Internet Engineering Task Force (IETF) D. Eastlake 3rd

Internet Engineering Task Force (IETF) D. Eastlake 3rd
Request for Comments: 7961 Y. Li
Category: Standards Track Huawei
ISSN: 2070-1721 August 2016

Transparent Interconnection of Lots of Links (TRILL):
Interface Addresses APPsub-TLV

Abstract

This document specifies a TRILL (Transparent Interconnection of Lots
of Links) IS-IS application sub-TLV that enables the reporting by a
TRILL switch of sets of addresses. Each set of addresses reports all
of the addresses that designate the same interface (port) and also
reports the TRILL switch by which that interface is reachable. For
example, a 48-bit MAC (Media Access Control) address, IPv4 address,
and IPv6 address can be reported as all corresponding to the same
interface reachable by a particular TRILL switch. Such information
could be used in some cases to synthesize responses to, or bypass the
need for, the Address Resolution Protocol (ARP), the IPv6 Neighbor
Discovery (ND) protocol, or the flooding of unknown MAC addresses.

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 7841.

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/rfc7961.

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RFC 7961 TRILL: IA APPsub-TLV August 2016

Copyright Notice

Copyright (c) 2016 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 ..........................3
2. Format of the Interface Addresses APPsub-TLV ....................4
3. IA APPsub-TLV Sub-sub-TLVs ......................................9
3.1. AFN Size Sub-sub-TLV ......................................10
3.2. Fixed Address Sub-sub-TLV .................................11
3.3. Data Label Sub-sub-TLV ....................................12
3.4. Topology Sub-sub-TLV ......................................12
4. Security Considerations ........................................13
5. IANA Considerations ............................................14
5.1. Allocation of AFN Values ..................................14
5.2. IA APPsub-TLV Sub-sub-TLVs Sub-registry ...................15
5.3. IA APPsub-TLV Number ......................................16
6. Additional AFN Information .....................................16
7. Processing Address Sets ........................................16
8. References .....................................................18
8.1. Normative References ......................................18
8.2. Informative References ....................................20
Appendix A. Examples ..............................................21
A.1. Simple Example ............................................21
A.2. Complex Example ...........................................22
Acknowledgments ...................................................24
Authors' Addresses ................................................24

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RFC 7961 TRILL: IA APPsub-TLV August 2016

1. Introduction

This document specifies a TRILL (Transparent Interconnection of Lots
of Links) [RFC6325] IS-IS application sub-TLV (APPsub-TLV) [RFC6823]
that enables the convenient representation of sets of addresses where
all of the addresses in each set designate the same interface (port).
For example, a 48-bit MAC (Media Access Control) [RFC7042] address,
IPv4 address, and IPv6 address can be reported as all three
designating the same interface. In addition, a Data Label (VLAN or
Fine-Grained Label (FGL) [RFC7172]) is specified for the interface,
along with the TRILL switch and, optionally, the TRILL switch port
from which the interface is reachable. Such information could be
used in some cases to synthesize responses to, or bypass the need
for, the Address Resolution Protocol (ARP) [RFC826], the IPv6
Neighbor Discovery (ND) [RFC4861] protocol, the Reverse Address
Resolution Protocol (RARP) [RFC903], or the flooding of unknown
destination MAC addresses [ARPND]. If the information reported is
complete, it can also be used to detect and discard packets with
forged source addresses.

This APPsub-TLV appears inside the TRILL GENINFO TLV specified in the
End Station Address Distribution Information (ESADI) RFC [RFC7357]
but may also occur in other application contexts. The
"directory assistance" TRILL Edge services [DirectoryScheme] are
expected to make use of this APPsub-TLV.

Although in some IETF protocols address field types are represented
by an Ethertype [RFC7042] or a hardware address type [RFC5494], only
the Address Family Number (AFN) is used in this APPsub-TLV to
represent the address field type.

1.1. 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].
Capitalized IANA-related terms such as "Expert Review" are to be
interpreted as described in [RFC5226].

The terminology and acronyms of [RFC6325] are used herein, along with
the following additional acronyms and terms:

AFN: Address Family Number
(http://www.iana.org/assignments/address-family-numbers/)

APPsub-TLV: Application sub-TLV [RFC6823]

Data Label: VLAN or FGL

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RFC 7961 TRILL: IA APPsub-TLV August 2016

FGL: Fine-Grained Label [RFC7172]

IA: Interface Address(es)

MAC: Media Access Control

Nickname: A 16-bit TRILL switch identifier, as specified in
Section 3.7 of [RFC6325] and as updated by Section 4 of [RFC7780]

RBridge: An alternative name for a TRILL switch

TRILL switch: A device that implements the TRILL protocol

2. Format of the Interface Addresses APPsub-TLV

The Interface Addresses (IA) APPsub-TLV is used to advertise a set of
addresses indicating the same interface (port) within a Data Label
(VLAN or FGL). It also associates that interface with the TRILL
switch and, optionally, the TRILL switch port by which the interface
is reachable. These addresses can be in different address families.
For example, the IA APPsub-TLV can be used to declare that a
particular interface with specified IPv4, IPv6, and 48-bit MAC
addresses in some particular Data Label is reachable from a
particular TRILL switch. While those three types of addresses are
likely to be the only types of interest, any address type for which
an AFN has been assigned by IANA can be represented.

The Template field in a particular IA APPsub-TLV indicates the format
of each Address Set it carries. Certain well-known sets of addresses
are represented by special values. Other sets of addresses are
specified by a list of AFNs. The Template format that uses a list of
AFNs provides an explicit pattern for the type and order of addresses
in each Address Set in the IA APPsub-TLV that includes that Template.

A device or application making use of IA APPsub-TLV data is not
required to make use of all IA data. For example, a device or
application that was only interested in MAC and IPv6 addresses could
ignore any IPv4 or other types of address information that was
present.

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RFC 7961 TRILL: IA APPsub-TLV August 2016

Figure 1 shows an IA APPsub-TLV as it would appear inside an IS-IS
Flooding Scope Link State PDU (FS-LSP) using an extended flooding
scope [RFC7356] TLV -- for example, in ESADI [RFC7357]. Within an
IS-IS FS-LSP using traditional [ISO-10589] TLVs, the Type and Length
would be 1-byte unsigned integers equal to or less than 255, but with
an extended TLV, the Type and Length are 2-byte unsigned integers.

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = (10) | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Addr Sets End | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Nickname | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | (1 byte)
+-+-+-+-+-+-+-+-+
| Confidence | (1 byte)
+-+-+-+-+-+-+-+-+-+-
| Template ... (variable)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...-+
| Address Set 1 (size determined by Template) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...-+
| Address Set 2 (size determined by Template) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...-+
| ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...-+
| Address Set N (size determined by Template) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...-+
| optional sub-sub-TLVs ...
+-+-+-+-+-+-+-+-+-+-+-+-...

Figure 1: Interface Addresses APPsub-TLV

o Type: Interface Addresses TRILL APPsub-TLV type; set to 10
(IA-SUBTLV).

o Length: Variable; minimum 7. If Length is 6 or less or if the
APPsub-TLV extends beyond the size of an encompassing TRILL
GENINFO TLV or other context, the APPsub-TLV MUST be ignored. For
manageability, a counter reflecting the receipt of such malformed
IA APPsub-TLVs should be maintained.

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RFC 7961 TRILL: IA APPsub-TLV August 2016

o Addr Sets End: The unsigned integer byte number, within the IA
APPsub-TLV value part, of the last byte of the last Address Set,
where the first byte is numbered 1. This will be the number of
the byte just before the first sub-sub-TLV if any sub-sub-TLVs are
present (see Section 3). The processing is as follows:

- If this field is greater than Length or points to before the
end of the Template, the IA APPsub-TLV is corrupt and MUST be
discarded.

- If this field is equal to Length, there are no sub-sub-TLVs.

- If this field is less than Length, sub-sub-TLVs are parsed as
specified in Section 3.

Note: This field is always 2 bytes in size.

o Nickname: The nickname (see Section 1.1) of the TRILL switch by
which the Address Sets are reachable. If 0, the Address Sets are
reachable from the TRILL switch originating the message containing
the APPsub-TLV (for example, an ESADI [RFC7357] message).

o Flags: A byte of flags, as follows:

0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
|D|L| RESV |
+-+-+-+-+-+-+-+-+

D: Directory flag: If D is 1, the APPsub-TLV contains directory
information [RFC7067].

L: Local flag: If L is 1, the APPsub-TLV contains information
learned locally by observing ingressed frames [RFC6325].
(Both D and L can be set to 1 in the same IA APPsub-TLV if a
TRILL switch had learned an address locally and also
advertised it as a directory.)

RESV: Additional reserved flag bits that MUST be sent as zero
and ignored on receipt.

o Confidence: This 8-bit unsigned quantity in the range 0 to 254
indicates the confidence level in the addresses being transported
(see Section 4.8.2 of [RFC6325]). A value of 255 is treated as if
it was 254.

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RFC 7961 TRILL: IA APPsub-TLV August 2016

o Template: The initial byte of this field is the unsigned integer
K. If K has a value from 1 to 31, it indicates that this initial
byte is followed by a list of K AFNs that specify the exact
structure and order of each Address Set occurring later in the
APPsub-TLV. K can be 1, which is the minimum valid value. If K
is 0, the IA APPsub-TLV is ignored. If K is 32 to 254, the length
of the Template field is 1 byte, and its value is intended to
correspond to a particular ordered set of AFNs, some of which are
specified below. The value of 255 for K is reserved for future
definition and causes the IA APPsub-TLV to be ignored.

If the Template uses explicit AFNs, it looks like the following,
with the number of AFNs, up to 31, equal to K.

+-+-+-+-+-+-+-+-+
| K | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AFN 1 | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AFN 2 | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AFN K | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

For K in the range 32 to 39, values indicate a specific sequence,
as specified below. The values of K from 40 to 254 are reserved
for future specification. If the value of K is not understood by
a receiver of the IA-APPsub-TLV, any Address Sets present are
ignored.

K Addresses in order of occurrence
--- --------------------------------
32 48-bit MAC
33 48-bit MAC, IPv4
34 48-bit MAC, IPv6
35 48-bit MAC, IPv4, IPv6
36 48-bit MAC, RBridge port
37 48-bit MAC, IPv4, RBridge port
38 48-bit MAC, IPv6, RBridge port
39 48-bit MAC, IPv4, IPv6, RBridge port

For ease of decoding, note that for values of K between 32 and 39
inclusive, the 0x01 bit indicates that an IPv4 address is present,
the 0x02 bit indicates that an IPv6 address is present, and the
0x04 bit indicates that an RBridge Port ID is present.

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RFC 7961 TRILL: IA APPsub-TLV August 2016

o AFN: A 2-byte Address Family Number. The number of AFNs present
is given by K, except that there are no AFNs if K is greater than
31. The AFN sequence specifies the structure of the Address Sets
occurring later in the TLV. For example, if the Template size is
2 and the two AFNs present are the AFNs for a 48-bit MAC and an
IPv4 address, in that order, then each Address Set present will
consist of a 6-byte MAC address followed by a 4-byte IPv4 address.
If any AFNs are present that are unknown to the receiving IS and
the length of the corresponding address is not provided by a
sub-sub-TLV as specified below, the receiving IS will be unable to
parse the Address Sets and MUST ignore the IA APPsub-TLV.

o Address Set: Each Address Set in the APPsub-TLV consists of
exactly the same sequence of addresses and types as specified by
the Template earlier in the APPsub-TLV. No alignment, other than
to a byte boundary, is provided. The addresses in each Address
Set are contiguous with no unused bytes between them, and the
Address Sets are contiguous with no unused bytes between
successive Address Sets. The Address Sets must fit within the
TLV. See Section 7 on interpreting certain Address Sets.

o sub-sub-TLVs: If the Address Sets indicated by Addr Sets End do
not completely fill the length of the APPsub-TLV (as indicated by
the Length field), then per Section 4 of [RFC5305] the remaining
bytes are parsed as sub-sub-TLVs. Any such sub-sub-TLVs that are
not known to the receiving TRILL switch are ignored. Should this
parsing not be possible -- for example, there is only one
remaining byte or an apparent sub-sub-TLV extends beyond the end
of the TLV -- the containing IA APPsub-TLV is considered corrupt
and is ignored. (Several sub-sub-TLV types are specified in
Section 3.)

Different IA APPsub-TLVs within the same or different LSPs or other
data structures may have different Templates. The same AFN may occur
more than once in a Template, and the same address may occur in
different Address Sets. For example, a 48-bit MAC address interface
might have three different IPv6 addresses. This could be represented
by an IA APPsub-TLV whose Template specifically provided for one
EUI-48 address and three IPv6 addresses; this might be an efficient
format if there were multiple interfaces with that pattern.
Alternatively, a Template with one 48-bit MAC and one IPv6 address
could be used in an IA APPsub-TLV with three Address Sets each having
the same MAC address but different IPv6 addresses; this might be the
most efficient format if only one interface had multiple IPv6
addresses and other interfaces had only one IPv6 address.

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RFC 7961 TRILL: IA APPsub-TLV August 2016

In order to be able to parse the Address Sets, a receiving TRILL
switch must know at least the size of the address for each AFN or
address type the Template specifies; however, the presence of the
Addr Sets End field means that the sub-sub-TLVs, if any, can always
be located by a receiver. A TRILL switch can be assumed to know the
size of the AFNs mentioned in Section 5. Should a TRILL switch wish
to include an AFN that some receiving TRILL switch in the campus may
not know, it SHOULD include an AFN Size sub-sub-TLV as described in
Section 3.1. If an IA APPsub-TLV is received with one or more AFNs
in its Template for which the receiving TRILL switch does not know
the length and for which an AFN Size sub-sub-TLV is not present, that
IA APPsub-TLV MUST be ignored.

For manageability, a counter of ill-formed IA APPsub-TLVs received
and ignored due to unknown K, unknown AFN, and the like (as described
above) should be maintained.

3. IA APPsub-TLV Sub-sub-TLVs

IA APPsub-TLVs can have sub-sub-TLVs (sub-TLVs of sub-TLVs [RFC5305])
at the end, as specified below. These sub-sub-TLVs occur after the
Address Sets. The amount of space available for sub-sub-TLVs is
determined from the overall IA APPsub-TLV length and the value of the
Addr Sets End byte.

There is no ordering restriction on sub-sub-TLVs. Unless otherwise
specified, each sub-sub-TLV type can occur zero, one, or many times
in an IA APPsub-TLV. Any sub-sub-TLVs for which the Type is unknown
are ignored. For manageability, a counter of sub-sub-TLVs received
and ignored due to an unknown Type or other reasons, as described
below, should be maintained.

The data structures of the sub-sub-TLVs shown below, with 2-byte
Types and Lengths, assume that the enclosing IA APPsub-TLV is in an
extended LSP TLV [RFC7356] or some non-LSP context. If they were
used in an IA APPsub-TLV in a non-extended LSP [ISO-10589], then only
1-byte Types and Lengths could be used. As a result, any sub-sub-TLV
types greater than 255 could not be used, and Length would be limited
to 255.

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RFC 7961 TRILL: IA APPsub-TLV August 2016

3.1. AFN Size Sub-sub-TLV

Using this sub-sub-TLV, the originating TRILL switch can specify the
size of an address type. This is useful under the following two
circumstances:

1. One or more AFNs that are unknown to the receiving TRILL switch
appear in the Template. If an AFN Size sub-sub-TLV is present for
each such AFN, then at least the IA APPsub-TLV can be parsed, and
possibly other addresses in each Address Set can still be used.

2. If an AFN occurs in the Template that represents a variable-length
address, this sub-sub-TLV gives its size for all occurrences in
that IA APPsub-TLV.

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = AFNsz | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AFN Size Record 1 | (3 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AFN Size Record 2 | (3 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AFN Size Record N | (3 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 2: AFN Size Sub-sub-TLV

Where each AFN Size Record is structured as follows:

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AFN | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AdrSize | (1 byte)
+-+-+-+-+-+-+-+-+

o Type: AFN Size sub-sub-TLV type; set to 1 (AFNsz).

o Length: 3*N, where N is the number of AFN Size Records present.
If Length is not a multiple of 3, the sub-sub-TLV MUST be ignored.

o AFN Size Record(s): Zero or more 3-byte records, each giving the
size of an address type identified by an AFN.

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RFC 7961 TRILL: IA APPsub-TLV August 2016

o AFN: The AFN whose length is being specified by the AFN Size
Record.

o AdrSize: The length, in bytes, of addresses specified by the AFN
field as an unsigned integer.

An AFN Size sub-sub-TLV for any AFN known to the receiving TRILL
switch is compared with the size known to the TRILL switch. If they
differ, the IA APPsub-TLV is assumed to be corrupt and MUST be
ignored.

3.2. Fixed Address Sub-sub-TLV

There may be cases where, in a particular IA APPsub-TLV, the same
address would appear in every Address Set across the IA APPsub-TLV.
To avoid wasted space, this sub-sub-TLV can be used to indicate such
a fixed address. The address or addresses incorporated into the sets
by this sub-sub-TLV are NOT mentioned in the IA APPsub-TLV Template.

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = FIXEDADR | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AFN | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Fixed Address (variable)
+-+-+-+-+-+-+-+-+-+-+-+-+-...

Figure 3: Fixed Address Sub-sub-TLV

o Type: Data Label sub-sub-TLV type; set to 2 (FIXEDADR).

o Length: Variable; minimum 2. If Length is 0 or 1, the sub-sub-TLV
MUST be ignored.

o AFN: Address Family Number of the Fixed Address.

o Fixed Address: The address of the Type indicated by the preceding
AFN field that is considered to be part of every Address Set in
the IA APPsub-TLV.

The Length field implies a size for the Fixed Address. If that size
differs from the size of the address type for the given AFN as known
by the receiving TRILL switch, the Fixed Address sub-sub-TLV is
considered corrupt and MUST be ignored.

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RFC 7961 TRILL: IA APPsub-TLV August 2016

3.3. Data Label Sub-sub-TLV

This sub-sub-TLV indicates the Data Label within which the interfaces
listed in the IA APPsub-TLV are reachable. It is useful if the IA
APPsub-TLV occurs outside of the context of a message specifying the
Data Label or if it is desired and permitted to override that
specification. Multiple occurrences of this sub-sub-TLV indicate
that the interfaces are reachable in all of the Data Labels given.

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Type = DATALEN | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data Label (variable)
+-+-+-+-+-+-+-+-+-+-+-+-+-...

Figure 4: Data Label Sub-sub-TLV

o Type: Data Label sub-TLV type; set to 3 (DATALEN).

o Length: 2 or 3. If Length is some other value, the sub-sub-TLV
MUST be ignored.

o Data Label: If Length is 2, the bottom 12 bits of the Data Label
are a VLAN ID and the top 4 bits are reserved (MUST be sent as
zero and ignored on receipt). If Length is 3, the three Data
Label bytes contain an FGL [RFC7172].

3.4. Topology Sub-sub-TLV

The presence of this sub-sub-TLV indicates that the interfaces given
in the IA APPsub-TLV are reachable in the topology given. It is
useful if the IA APPsub-TLV occurs outside of the context of a
message indicating the topology or if it is desired and permitted to
override that specification. If it occurs multiple times, then the
Address Sets are in all of the topologies given.

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Type = TOPOLOGY | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RESV | Topology | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 5: Topology Sub-sub-TLV

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RFC 7961 TRILL: IA APPsub-TLV August 2016

o Type: Topology sub-TLV type; set to 4 (TOPOLOGY).

o Length: 2. If Length is some other value, the sub-sub-TLV MUST be
ignored.

o RESV: 4 reserved bits. MUST be sent as zero and ignored on
receipt.

o Topology: The 12-bit topology number [RFC5120].

4. Security Considerations

The integrity of address mapping and reachability information as well
as the correctness of Data Labels (VLANs or FGLs [RFC7172]) are very
important. Forged, altered, or incorrect address mapping or data
labeling can lead to delivery of packets to the incorrect party,
violating security policy. However, this document merely describes a
data format and does not provide any explicit mechanisms for securing
that information, other than a few simple consistency checks that
might detect some corrupted data. Security on the wire, or in
storage, for this data is to be provided by the transport or storage
used. For example, when transported with ESADI [RFC7357] or RBridge
Channel [RFC7178], ESADI security or Channel Tunnel [ChannelTunnel]
security mechanisms can be used, respectively.

The address mapping and reachability information, if known to be
complete and correct, can be used to detect some cases of forged
packet source addresses [RFC7067]. In particular, if native traffic
from an end station is received by a TRILL switch that would
otherwise accept it but authoritative data indicates that the source
address should not be reachable from the receiving TRILL switch, that
traffic should be discarded. The data format specified in this
document may optionally include a TRILL switch Port ID number so that
this forged address filtering can be optionally applied with port
granularity. For manageability, a counter of frames so discarded
should be maintained.

See [RFC6325] for general TRILL security considerations.

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RFC 7961 TRILL: IA APPsub-TLV August 2016

5. IANA Considerations

The following subsections specify IANA allocations.

5.1. Allocation of AFN Values

IANA has allocated values in the "Address Family Numbers" registry
that may be useful for IA APPsub-TLVs. The values are as follows:

Hex Decimal Description References
----- ------- ----------- ----------
0001 1 IPv4
0002 2 IPv6
4005 16389 48-bit MAC Section 2.1 of [RFC7042]
4006 16390 64-bit MAC Section 2.2 of [RFC7042]
4007 16391 OUI Section 6 of RFC 7961
4008 16392 MAC/24 Section 6 of RFC 7961
4009 16393 MAC/40 Section 6 of RFC 7961
400A 16394 IPv6/64 Section 6 of RFC 7961
400B 16395 RBridge Port ID Section 6 of RFC 7961

Other AFNs can be found at <http://www.iana.org/assignments/
address-family-numbers>.

See Section 7 on interpreting Address Sets.

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RFC 7961 TRILL: IA APPsub-TLV August 2016

5.2. IA APPsub-TLV Sub-sub-TLVs Sub-registry

IANA has established a new sub-registry of the "Transparent
Interconnection of Lots of Links (TRILL) Parameters" registry for
sub-sub-TLVs of the Interface Addresses APPsub-TLV, with the
following initial contents:

Name: Interface Addresses APPsub-TLV Sub-sub-TLVs

Procedure: Expert Review

Note: Types greater than 255 are not usable in some contexts.

Reference: RFC 7961

Type Description Reference
------ ----------- ---------
0 Reserved RFC 7961
1 AFN Size RFC 7961
2 Fixed Address RFC 7961
3 Data Label RFC 7961
4 Topology RFC 7961
5-254 Unassigned
255 Reserved RFC 7961
256-65534 Unassigned
65535 Reserved RFC 7961

Expert Guidance: A designated expert for this registry should decide
whether to permit the assignment of a type based on clear
documentation of the proposed type as provided by the requester,
such as a complete Internet-Draft. New types should not duplicate
existing types. Requests should indicate whether a type less than
255 is desired; such types can be used in contexts where only
1 byte of a type (and usually only 1 byte of the length) is
permitted. Types greater than 255 can only be used where 2-byte
types are allowed, such as in Extended Level 1 Flooding Scope
(E-L1FS) or Extended Level 1 Circuit Scope (E-L1CS) extended
FS-LSPs [RFC7356]; in those contexts, lengths up to 65535 bytes
can also be expressed, although they may not be usable if the
resulting TLV would not fit into a larger context restricted by an
MTU setting or the like. Values within the region below 255 and
the region above 255 should be allocated sequentially, unless
there is an extraordinary reason for a special value.

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RFC 7961 TRILL: IA APPsub-TLV August 2016

5.3. IA APPsub-TLV Number

IANA has allocated type 10 as the IA APPsub-TLV in the "TRILL
APPsub-TLV Types under IS-IS TLV 251 Application Identifier 1"
registry from the range under 256. In the registry, the name is "IA"
and the reference is this document.

6. Additional AFN Information

This section provides additional information concerning AFNs that
were allocated in connection with this document. These AFNs are not
restricted to use in the IA APPsub-TLV and may be used in other
protocols where they would be appropriate.

OUI: A 3-byte (24-bit) Organizationally Unique Identifier used as the
initial 3 bytes of a MAC address. See Sections 2.1 and 2.2 of
[RFC7042], and Section 7 below.

MAC/24: A 3-byte (24-bit) quantity used as the final 3 bytes of a
48-bit MAC address. See Section 2.1 of [RFC7042] and Section 7
below.

MAC/40: A 5-byte (40-bit) quantity used as the final 5 bytes of a
64-bit MAC address. See Section 2.2 of [RFC7042] and Section 7
below.

IPv6/64: An 8-byte (64-bit) quantity used as the initial 8 bytes of
an IPv6 address. See Section 7 below.

RBridge Port ID: A 16-bit quantity that uniquely identifies a port on
a TRILL switch (RBridge). See Section 4.4.2 of [RFC6325].

7. Processing Address Sets

The following processes should be followed in interpreting sets of
AFN values in an IA APPsub-TLV to synthesize addresses. These apply
whether the AFN values came from sub-sub-TLVs, appeared within an
Address Set, or came from both sources. In general, the processing
is applied separately to each Address Set as supplemented by any
Fixed Address sub-sub-TLVs that are present.

The OUI AFN value is provided so that MAC addresses can be
abbreviated if they have the same upper 24 bits. A MAC/24 is a
24-bit suffix intended to be prefixed by an OUI to create a 48-bit
MAC address [RFC7042]; in the absence of an OUI, a MAC/24 entry
cannot be used. A MAC/40 is a 40-bit suffix intended to be prefixed
by an OUI to create a 64-bit MAC address [RFC7042]; in the absence of
an OUI, a MAC/40 entry cannot be used.

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RFC 7961 TRILL: IA APPsub-TLV August 2016

Typically, an OUI would be provided as a Fixed Address sub-sub-TLV
(see Section 3.2) using the OUI AFN, but there is no prohibition
against one or more OUIs appearing in an Address Set.

Each Address Set, after being supplemented by any Fixed Address
sub-sub-TLVs, is processed by combining each OUI in the Address Set
with each MAC/24 and each MAC/40 address in the Address Set.
Depending on how many of each of these address types are present,
zero or more 48-bit and/or 64-bit MAC addresses may be synthesized
that are subsequently processed as if they had been part of the
Address Set. If there are no MAC/24 or MAC/40 addresses present, any
OUIs are ignored. If there are no OUIs, any MAC/24s and/or MAC/40s
are ignored. If there are K1 OUIs, K2 MAC/24s, and K3 MAC/40s, K1*K2
48-bit MACs are synthesized and K1*K3 64-bit MACs are synthesized.

IPv6/64 is an 8-byte quantity that is the first 64 bits of an IPv6
address. IPv6/64s are ignored unless, after the processing described
above in this subsection, there are one or more 48-bit and/or 64-bit
MAC addresses in the Address Set to provide the lower 64 bits of the
IPv6 address. For this purpose, a 48-bit MAC address is expanded to
64 bits as described in Section 2.2.1 of [RFC7042]. If there are K4
IPv6/64s present and K5 48-bit and 64-bit MAC addresses present,
K4*K5 128-bit IPv6 addresses are synthesized.

Synthesized addresses are treated as if they had been members of the
Address Set.

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RFC 7961 TRILL: IA APPsub-TLV August 2016

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)",
ISO Standard 10589, 2002.

[RFC826] Plummer, D., "Ethernet Address Resolution Protocol: Or
Converting Network Protocol Addresses to 48.bit Ethernet
Address for Transmission on Ethernet Hardware", STD 37,
RFC 826, DOI 10.17487/RFC0826, November 1982,
<http://www.rfc-editor.org/info/rfc826>.

[RFC903] Finlayson, R., Mann, T., Mogul, J., and M. Theimer, "A
Reverse Address Resolution Protocol", STD 38, RFC 903,
DOI 10.17487/RFC0903, June 1984,
<http://www.rfc-editor.org/info/rfc903>.

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.

[RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
"Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
DOI 10.17487/RFC4861, September 2007,
<http://www.rfc-editor.org/info/rfc4861>.

[RFC5120] Przygienda, T., Shen, N., and N. Sheth, "M-ISIS:
Multi Topology (MT) Routing in Intermediate System to
Intermediate Systems (IS-ISs)", RFC 5120,
DOI 10.17487/RFC5120, February 2008,
<http://www.rfc-editor.org/info/rfc5120>.

[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
DOI 10.17487/RFC5226, May 2008,
<http://www.rfc-editor.org/info/rfc5226>.

[RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic
Engineering", RFC 5305, DOI 10.17487/RFC5305,
October 2008, <http://www.rfc-editor.org/info/rfc5305>.

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RFC 7961 TRILL: IA APPsub-TLV August 2016

[RFC6325] Perlman, R., Eastlake 3rd, D., Dutt, D., Gai, S., and A.
Ghanwani, "Routing Bridges (RBridges): Base Protocol
Specification", RFC 6325, DOI 10.17487/RFC6325, July 2011,
<http://www.rfc-editor.org/info/rfc6325>.

[RFC6823] Ginsberg, L., Previdi, S., and M. Shand, "Advertising
Generic Information in IS-IS", RFC 6823,
DOI 10.17487/RFC6823, December 2012,
<http://www.rfc-editor.org/info/rfc6823>.

[RFC7042] Eastlake 3rd, D. and J. Abley, "IANA Considerations and
IETF Protocol and Documentation Usage for IEEE 802
Parameters", BCP 141, RFC 7042, DOI 10.17487/RFC7042,
October 2013, <http://www.rfc-editor.org/info/rfc7042>.

[RFC7172] Eastlake 3rd, D., Zhang, M., Agarwal, P., Perlman, R., and
D. Dutt, "Transparent Interconnection of Lots of Links
(TRILL): Fine-Grained Labeling", RFC 7172,
DOI 10.17487/RFC7172, May 2014,
<http://www.rfc-editor.org/info/rfc7172>.

[RFC7356] Ginsberg, L., Previdi, S., and Y. Yang, "IS-IS Flooding
Scope Link State PDUs (LSPs)", RFC 7356,
DOI 10.17487/RFC7356, September 2014,
<http://www.rfc-editor.org/info/rfc7356>.

[RFC7357] Zhai, H., Hu, F., Perlman, R., Eastlake 3rd, D., and O.
Stokes, "Transparent Interconnection of Lots of Links
(TRILL): End Station Address Distribution Information
(ESADI) Protocol", RFC 7357, DOI 10.17487/RFC7357,
September 2014, <http://www.rfc-editor.org/info/rfc7357>.

[RFC7780] Eastlake 3rd, D., Zhang, M., Perlman, R., Banerjee, A.,
Ghanwani, A., and S. Gupta, "Transparent Interconnection
of Lots of Links (TRILL): Clarifications, Corrections, and
Updates", RFC 7780, DOI 10.17487/RFC7780, February 2016,
<http://www.rfc-editor.org/info/rfc7780>.

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RFC 7961 TRILL: IA APPsub-TLV August 2016

8.2. Informative References

[ARPND] Li, Y., Eastlake 3rd, D., Dunbar, L., and R. Perlman,
"TRILL: ARP/ND Optimization", Work in Progress,
draft-ietf-trill-arp-optimization-06, April 2016.

[ChannelTunnel]
Eastlake 3rd, D., Umair, M., and Y. Li, "TRILL: RBridge
Channel Header Extension", Work in Progress,
draft-ietf-trill-channel-tunnel-11, August 2016.

[DirectoryScheme]
Eastlake 3rd, D., Dunbar, L., Perlman, R., and Y. Li,
"TRILL: Edge Directory Assist Mechanisms", Work in
Progress, draft-ietf-trill-directory-assist-mechanisms-07,
February 2016.

[RFC5494] Arkko, J. and C. Pignataro, "IANA Allocation Guidelines
for the Address Resolution Protocol (ARP)", RFC 5494,
DOI 10.17487/RFC5494, April 2009,
<http://www.rfc-editor.org/info/rfc5494>.

[RFC7067] Dunbar, L., Eastlake 3rd, D., Perlman, R., and I.
Gashinsky, "Directory Assistance Problem and High-Level
Design Proposal", RFC 7067, DOI 10.17487/RFC7067,
November 2013, <http://www.rfc-editor.org/info/rfc7067>.

[RFC7178] Eastlake 3rd, D., Manral, V., Li, Y., Aldrin, S., and D.
Ward, "Transparent Interconnection of Lots of Links
(TRILL): RBridge Channel Support", RFC 7178,
DOI 10.17487/RFC7178, May 2014,
<http://www.rfc-editor.org/info/rfc7178>.

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Appendix A. Examples

Below are example IA APPsub-TLVs. "0x" indicates that the quantity
is in hexadecimal. "0b" indicates that the quantity is in binary.
Leading zeros are retained.

A.1. Simple Example

Below is an annotated IA APPsub-TLV carrying two simple pairs of
EUI-48 MAC addresses and IPv4 addresses from a Push Directory
(a directory conforming to the Push Model [RFC7067]). No
sub-sub-TLVs are included.

0x0002(10) Type: Interface Addresses
0x001B Length: 27 (= 0x1B)
0x001B Address Sets End: 27 (= 0x1B)
0x1234 RBridge Nickname from which reachable
0b10000000 Flags: Push Directory data
0xE3 Confidence = 227
33 Template: 33 (0x21) = 32 + 1(IPv4)

Address Set One
0x00005E0053A9 48-bit MAC address
198.51.100.23 IPv4 address

Address Set Two
0x00005E00536B 48-bit MAC address
203.0.113.201 IPv4 address

The size includes 7 for the fixed fields through and including the
1-byte Template, plus 2 times the Address Set size. Each Address Set
is 10 bytes: 6 for the 48-bit MAC address plus 4 for the IPv4
address. Therefore, the total size is 7 + 2*10 = 27.

See Section 2 for more information on the Template.

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A.2. Complex Example

Below is an annotated IA APPsub-TLV carrying three sets of addresses,
each consisting of an EUI-48 MAC address, an IPv4 address, an IPv6
address, and an RBridge Port ID, all from a Push Directory
(a directory conforming to the Push Model [RFC7067]). The IPv6
address for each Address Set is synthesized from the MAC address
given in that set and the IPv6/64 64-bit prefix provided through a
Fixed Address sub-sub-TLV. In addition, a sub-sub-TLV is included
that provides an FGL that overrides whatever Data Label may be
provided by the envelope (for example, an ESADI-LSP [RFC7357]) within
which this IA APPsub-TLV occurs.

0x0002(10) Type: Interface Addresses
0x0036 Length: 64 (= 0x40)
0x0021 Address Sets End: 43 (= 0x2B)
0x4321 RBridge Nickname from which reachable
0b10000000 Flags: Push Directory data
0xD3 Confidence = 211
37 Template: 37(0x25) = 32 + 1(IPv4) + 4(Port)

Address Set One
0x00005E0053DE 48-bit MAC address
198.51.100.105 IPv4 address
0x1DE3 RBridge Port ID

Address Set Two
0x00005E0053E3 48-bit MAC address
203.0.113.89 IPv4 address
0x1DEE RBridge Port ID

Address Set Three
0x00005E0053D3 48-bit MAC address
192.0.2.139 IPv4 address
0x01DE RBridge Port ID

sub-sub-TLV One
0x0003 Type: Data Label
0x0003 Length: Implies FGL
0xD3E3E3 Fine-Grained Label

sub-sub-TLV Two
0x0002 Type: Fixed Address
0x000A Size: 0x0A = 10
0x400A AFN: IPv6/64
0x20010db800000000 IPv6 Prefix: 2001:db8::

See Section 2 for more information on the Template.

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The Fixed Address sub-sub-TLV causes the IPv6/64 value given to be
treated as if it occurred as a fourth entry inside each of the three
Address Sets. When there is an IPv6/64 entry and a 48-bit MAC entry,
the MAC value is expanded by inserting 0xfffe immediately after the
OUI, and the local/global bit is inverted. The resulting
Modified EUI-64-bit value is used as the lower 64 bits of the
resulting IPv6 address (Section 2.2.1 of [RFC7042]). As a result, a
receiving TRILL switch would treat the three Address Sets shown as if
they had an IPv6 address in them, as follows:

Address Set One
0x20010db80000000002005efffe0053de IPv6 Address

Address Set Two
0x20010db80000000002005efffe0053e3 IPv6 Address

Address Set Three
0x20010db80000000002005efffe0053d3 IPv6 Address

As an alternative to the compact "well-known value" Template encoding
used in the example above, the less compact explicit AFN encoding
could have been used. In that case, the IA APPsub-TLV would have
started as follows:

0x0002(10) Type: Interface Addresses
0x003C Length: 60 (= 0x3C)
0x0027 Address Sets End: 39 (= 0x27)
0x4321 RBridge Nickname from which reachable
0b10000000 Flags: Push Directory data
0xD3 Confidence = 211
0x3 Template: 3 AFNs
0x4005 AFN: 48-bit MAC
0x0001 AFN: IPv4
0x400B AFN: RBridge Port ID

As a final point, since the 48-bit MAC addresses in these three
Address Sets all have the same OUI (the IANA OUI [RFC7042]), it would
have been possible to just have a MAC/24 value giving the lower
24 bits of the MAC in each Address Set. The OUI would then be
supplied by a second Fixed Address sub-sub-TLV providing the OUI.
With N Address Sets, this would have saved 3*N or 9 bytes, at a cost
of 9 bytes (2 each for the Type and Length of the sub-sub-TLV, 2 for
the OUI AFN, and 3 for the OUI). So, with just three Address Sets,
there would be no net savings; however, with a larger number of
Address Sets, there would be a net savings.

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Acknowledgments

The authors gratefully acknowledge the contributions and review by
the following:

Linda Dunbar, Sue Hares, Paul Kyzivat, Danny McPherson, and
Gayle Noble

Authors' Addresses

Donald Eastlake 3rd
Huawei Technologies
155 Beaver Street
Milford, MA 01757
United States of America

Phone: +1-508-333-2270
Email: [email protected]

Yizhou Li
Huawei Technologies
101 Software Avenue
Nanjing 210012
China

Phone: +86-25-56622310
Email: [email protected]

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