TRILL Working Group Radia Perlman
INTERNET-DRAFT Sun Microsystems
Intended status: Proposed Standard Dinesh Dutt
Cisco
Donald Eastlake 3rd
Eastlake Enterprises
Expires: April 2009 October 2008
RBridge VLAN Mapping
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<draft-perlman-trill-rbridge-vlan-mapping-00.txt>
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Abstract
Some bridge products perform a feature known as "VLAN mapping", in
which a bridge translates a data frame's VLAN ID from one VLAN to
another when it forwards a frame from one port to another. This
feature facilitates scenarios such as combining two bridged LANs with
overlapping VLAN IDs into one bridged LAN without merging two
communities just because they have been given the same VLAN ID in the
original two clouds. This document describes how RBridges can achieve
the same functionality.
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Table of Contents
Status of This Document....................................1
Abstract...................................................1
1. Introduction............................................3
1.1 Terminology............................................4
2. Internal RBridges and VLAN Mapping......................5
3. Configuration of Cut Set VLAN Mapping RBridges..........5
4. Advertisement of VLAN Mappings..........................5
5. Translation of VLAN IDs by Cut Set RBridges.............6
6. Reporting Attached VLANs by Cut Set RBridges in LSPs....6
7. Advertising of Multicast Groups by Cut Set RBridges.....6
8. Endnode Advertisements by cut set RBridges..............7
9. IANA Considerations.....................................8
10. Security Considerations................................8
11. Normative References...................................9
12. Informative References.................................9
Copyright, Disclaimer, and Additional IPR Provisions......10
Authors Addresses.........................................11
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1. Introduction
Bridges perform a feature known as "VLAN mapping", in which two or
more layer 2 clouds are connected together using a set of bridges,
but in which the VLAN IDs are not consistent in the different clouds.
The set of bridges interconnecting the clouds are known as the "cut
set", meaning that if that set of bridges are removed, the clouds are
separated.
Bridges in the cut set are configured to translate some set of VLAN
IDs in one cloud to different VLAN IDs when forwarding from one cloud
to the other.
One reason to do this is to intentionally not merge VLAN-A endnodes
in one layer 2 cloud with the community of VLAN-A endnodes in the
other cloud.
Another reason to do this is to intentionally merge two communities,
marked with different VLAN IDs in the different clouds.
This feature is accomplished with bridges solely by configuring
bridges on the cut set.
This document explains how to accomplish the same functionality with
RBridges. In this document we will assume there are two clouds
"East" and "West", and RBridges RB1, RB2, and RB3 that interconnect
the two clouds.
. . . +-----+ . . .
. . . + - - - - + RB1 + - - - - + . . .
. W . +-----+ . . E .
. e . . . a .
. s . +-----+ . s . .
. t . .+ - - - - -+ RB2 + - - - - - - +. t .
. . . -+-+---+ . . .
. C . . / | _ _ _ _ _ _+. C . .
l . + - - - | / . l . .
. o . . +-+---+ . o . .
u . .+ - - - -+ RB3 + - - - - - - - +. u . .
. d . . +-----+ d . .
. . . . . . .
We will refer to RBridges other than the cut set of RBridges as
"internal RBridges".
General familiarity with the base TRILL protocol [RFCtrill] is
assumed in this document.
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1.1 Terminology
The same terminology and acronyms are used in this document as in
[RFCtrill].
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].
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2. Internal RBridges and VLAN Mapping
Internal RBridges will not be aware that VLAN mapping is going on.
They will behave exactly as they would without VLAN mapping. The
only evidence they will have of VLAN mapping is the existence of an
optional TLV field that a cut set RBridge, RB1, MAY include in its
LSP, listing the VLAN mappings that RB1 is configured to be
performing.
Internal RBridges will ignore this field. It is only there for
detection of misconfiguration.
3. Configuration of Cut Set VLAN Mapping RBridges
If VLAN A in cloud "East" is to be translated into VLAN B in cloud
"West", a cut set RBridge RB1 must be configured, for each port, as
to whether that port is in East or West, and configured with VLAN
mappings, such as:
"East/VLAN A <----> West/VLAN B"
That mapping means that when RB1 forwards a frame on a port
configured to be in East to a port configured to be in West, with the
VLAN tag of A, it replaces the VLAN tag "A" with "B" in the inner
encapsulated frame.
Note that mappings are always symmetric, meaning that if RB1 is
translating tag "VLAN A" to tag "VLAN B" when forwarding from East to
West, it will translate tag "VLAN B" to tag "VLAN A" when forwarding
from West to East.
4. Advertisement of VLAN Mappings
To detect misconfiguration, a cut set RBridge RB1 MAY advertise its
VLAN mappings. This would be done by assigning IDs to each of the
clouds. All cut set RBridges SHOULD be configured with the same IDs
for the clouds. So, in our example, if "East" is "1" and "West" is
"2", and VLAN A in East is mapped to VLAN B in West, the TLV would
report a set of mappings, including:
{(1:A,2:B)}
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5. Translation of VLAN IDs by Cut Set RBridges
If RB1 is configured to believe port a is in "East" and port b is in
"West", and RB1 is configured such that "East/VLAN A <----> West/VLAN
B", then when RB1 forwards a data frame from port a to port b, if the
received frame from port a has (inner header VLAN ID) VLAN x , then
RB1 changes the VLAN tag from VLAN A to VLAN B as it forwards onto
port b.
Note: This is true whether RB1 is the appointed forwarder on port a
for VLAN x and the frame arrives unencapsulated, or whether the frame
has arrived already encapsulated as a VLAN A frame.
Likewise, RB1 performs the same VLAN translation whether the frame is
unicast or multicast.
6. Reporting Attached VLANs by Cut Set RBridges in LSPs
If RB1 is configured to translate VLAN A to VLAN B, then RB1 reports,
in its LSP, that it is connected to both VLAN A and VLAN B, even if
RB1 is not appointed forwarder for either or both VLAN A or VLAN B.
The reason RB1 must claim to be attached to VLAN A and VLAN B is so
that multicast data frames for VLAN A originating in West will not
get filtered before reaching RB1, and multicast data frames for VLAN
B originating in East will also not get prematurely filtered.
7. Advertising of Multicast Groups by Cut Set RBridges
If RB1 is configured to translate VLAN A in East to VLAN B in West,
then RB1 MUST do one of the following, in order to ensure that a
multicast packet for group G in VLAN A will not be filtered inside
the West cloud, if there are receivers for (VLAN A, group G) in East.
If the cut set RBridges do nothing, then a multicast for VLAN B,
group G would be filtered inside the West cloud, since RBridges
inside the East cloud will only be requesting receipt of VLAN A,
group G.
Thus, RB1 MUST do one of the following for each mapped VLAN. It may
use different strategies for different VLANs.
a) for all IP-derived multicast addresses that have been requested by
any RBridges in East for VLAN A, RB1 reports connectivity to those
multicast addresses in VLAN B. Likewise, for all IP-derived
multicast addresses that have been requested by any RBridges in
West for VLAN B, RB1 reports connectivity to those multicast
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addresses in VLAN A.
b) RB1 reports connectivity to an IPv4 multicast router and an IPv6
multicast router.
8. Endnode Advertisements by cut set RBridges
TRILL allows RBridges to optionally advertise attached endnodes. This
endnode advertisement protocol uses special instances of IS-IS known
as ESADI (End System Address Distribution Instance).
If cut set RBridge RB1 is translating VLAN A (in East) to VLAN B (in
West), and RB1 is doing ESADI for its attached endnodes in VLAN A, it
should transmit the ESADI advertisement tagged with VLAN A when
forwarding onto ports labeled as "East", and transmit the same ESADI
advertisement when forwarding onto ports labeled as "West". An East
VLAN-A ESADI generated by any RBridge in East will automatically get
translated into a VLAN B ESADI when forwarding into West, because
ESADIs are handled just like ordinary encapsulated data frames, the
VLAN tag to which the ESADI belongs is the VLAN tag on the inner data
frame, and that VLAN tag will be translated by (properly configured)
cut set RBridges when forwarding between East and West.
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9. IANA Considerations
This document requires no IANA actions. This section should be
deleted by the RFC Editor on publication.
10. Security Considerations
See [RFCtrill] for general RBridge Security Considerations.
If cut set RBridges have misconfigured VLAN mappings, VLANs may be
inadvertently partitioned or inadvertently merged and frames may be
delivered in the wrong VLAN. However, misconfiguration of VLAN
mapping will not cause loops.
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11. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997
[RFCtrill] R. Perlman, D. Eastlake, D. Dutt, S. Gai, and A. Ghanwani,
draft-ietf-trill-rbridge-protocol-09.txt, work in progress.
12. Informative References
None.
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Copyright, Disclaimer, and Additional IPR Provisions
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Authors Addresses
Radia Perlman
Sun Microsystems
16 Network Circle
Menlo Park, CA 94025
Phone: +1-650-960-1300
Email: Radia.Perlman@sun.com
Dinesh G. Dutt
Cisco Systems
170 Tasman Drive
San Jose, CA 95134-1706 USA
Phone: +1-408-527-0955
EMail: ddutt@cisco.com
Donald Eastlake 3rd
Eastlake Enterprises
155 Beaver Street
Milford, MA 01757
Tel: +1-508-634-2066
Email: d3e3e3@gmail.com
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