
[RFC4732] Handley, M., Ed., Rescorla, E., Ed., and IAB, "Internet
Denial-of-Service Considerations", RFC 4732, December
2006.
[Y.1731] ITU-T, "OAM Functions and Mechanisms for Ethernet based
networks", ITU-T Y.1731, 2006.
20. Acknowledgments
The authors would like to thank Ayan Banerjee, Mick Seaman, Janos
Farkas, Les Ginsberg, Stewart Bryant , Donald Eastlake, Matthew Bocci
and Mike Shand for contributions and/or detailed review.
Fedyk, et al. Standards Track [Page 36]
RFC 6329 IS-IS Support of IEEE 802.1aq April 2012
Authors' Addresses
Don Fedyk (editor)
Alcatel-Lucent
Groton, MA 01450
USA
EMail: Donald.Fedyk@alcatel-lucent.com
Peter Ashwood-Smith (editor)
Huawei Technologies Canada Ltd.
303 Terry Fox Drive, Suite 400
Kanata, Ontario, K2K 3J1
CANADA
EMail: Peter.AshwoodSmith@huawei.com
Dave Allan
Ericsson
300 Holger Way
San Jose, CA 95134
USA
EMail: david.i.allan@ericsson.com
Nigel Bragg
Ciena Limited
Ciena House
43-51 Worship Street
London EC2A 2DX
UK
EMail: nbragg@ciena.com
Paul Unbehagen
Avaya
8742 Lucent Boulevard
Highlands Ranch, CO 80129
USA
EMail: unbehagen@avaya.com
Fedyk, et al. Standards Track [Page 37]