wdiff rfc7978.original rfc7978.txt

INTERNET-DRAFT Donald
Internet Engineering Task Force (IETF) D. Eastlake 3rd
Request for Comments: 7978 Huawei
Updates: 7178 Huawei
Intended status: Proposed Standard Mohammed M. Umair
Category: Standards Track IPinfusion
Yizhou
ISSN: 2070-1721 Y. Li
Huawei
Expires: February 4, 2017 August 5,
September 2016

TRILL:

Transparent Interconnection of Lots of Links (TRILL):
RBridge Channel Header Extension
<draft-ietf-trill-channel-tunnel-11.txt>

Abstract

The IETF TRILL (Transparent Interconnection of Lots of Links)
protocol includes an optional mechanism (specified in RFC 7178)
called RBridge Channel for the transmission of typed messages between
TRILL switches in the same campus and the transmission of such
messages between TRILL switches and end stations on the same link.
This document specifies extensions to the RBridge Channel protocol
header to support two features as follows: (1) a standard method to
tunnel payloads whose type can be indicated by Ethertype through
encapsulation in RBridge Channel messages; and (2) a method to
support security facilities for RBridge Channel messages. This
document updates RFC 7178.

Status of This Memo

This Internet-Draft is submitted to IETF in full conformance with the
provisions of BCP 78 and BCP 79.

Distribution of this an Internet Standards Track document.

This document is unlimited. Comments should be sent
to the authors or the TRILL working group mailing list:
trill@ietf.org

Internet-Drafts are working documents a product of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.

Internet-Drafts are draft documents valid for a maximum
(IETF). It represents the consensus of six months the IETF community. It has
received public review and may be updated, replaced, or obsoleted has been approved for publication by other documents at any
time. It the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work available in progress."

The list Section 2 of RFC 7841.

Information about the current Internet-Drafts can be accessed at
http://www.ietf.org/1id-abstracts.html. The list status of Internet-Draft
Shadow Directories can this document, any errata,
and how to provide feedback on it may be accessed obtained at
http://www.ietf.org/shadow.html.

INTERNET-DRAFT TRILL: RBridge Channel Extension
http://www.rfc-editor.org/info/rfc7978.

Table of Contents

1. Introduction............................................3
1.1 Introduction ....................................................3
1.1. Terminology and Acronyms..............................3 Acronyms ...................................3
2. RBridge Channel Header Extension Format.................5 Format .........................4
3. Extended RBridge Channel Payload Types..................8
3.1 Types ..........................7
3.1. Null Payload...........................................8
3.2 Payload ...............................................7
3.2. Ethertyped Payload.....................................8
3.2.1 Payload .........................................8
3.2.1. RBridge Channel Message as the Payload...............9
3.2.2 Payload ..............8
3.2.2. TRILL Data Packet as the Payload.....................9
3.2.3 Payload ....................9
3.2.3. TRILL IS-IS Packet as the Payload...................10
3.3 Payload ...................9
3.3. Ethernet Frame........................................11 Frame ............................................10
4. Extended RBridge Channel Security......................14
4.1 Security ..............................12
4.1. Derived Keying Material...............................14
4.2 Material ...................................13
4.2. SType None............................................15
4.3 [RFC5310]-Based Authentication........................15
4.4 None ................................................13
4.3. IS-IS CRYPTO_AUTH-Based Authentication ....................14
4.4. DTLS Pairwise Security................................17
4.5 Security ....................................16
4.5. Composite Security....................................18 Security ........................................17
5. Extended RBridge Channel Errors........................19
5.1 SubERRs...............................................19
5.2 Errors ................................17
5.1. SubERRs ...................................................18
5.2. Secure Nested RBridge Channel Errors..................19 Errors ......................18
6. IANA Considerations....................................21
6.1 Considerations ............................................18
6.1. Extended RBridge Channel Protocol Number..............21
6.2 Number ..................19
6.2. RBridge Channel Protocol Subregistries................21
6.2.1 Subregistries ....................19
6.2.1. RBridge Channel Error Codes.........................21
6.2.2 Codes ........................19
6.2.2. RBridge Channel SubError Codes......................21
6.2.3 Codes .....................19
6.2.3. Extended RBridge Channel Payload Types Subregistry..22
6.2.4
Subregistry ........................................19
6.2.4. Extended RBridge Channel Security Types Subregistry.22
Subregistry ........................................20
7. Security Considerations................................23 Considerations ........................................20
8. Normative References......................................24 References ...........................................21
9. Informative References....................................25

Appendix Z: Change History................................27
Acknowledgements..........................................29 References .........................................22
Acknowledgements ..................................................24
Authors' Addresses........................................30

INTERNET-DRAFT TRILL: RBridge Channel Extension Addresses ................................................24

1. Introduction

The IETF TRILL base protocol [RFC6325] [RFC7780] has been extended
with the RBridge Channel [RFC7178] facility to support transmission
of typed messages (for example BFD (Bidirectional example, Bidirectional Forwarding
Detection) Detection
(BFD) [RFC7175]) between two TRILL switches (RBridges) in the same
campus and the transmission of such messages between RBridges and end
stations on the same link. When sent between RBridges in the same
campus, a TRILL Data packet with a TRILL Header is used used, and the
destination RBridge is indicated by nickname. When sent between a
RBridge and an end station on the same link in either direction, a
native RBridge Channel message [RFC7178] is used with no TRILL Header
Header, and the destination port or ports are indicated by a MAC Media
Access Control (MAC) address. (There is no mechanism to stop end
stations on the same link from sending native RBridge Channel
messages to each other; however, such use is outside the scope of
this document.)

This document updates [RFC7178] and specifies extensions to the
RBridge Channel header that provide two additional facilities as
follows:

(1) A standard method to tunnel payloads payloads, whose type may be
indicated by Ethertype Ethertype, through encapsulation in RBridge
Channel messages.

(2) A method to provide security facilities for RBridge Channel
messages. Example uses requiring such facilities are the
security of Pull Directory messages [RFC7067], address flush
messages [AddrFlush], and port shutdown messages [rfc6439bis]. [TRILL-AF].

Use of each of these facilities is optional, except that, as
specified below, if this header extension is implemented implemented, there are
two payload types that MUST be implemented. Both of the above
facilities can be used in the same packet. In case of conflict
between this document and [RFC7178], this document takes precedence.

1.1

1.1. Terminology and Acronyms

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
[RFC2119].

This document uses terminology and acronyms abbreviations defined in [RFC6325]
and [RFC7178]. Some of these are repeated listed below for convenience along
with additional new terms and acronyms. abbreviations.

application_data - A DTLS [RFC6347] message type.

INTERNET-DRAFT TRILL: RBridge Channel Extension

Data Label - VLAN or FGL.

DTLS - Datagram Transport Level Layer Security [RFC6347].

FCS - Frame Check Sequence.

FGL - Fine Grained Fine-Grained Label [RFC7172].

HKDF - HMAC-based Key Derivation Function [RFC5869].

IS-IS - Intermediate System to Intermediate Systems System [IS-IS].

PDU - Protocol Data Unit.

MTU - Maximum Transmission Unit.

RBridge - An alternative term for a TRILL switch.

SHA - Secure Hash Algorithm [RFC6234].

Sz - Campus-wide minimum link MTU [RFC6325] [RFC7780].

TRILL - Transparent Interconnection of Lots of Links or Tunneled
Routing in the Link Layer.

TRILL switch - A device that implements the TRILL protocol
[RFC6325] [RFC7780], sometimes referred to as an RBridge.

INTERNET-DRAFT TRILL: RBridge Channel Extension

2. RBridge Channel Header Extension Format

The general structure of an RBridge Channel message between two TRILL
switches (RBridges) in the same campus is shown in Figure 2.1 1 below.
The structure of a native RBridge Channel message sent between an
RBridge and an end station on the same link, in either direction, is
shown in Figure 2.2 2 and, compared with the first case, omits the TRILL
Header, inner Ethernet addresses, and Data Label. A Protocol field
in the RBridge Channel Header gives the type of RBridge Channel
message and indicates how to interpret the Channel Protocol Specific Channel-Protocol-Specific
Payload [RFC7178].

+-----------------------------------+
| Link Header |
+-----------------------------------+
| TRILL Header |
+-----------------------------------+
| Inner Ethernet Addresses |
+-----------------------------------+
| Data Label (VLAN or FGL) |
+-----------------------------------+
| RBridge Channel Header |
+-----------------------------------+
| Channel Protocol Specific Channel-Protocol-Specific Payload |
+-----------------------------------+
| Link Trailer (FCS if Ethernet) |
+-----------------------------------+

Figure 2.1 1: RBridge Channel Packet Structure

+-----------------------------------+
| Ethernet Link Header |
+-----------------------------------+
| RBridge Channel Header |
+-----------------------------------+
| Channel Protocol Specific Channel-Protocol-Specific Payload |
+-----------------------------------+
| FCS |
+-----------------------------------+

Figure 2.2 2: Native RBridge Channel Frame

The RBridge Channel Header looks like this:

INTERNET-DRAFT TRILL: RBridge Channel Extension

1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0x8946 | CHV=0 | Channel Protocol |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | ERR | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ /
/ Channel Protocol Specific Channel-Protocol-Specific Data /
/-+-+-+-+-+- /

Figure 2.3 3: RBridge Channel Header

where 0x8946 is the RBridge Channel RBridge-Channel Ethertype and CHV is the Channel
Header Version. This document is based on RBridge Channel version
zero.

The header extensions specified herein are in the form of an RBridge
Channel protocol, the Extended RBridge Channel Protocol. Figure 2.4 4
below expands the RBridge Channel Header and Protocol Specific Protocol-Specific
Payload above for the case where the header extension is present.

Figure 2.4 4: RBridge Channel Header Extension Structure

The RBridge Channel Header Protocol field is used to indicate that
the header extension is present. Its contents MUST be the value
allocated for this purpose (see Section 6). The use of an RBridge
Channel protocol to indicate extension extensions makes it easy to determine if
a remote RBridge in the campus supports extension extensions since RBridges
advertise in their LSP which such protocols they support.

The Extended RBridge Channel Protocol Specific Channel-Protocol-Specific Data fields are as
follows:

INTERNET-DRAFT TRILL: RBridge Channel Extension

SubERR: This field provides further details when an error is
indicated in the RBridge Channel ERR field. If ERR is zero,
then SubERR MUST be sent as zero and ignored on receipt. See
Section 5.

RESV4: This field MUST be sent as zero. If non-zero when
received, this is an error condition (see condition. See Section 5). 5.

SType: This field describes the type of security information and
features, including keying material, being used or provided by
the extended RBridge Channel message. See Section 4.

PType: Payload type. Type. This describes the tunneled data. See
Section
3 below. 3.

Security Information: Variable length Variable-length information. Length is zero
if SType is zero. See Section 4.

The RBridge Channel Header Extension is integrated with the RBridge
Channel facility. Extension errors are reported as if they were
RBridge Channel errors, using newly allocated code points in the ERR
field of the RBridge Channel Header supplemented by the SubERR field.

INTERNET-DRAFT TRILL: RBridge Channel Extension

3. Extended RBridge Channel Payload Types

The Extended RBridge Channel Protocol can carry a variety of payloads
as indicated by the PType (Payload Type) field. Values are shown in
the table below with further explanation after below the table (see also
Section 6.2.2).

PType Description Reference
----- ----------- ---------
0 Reserved
1 Null Section 3.1 of [this doc] RFC 7978
2 Ethertyped Payload Section 3.2 of [this doc] RFC 7978
3 Ethernet Frame Section 3.3 of [this doc] RFC 7978
4-14 Unassigned
15 Reserved

Table 3.1 1: Payload Type Values

While implementation of the RBridge Channel Header Extension is
optional, if it is implemented implemented, PType 1 (Null) MUST be implemented
and PType 2 (Ethertyped Payload) with the RBridge Channel RBridge-Channel Ethertype
MUST be implemented. PType 2 for any Ethertypes other than the RBridge
Channel
RBridge-Channel Ethertype MAY be implemented. PType 3 MAY be
implemented.

The processing of any particular extended header RBridge Channel
message and its payload depends on meeting local security and other
policy at the destination TRILL switch or end station.

3.1

3.1. Null Payload

The Null payload type (PType = 1) is intended to be used for testing
or for messages such as key negotiation or the like where only
security information is present. It indicates that there is no user
data payload. Any tunneled user data after the Security Information
field is ignored. If the RBridge Channel Header Extension is
implemented, the Null Payload MUST be supported in the sense that an
"Unsupported PType" error is not returned (see Section 5). Any
particular use of the Null Payload should specify what VLAN or FGL
and what priority should be used in the inner Data Label of the
RBridge Channel message (or in an outer VLAN tag for the native
RBridge Channel message case) when those values are relevant.

3.2

3.2. Ethertyped Payload

A PType of 2 indicates that the payload (tunneled data) of the
extended RBridge Channel message begins with an Ethertype. A TRILL

INTERNET-DRAFT TRILL: RBridge Channel Extension
switch supporting the RBridge Channel Header Extension MUST support a
PType of 2 with a payload beginning with the RBridge Channel RBridge-Channel
Ethertype as described in Section 3.2.1. Other Ethertypes, including
the TRILL and L2-IS-IS Ethertypes as described in Section Sections 3.2.2 and
3.2.3, MAY be supported.

3.2.1

3.2.1. RBridge Channel Message as the Payload

A PType of 2 whose payload has an initial RBridge Channel RBridge-Channel Ethertype
indicates an encapsulated RBridge Channel message. A typical reason
for sending an RBridge Channel message inside an extended RBridge
Channel message is to provide security services, such as
authentication or encryption, for the encapsulated message.

This RBridge Channel message type looks like the following:

Figure 3.1 5: Message Structure with RBridge Channel Payload

3.2.2

3.2.2. TRILL Data Packet as the Payload

A PType of 2 whose payload has an initial TRILL Ethertype indicates
an encapsulated TRILL Data packet as shown in the figure below. Figure 6. If this
Ethertype is supported for PType = 2 and the message meets local
policy for acceptance, the TRILL Data packet is handled as if it had
been received by the destination TRILL switch on the port where the
Extended RBridge Channel message was received.

INTERNET-DRAFT TRILL: RBridge Channel Extension

1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RBridge-Channel (0x8946) | CHV=0 | Channel Protocol=[TBD]| Protocol=0x004|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | ERR | SubERR| RESV4 | SType | 0x2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ Security Information, variable length (0 length if SType = 0) /
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TRILL (0x22F3) | V |A|C|M| RESV |F| Hop Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Egress Nickname | Ingress Nickname |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ Optional Flags Word /
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Inner.MacDA |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Inner.MacDA continued | Inner.MacSA |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Inner.MacSA (cont.) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Inner Data Label (2 or 4 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...
| TRILL Data Packet payload
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...

Figure 3.2 6: Message Structure with TRILL Data Packet Payload

The optional flags word is only present if the F bit in the TRILL
Header is one [RFC7780].

3.2.3

3.2.3. TRILL IS-IS Packet as the Payload

A PType of 2 and an initial L2-IS-IS Ethertype indicates indicate that the
payload of the Extended RBridge Channel protocol message is an
encapsulated TRILL IS-IS PDU as shown in Figure 3.3. 7. If this Ethertype
is supported for PType = 2, the tunneled TRILL IS-IS packet is
processed by the destination RBridge if it meets local policy. One
possible use is to expedite the receipt of a link state PDU (LSP) by
some TRILL switch or switches with an immediate requirement for the
link state information. A link local IS-IS PDU (Hello, CSNP, or PSNP
[IS-IS]; MTU-probe or MTU-ack [RFC7176]; or circuit scoped FS-LSP,
FS-CSNP or FS-PSNP [RFC7356]) would not normally be
sent via this Extended RBridge Channel method except possibly to
encrypt it the PDU since such PDUs can just be transmitted on the link
and do not normally need RBridge Channel handling.

INTERNET-DRAFT TRILL: RBridge Channel Extension (Link local IS-IS
PDUs are (1) Hello, CSNP, PSNP [IS-IS]; (2) MTU-probe, MTU-ack
[RFC7176]; and (3) circuit scoped FS-LSP, FS-CSNP, and FS-PSNP
[RFC7356].)

Figure 3.3 7: Message Structure with TRILL IS-IS Packet Payload

3.3

3.3. Ethernet Frame

If PType is 3, the extended RBridge Channel payload is an Ethernet
frame as might be received from or sent to an end station except that
the encapsulated Ethernet frame's FCS is omitted, as shown in
Figure
3.4. 8. (There is still an overall final FCS if the RBridge
Channel message is being sent on an Ethernet link.) If this PType is
implemented and the message meets local policy, the encapsulated
frame is handled as if it had been received on the port on which the
Extended RBridge Channel message was received.

The priority of the RBridge Channel message can be copied from the
Ethernet frame VLAN tag, if one is present, except that priority 7
SHOULD only be used for messages critical to establishing or
maintaining adjacency and priority 6 SHOULD only be used for other
important control messages.

INTERNET-DRAFT TRILL: RBridge Channel Extension

Figure 3.4 8: Message Structure with Ethernet Frame Payload

In the case of a non-Ethernet link, such as a PPP (Point-to-Point
Protocol) link [RFC6361], the ports on the link are considered to
have link-local synthetic 48-bit MAC addresses constructed as
described below. Such a constructed address MAY be used as a MacSA.
If the RBridge Channel message is individually addressed to a link link-
local port, the source TRILL switch will have the information to
construct such a MAC address for the destination TRILL switch port port,
and that MAC address MAY be used as the MacDA. By the use of such a
MacSA and either such a unicast MacDA or a group addressed group-addressed MacDA, an
Ethernet frame can be sent between two TRILL switch ports connected
by a non-Ethernet link.

These synthetic TRILL switch port MAC addresses for non-Ethernet
ports are constructed as follows: follows (and as shown in Figure 9): 0xFEFF,
the nickname of the TRILL switch used in TRILL Hellos sent on that
port, and the Port ID that the TRILL switch has assigned to that port, as shown in Figure 3.5.
port. (Both the Port ID of the port on which a TRILL Hello is sent
and the nickname of the sending TRILL switch appear in the Special
VLANs and Flags sub-TLV [RFC7176] in TRILL IS-IS Hellos.) The
resulting MAC address has the Local bit on and the Group bit off
[RFC7042]. However, since there will be no Ethernet end stations on
a non-
Ethernet non-Ethernet link in a TRILL campus, such synthetic MAC addresses
cannot conflict on the link with a real Ethernet port address
regardless of their value.

INTERNET-DRAFT TRILL: RBridge Channel Extension values.

1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0xFEFF | Nickname |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Port ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 3.5 9: Synthetic MAC Address

INTERNET-DRAFT TRILL: RBridge Channel Extension

4. Extended RBridge Channel Security

Table 4.1 2 below gives the assigned values of the SType (Security Type)
field and their meaning. Use of DTLS Pairwise Security (SType = 2)
or Composite Security (SType = 3) is RECOMMENDED.

While [RFC5310]-based IS-IS CRYPTO_AUTH-based authentication is also specified and
can be used for both pairwise and multi-destination traffic, it
provides only authentication and is not considered to meet current
security standards. For example, it does not provide for key
negotiation; thus, its use is NOT RECOMMENDED.

The Extended RBridge Channel DTLS-based security specified in
Section 4.4 and the Composite Security specified in Section 4.5 below are
intended for pairwise (known unicast) use. That is, the case where
the M bit in the TRILL Header is zero and any Outer.MacDA is
individually addressed.

Multi-destination Extended RBridge Channel packets would be those
with the M bit in the TRILL Header set to one or, in the native
RBridge Channel case, the Outer.MacDA would be group addressed. The
DTLS Pairwise Security and Composite Security STypes can also be used
in the multi-destination case by serially unicasting the messages to
all data-accessible RBridges (or stations in the native RBridge
Channel case) in the recipient group. For TRILL Data packets, that
group is specified by the Data Label; for native frames, the group is
specified by the groupcast destination MAC address. It is intended
to specify a true group keyed SType to secure multi-destination
packets in a separate document [GroupKey].

SType Description Reference
----- ----------- ---------
0 None Section 4.2 of [this doc] RFC 7978
1 [RFC5310]-Based Authentication IS-IS CRYPTO_AUTH-Based Section 4.3 of [this doc] RFC 7978
Authentication
2 DTLS Pairwise Security Section 4.4 of [this doc] RFC 7978
3 Composite Security Section 4.5 of [this doc] RFC 7978
4-14 Unassigned
15 Reserved

Table 4.1 2: SType Values

4.1

4.1. Derived Keying Material

In some cases, it is possible to use material derived from [RFC5310] IS-IS
CRYPTO_AUTH keying material [RFC5310] as an element of Extended
RBridge Channel security. It is assumed that the IS-IS keying
material is of high quality. The material actually used is derived
from the IS-IS keying material as follows:

INTERNET-DRAFT TRILL: RBridge Channel Extension

Derived Material =
HKDF-Expand-SHA256 ( IS-IS-key, "Extended Channel" | 0x0S, L )

where "|" indicates concatenation, HKDF is as in [RFC5869], SHA256 is
as in [RFC6234], IS-IS-key is the input IS-IS keying material,
"Extended Channel" is the 16-character ASCII [RFC20] string indicated
without any leading length byte or trailing zero byte, 0x0S is a
single byte where S is the SType for which this key derivation is
being used and the upper nibble is zero, and L is the length of the
output-derived material needed.

Whenever IS-IS keying material is being used as above, the underlying
[RFC5310]
IS-IS CRYPTO_AUTH keying material [RFC5310] might expire or be
invalidated. At the time of or before such expiration or
invalidation, the use of the Derived Material from the IS-IS keying
material MUST cease. Continued security MAY use new derived material
from currently valid [RFC5310] IS-IS CRYPTO_AUTH keying material.

4.2

4.2. SType None

No security services are being invoked. The length of the Security
Information field (see Figure 2.4) 4) is zero.

4.3 [RFC5310]-Based

4.3. IS-IS CRYPTO_AUTH-Based Authentication

This SType provides security for Extended RBridge Channel messages
similar to that provided for [IS-IS] PDUs by the [IS-IS]
Authentication TLV. The Security Information (see Figure 2.4) 4) is as
shown in Figure 4.1. 10.

1 1 1 1 1 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RESV | Size |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Key ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+
| Authentication Data (Variable)
+
|
+-+-+-+-+-+-+-+-+-+-+-+-+-...

Figure 4.1 10: SType 1 Security Information

INTERNET-DRAFT TRILL: RBridge Channel Extension

o RESV: Four bits that MUST be sent as zero and ignored on receipt.

o Size: Set to 2 + the size of Authentication Data in bytes.

o Key ID: specifies the keying value and authentication algorithm
that the Key ID specifies for TRILL IS-IS LSP [RFC5310]
Authentication TLVs. The keying material actually used is always
derived as shown in Section 4.1.

o Authentication Data: The authentication data produced by the
derived key and algorithm associated with the Key ID acting on the
part of the TRILL Data packet shown. Length of the authentication
data depends on the algorithm. The authentication value is
included in the security information field and is treated as zero
when authentication is calculated.

As show in Figure 4.2, 11, the area covered by this authentication starts
with the byte immediately after the TRILL Header optional Flag Word
if it is present. If the Flag Word is not present, it starts after
the TRILL Header Ingress Nickname. In either case, it extends to
just before the TRILL Data packet link trailer. For example, for an
Ethernet packet it would extend to just before the FCS.

+-----------------------------+
| Link Header |
+-----------------------------+
| TRILL Header |
| (plus optional flag word) Flag Word) |
+-----------------------------+ ^
| Inner Ethernet Addresses | |
+-----------------------------+ .
| Data Label (VLAN or FGL) | |
+-----------------------------+ .
| RBridge Channel Header | | <-authentication
+-----------------------------+ .
| Extended Channel Header | |
| (plus Security Information)| .
+-----------------------------+ |
| Payload | .
+-----------------------------+ v
| Link Trailer |
+-----------------------------+

Figure 4.2. 11: SType 1 Authentication Coverage

In the native RBridge Channel case case, this authentication coverage is
as specified in the above paragraph except that it starts with the
RBridge Channel
RBridge-Channel Ethertype, since there is no TRILL Header, inner
Ethernet addresses, or inner Data Label (see Figure 4.3).

INTERNET-DRAFT TRILL: RBridge Channel Extension 12).

+-----------------------------+
| Ethernet Header |
+-----------------------------+ ^
| RBridge Channel Header | |
+-----------------------------+ .
| Extended Channel Header | | <-authentication
| (plus Security Information)| .
+-----------------------------+ |
| Payload | .
+-----------------------------+ v
| Ethernet Trailer |
+-----------------------------+

Figure 4.3. 12: Native SType 1 Authentication Coverage

While

RBridges, which are IS-IS routers, can reasonably be expected to hold [RFC5310]
IS-IS CRYPTO_AUTH keying material [RFC5310] so that this SType can be
used for RBridge Channel messages, how which go between RBridges. How
end stations might come to hold [RFC5310] IS-IS CRYPTO_AUTH keying material is
beyond the scope of this document. Thus Thus, this SType might not be
applicable to native RBridge Channel messages.

4.4 messages, which are between an
RBridge and an end station.

4.4. DTLS Pairwise Security

DTLS [RFC6347] supports key negotiation and provides both encryption
and authentication. The RBridge Channel Extended Header DTLS
Pairwise SType uses a negotiated DTLS version that MUST NOT be less
than 1.2.

When DTLS pairwise security is used, the entire payload of the
Extended RBridge Channel packet, starting just after the null
Security Information and ending just before the link trailer, is one
or more DTLS records [RFC6347]. As specified in [RFC6347], DTLS
records MUST be limited by the path MTU, in this case so that each
record fits entirely within a single Extended RBridge Channel
message. A minimum path MTU can be determined from the TRILL campus
minimum MTU Sz, which will not be less than 1470 bytes, by allowing
for the TRILL Data packet, extended RBridge Channel, and DTLS framing
overhead. With this SType, the security information between the
extended RBridge Channel header and the payload is null because all
the security information is in the payload area.

The DTLS Pairwise keying is set up between a pair of RBridges RBridges,
independent of Data Label Label, using messages of a priority configurable
at the RBridge level level, which defaults to priority 6. DTLS message
types other than application_data can be the payload of an extended
RBridge Channel message with a TRILL Header using any Data Label Label,
and, for such DTLS message types, the PType in the RBridge Channel
Header Extension is ignored.

INTERNET-DRAFT TRILL: RBridge Channel Extension

Actual application_data sent within such a message using this SType
SHOULD use the Data Label and priority as specified for that
application_data. In this case, the PType value in the RBridge
Channel Header Extension applies to the decrypted application_data.

TRILL switches that implement the extended RBridge Channel DTLS
Pairwise SType SHOULD support the use of certificates for DTLS DTLS, but
certificate size may be limited by the DTLS requirement that each
record fit within a single message. Appropriate certificate contents
is
are out of scope for this document.

TRILL switches that support the extended RBridge Channel DTLS
Pairwise SType MUST support the use of pre-shared keys. If the
psk_identity (see [RFC4279]) is two bytes, it is interpreted as a
[RFC5310] Key
ID as defined in [RFC5310], and the value derived as shown in
Section 4.1 from that key is used as a pre-shared key for DTLS
negotiation. A psk_identity with a length other than two bytes MAY
be used to indicate other implementation dependent implementation-dependent pre-shared keys.
Pre-shared keys used for DTLS negotiation SHOULD be shared only by
the pair of
end points; endpoints; otherwise, security could be attacked by
diverting messages to another end point endpoint holding that pre-shared key.

4.5

4.5. Composite Security

Composite Security (SType = 3) is the combination of DTLS Pairwise
Security and [RFC5310]-Based IS-IS CRYPTO_AUTH-Based Authentication. On
transmission, the DTLS record or records to be sent are secured as
specified in Section 4.4 then used as the payload for the application
of Authentication as specified in Section 4.3. On reception, the [RFC5310]-based IS-
IS CRYPTO_AUTH-based authentication is verified first and an error is
returned if it fails. If the [RFC5310]-based IS-IS CRYPTO_AUTH-based authentication
succeeds, then the DTLS
record(s) record or records are processed.

An advantage of Composite Security is that the payload is
authenticated and encrypted with a modern security protocol and, protocol; in
addition, the RBridge Channel Header and (except in the native case)
preceding the MAC addresses and Data Label are provided with some
authentication.

INTERNET-DRAFT TRILL: RBridge Channel Extension

5. Extended RBridge Channel Errors

RBridge Channel Header Extension errors are reported like RBridge
Channel errors. The ERR field is set to one of the following error
codes:

Value RBridge Channel Error Code Meaning
----- ------------------------------------
6 Unknown or unsupported field value
7 Authentication failure
8 Error in nested RBridge Channel message

Table 5.1 3: Additional ERR Values

5.1

5.1. SubERRs

If the ERR field is 6, the SubERR field indicates the problematic
field or value as shown in the table below. At this time no
suberrror codes are assigned under any other ERR field value.

Err SubERR Meaning (for ERR = 6)
--- ------ -----------------------
0 No Error, Error; suberrors not allowed
1-5 (no suberrors assigned)
6 0 Reserved
6 1 Non-zero RESV4 nibble
6 2 Unsupported SType
6 3 Unsupported PType
6 4 Unknown Key ID
6 5 Unsupported Ethertype with PType = 2
6 6 Unsupported authentication algorithm for SType = 1
6 7 Non-zero SubERR with zero ERR field
7-14 (no suberrors assigned)
15 (Reserved) Reserved

Table 5.2 4: SubERR values

5.2 Values

5.2. Secure Nested RBridge Channel Errors

If
o an extended RBridge Channel message is sent with security and with
a payload type (PType) indicating an Ethertyped payload and the
Ethertype indicates a nested RBridge Channel message and
o there is an error in the processing of that nested message that
results in a return RBridge Channel message with a non-zero ERR

INTERNET-DRAFT TRILL: RBridge Channel Extension
field,
then that returned message SHOULD also be nested in an extended
RBridge Channel message using the same type of security. In this
case, the ERR field in the Extended RBridge Channel envelope is set
to 8 indicating that there is a nested error in the message being
tunneled back.

INTERNET-DRAFT TRILL: RBridge Channel Extension

6. IANA Considerations

This section lists IANA Considerations.

6.1

6.1. Extended RBridge Channel Protocol Number

IANA is requested to assign TBD [4 recommended] has assigned 0x004 from the range assigned by Standards Action
[RFC5226] as the RBridge Channel protocol number to indicate RBridge
Channel Header Extension.

The added RBridge "RBridge Channel protocols Protocols" registry entry on in the TRILL
Parameters web page registry is as follows:

Protocol Description Reference
-------- -------------------------- ----------------
TBD[4]
0x004 RBridge Channel Extension [this document]

6.2 RFC 7978

6.2. RBridge Channel Protocol Subregistries

IANA is requested to create has created three subregistries under the "RBridge Channel
Protocols" registry as detailed in the subsections below.

6.2.1

6.2.1. RBridge Channel Error Codes

IANA is requested to assign has assigned three additional code points in the "RBridge
Channel Error Codes" registry on subregistry in the TRILL Parameters web
page. "Transparent Interconnection
of Lots of Links (TRILL) Parameters" registry. The additional
entries are as show shown in Table 5.1 3 in Section 5 and the "Reference"
column value is "[this document]".

6.2.2 "RFC 7978" for those rows.

6.2.2. RBridge Channel SubError Codes

IANA is request to create has created a subregistry indented under the RBridge "RBridge Channel
Error Codes Codes" registry, for RBridge Chanel Channel SubError Code. Codes. The
initial contents of this subregistry is as show are shown in Table 5.2 4 in Section
5.1 except that a and the fourth column "Reference" is added with includes value "[this document]" "RFC 7978" for
all rows. The header information is as follows:

Registry Name: RBridge Channel SubError Codes
Registration Procedures: IETF Review
Reference: [this document]

INTERNET-DRAFT TRILL: RBridge Channel Extension

6.2.3 RFC 7978

6.2.3. Extended RBridge Channel Payload Types Subregistry

IANA is requested to create has created an "Extended RBridge Channel Payload Types" registry
subregistry after the "RBridge Channel Protocols" registry on in the
TRILL Parameters web page.
"Transparent Interconnection of Lots of Links (TRILL) Parameters"
registry. The header information is as follows:

Registration Procedures: IETF Review
Reference: [this document] RFC 7978

The initial registry content is in Table 3.1 1 in Section 3 of this
document.

6.2.4

6.2.4. Extended RBridge Channel Security Types Subregistry

IANA is requested to create has created an "Extended RBridge Channel Security Types" registry
subregistry after the "Extended RBridge Channel Payload Types"
registry on in the TRILL Parameters web page. "Transparent Interconnection of Lots of Links (TRILL)
Parameters" registry. The header information is as follows:

Registration Procedures: IETF Review
Reference: [this document] RFC 7978

The initial registry content is in Table 4.1 2 in Section 4 of this
document.

INTERNET-DRAFT TRILL: RBridge Channel Extension

7. Security Considerations

The RBridge Channel Header Extension has potentially positive and
negative effects on security.

On the positive side, it provides optional security that can be used
to authenticate and/or encrypt RBridge Channel messages. Some
RBridge Channel message payloads, such as BFD [RFC7175], provide
their own security but where this is not true, consideration should
be given, when specifying an RBridge Channel protocol, to
recommending or requiring use of the security features of the RBridge
Channel Header Extension.

On the negative side, the optional ability to tunnel more payload
types
types, and to tunnel them between TRILL switches and to and from end
stations
stations, can increase risk unless precautions are taken. The
processing of decapsulated extended RBridge Channel payloads is a
place where you SHOULD NOT be liberal in what you accept. This is
because the tunneling facility makes it easier for unexpected
messages to pop up in unexpected places in a TRILL campus due to
accidents or the actions of an adversary. Local policies SHOULD
generally be strict and only accept payload types required and then
only with adequate security for the particular circumstances.

See the first paragraph of Section 4 for recommendations on SType
usage.

See [RFC7457] for Security Considerations security considerations of DTLS for security. DTLS.

If IS-IS authentication is not being used, then [RFC5310] IS-IS CRYPTO_AUTH
keying
information material [RFC5310] would not normally be available but that
presumably represents a judgment by the TRILL campus operator that no
security is needed.

See [RFC7178] for general RBridge Channel Security Considerations security considerations and
[RFC6325] for general TRILL Security Considerations.

INTERNET-DRAFT TRILL: RBridge Channel Extension security considerations.

8. Normative References

[IS-IS] - ISO/IEC 10589:2002, Second Edition, International Organization for Standardization,
"Information technology -- Telecommunications and
information exchange between systems -- 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/IEC 10589:2002, Second Edition, 2002.

[RFC20] - Cerf, V., "ASCII format for network interchange", STD 80,
RFC 20, DOI 10.17487/RFC0020, October 1969, <http://www.rfc-
editor.org/info/rfc20>.
<http://www.rfc-editor.org/info/rfc20>.

[RFC2119] - BBradner, 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>.

[RFC4279] - Eronen, P., Ed., and H. Tschofenig, Ed., "Pre-Shared Key
Ciphersuites for Transport Layer Security (TLS)", RFC 4279,
DOI 10.17487/RFC4279, December 2005, <http://www.rfc-
editor.org/info/rfc4279>.
<http://www.rfc-editor.org/info/rfc4279>.

[RFC5310] - Bhatia, M., Manral, V., Li, T., Atkinson, R., White, R.,
and M. Fanto, "IS-IS Generic Cryptographic Authentication",
RFC 5310, DOI 10.17487/RFC5310, 10.17487/RFC5310,v February 2009, <http://www.rfc-
editor.org/info/rfc5310>.
<http://www.rfc-editor.org/info/rfc5310>.

[RFC5869] - Krawczyk, H. and P. Eronen, "HMAC-based Extract-and-
Expand Extract-and-Expand
Key Derivation Function (HKDF)", RFC 5869,
DOI 10.17487/RFC5869, May 2010,
<http://www.rfc-editor.org/info/rfc5869>.

[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>.

[RFC6347] - Rescorla, E. and N. Modadugu, "Datagram Transport Layer
Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347,
January 2012, <http://www.rfc-
editor.org/info/rfc6347>. <http://www.rfc-editor.org/info/rfc6347>.

[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>.
<http://www.rfc-editor.org/info/rfc7172>.

[RFC7176] - Eastlake 3rd, D., Senevirathne, T., Ghanwani, A., Dutt, D.,
and A. Banerjee, "Transparent Interconnection of Lots of
Links (TRILL) Use of IS-IS", RFC 7176,
DOI 10.17487/RFC7176, May 2014,
<http://www.rfc-editor.org/info/rfc7176>.

INTERNET-DRAFT TRILL: RBridge Channel Extension

[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>.

[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>.

[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>.

9. Informative References

[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>.

[RFC6234] - Eastlake 3rd, D. and T. Hansen, "US Secure Hash Algorithms
(SHA and SHA-based HMAC and HKDF)", RFC 6234,
DOI 10.17487/RFC6234, May 2011, <http://www.rfc-
editor.org/info/rfc6234>.
<http://www.rfc-editor.org/info/rfc6234>.

[RFC6361] - Carlson, J. and D. Eastlake 3rd, "PPP Transparent
Interconnection of Lots of Links (TRILL) Protocol Control
Protocol", RFC 6361, DOI 10.17487/RFC6361, August 2011 2011,
<http://www.rfc-editor.org/info/rfc6361>.

[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. 2013, <http://www.rfc-editor.org/info/rfc7042>.

[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>.

[RFC7175] - Manral, V., Eastlake 3rd, D., Ward, D., and A. Banerjee,
"Transparent Interconnection of Lots of Links (TRILL):
Bidirectional Forwarding Detection (BFD) Support",
RFC 7175, DOI 10.17487/RFC7175, May 2014. 2014,
<http://www.rfc-editor.org/info/rfc7175>.

[RFC7457] - Sheffer, Y., Holz, R., and P. Saint-Andre, "Summarizing
Known Attacks on Transport Layer Security (TLS) and
Datagram TLS (DTLS)", RFC 7457, DOI 10.17487/RFC7457,
February 2015, <http://www.rfc-
editor.org/info/rfc7457>. <http://www.rfc-editor.org/info/rfc7457>.

[AddrFlush] - W.
Hao, D. W., Eastlake, D., and Y. Li, "TRILL: Address Flush
Message", draft-ietf-trill-address-flush, work Work in progress.

INTERNET-DRAFT TRILL: RBridge Channel Extension Progress, draft-ietf-trill-address-
flush-00, May 2016.

[GroupKey] - D. Eastlake et al, "Group Keying Protocol", draft-
eastlake-trill-group-keying, work
Eastlake, D., "TRILL: Group Keying", Work in progress.

[rfc6439bis] - D. Progress,
draft-eastlake-trill-group-keying-00, July 2016.

[TRILL-AF]
Eastlake, Y. D., Li, M. Y., Umair, A. M., Banerjee, H. Fangwei, A., and F. Hu,
"TRILL: Appointed Forwarders", draft-ietf-trill-rfc6439bis,
work in progress.

INTERNET-DRAFT TRILL: RBridge Channel Extension

Appendix Z: Change History

RFC Editor: Please delete this Appendix before publication.

From -00 to -01

1. Fix references for RFCs published, etc.

2. Explicitly mention Work in Progress, draft-
ietf-trill-rfc6439bis-03, August 2016.

Acknowledgements

The contributions of the Abstract following are hereby gratefully
acknowledged:

Stephen Farrell, Jonathan Hardwick, Susan Hares, Gayle Noble, Alvaro
Retana, Yaron Sheffer, and Introduction that this Peter Yee.

The document updates [RFC7178].

3. Add this Change History Appendix.

From -01 to -02

1. Remove section on the "Scope" feature as mentioned was originally prepared in
http://www.ietf.org/mail-archive/web/trill/current/msg06531.html

2. Editorial changes to IANA Considerations to correspond to draft-
leiba-cotton-iana-5226bis-11.txt.

3. Improvements to the Ethernet frame payload type.

4. Other Editorial changes.

From -02 to -03

1. Update TRILL Header to correspond to [RFC7780].

2. Remove a few remnants of the "Scope" feature that was removed from
-01 to -02.

3. Substantial changes to and expansion of Section 4 including adding
details of DTLS security.

4. Updates and additions to the References.

5. Other minor editorial changes.

From -03 to -04

1. Add SType for [RFC5310] keying based security that provides
encryption as well as authentication.

2. Editorial improvements and fixes.

From -04 to -05

1. Primary change is collapsing the previous PTypes 2, 3, and 4 for
RBridge Channel message, TRILL Data, and TRILL IS-IS into one by

INTERNET-DRAFT TRILL: RBridge Channel Extension

including the Ethertype. Previous PType 5 is renumbered as 3.

2. Add Channel Tunnel Crypto Suites to IANA Considerations

3. Add some material to Security Considerations,

4. Assorted Editorial changes.

From -05 to -06

Fix editorials found during WG Last Call.

From -06 to -07

Minor editorial changes resulting for Shepherd review.

From -07 to -08

Move group keyed security out of the draft. Simplify and improve
remaining security provisions.

From -08 to -09

1. Updates based on Routing Directorate review.

2. Improvements to specification of pairwise DTLS and significant
other security improvements.

From -09 to -10

Update based on GENART review.

From -10 to -11

1. Add IANA registry for suberror codes and make other minor IANA
Considerations changes.

2. Add informational references to [RFC7067], address flush, and
rfc6439bis.

3. Add RFC 2119 keyword emphasis to Security Considerations caution
in handling decapsulated extended RBridge Channel payloads.

INTERNET-DRAFT TRILL: RBridge Channel Extension

Acknowledgements

The contributions of the following are hereby gratefully
acknowledged:

Stephen Farrell, Jonathan Hardwick, Susan Hares, Gayle Noble,
Alvaro Retana, Yaron Sheffer, and Peter Yee.

The document was prepared in raw nroff. All macros used were defined
within raw nroff. All macros used
were defined within the source file.

INTERNET-DRAFT TRILL: RBridge Channel Extension

Authors' Addresses

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

Phone: +1-508-333-2270
EMail:
Email: d3e3e3@gmail.com

Mohammed Umair
IPinfusion

EMail:

Email: mohammed.umair2@gmail.com

Yizhou Li
Huawei Technologies
101 Software Avenue, Avenue
Nanjing 210012, 210012
China

Phone: +86-25-56622310
EMail:
Email: liyizhou@huawei.com

INTERNET-DRAFT TRILL: RBridge Channel Extension

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