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IETF RFC 7176
Last modified on Thursday, May 8th, 2014
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Internet Engineering Task Force (IETF) D. Eastlake 3rd
Request for Comments: 7176 Huawei
Obsoletes: 6326 T. Senevirathne
Category: Standards Track Cisco
ISSN: 2070-1721 A. Ghanwani
Dell
D. Dutt
Cumulus Networks
A. Banerjee
Insieme Networks
May 2014
Transparent Interconnection of Lots of Links (TRILL) Use of IS-IS
 Abstract
The IETF Transparent Interconnection of Lots of Links (TRILL)
protocol provides optimal pair-wise data frame forwarding without
configuration in multi-hop networks with arbitrary topology and link
technology; it also provides support for multipathing of both unicast
and multicast traffic. This document specifies the data formats and
code points for the IS-IS extensions to support TRILL. These data
formats and code points may also be used by technologies other than
TRILL. This document obsoletes RFC 6326.
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/RFC 7176.
Eastlake, et al. Standards Track PAGE 1 
RFC 7176 TRILL Use of IS-IS May 2014
Copyright Notice
Copyright (c) 2014 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.
Table of Contents
1. Introduction ....................................................3
1.1. Conventions Used in This Document ..........................4
2. TLV and Sub-TLV Extensions to IS-IS for TRILL ...................4
2.1. Group Address TLV ..........................................5
2.1.1. Group MAC Address Sub-TLV ...........................5
2.1.2. Group IPv4 Address Sub-TLV ..........................7
2.1.3. Group IPv6 Address Sub-TLV ..........................8
2.1.4. Group Labeled MAC Address Sub-TLV ...................9
2.1.5. Group Labeled IPv4 Address Sub-TLV .................10
2.1.6. Group Labeled IPv6 Address Sub-TLV .................11
2.2. Multi-Topology-Aware Port Capability Sub-TLVs .............12
2.2.1. Special VLANs and Flags Sub-TLV ....................12
2.2.2. Enabled-VLANs Sub-TLV ..............................13
2.2.3. Appointed Forwarders Sub-TLV .......................14
2.2.4. Port TRILL Version Sub-TLV .........................15
2.2.5. VLANs Appointed Sub-TLV ............................17
2.3. Sub-TLVs of the Router Capability and MT-Capability TLVs ..17
2.3.1. TRILL Version Sub-TLV ..............................18
2.3.2. Nickname Sub-TLV ...................................19
2.3.3. Trees Sub-TLV ......................................20
2.3.4. Tree Identifiers Sub-TLV ...........................20
2.3.5. Trees Used Identifiers Sub-TLV .....................21
2.3.6. Interested VLANs and Spanning Tree Roots Sub-TLV ...22
2.3.7. VLAN Group Sub-TLV .................................24
2.3.8. Interested Labels and Spanning Tree Roots Sub-TLV ..25
2.3.9. RBridge Channel Protocols Sub-TLV ..................27
2.3.10. Affinity Sub-TLV ..................................29
2.3.11. Label Group Sub-TLV ...............................30
2.4. MTU Sub-TLV for Extended Reachability and MT-ISN TLVs .....31
2.5. TRILL Neighbor TLV ........................................31
3. MTU PDUs .......................................................33
Eastlake, et al. Standards Track PAGE 2
RFC 7176 TRILL Use of IS-IS May 2014
4. Use of Existing PDUs and TLVs ..................................35
4.1. TRILL IIH PDUs ............................................35
4.2. Area Address ..............................................35
4.3. Protocols Supported .......................................35
4.4. Link State PDUs (LSPs) ....................................35
4.5. Originating LSP Buffer Size ...............................36
5. IANA Considerations ............................................36
5.1. TLVs ......................................................36
5.2. Sub-TLVs ..................................................36
5.3. PDUs ......................................................38
5.4. Reserved and Capability Bits ..............................38
5.5. TRILL Neighbor Record Flags ...............................39
6. Security Considerations ........................................39
7. Changes from RFC 6326 ..........................................39
8. References .....................................................41
8.1. Normative References ......................................41
8.2. Informative References ....................................43
9. Acknowledgements ...............................................44
1. Introduction
The IETF Transparent Interconnection of Lots of Links (TRILL)
protocol [RFC 6325] [RFC 7177] provides transparent forwarding in
multi-hop networks with arbitrary topology and link technologies
using a header with a hop count and link-state routing. TRILL
provides optimal pair-wise forwarding without configuration, safe
forwarding even during periods of temporary loops, and support for
multipathing of both unicast and multicast traffic. Intermediate
Systems (ISs) implementing TRILL are called Routing Bridges
(RBridges) or TRILL Switches.
This document, in conjunction with [RFC 6165], specifies the data
formats and code points for the IS-IS [ISO-10589] [RFC 1195]
extensions to support TRILL. These data formats and code points may
also be used by technologies other than TRILL.
This document obsoletes [RFC 6326], which generally corresponded to
the base TRILL protocol [RFC 6325]. There has been substantial
development of TRILL since the publication of those documents. The
main changes from [RFC 6326] are summarized below, and a full list is
given in Section 7.
1. Added multicast group announcements by IPv4 and IPv6 address.
2. Added facilities for announcing capabilities supported.
3. Added a tree affinity sub-TLV whereby ISs can request
distribution tree association.
Eastlake, et al. Standards Track PAGE 3
RFC 7176 TRILL Use of IS-IS May 2014
4. Added multi-topology support.
5. Added control-plane support for TRILL Data frame fine-grained
labels. This support is independent of the data-plane
representation.
6. Fixed the verified erratum [Err2869] in [RFC 6326].
Changes herein to TLVs and sub-TLVs specified in [RFC 6326] are
backward compatible.
1.1. Conventions Used in This Document
The terminology and acronyms defined in [RFC 6325] are used herein
with the same meaning.
Additional acronyms and phrases used in this document are:
BVL - Bit Vector Length
BVO - Bit Vector Offset
IIH - IS-IS Hello
IS - Intermediate System. For this document, all relevant
intermediate systems are RBridges [RFC 6325].
MAC - Media Access Control
MT - Multi-Topology
NLPID - Network Layer Protocol Identifier
SNPA - Subnetwork Point of Attachment (MAC Address)
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].
2. TLV and Sub-TLV Extensions to IS-IS for TRILL
This section, in conjunction with [RFC 6165], specifies the data
formats and code points for the TLVs and sub-TLVs for IS-IS to
support the IETF TRILL protocol. Information as to the number of
occurrences allowed, such as for a TLV in a PDU or set of PDUs or for
a sub-TLV in a TLV, is summarized in Section 5.
Eastlake, et al. Standards Track PAGE 4
RFC 7176 TRILL Use of IS-IS May 2014
2.1. Group Address TLV
The Group Address (GADDR) TLV, IS-IS TLV type 142, is carried in an
LSP PDU and carries sub-TLVs that in turn advertise multicast group
listeners. The sub-TLVs that advertise listeners are specified
below. The sub-TLVs under GADDR constitute a new series of sub-TLV
types (see Section 5.2).
GADDR has the following format:
+-+-+-+-+-+-+-+-+
|Type=GADDR-TLV | (1 byte)
+-+-+-+-+-+-+-+-+
| Length | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...
| sub-TLVs...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-...
o Type: TLV type, set to GADDR-TLV 142.
o Length: variable depending on the sub-TLVs carried.
o sub-TLVs: The Group Address TLV value consists of sub-TLVs
formatted as described in [RFC 5305].
2.1.1. Group MAC Address Sub-TLV
The Group MAC Address (GMAC-ADDR) sub-TLV is sub-TLV type number 1
within the GADDR TLV. In TRILL, it is used to advertise multicast
listeners by MAC address as specified in Section 4.5.5 of [RFC 6325].
It has the following format:
Eastlake, et al. Standards Track PAGE 5
RFC 7176 TRILL Use of IS-IS May 2014
+-+-+-+-+-+-+-+-+
|Type=GMAC-ADDR | (1 byte)
+-+-+-+-+-+-+-+-+
| Length | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RESV | Topology-ID | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RESV | VLAN ID | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Num Group Recs | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| GROUP RECORDS (1) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| GROUP RECORDS (2) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ................. |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| GROUP RECORDS (N) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where each group record is of the following form with k=6:
+-+-+-+-+-+-+-+-+
| Num of Sources| (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Group Address (k bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source 1 Address (k bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source 2 Address (k bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ..... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source M Address (k bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
o Type: GADDR sub-TLV type, set to 1 (GMAC-ADDR).
o Length: 5 + m + k*n = 5 + m + 6*n, where m is the number of group
records and n is the sum of the number of group and source
addresses.
o RESV: Reserved. 4-bit fields that MUST be sent as zero and
ignored on receipt.
o Topology-ID: This field carries a topology ID [RFC 5120] or zero if
topologies are not in use.
Eastlake, et al. Standards Track PAGE 6
RFC 7176 TRILL Use of IS-IS May 2014
o VLAN ID: This carries the 12-bit VLAN identifier for all
subsequent MAC addresses in this sub-TLV, or the value zero if no
VLAN is specified.
o Num Group Recs: A 1-byte unsigned integer that is the number of
group records in this sub-TLV.
o GROUP RECORDS: Each group record carries the number of sources.
If this field is zero, it indicates a listener for (*,G), that is,
a listener not restricted by source. It then has a 6-byte
(48-bit) multicast MAC address followed by 6-byte source MAC
addresses. If the sources do not fit in a single sub-TLV, the
same group address may be repeated with different source addresses
in another sub-TLV of another instance of the Group Address TLV.
The GMAC-ADDR sub-TLV is carried only within a GADDR TLV.
2.1.2. Group IPv4 Address Sub-TLV
The Group IPv4 Address (GIP-ADDR) sub-TLV is IS-IS sub-TLV type 2
within the GADDR TLV. It has the same format as the Group MAC
Address sub-TLV described in Section 2.1.1 except that k=4. The
fields are as follows:
o Type: sub-TLV type, set to 2 (GIP-ADDR).
o Length: 5 + m + k*n = 5 + m + 4*n, where m is the number of group
records and n is the sum of the number of group and source
addresses.
o Topology-ID: This field carries a topology ID [RFC 5120] or zero if
topologies are not in use.
o RESV: Must be sent as zero on transmission and is ignored on
receipt.
o VLAN ID: This carries a 12-bit VLAN identifier that is valid for
all subsequent addresses in this sub-TLV, or the value zero if no
VLAN is specified.
o Num Group Recs: A 1-byte unsigned integer that is the number of
group records in this sub-TLV.
Eastlake, et al. Standards Track PAGE 7
RFC 7176 TRILL Use of IS-IS May 2014
o GROUP RECORDS: Each group record carries the number of sources.
If this field is zero, it indicates a listener for (*,G), that is,
a listener not restricted by source. It then has a 4-byte
(32-bit) IPv4 Group Address followed by 4-byte source IPv4
addresses. If the number of sources do not fit in a single sub-
TLV, it is permitted to have the same group address repeated with
different source addresses in another sub-TLV of another instance
of the Group Address TLV.
The GIP-ADDR sub-TLV is carried only within a GADDR TLV.
2.1.3. Group IPv6 Address Sub-TLV
The Group IPv6 Address (GIPV6-ADDR) sub-TLV is IS-IS sub-TLV type 3
within the GADDR TLV. It has the same format as the Group MAC
Address sub-TLV described in Section 2.1.1 except that k=16. The
fields are as follows:
o Type: sub-TLV type, set to 3 (GIPV6-ADDR).
o Length: 5 + m + k*n = 5 + m + 16*n, where m is the number of group
records and n is the sum of the number of group and source
addresses.
o Topology-Id: This field carries a topology ID [RFC 5120] or zero if
topologies are not in use.
o RESV: Must be sent as zero on transmission and is ignored on
receipt.
o VLAN ID: This carries a 12-bit VLAN identifier that is valid for
all subsequent addresses in this sub-TLV, or the value zero if no
VLAN is specified.
o Num Group Recs: A 1-byte unsigned integer that is the number of
group records in this sub-TLV.
o GROUP RECORDS: Each group record carries the number of sources.
If this field is zero, it indicates a listener for (*,G), that is,
a listener not restricted by source. It then has a 16-byte
(128-bit) IPv6 Group Address followed by 16-byte source IPv6
addresses. If the number of sources do not fit in a single sub-
TLV, it is permitted to have the same group address repeated with
different source addresses in another sub-TLV of another instance
of the Group Address TLV.
The GIPV6-ADDR sub-TLV is carried only within a GADDR TLV.
Eastlake, et al. Standards Track PAGE 8
RFC 7176 TRILL Use of IS-IS May 2014
2.1.4. Group Labeled MAC Address Sub-TLV
The GMAC-ADDR sub-TLV of the Group Address (GADDR) TLV specified in
Section 2.1.1 provides for a VLAN ID. The Group Labeled MAC Address
sub-TLV, below, extends this to a fine-grained label.
+-+-+-+-+-+-+-+-+
|Type=GLMAC-ADDR| (1 byte)
+-+-+-+-+-+-+-+-+
| Length | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RESV | Topology-ID | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Fine-Grained Label | (3 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Num Group Recs | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| GROUP RECORDS (1) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| GROUP RECORDS (2) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ................. |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| GROUP RECORDS (N) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where each group record is of the following form with k=6:
+-+-+-+-+-+-+-+-+
| Num of Sources| (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Group Address (k bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source 1 Address (k bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source 2 Address (k bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ..... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source M Address (k bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
o Type: GADDR sub-TLV type, set to 4 (GLMAC-ADDR).
o Length: 6 + m + k*n = 6 + m + 6*n, where m is the number of group
records and n is the sum of the number of group and source
addresses.
Eastlake, et al. Standards Track PAGE 9
RFC 7176 TRILL Use of IS-IS May 2014
o RESV: Reserved. 4-bit field that MUST be sent as zero and ignored
on receipt.
o Topology-ID: This field carries a topology ID [RFC 5120] or zero if
topologies are not in use.
o Label: This carries the fine-grained label [RFC 7172] identifier
for all subsequent MAC addresses in this sub-TLV, or the value
zero if no label is specified.
o Num Group Recs: A 1-byte unsigned integer that is the number of
group records in this sub-TLV.
o GROUP RECORDS: Each group record carries the number of sources.
If this field is zero, it indicates a listener for (*,G), that is,
a listener not restricted by source. It then has a 6-byte
(48-bit) multicast address followed by 6-byte source MAC
addresses. If the sources do not fit in a single sub-TLV, the
same group address may be repeated with different source addresses
in another sub-TLV of another instance of the Group Address TLV.
The GLMAC-ADDR sub-TLV is carried only within a GADDR TLV.
2.1.5. Group Labeled IPv4 Address Sub-TLV
The Group Labeled IPv4 Address (GLIP-ADDR) sub-TLV is IS-IS sub-TLV
type 5 within the GADDR TLV. It has the same format as the Group
Labeled MAC Address sub-TLV described in Section 2.1.4 except that
k=4. The fields are as follows:
o Type: sub-TLV type, set to 5 (GLIP-ADDR).
o Length: 6 + m + k*n = 6 + m + 4*n, where m is the number of group
records and n is the sum of the number of group and source
addresses.
o Topology-ID: This field carries a topology ID [RFC 5120] or zero if
topologies are not in use.
o RESV: Must be sent as zero on transmission and is ignored on
receipt.
o Label: This carries the fine-grained label [RFC 7172] identifier
for all subsequent IPv4 addresses in this sub-TLV, or the value
zero if no label is specified.
o Num Group Recs: A 1-byte unsigned integer that is the number of
group records in this sub-TLV.
Eastlake, et al. Standards Track PAGE 10
RFC 7176 TRILL Use of IS-IS May 2014
o GROUP RECORDS: Each group record carries the number of sources.
If this field is zero, it indicates a listener for (*,G), that is,
a listener not restricted by source. It then has a 4-byte
(32-bit) IPv4 Group Address followed by 4-byte source IPv4
addresses. If the number of sources do not fit in a single sub-
TLV, it is permitted to have the same group address repeated with
different source addresses in another sub-TLV of another instance
of the Group Address TLV.
The GLIP-ADDR sub-TLV is carried only within a GADDR TLV.
2.1.6. Group Labeled IPv6 Address Sub-TLV
The Group Labeled IPv6 Address (GLIPV6-ADDR) sub-TLV is IS-IS sub-TLV
type 6 within the GADDR TLV. It has the same format as the Group
Labeled MAC Address sub-TLV described in Section 2.1.4 except that
k=16. The fields are as follows:
o Type: sub-TLV type, set to 6 (GLIPV6-ADDR).
o Length: 6 + m + k*n = 6 + m + 16*n, where m is the number of group
records and n is the sum of the number of group and source
addresses.
o Topology-Id: This field carries a topology ID [RFC 5120] or zero if
topologies are not in use.
o RESV: Must be sent as zero on transmission and is ignored on
receipt.
o Label: This carries the fine-grained label [RFC 7172] identifier
for all subsequent IPv6 addresses in this sub-TLV, or the value
zero if no label is specified.
o Num Group Recs: A 1-byte unsigned integer that is the number of
group records in this sub-TLV.
o GROUP RECORDS: Each group record carries the number of sources.
If this field is zero, it indicates a listener for (*,G), that is,
a listener not restricted by source. It then has a 16-byte
(128-bit) IPv6 Group Address followed by 16-byte source IPv6
addresses. If the number of sources do not fit in a single sub-
TLV, it is permitted to have the same group address repeated with
different source addresses in another sub-TLV of another instance
of the Group Address TLV.
The GLIPV6-ADDR sub-TLV is carried only within a GADDR TLV.
Eastlake, et al. Standards Track PAGE 11
RFC 7176 TRILL Use of IS-IS May 2014
2.2. Multi-Topology-Aware Port Capability Sub-TLVs
TRILL makes use of the Multi-Topology-Aware Port Capability TLV (MT-
Port-Cap-TLV) as specified in [RFC 6165]. The following subsections
specify the sub-TLVs transported by the MT-Port-Cap-TLV for TRILL.
2.2.1. Special VLANs and Flags Sub-TLV
In TRILL, a Special VLANs and Flags (VLAN-FLAGS) sub-TLV is carried
in every IIH PDU. It has the following format:
+--+--+--+--+--+--+--+--+
| Type | (1 byte)
+--+--+--+--+--+--+--+--+
| Length | (1 byte)
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| Port ID | (2 bytes)
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| Sender Nickname | (2 bytes)
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|AF|AC|VM|BY| Outer.VLAN | (2 bytes)
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|TR|R |R |R | Designated-VLAN | (2 bytes)
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
o Type: sub-TLV type, set to MT-Port-Cap-TLV VLAN-FLAGS sub-TLV 1.
o Length: 8.
o Port ID: An ID for the port on which the enclosing TRILL IIH PDU
is being sent as specified in [RFC 6325], Section 4.4.2.
o Sender Nickname: If the sending IS is holding any nicknames as
discussed in [RFC 6325], Section 3.7, one MUST be included here.
Otherwise, the field is set to zero. This field is to support
intelligent end stations that determine the egress IS (RBridge)
for unicast data through a directory service or the like and that
need a nickname for their first hop to insert as the ingress
nickname to correctly format a TRILL Data frame (see [RFC 6325],
Section 4.6.2, point 8). It is also referenced in connection with
the VLANs Appointed Sub-TLV (see Section 2.2.5) and can be used as
the egress on one-hop RBridge Channel messages [RFC 7178], for
example, those use for BFD over TRILL [RFC 7175].
o Outer.VLAN: A copy of the 12-bit outer VLAN ID of the TRILL IIH
frame containing this sub-TLV, as specified in [RFC 6325], Section
4.4.5.
Eastlake, et al. Standards Track PAGE 12
RFC 7176 TRILL Use of IS-IS May 2014
o Designated-VLAN: The 12-bit ID of the Designated VLAN for the
link, as specified in [RFC 6325], Section 4.2.4.2.
o AF, AC, VM, BY, and TR: These flag bits have the following
meanings when set to one, as specified in the listed section of
[RFC 6325]:
RFC 6325
Bit Section Meaning if bit is one
--------------------------------------
AF 4.4.2 Originating IS believes it is Appointed
Forwarder for the VLAN and port on which the
containing IIH PDU was sent.
AC 4.9.1 Originating port configured as an access port
(TRILL traffic disabled).
VM 4.4.5 VLAN mapping detected on this link.
BY 4.4.2 Bypass pseudonode.
TR 4.9.1 Originating port configured as a trunk port
(end-station service disabled).
o R: Reserved bit. MUST be sent as zero and ignored on receipt.
2.2.2. Enabled-VLANs Sub-TLV
The optional Enabled-VLANs sub-TLV specifies the VLANs enabled at the
port of the originating IS on which the containing Hello was sent, as
specified in [RFC 6325], Section 4.4.2. It has the following format:
+-+-+-+-+-+-+-+-+
| Type | (1 byte)
+-+-+-+-+-+-+-+-+
| Length | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RESV | Start VLAN ID | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| VLAN bit-map....
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
o Type: sub-TLV type, set to MT-Port-Cap-TLV Enabled-VLANs sub-TLV
2.
o Length: Variable, minimum 3.
Eastlake, et al. Standards Track PAGE 13
RFC 7176 TRILL Use of IS-IS May 2014
o RESV: 4 reserved bits that MUST be sent as zero and ignored on
receipt.
o Start VLAN ID: The 12-bit VLAN ID that is represented by the high-
order bit of the first byte of the VLAN bit-map.
o VLAN bit-map: The highest-order bit indicates the VLAN equal to
the start VLAN ID, the next highest bit indicates the VLAN equal
to start VLAN ID + 1, continuing to the end of the VLAN bit-map
field.
If this sub-TLV occurs more than once in a Hello, the set of enabled
VLANs is the union of the sets of VLANs indicated by each of the
Enabled-VLAN sub-TLVs in the Hello.
2.2.3. Appointed Forwarders Sub-TLV
The Designated RBridge (DRB) on a link uses the Appointed Forwarders
sub-TLV to inform other ISs on the link that they are the designated
VLAN-x forwarder for one or more ranges of VLAN IDs as specified in
[RFC 6439]. It has the following format:
+-+-+-+-+-+-+-+-+
| Type | (1 byte)
+-+-+-+-+-+-+-+-+
| Length | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Appointment Information (1) | (6 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Appointment Information (2) | (6 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ................. |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Appointment Information (N) | (6 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where each appointment is of the form:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Appointee Nickname | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RESV | Start.VLAN | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RESV | End.VLAN | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Eastlake, et al. Standards Track PAGE 14
RFC 7176 TRILL Use of IS-IS May 2014
o Type: sub-TLV type, set to MT-Port-Cap-TLV AppointedFwrdrs sub-TLV
3.
o Length: 6*n bytes, where there are n appointments.
o Appointee Nickname: The nickname of the IS being appointed a
forwarder.
o RESV: 4 bits that MUST be sent as zero and ignored on receipt.
o Start.VLAN, End.VLAN: This VLAN ID range is inclusive. Setting
both Start.VLAN and VLAN.end to the same value indicates a range
of one VLAN ID. If Start.VLAN is not equal to VLAN.end and
Start.VLAN is 0x000, the sub-TLV is interpreted as if Start.VLAN
was 0x001. If Start.VLAN is not equal to VLAN.end and VLAN.end is
0xFFF, the sub-TLV is interpreted as if VLAN.end was 0xFFE. If
VLAN.end is less than Start.VLAN, the sub-TLV is ignored. If both
Start.VLAN and VLAN.end are 0x000 or both are 0xFFF, the sub-TLV
is ignored. The values 0x000 or 0xFFF are not valid VLAN IDs, and
a port cannot be enabled for them.
An IS's nickname may occur as Appointed Forwarder for multiple VLAN
ranges by occurrences of this sub-TLV within the same or different MT
Port Capability TLVs within an IIH PDU. See [RFC 6439].
2.2.4. Port TRILL Version Sub-TLV
The Port TRILL Version (PORT-TRILL-VER) sub-TLV indicates the maximum
version of the TRILL standard supported and the support of optional
hop-by-hop capabilities. By implication, lower versions are also
supported. If this sub-TLV is missing from an IIH, it is assumed
that the originating IS only supports the base version (version zero)
of the protocol [RFC 6325] and supports no optional capabilities
indicated by this sub-TLV.
+-+-+-+-+-+-+-+-+
| Type | (1 byte)
+-+-+-+-+-+-+-+-+
| Length | (1 byte)
+-+-+-+-+-+-+-+-+
| Max-version | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...-+
| Capabilities and Header Flags Supported | (4 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...-+-+
0 1 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 0 1
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RFC 7176 TRILL Use of IS-IS May 2014
o Type: MT-Port-Cap-TLV sub-TLV type, set to 7 (PORT-TRILL-VER).
o Length: 5.
o Max-version: A one-byte unsigned integer set to the maximum
version supported.
o Capabilities and Header Flags Supported: A bit vector of 32 bits
numbered 0 through 31 in network order. Bits 3 through 13
indicate that the corresponding TRILL Header hop-by-hop extended
flags [RFC 7179] are supported. Bits 0 through 2 and 14 to 31 are
reserved to indicate support of optional capabilities. A one bit
indicates that the flag or capability is supported by the sending
IS. Bits in this field MUST be set to zero except as permitted
for a capability being advertised or if a hop-by-hop extended
header flag is supported.
This sub-TLV, if present, MUST occur in an MT-Port-Cap-TLV in a TRILL
IIH. If there is more than one occurrence, the minimum of the
supported versions is assumed to be correct and a capability or
header flag is assumed to be supported only if indicated by all
occurrences. The flags and capabilities for which support can be
indicated in this sub-TLV are disjoint from those in the TRILL-VER
sub-TLV (Section 2.3.1) so they cannot conflict. The flags and
capabilities indicated in this sub-TLV relate to hop-by-hop
processing that can differ between the ports of an IS (RBridge) and
thus must be advertised in IIHs. For example, a capability requiring
cryptographic hardware assist might be supported on some ports and
not others. However, the TRILL version is the same as that in the
PORT-TRILL-VER sub-TLV. An IS, if it is adjacent to the sending IS
of TRILL version sub-TLV(s), uses the TRILL version it received in
PORT-TRILL-VER sub-TLV(s) in preference to that received in TRILL-VER
sub-TLV(s).
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2.2.5. VLANs Appointed Sub-TLV
The optional VLANs Appointed sub-TLV specifies, for the port of the
originating IS on which the containing Hello was sent, the VLANs for
which it is Appointed Forwarder. This sub-TLV has the following
format:
+-+-+-+-+-+-+-+-+
| Type | (1 byte)
+-+-+-+-+-+-+-+-+
| Length | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RESV | Start VLAN ID | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| VLAN bit-map....
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
o Type: sub-TLV type, set to MT-Port-Cap-TLV VLANS-Appointed sub-TLV
8.
o Length: Variable, minimum 3.
o RESV: 4 reserved bits that MUST be sent as zero and ignored on
receipt.
o Start VLAN ID: The 12-bit VLAN ID that is represented by the high-
order bit of the first byte of the VLAN bit-map.
o VLAN bit-map: The highest-order bit indicates the VLAN equal to
the start VLAN ID, the next highest bit indicates the VLAN equal
to start VLAN ID + 1, continuing to the end of the VLAN bit-map
field.
If this sub-TLV occurs more than once in a Hello, the originating IS
is declaring that it believes itself to be Appointed Forwarder on the
port on which the enclosing IIH was sent for the union of the sets of
VLANs indicated by each of the VLANs-Appointed sub-TLVs in the Hello.
2.3. Sub-TLVs of the Router Capability and MT-Capability TLVs
The Router Capability TLV is specified in [RFC 4971] and the MT-
Capability TLV in [RFC 6329]. All of the following sub-sections
specify sub-TLVs that can be carried in the Router Capability TLV
(#242) and the MT-Capability TLV (#144) with the same sub-TLV number
for both TLVs. These TLVs are in turn carried only by LSPs.
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2.3.1. TRILL Version Sub-TLV
The TRILL Version (TRILL-VER) sub-TLV indicates the maximum version
of the TRILL standard supported and the support of optional
capabilities by the originating IS. By implication, lower versions
are also supported. If this sub-TLV is missing, it is assumed that
the originating IS only supports the base version (version zero) of
the protocol [RFC 6325], and no optional capabilities indicated by
this sub-TLV are supported.
+-+-+-+-+-+-+-+-+
| Type | (1 byte)
+-+-+-+-+-+-+-+-+
| Length | (1 byte)
+-+-+-+-+-+-+-+-+
| Max-version | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...-+
| Capabilities and Header Flags Supported | (4 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...-+-+
0 1 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 0 1
o Type: Router Capability sub-TLV type, set to 13 (TRILL-VER).
o Length: 5.
o Max-version: A one-byte unsigned integer set to the maximum
version supported.
o Capabilities and Header Flags Supported: A bit vector of 32 bits
numbered 0 through 31 in network order. Bits 14 through 31
indicate that the corresponding TRILL Header extended flags
[RFC 7179] are supported. Bits 0 through 13 are reserved to
indicate support of optional capabilities. A one bit indicates
that the originating IS supports the flag or capability. For
example, support of multi-level TRILL IS-IS [MultiLevel]. Bits in
this field MUST be set to zero except as permitted for a
capability being advertised or an extended header flag supported.
This sub-TLV, if present in a Router Capability TLV, MUST occur in
the LSP number zero for the originating IS. If found in a Router
Capability TLV in other fragments, it is ignored. If there is more
than one occurrence in LSP number zero, the minimum of the supported
versions is assumed to be correct, and an extended header flag or
capability is assumed to be supported only if indicated by all
occurrences. The flags and capabilities for which support can be
indicated in this sub-TLV are disjoint from those in the PORT-TRILL-
VER sub-TLV (Section 2.2.4) so they cannot conflict. However, the
Eastlake, et al. Standards Track PAGE 18
RFC 7176 TRILL Use of IS-IS May 2014
TRILL version is the same as that in the PORT-TRILL-VER sub-TLV, and
an IS that is adjacent to the originating IS of TRILL-VER sub-TLV(s)
uses the TRILL version it received in PORT-TRILL-VER sub-TLV(s) in
preference to that received in TRILL-VER sub-TLV(s).
For multi-topology-aware TRILL Switches, the TRILL version and
capabilities announced for the base topology are assumed to apply to
all topologies for which a separate TRILL version announcement does
not occur in an MT-Capability TLV. Such announcements for non-zero
topologies need not occur in fragment zero.
2.3.2. Nickname Sub-TLV
The Nickname (NICKNAME) Router Capability sub-TLV carries information
about the nicknames of the originating IS, along with information
about its priority to hold those nicknames and the priority for each
nickname to be a tree root as specified in [RFC 6325], Section 3.7.3.
Multiple instances of this sub-TLV may occur.
+-+-+-+-+-+-+-+-+
|Type = NICKNAME| (1 byte)
+-+-+-+-+-+-+-+-+
| Length | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NICKNAME RECORDS (1) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NICKNAME RECORDS (2) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ................. |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NICKNAME RECORDS (N) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where each nickname record is of the form:
+-+-+-+-+-+-+-+-+
| Nickname.Pri | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tree Root Priority | (2 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Nickname | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
o Type: Router Capability and MT-Capability sub-TLV type, set to 6
(NICKNAME).
o Length: 5*n, where n is the number of nickname records present.
Eastlake, et al. Standards Track PAGE 19
RFC 7176 TRILL Use of IS-IS May 2014
o Nickname.Pri: An 8-bit unsigned integer priority to hold a
nickname as specified in Section 3.7.3 of [RFC 6325].
o Tree Root Priority: This is an unsigned 16-bit integer priority to
be a tree root as specified in Section 4.5 of [RFC 6325].
o Nickname: This is an unsigned 16-bit integer as specified in
Section 3.7 of [RFC 6325].
2.3.3. Trees Sub-TLV
Each IS providing TRILL service uses the TREES sub-TLV to announce
three numbers related to the computation of distribution trees as
specified in Section 4.5 of [RFC 6325]. Its format is as follows:
+-+-+-+-+-+-+-+-+
|Type = TREES | (1 byte)
+-+-+-+-+-+-+-+-+
| Length | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Number of trees to compute | (2 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Maximum trees able to compute | (2 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Number of trees to use | (2 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
o Type: Router Capability and MT-Capability sub-TLV type, set to 7
(TREES).
o Length: 6.
o Number of trees to compute: An unsigned 16-bit integer as
specified in Section 4.5 of [RFC 6325].
o Maximum trees able to compute: An unsigned 16-bit integer as
specified in Section 4.5 of [RFC 6325].
o Number of trees to use: An unsigned 16-bit integer as specified in
Section 4.5 of [RFC 6325].
2.3.4. Tree Identifiers Sub-TLV
The Tree Identifiers (TREE-RT-IDs) sub-TLV is an ordered list of
nicknames. When originated by the IS that has the highest priority
to be a tree root, it lists the distribution trees that the other ISs
are required to compute as specified in Section 4.5 of [RFC 6325]. If
Eastlake, et al. Standards Track PAGE 20
RFC 7176 TRILL Use of IS-IS May 2014
this information is spread across multiple sub-TLVs, the starting
tree number is used to allow the ordered lists to be correctly
concatenated. The sub-TLV format is as follows:
+-+-+-+-+-+-+-+-+
|Type=TREE-RT-IDs| (1 byte)
+-+-+-+-+-+-+-+-+
| Length | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Starting Tree Number | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Nickname (K-th root) | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Nickname (K+1 - th root) | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Nickname (...) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
o Type: Router Capability and MT-Capability sub-TLV type, set to 8
(TREE-RT-IDs).
o Length: 2 + 2*n, where n is the number of nicknames listed.
o Starting Tree Number: This identifies the starting tree number of
the nicknames that are trees for the domain. This is set to 1 for
the sub-TLV containing the first list. Other Tree-Identifiers
sub-TLVs will have the number of the starting list they contain.
In the event the same tree identifier can be computed from two
such sub-TLVs and they are different, then it is assumed that this
is a transient condition that will get cleared. During this
transient time, such a tree SHOULD NOT be computed unless such
computation is indicated by all relevant sub-TLVs present.
o Nickname: The nickname at which a distribution tree is rooted.
2.3.5. Trees Used Identifiers Sub-TLV
This Router Capability sub-TLV has the same structure as the Tree
Identifiers sub-TLV specified in Section 2.3.4. The only difference
is that its sub-TLV type is set to 9 (TREE-USE-IDs), and the trees
listed are those that the originating IS wishes to use as specified
in [RFC 6325], Section 4.5.
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2.3.6. Interested VLANs and Spanning Tree Roots Sub-TLV
The value of this sub-TLV consists of a VLAN range and information in
common to all of the VLANs in the range for the originating IS. This
information consists of flags, a variable length list of spanning
tree root bridge IDs, and an Appointed Forwarder status lost counter,
all as specified in the sections of [RFC 6325] listed with the
respective information items below.
In the set of LSPs originated by an IS, the union of the VLAN ranges
in all occurrences of this sub-TLV MUST be the set of VLANs for which
the originating IS is Appointed Forwarder on at least one port, and
the VLAN ranges in multiple VLANs sub-TLVs for an IS MUST NOT overlap
unless the information provided about a VLAN is the same in every
instance. However, as a transient state, these conditions may be
violated. If a VLAN is not listed in any INT-VLAN sub-TLV for an IS,
that IS is assumed to be uninterested in receiving traffic for that
VLAN. If a VLAN appears in more than one INT-VLAN sub-TLV for an IS
with different information in the different instances, the following
apply:
- If those sub-TLVs provide different nicknames, it is unspecified
which nickname takes precedence.
- The largest Appointed Forwarder status lost counter, using serial
number arithmetic [RFC 1982], is used.
- The originating IS is assumed to be attached to a multicast IPv4
router for that VLAN if any of the INT-VLAN sub-TLVs assert that
it is so connected and similarly for IPv6 multicast router
attachment.
- The root bridge lists from all of the instances of the VLAN for
the originating IS are merged.
To minimize such occurrences, wherever possible, an implementation
SHOULD advertise the update to an interested VLAN and Spanning Tree
Roots sub-TLV in the same LSP fragment as the advertisement that it
replaces. Where this is not possible, the two affected LSP fragments
should be flooded as an atomic action. An IS that receives an update
to an existing interested VLAN and Spanning Tree Roots sub-TLV can
minimize the potential disruption associated with the update by
employing a hold-down timer prior to processing the update so as to
allow for the receipt of multiple LSP fragments associated with the
same update prior to beginning processing.
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RFC 7176 TRILL Use of IS-IS May 2014
The sub-TLV layout is as follows:
+-+-+-+-+-+-+-+-+
|Type = INT-VLAN| (1 byte)
+-+-+-+-+-+-+-+-+
| Length | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Nickname | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...+-+-+-+
| Interested VLANS | (4 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...+-+-+-+
| Appointed Forwarder Status Lost Counter | (4 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...+
| Root Bridges | (6*n bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...+-+-+
o Type: Router Capability and MT-Capability sub-TLV type, set to 10
(INT-VLAN).
o Length: 10 + 6*n, where n is the number of root bridge IDs.
o Nickname: As specified in [RFC 6325], Section 4.2.4.4, this field
may be used to associate a nickname held by the originating IS
with the VLAN range indicated. When not used in this way, it is
set to zero.
o Interested VLANS: The Interested VLANs field is formatted as shown
below.
0 1 2 3 4 - 15 16 - 19 20 - 31
+----+----+----+----+------------+----------+------------+
| M4 | M6 | R | R | VLAN.start | RESV | VLAN.end |
+----+----+----+----+------------+----------+------------+
- M4, M6: These bits indicate, respectively, that there is an
IPv4 or IPv6 multicast router on a link for which the
originating IS is Appointed Forwarder for every VLAN in the
indicated range as specified in [RFC 6325], Section 4.2.4.4,
item 5.1.
- R, RESV: These reserved bits MUST be sent as zero and are
ignored on receipt.
- VLAN.start and VLAN.end: This VLAN ID range is inclusive.
Setting both VLAN.start and VLAN.end to the same value
indicates a range of one VLAN ID. If VLAN.start is not equal
to VLAN.end and VLAN.start is 0x000, the sub-TLV is interpreted
as if VLAN.start was 0x001. If VLAN.start is not equal to
Eastlake, et al. Standards Track PAGE 23
RFC 7176 TRILL Use of IS-IS May 2014
VLAN.end and VLAN.end is 0xFFF, the sub-TLV is interpreted as
if VLAN.end was 0xFFE. If VLAN.end is less than VLAN.start,
the sub-TLV is ignored. If both VLAN.start and VLAN.end are
0x000 or both are 0xFFF, the sub-TLV is ignored. The values
0x000 or 0xFFF are not valid VLAN IDs, and a port cannot be
enabled for them.
o Appointed Forwarder Status Lost Counter: This is a count of how
many times a port that was Appointed Forwarder for the VLANs in
the range given has lost the status of being an Appointed
Forwarder for some port as discussed in Section 4.8.3 of
[RFC 6325]. It is initialized to zero at an IS when the zeroth LSP
sequence number is initialized. No special action need be taken
at rollover; the counter just wraps around.
o Root Bridges: The list of zero or more spanning tree root bridge
IDs is the set of root bridge IDs seen for all ports for which the
IS is Appointed Forwarder for the VLANs in the specified range as
discussed in [RFC 6325], Section 4.9.3.2. While, of course, at
most one spanning tree root could be seen on any particular port,
there may be multiple ports in the same VLANs connected to
different bridged LANs with different spanning tree roots.
An INT-VLAN sub-TLV asserts that the information provided (multicast
router attachment, Appointed Forwarder status lost counter, and root
bridges) is the same for all VLANs in the range specified. If this
is not the case, the range MUST be split into subranges meeting this
criteria. It is always safe to use sub-TLVs with a "range" of one
VLAN ID, but this may be too verbose.
2.3.7. VLAN Group Sub-TLV
The VLAN Group sub-TLV consists of two or more VLAN IDs as specified
in [RFC 6325], Section 4.8.4. This sub-TLV indicates that shared VLAN
learning is occurring at the originating IS between the listed VLANs.
It is structured as follows:
+-+-+-+-+-+-+-+-+
|Type=VLAN-GROUP| (1 byte)
+-+-+-+-+-+-+-+-+
| Length | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RESV | Primary VLAN ID | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RESV | Secondary VLAN ID | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| more Secondary VLAN IDs ... (2 bytes each)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Eastlake, et al. Standards Track PAGE 24
RFC 7176 TRILL Use of IS-IS May 2014
o Type: Router Capability and MT-Capability sub-TLV type, set to 14
(VLAN-GROUP).
o Length: 4 + 2*n, where n is the number of secondary VLAN ID fields
beyond the first. n MAY be zero.
o RESV: a 4-bit field that MUST be sent as zero and ignored on
receipt.
o Primary VLAN ID: This identifies the primary VLAN ID.
o Secondary VLAN ID: This identifies a secondary VLAN in the VLAN
Group.
o more Secondary VLAN IDs: zero or more byte pairs, each with the
top 4 bits as a RESV field and the low 12 bits as a VLAN ID.
2.3.8. Interested Labels and Spanning Tree Roots Sub-TLV
An IS that can handle fine-grained labeling [RFC 7172] announces its
fine-grained label connectivity and related information in the
Interested Labels and Spanning Tree Roots sub-TLV (INT-LABEL). It is
a variation of the Interested VLANs and Spanning Tree Roots sub-TLV
(INT-VLAN) and is structured as follows.
+-+-+-+-+-+-+-+-+
|Type=INT-LABEL | (1 byte)
+-+-+-+-+-+-+-+-+
| Length | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Nickname | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...+-+-+-+-+
| Interested Labels | (7 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...+-+-+-+-+
| Appointed Forwarder Status Lost Counter | (4 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...+-+-+
| Root Bridges | (6*n bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...+-+-+
o Type: Router Capability and MT-Capability sub-TLV type, set to 15
(INT-LABEL).
o Length: 11 + 6*n, where n is the number of root bridge IDs.
o Nickname: This field may be used to associate a nickname held by
the originating IS with the Interested Labels indicated. When not
used in this way, it is set to zero.
Eastlake, et al. Standards Track PAGE 25
RFC 7176 TRILL Use of IS-IS May 2014
o Interested Labels: The Interested Labels field is seven bytes long
and formatted as shown below.
0 1 2 3 4 5 6 7
+--+--+--+--+--+--+--+--+
|M4|M6|BM| R| R| R| R| R| . .
+--+--+--+--+--+--+--+--+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label.start - 24 bits |
+--+--+--+--+--+--+--+--+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label.end or bit-map - 24 bits |
+--+--+--+--+--+--+--+--+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
0 1 2
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
- M4, M6: These bits indicate, respectively, that there is an
IPv4 or IPv6 multicast router on a link to which the
originating IS is Appointed Forwarder for the VLAN
corresponding to every label in the indicated range.
- BM: If the BM (bit-map) bit is zero, the last three bytes of
the Interested Labels is a Label.end label number. If the BM
bit is one, those bytes are a bit-map as described below.
- R: These reserved bits MUST be sent as zero and are ignored on
receipt.
- Label.start and Label.end: If the BM bit is zero, this fine-
grained label [RFC 7172] ID range is inclusive. These fields
are treated as unsigned integers. Setting them both to the
same label ID value indicates a range of one label ID. If
Label.end is less than Label.start, the sub-TLV is ignored.
- Label.start and bit-map: If the BM bit is one, the fine-grained
labels that the IS is interested in are indicated by a 24-bit
bit-map. The interested labels are the Label.start number plus
the bit number of each one bit in the bit-map. So, if bit zero
of the bit-map is a one, the IS is interested in the label with
value Label.start, and if bit 23 of the bit-map is a one, the
IS is interested in the label with value Label.start+23.
o Appointed Forwarder Status Lost Counter: This is a count of how
many times a port that was Appointed Forwarder for a VLAN mapping
to the fine-grained label in the range or bit-map given has lost
the status of being an Appointed Forwarder as discussed in Section
4.8.3 of [RFC 6325]. It is initialized to zero at an IS when the
zeroth LSP sequence number is initialized. No special action need
be taken at rollover; the counter just wraps around.
Eastlake, et al. Standards Track PAGE 26
RFC 7176 TRILL Use of IS-IS May 2014
o Root Bridges: The list of zero or more spanning tree root bridge
IDs is the set of root bridge IDs seen for all ports for which the
IS is Appointed Forwarder for a VLAN mapping to the fine-grained
label in the specified range or bit-map. (See [RFC 6325], Section
4.9.3.2.) While, of course, at most one spanning tree root could
be seen on any particular port, there may be multiple relevant
ports connected to different bridged LANs with different spanning
tree roots.
An INT-LABEL sub-TLV asserts that the information provided (multicast
router attachment, Appointed Forwarder status lost counter, and root
bridges) is the same for all labels specified. If this is not the
case, the sub-TLV MUST be split into subranges and/or separate bit
maps meeting this criteria. It is always safe to use sub-TLVs with a
"range" of one VLAN ID, but this may be too verbose.
2.3.9. RBridge Channel Protocols Sub-TLV
An IS announces the RBridge Channel protocols [RFC 7178] it supports
through use of this sub-TLV.
+-+-+-+-+-+-+-+-+
|Type=RBCHANNELS| (1 byte)
+-+-+-+-+-+-+-+-+
| Length | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...
| Zero or more bit vectors (variable)
+-+-+-+-...
o Type: Router Capability and MT-Capability RBridge Channel
Protocols sub-TLV, set to 16 (RBCHANNELS).
o Length: variable.
o Bit Vectors: Zero or more byte-aligned bit vectors where a one bit
indicates support of a particular RBridge Channel protocol. Each
byte-aligned bit vector is formatted as follows:
| 0 1 2 3 4 5 6 7| 8 9 10 11 12 13 14 15|
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| Bit Vector Length | Bit Vector Offset |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| bits
+--+--+--...
The Bit Vector Length (BVL) is a seven-bit unsigned integer field
giving the number of bytes of bit vector. The Bit Vector Offset
(BVO) is a nine-bit unsigned integer field.
Eastlake, et al. Standards Track PAGE 27
RFC 7176 TRILL Use of IS-IS May 2014
The bits in each bit vector are numbered in network order, the
high-order bit of the first byte of bits being bit 0 + 8*BVO, the
low-order bit of that byte being 7 + 8*BVO, the high order bit of
the second byte being 8 + 8*BVO, and so on for BVL bytes. A bit
vector of RBridge Channel protocols supported MUST NOT extend
beyond the end of the value in the sub-TLV in which it occurs. If
it does, it is ignored. If multiple byte-aligned bit vectors are
present in one such sub-TLV, their representations are contiguous,
the BVL field for the next starting immediately after the last
byte of bits for the previous bit vector. The one or more bit
vectors present MUST exactly fill the sub-TLV value. If there are
one or two bytes of value left over, they are ignored; if more
than two, an attempt is made to parse them as one or more bit
vectors.
If different bit vectors overlap in the protocol number space they
refer to and they have inconsistent bit values for a channel
protocol, support for the protocol is assumed if any of these bit
vectors has a 1 for that protocol.
The absence of any occurrences of this sub-TLV in the LSP for an
IS implies that the IS does not support the RBridge Channel
facility. To avoid wasted space, trailing bit vector zero bytes
SHOULD be eliminated by reducing BVL, any null bit vectors (ones
with BVL equal to zero) eliminated, and generally the most compact
encoding used. For example, support for channel protocols 1 and
32 could be encoded as
BVL = 5
BVO = 0
0b01000000
0b00000000
0b00000000
0b00000000
0b10000000
or as
BVL = 1
BVO = 0
0b01000000
BLV = 1
BVO = 4
0b1000000
The first takes 7 bytes while the second takes only 6; thus, the
second would be preferred.
Eastlake, et al. Standards Track PAGE 28
RFC 7176 TRILL Use of IS-IS May 2014
In multi-topology-aware RBridges, RBridge Channel protocols for which
support is announced in the base topology are assumed to be supported
in all topologies for which there is no separate announcement for
RBridge Channel protocol support.
2.3.10. Affinity Sub-TLV
Association of an IS to a multi-destination distribution tree through
a specific path is accomplished by using the Affinity sub-TLV. The
announcement of an Affinity sub-TLV by RB1 with the nickname of RB2
as the first part of an Affinity Record in the sub-TLV value is a
request by RB1 that all ISs in the campus connect RB2 as a child of
RB1 when calculating any of the trees listed in that Affinity Record.
Examples of use include [Affinity] and [Resilient].
The structure of the Affinity sub-TLV is shown below.
+-+-+-+-+-+-+-+-+
| Type=AFFINITY | (1 byte)
+-+-+-+-+-+-+-+-+
| Length | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AFFINITY RECORD 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AFFINITY RECORD 2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ..........
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AFFINITY RECORD N |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where each AFFINITY RECORD is structured as follows:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Nickname | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Affinity Flags | (1 byte)
+-+-+-+-+-+-+-+-+
|Number of trees| (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tree-num of 1st root | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tree-num of 2nd root | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| .......... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tree-num of Nth root | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Eastlake, et al. Standards Track PAGE 29
RFC 7176 TRILL Use of IS-IS May 2014
o Type: Router Capability and MT-Capability sub-TLV type, set to 17
(AFFINITY).
o Length: size of all Affinity Records included, where an Affinity
Record listing n tree roots is 4+2*n bytes long.
o Nickname: 16-bit nickname of the IS whose associations to the
multi-destination trees listed in the Affinity Record are through
the originating IS.
o Affinity Flags: 8 bits reserved for future needs to provide
additional information about the affinity being announced. MUST
be sent as zero and ignored on receipt.
o Number of trees: A one-byte unsigned integer giving the number of
trees for which affinity is being announced by this Affinity
Record.
o Tree-num of roots: The tree numbers of the distribution trees this
Affinity Record is announcing.
There is no need for a field giving the number of Affinity Records as
this can be determined by processing those records.
2.3.11 Label Group Sub-TLV
The Label Group sub-TLV consists of two or more fine-grained label
[RFC 7172] IDs. This sub-TLV indicates that shared label MAC address
learning is occurring at the announcing IS between the listed labels.
It is structured as follows:
+-+-+-+-+-+-+-+-+
|Typ=LABEL-GROUP| (1 byte)
+-+-+-+-+-+-+-+-+
| Length | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Primary Label ID | (3 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Secondary Label ID | (3 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| more Secondary Label IDs ... (3 bytes each)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
o Type: Router Capability and MT-Capability sub-TLV type, set to 18
(LABEL-GROUP).
o Length: 6 + 3*n, where n is the number of secondary VLAN ID fields
beyond the first. n MAY be zero.
Eastlake, et al. Standards Track PAGE 30
RFC 7176 TRILL Use of IS-IS May 2014
o Primary Label ID: This identifies the primary Label ID.
o Secondary Label ID: This identifies a secondary Label ID in the
Label Group.
o more Secondary Label IDs: zero or more byte triples, each with a
Label ID.
2.4. MTU Sub-TLV for Extended Reachability and MT-ISN TLVs
The MTU sub-TLV is used to optionally announce the MTU of a link as
specified in [RFC 6325], Section 4.2.4.4. It occurs within the
Extended Reachability (#22) and MT-ISN (Intermediate System
Neighbors) (#222) TLVs.
+-+-+-+-+-+-+-+-+
| Type = MTU | (1 byte)
+-+-+-+-+-+-+-+-+
| Length | (1 byte)
+-+-+-+-+-+-+-+-+
|F| RESV | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MTU | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
o Type: Extended Reachability and MT-ISN sub-TLV type, set to MTU
sub-TLV 28.
o Length: 3.
o F: Failed. This bit is a one if MTU testing failed on this link
at the required campus-wide MTU.
o RESV: 7 bits that MUST be sent as zero and ignored on receipt.
o MTU: This field is set to the largest successfully tested MTU size
for this link or zero if it has not been tested, as specified in
Section 4.3.2 of [RFC 6325].
2.5. TRILL Neighbor TLV
The TRILL Neighbor TLV is used in TRILL broadcast link IIH PDUs (see
Section 4.1 below) in place of the IS Neighbor TLV, as specified in
Section 4.4.2.1 of [RFC 6325] and in [RFC 7177]. The structure of the
TRILL Neighbor TLV is as follows:
Eastlake, et al. Standards Track PAGE 31
RFC 7176 TRILL Use of IS-IS May 2014
+-+-+-+-+-+-+-+-+
| Type | (1 byte)
+-+-+-+-+-+-+-+-+
| Length | (1 byte)
+-+-+-+-+-+-+-+-+
|S|L|R| SIZE | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Neighbor RECORDS (1) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Neighbor RECORDS (2) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ................. |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Neighbor RECORDS (N) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The information present for each neighbor is as follows:
+-+-+-+-+-+-+-+-+
|F|O| RESV | (1 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MTU | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...+-+-+-+-+-+
| SNPA (MAC Address) | (SIZE bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...+-+-+-+-+-+
o Type: TLV type, set to TRILL Neighbor TLV 145.
o Length: 1 + (SIZE+3)*n, where n is the number of neighbor records,
which may be zero.
o S: Smallest flag. If this bit is a one, then the list of
neighbors includes the neighbor with the smallest MAC address
considered as an unsigned integer.
o L: Largest flag. If this bit is a one, then the list of neighbors
includes the neighbor with the largest MAC address considered as
an unsigned integer.
o R, RESV: These bits are reserved and MUST be sent as zero and
ignored on receipt.
o SIZE: The SNPA size as an unsigned integer in bytes except that 6
is encoded as zero. An actual size of zero is meaningless and
cannot be encoded. The meaning of the value 6 in this field is
reserved, and TRILL Neighbor TLVs received with a SIZE of 6 are
ignored. The SIZE is inherent to the technology of a link and is
fixed for all TRILL Neighbor TLVs on that link but may vary
Eastlake, et al. Standards Track PAGE 32
RFC 7176 TRILL Use of IS-IS May 2014
between different links in the campus if those links are different
technologies, for example, 6 for EUI-48 SNPAs or 8 for EUI-64
SNPAs [RFC 7042]. (The SNPA size on the various links in a TRILL
campus is independent of the System ID size.)
o F: Failed. This bit is a one if MTU testing to this neighbor
failed at the required campus-wide MTU (see [RFC 6325], Section
4.3.1).
o O: OOMF. This bit is a one if the IS sending the enclosing TRILL
Neighbor TLV is willing to offer the Overload Originated Multi-
destination Frame (OOMF) service [RFC 7180] to the IS whose port
has the SNPA in the enclosing Neighbor RECORD.
o MTU: This field is set to the largest successfully tested MTU size
for this neighbor or to zero if it has not been tested.
o SNPA (MAC Address): Subnetwork Point of Attachment of the
neighbor.
As specified in [RFC 7177] and Section 4.4.2.1 of [RFC 6325], all MAC
addresses may fit into one TLV, in which case both the S and L flags
would be set to one in that TLV. If the MAC addresses don't fit into
one TLV, the highest MAC address in a TRILL Neighbor TLV with the L
flag zero MUST also appear as a MAC address in some other TRILL
Neighbor TLV (possibly in a different TRILL IIH PDU). Also, the
lowest MAC address in a TRILL Neighbor TLV with the S flag zero MUST
also appear in some other TRILL Neighbor TLV (possibly in a different
TRILL IIH PDU). If an IS believes it has no neighbors, it MUST send
a TRILL Neighbor TLV with an empty list of neighbor RECORDS, which
will have both the S and L bits on.
3. MTU PDUs
The IS-IS MTU-probe and MTU-ack PDUs are used to optionally determine
the MTU on a link between ISs as specified in Section 4.3.2 of
[RFC 6325] and in [RFC 7177].
The MTU PDUs have the IS-IS PDU common header (up through the Maximum
Area Addresses byte) with PDU Type numbers as indicated in Section 5.
They also have a common fixed MTU PDU header as shown below that is 8
+ 2*(ID Length) bytes long, 20 bytes in the case of the usual 6-bytes
System IDs.
Eastlake, et al. Standards Track PAGE 33
RFC 7176 TRILL Use of IS-IS May 2014
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PDU Length | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+.....+-+-+
| Probe ID (6 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+.....+-+-+
| Probe Source ID (ID Length bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+.....+-+-+
| Ack Source ID (ID Length bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+.....+-+-+
As with other IS-IS PDUs, the PDU Length gives the length of the
entire IS-IS packet starting with and including the IS-IS common
header.
The Probe ID field is an opaque 48-bit quantity set by the IS issuing
an MTU-probe and copied by the responding IS into the corresponding
MTU-ack. For example, an IS creating an MTU-probe could compose this
quantity from a port identifier and probe sequence number relative to
that port.
The Probe Source ID is set by an IS issuing an MTU-probe to its
System ID and copied by the responding IS into the corresponding MTU-
ack. The Ack Source ID is set to zero in MTU-probe PDUs and ignored
on receipt. An IS issuing an MTU-ack sets the Ack Source ID field to
its System ID. The System ID length is usually 6 bytes but could be
a different value as indicated by the ID Length field in the IS-IS
PDU Header.
The TLV area follows the MTU PDU header area. This area MAY contain
an Authentication TLV and MUST be padded with the Padding TLV to the
exact size being tested. Since the minimum size of the Padding TLV
is 2 bytes, it would be impossible to pad to exact size if the total
length of the required information-bearing fixed fields and TLVs
added up to 1 byte less than the desired length. However, the length
of the fixed fields and substantive TLVs for MTU PDUs is expected to
be quite small compared with their minimum length (minimum 1470-byte
MTU on an IEEE 802.3 link, for example), so this should not be a
problem.
Eastlake, et al. Standards Track PAGE 34
RFC 7176 TRILL Use of IS-IS May 2014
4. Use of Existing PDUs and TLVs
The sub-sections below provide details of TRILL use of existing PDUs
and TLVs.
4.1. TRILL IIH PDUs
The TRILL IIH PDU is the variation of the IIH PDU used by the TRILL
protocol. Section 4.4 of the TRILL standard [RFC 6325] and [RFC 7177]
specify the contents of the TRILL IIH and how its use in TRILL
differs from Layer 3 LAN IIH PDU use. The adjacency state machinery
for TRILL neighbors is specified in detail in [RFC 7177].
In a TRILL IIH PDU, the IS-IS common header and the fixed PDU Header
are the same as a Level 1 IIH PDU.
The IS-IS Neighbor TLV (6) is not used in a TRILL IIH and is ignored
if it appears there. Instead, TRILL LAN IIH PDUs use the TRILL
Neighbor TLV (see Section 2.5).
4.2. Area Address
TRILL uses a fixed zero Area Address as specified in [RFC 6325],
Section 4.2.3. This is encoded in a 4-byte Area Address TLV (TLV #1)
as follows:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0x01, Area Address Type | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0x02, Length of Value | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0x01, Length of Address | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0x00, zero Area Address | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4.3. Protocols Supported
NLPID (Network Layer Protocol ID) 0xC0 has been assigned to TRILL
[RFC 6328]. A Protocols Supported TLV (#129, [RFC 1195]) including
that value appears in TRILL IIH PDUs and LSP number zero PDUs.
4.4. Link State PDUs (LSPs)
An LSP number zero MUST NOT be originated larger than 1470 bytes, but
a larger LSP number zero successfully received MUST be processed and
forwarded normally.
Eastlake, et al. Standards Track PAGE 35
RFC 7176 TRILL Use of IS-IS May 2014
4.5. Originating LSP Buffer Size
The originatingLSPBufferSize TLV (#14) MUST be in LSP number zero;
however, if found in other LSP fragments, it is processed normally.
Should there be more than one originatingLSPBufferSize TLV for an IS,
the minimum size, but not less than 1470, is used.
5. IANA Considerations
This section gives IANA considerations for the TLVs, sub-TLVs, and
PDUs specified herein. A number of new code points are assigned, and
those that were assigned by [RFC 6326] are included here for
convenience. IANA has replaced all [RFC 6326] references in the IANA
registries with references to this document.
5.1. TLVs
This document specifies two IS-IS TLV types -- namely, the Group
Address TLV (GADDR-TLV; type 142) and the TRILL Neighbor TLV (type
145). The PDUs in which these TLVs are permitted for TRILL are shown
in the table below along with the section of this document where they
are discussed. The final "NUMBER" column indicates the permitted
number of occurrences of the TLV in their PDU, or set of PDUs in the
case of LSPs, which in these two cases is "*" indicating that the TLV
MAY occur 0, 1, or more times.
IANA has registered these two code points in the IANA IS-IS TLV
registry (ignoring the "Section" and "NUMBER" columns, which are
irrelevant to that registry).
Section TLV IIH LSP SNP Purge NUMBER
======= === === === === ===== ======
GADDR-TLV 2.1 142 n y n n *
TRILL Neighbor TLV 2.5 145 y n n n *
5.2. Sub-TLVs
This document specifies a number of sub-TLVs. The TLVs in which
these sub-TLVs occur are shown in the second table below along with
the section of this document where they are discussed. The TLVs
within which these sub-TLVs can occur are determined by the presence
of an "X" in the relevant column; the column headers are described in
the first table below. In some cases, the column header corresponds
to two different TLVs in which the sub-TLV can occur.
Eastlake, et al. Standards Track PAGE 36
RFC 7176 TRILL Use of IS-IS May 2014
Column Head TLV RFC TLV Name
=========== ===== ======== ==============
Grp. Adr. 142 7176 Group Address
MT Port 143 6165 MT-Port-Cap-TLV
MT Cap. 242 4971 Router CAPABILITY
144 6329 MT-Capability
Ext. Reach 22 5305 Extended IS Reachability
222 5120 MT-ISN
The final "NUMBER" column below indicates the permitted number of
occurrences of the sub-TLV cumulatively within all occurrences of
their TLV(s) in those TLVs' carrying a PDU (or set of PDUs in the
case of LSPs), as follows:
0-1 = MAY occur zero or one times.
1 = MUST occur exactly once. If absent, the PDU is ignored. If it
occurs more than once, results are unspecified.
* = MAY occur 0, 1, or more times.
The values in the "Section" and "NUMBER" columns are irrelevant to
the IANA sub-registries.
sub- Grp. MT MT Ext.
Name Section TLV# Adr. Port Cap. Reach NUMBER
=================================================================
GMAC-ADDR 2.1.1 1 X - - - *
GIP-ADDR 2.1.2 2 X - - - *
GIPV6-ADDR 2.1.3 3 X - - - *
GLMAC-ADDR 2.1.4 4 X - - - *
GLIP-ADDR 2.1.5 5 X - - - *
GLIPV6-ADDR 2.1.6 6 X - - - *
VLAN-FLAGS 2.2.1 1 - X - - 1
Enabled-VLANs 2.2.2 2 - X - - *
AppointedFwrdrs 2.2.3 3 - X - - *
PORT-TRILL-VER 2.2.4 7 - X - - 0-1
VLANs-Appointed 2.2.5 8 - X - - *
NICKNAME 2.3.2 6 - - X - *
TREES 2.3.3 7 - - X - 0-1
TREE-RT-IDs 2.3.4 8 - - X - *
TREE-USE-IDs 2.3.5 9 - - X - *
INT-VLAN 2.3.6 10 - - X - *
TRILL-VER 2.3.1 13 - - X - 0-1
VLAN-GROUP 2.3.7 14 - - X - *
INT-LABEL 2.3.8 15 - - X - *
RBCHANNELS 2.3.9 16 - - X - *
Eastlake, et al. Standards Track PAGE 37
RFC 7176 TRILL Use of IS-IS May 2014
AFFINITY 2.3.10 17 - - X - *
LABEL-GROUP 2.3.11 18 - - X - *
MTU 2.4 28 - - - X 0-1
=================================================================
Name Section sub- Grp. MT MT Ext. NUMBER
TLV# Adr. Port Cap. Reach
IANA has entered the newly assigned sub-TLV numbers in the above
table in the relevant existing sub-TLV registries, as determined by
which column has an X for that sub-TLV. For the sub-TLVs from
NICKNAME through and including VLAN-GROUP, which previously existed
only in the registry of sub-TLVs under TLV 242, IANA has added each
sub-TLV with the same sub-TLV number to the existing registry for
sub-TLVs under TLV 144.
5.3. PDUs
The IS-IS PDUs registry remains as established in [RFC 6326] except
that the references to [RFC 6326] are updated to reference this
document.
5.4. Reserved and Capability Bits
Any reserved bits (R), bits in reserved fields (RESV), or
capabilities bits in the PORT-TRILL-VER and TRILL-VER sub-TLVs, which
are specified herein as "MUST be sent as zero and ignored on receipt"
or the like, are allocated based on IETF Review [RFC 5226].
Two sub-registries have been created within the TRILL Parameters
Registry as follows:
Sub-Registry Name: TRILL-VER Sub-TLV Capability Flags
Registration Procedures: IETF Review
Reference: (This document)
Bit Description Reference
===== ============= ===========
0 Affinity sub-TLV support. [Affinity]
1 FGL-safe [RFC 7172]
2-13 Unassigned
14-31 Extended header flag support. [RFC 7179]
Eastlake, et al. Standards Track PAGE 38
RFC 7176 TRILL Use of IS-IS May 2014
Sub-Registry Name: PORT-TRILL-VER Sub-TLV Capability Flags
Registration Procedures: IETF Review
Reference: (This document)
Bit Description Reference
===== ============= ===========
0 Hello reduction support. [RFC 7180]
1-2 Unassigned
3-13 Hop-by-hop extended flag support. [RFC 7179]
14-31 Unassigned
5.5. TRILL Neighbor Record Flags
A sub-registry has been created within the TRILL Parameters Registry
as follows:
Sub-Registry Name: TRILL Neighbor TLV NEIGHBOR RECORD Flags
Registration Procedures: Standards Action
Reference: (This document)
Bit Short Name Description Reference
============== ============= ===========================
0 Fail Failed MTU test [RFC 6325][RFC 7176][RFC 7177]
1 OOMF Offering OOMF service [RFC 7180]
2-7 - Unassigned
6. Security Considerations
For general TRILL protocol security considerations, see the TRILL
base protocol standard [RFC 6325].
This document raises no new security issues for IS-IS. IS-IS
security may be used to secure the IS-IS messages discussed here.
See [RFC 5304] and [RFC 5310]. Even when IS-IS authentication is used,
replays of Hello packets can create denial-of-service conditions; see
[RFC 6039] for details. These issues are similar in scope to those
discussed in Section 6.2 of [RFC 6325], and the same mitigations may
apply.
7. Changes from RFC 6326
Non-editorial changes from [RFC 6326] are summarized in the list
below:
1. Added five sub-TLVs under the Group Address (GADDR) TLV covering
VLAN-labeled IPv4 and IPv6 addresses and fine-grained-labeled
MAC, IPv4, and IPv6 addresses (Sections 2.1.2, 2.1.3, 2.1.4,
2.1.5, and 2.1.6).
Eastlake, et al. Standards Track PAGE 39
RFC 7176 TRILL Use of IS-IS May 2014
2. Added the PORT-TRILL-VER sub-TLV (Section 2.2.4).
3. Added the VLANs-Appointed sub-TLV (Section 2.2.5).
4. Changed the TRILL-VER sub-TLV as listed below.
a. Added 4 bytes of TRILL Header extended flags and capabilities
supported information.
b. Required that the TRILL-VER sub-TLV appear in LSP number
zero.
The above changes to TRILL-VER are backward compatible because
the [RFC 6326]-conformant implementations of TRILL thus far have
only supported version zero and not supported any optional
capabilities or extended flags, the level of support indicated by
the absence of the TRILL-VER sub-TLV. Thus, if an
[RFC 6326]-conformant implementation of TRILL rejects this sub-TLV
due to the changes specified in this document, it will, at worst,
decide that support of version zero and no extended flags or
capabilities is indicated, which is the best an
[RFC 6326]-conformant implementation of TRILL can do anyway.
Similarly, a TRILL implementation that supports TRILL-VER as
specified herein and rejects TRILL-VER sub-TLVs in an
[RFC 6326]-conformant TRILL implementation because they are not in
LSP number zero will decide that the implementation supports only
version zero with no extended flag or capabilities support, which
will be correct (Section 2.3.1).
5. Clarified the use of invalid VLAN IDs (0x000 and 0xFFF) in the
Appointed Forwarders sub-TLV and the Interested VLANs and
Spanning Tree Roots sub-TLV (Sections 2.2.3 and 2.3.6).
6. Added the Interested Labels and Spanning Tree Roots sub-TLV to
indicate attachment of an IS to a fine-grained label [RFC 7172]
analogous to the existing Interested VLANs and Spanning Tree
Roots sub-TLV for VLANs (Section 2.3.8).
7. Added the RBridge Channel Protocols sub-TLV so ISs can announce
the RBridge Channel protocols they support (Section 2.3.9).
8. Permitted specification of the length of the link SNPA field in
TRILL Neighbor TLVs. This change is backward compatible because
the size of 6 bytes is specially encoded as zero, the previous
value of the bits in the new SIZE field (Section 2.5).
Eastlake, et al. Standards Track PAGE 40
RFC 7176 TRILL Use of IS-IS May 2014
9. Made the size of the MTU PDU Header Probe Source ID and Ack
Source ID fields be the ID Length from the IS-IS PDU Header
rather than the fixed value 6 (Section 3).
10. For robustness, required that LSP number zero PDUs be originated
as no larger than 1470 bytes but processed regardless of size
(Section 4.4).
11. Required that the originatingLSPBufferSize TLV, if present,
appear in LSP number zero (Section 4.5).
12. Created sub-registries for and specified the IANA Considerations
policy for reserved and capability bits in the TRILL version sub-
TLVs (Section 5.4).
13. Added the distribution tree Affinity sub-TLV so ISs can request
distribution tree attachments (Section 2.3.10).
14. Added the LABEL-GROUP sub-TLV analogous to the VLAN-GROUP sub-TLV
(Section 2.3.11).
15. Added multi-topology to permit sub-TLVs previously only in the
Router Capability TLV to also appear in the MT-Capability TLV and
to permit the MTU sub-TLV previously limited to the Extended
Reachability TLV to also appear in the MT-ISN TLV.
16. Added a sub-registry for Neighbor TLV Neighbor RECORD flag bits
(Section 5.5).
17. Explicitly stated that if the number of sources in a GADDR-TLV
sub-TLV is zero, it indicates a listener for (*,G), that is, a
listener not restricted by source (Section 2.1).
8. References
8.1. Normative References
[ISO-10589]
International Organization for Standardization,
"Intermediate System to Intermediate System intra-domain
routeing information exchange protocol for use in
conjunction with the protocol for providing the
connectionless-mode network service (ISO 8473)", Second
Edition, November 2002.
[RFC 1195] Callon, R., "Use of OSI IS-IS for routing in TCP/IP and
dual environments", RFC 1195, December 1990.
Eastlake, et al. Standards Track PAGE 41
RFC 7176 TRILL Use of IS-IS May 2014
[RFC 1982] Elz, R. and R. Bush, "Serial Number Arithmetic", RFC 1982,
August 1996.
[RFC 2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC 4971] Vasseur, JP., Ed., Shen, N., Ed., and R. Aggarwal, Ed.,
"Intermediate System to Intermediate System (IS-IS)
Extensions for Advertising Router Information", RFC 4971,
July 2007.
[RFC 5120] 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.
[RFC 5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
May 2008.
[RFC 5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic
Engineering", RFC 5305, October 2008.
[RFC 6165] Banerjee, A. and D. Ward, "Extensions to IS-IS for Layer-2
Systems", RFC 6165, April 2011.
[RFC 6325] Perlman, R., Eastlake 3rd, D., Dutt, D., Gai, S., and A.
Ghanwani, "Routing Bridges (RBridges): Base Protocol
Specification", RFC 6325, July 2011.
[RFC 6328] Eastlake 3rd, D., "IANA Considerations for Network Layer
Protocol Identifiers", BCP 164, RFC 6328, July 2011.
[RFC 6329] Fedyk, D., Ed., Ashwood-Smith, P., Ed., Allan, D., Bragg,
A., and P. Unbehagen, "IS-IS Extensions Supporting IEEE
802.1aq Shortest Path Bridging", RFC 6329, April 2012.
[RFC 6439] Perlman, R., Eastlake, D., Li, Y., Banerjee, A., and F.
Hu, "Routing Bridges (RBridges): Appointed Forwarders",
RFC 6439, November 2011.
[RFC 7172] Eastlake 3rd, D., Zhang, M., Agarwal, P., Perlman, R., and
D. Dutt, "Transparent Interconnection of Lots of Links
(TRILL): Fine-Grained Labeling", RFC 7172, May 2014.
[RFC 7177] Eastlake 3rd, D., Perlman, R., Ghanwani, A., Yang, Y., and
V. Manral, "Transparent Interconnection of Lots of Links
(TRILL): Adjacency", RFC 7177, May 2014.
Eastlake, et al. Standards Track PAGE 42
RFC 7176 TRILL Use of IS-IS May 2014
[RFC 7178] Eastlake 3rd, D., Manral, V., Li, Y., Aldrin, S., and D.
Ward, "Transparent Interconnection of Lots of Links
(TRILL): RBridge Channel Support", RFC 7178, May 2014.
[RFC 7179] Eastlake 3rd, D., Ghanwani, A., Manral, V., Li, Y., and C.
Bestler, "Transparent Interconnection of Lots of Links
(TRILL): Header Extension", RFC 7179, May 2014.
[RFC 7180] Eastlake 3rd, D., Zhang, M., Ghanwani, A., Manral, V., and
A. Banerjee, "Transparent Interconnection of Lots of
Links (TRILL): Clarifications, Corrections, and Updates",
RFC 7180, May 2014.
8.2. Informative References
[Err2869] RFC Errata, Errata ID 2869, RFC 6326,
<http://www.rfc-editor.org>.
[RFC 5304] Li, T. and R. Atkinson, "IS-IS Cryptographic
Authentication", RFC 5304, October 2008.
[RFC 5310] Bhatia, M., Manral, V., Li, T., Atkinson, R., White, R.,
and M. Fanto, "IS-IS Generic Cryptographic
Authentication", RFC 5310, February 2009.
[RFC 6039] Manral, V., Bhatia, M., Jaeggli, J., and R. White, "Issues
with Existing Cryptographic Protection Methods for Routing
Protocols", RFC 6039, October 2010.
[RFC 6326] Eastlake, D., Banerjee, A., Dutt, D., Perlman, R., and A.
Ghanwani, "Transparent Interconnection of Lots of Links
(TRILL) Use of IS-IS", RFC 6326, July 2011.
[RFC 7042] Eastlake 3rd, D. and J. Abley, "IANA Considerations and
IETF Protocol and Documentation Usage for IEEE 802
Parameters", BCP 141, RFC 7042, October 2013.
[RFC 7175] Manral, V., Eastlake 3rd, D., Ward, D., and A. Banerjee,
"Transparent Interconnection of Lots of Links (TRILL):
Bidirectional Forwarding Detection (BFD) Support", RFC
7175, May 2014.
[Affinity] Senevirathne, T., Pathangi, J., and J. Hudson,
"Coordinated Multicast Trees (CMT) for TRILL", Work in
Progress, April 2014.
Eastlake, et al. Standards Track PAGE 43
RFC 7176 TRILL Use of IS-IS May 2014
[MultiLevel]
Perlman, R., Eastlake 3rd, D., Ghanwani, A., and H. Zhai,
"Flexible Multilevel TRILL (Transparent Interconnection of
Lots of Links)", Work in Progress, January 2014.
[Resilient]
Zhang, M. Senevirathne, T., Pathangi, J., Banerjee, A.,
and A. Ghanwani, "TRILL Resilient Distribution Trees",
Work in Progress, December 2013.
9. Acknowledgements
The authors gratefully acknowledge the contributions and reviews by
the following individuals: Ross Callon, Spencer Dawkins, Adrian
Farrel, Alexey Melnikov, Radia Perlman, Carlos Pignataro, and Joe
Touch.
The authors also acknowledge the contributions to [RFC 6326] by the
following individuals: Mike Shand, Stewart Bryant, Dino Farinacci,
Les Ginsberg, Sam Hartman, Dan Romascanu, Dave Ward, and Russ White.
In particular, thanks to Mike Shand for his detailed and helpful
comments.
Eastlake, et al. Standards Track PAGE 44
RFC 7176 TRILL Use of IS-IS May 2014
Authors' Addresses
Donald Eastlake 3rd
Huawei Technologies
155 Beaver Street
Milford, MA 01757
USA
Phone: +1-508-333-2270
EMail: d3e3e3@gmail.com
Tissa Senevirathne
Cisco Systems
375 East Tasman Drive,
San Jose, CA 95134
USA
Phone: +1-408-853-2291
EMail: tsenevir@cisco.com
Anoop Ghanwani
Dell
5450 Great America Parkway
Santa Clara, CA 95054
USA
EMail: anoop@alumni.duke.edu
Dinesh Dutt
Cumulus Networks
1089 West Evelyn Avenue
Sunnyvale, CA 94086
USA
EMail: ddutt.ietf@hobbesdutt.com
Ayan Banerjee
Insieme Networks
210 West Tasman Drive
San Jose, CA 95134
USA
EMail: ayabaner@gmail.com
Eastlake, et al. Standards Track PAGE 45
RFC TOTAL SIZE: 98059 bytes
PUBLICATION DATE: Thursday, May 8th, 2014
LEGAL RIGHTS: The IETF Trust (see BCP 78)
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