Internet DRAFT - draft-yong-trill-trill-o-mpls
draft-yong-trill-trill-o-mpls
TRILL Working Group Lucy Yong
INTERNET-DRAFT Donald Eastlake
Intended status: Informational Sam Aldrin
Huawei R&D USA
Jon Hudson
Brocade
Expires: September 9, 2012 March 10, 2012
Transparent Interconnection of Lots of Links (TRILL) over
MPLS Pseudo Wires
<draft-yong-trill-trill-o-mpls-01.txt>
Abstract
This informational document describes ways to interconnect TRILL
RBridges by using MPLS Pseudo Wire (PW) services with existing TRILL
and MPLS standards so as to form a unified TRILL campus.
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 document is unlimited. Comments should be sent
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Table of Contents
1. Introduction............................................3
1.1 Conventions used in this document......................3
2. Use Cases...............................................4
2.1 Point-To-Point Interconnection.........................4
2.1.1 Direct Point-to-Point................................5
2.1.2 Provider Point-to-Point Service......................5
2.2 Multi-Access Link Interconnection......................6
3. RBridge Behavior for MPLS Pseudo Wire...................9
4. IANA Considerations....................................10
5. Security Considerations................................10
6. Acknowledgements.......................................10
7. Normative References...................................11
8. Informative References.................................12
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1. Introduction
The IETF TRILL (Transparent Interconnection of Lots of Links)
standard [RFC6325] [RFC6326] provides optimal pair-wise data frame
forwarding without configuration in multi-hop networks with arbitrary
topology and link technology, and supports multipathing of both
unicast and multicast traffic. TRILL enables a new method to
construct a campus or data center network. Devices that implement
TRILL are called RBridges (Routing Bridges) or TRILL Switches.
This document describes the use of MPLS Pseudo Wire or VPLS links by
TRILL.
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].
Acronyms used in this document include the following:
AC - Attachment Circuit
IS-IS - Intermediate System to Intermediate System
MPLS - Multi-Protocol Label Switching
PE - Provider Edge
PPP - Point-to-Point Protocol
PW - Pseudo Wire
QoS - Quality of Service
RB - RBridge
RBridge - Routing Bridge
TRILL - Transparent Interconnection of Lots of Links
TRILL Switch - An alternative term for an RBridge
VPLS - Virtual Private LAN Service
VSI - Virtual Service Instance
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2. Use Cases
TRILL campuses at different locations may interconnect by networks
that are implemented with different technologies to form a unified
RBridge campus. This section describes use cases assuming that
IP/MPLS technology is available. From the MPLS network view, a pair
of RBridges can be directly connected with a pseudo wire or an
RBridge can act as a Customer Edge device that connects to a Provider
Edge device via an attachment circuit. RBridge ports [RFC6325], by
default, support both point-to-point links and multi-access links.
Section 2.1 describes point-to-point links, i.e. TRILL over an
Ethernet or PPP point-to-point link that is over an MPLS network.
Section 2.2 describes TRILL over a bridged LAN or equivalent that is
implemented by MPLS/VPLS.
2.1 Point-To-Point Interconnection
Either an Ethernet or PPP link over an MPLS network interconnets two
RBridge ports. This can be either a direct pseudo wire between the
RBridges or by attachment circuits from each RBridge port to Provider
Edge devices that provide a transparent tunnel between the provider
edge attachment points.
MPLS already supports many pseudo wire transport encapsulations
[RFC4446]. Two types of TRILL links between RBridges have been
standardized are Ethernet [RFC6325] and PPP [RFC6361]. Pseudo wire
encapsulations for these two interfaces are specified in [RFC4448]
and [RFC4618], respectively.
The method described in 2.1.1 below is typically suitable when the
TRILL and MPLS facilities have common management while the method
described in 2.1.2 is typically suittable when the TRILL and MPLS
facilities are separately managed. In the case of different
management, the core MPLS operator can sell a VPWS service to an
RBridge operator.
In both cases, the MPLS label switched routers involved need no
awareness of TRILL.
A pseudo wire may cross multiple MPLS domains [RFC5659]. In these
cases, RBridges may be considered to connect to T-PEs and it works in
the same way as a single domain. The MPLS network can provide
transport resiliency for a pseudo wire. The dual homing (two
attachment circuits) can be used for attachment circuit protection.
In this case, two TRILL links are established; RBridges can perform
load balancing over two links.
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2.1.1 Direct Point-to-Point
Two RBridge ports can be connected directly by an MPLS pseudo wire.
This implies that the RBridges, which are TRILL routers, are also
acting as label switched routers. The pseudo wire can be either
Ethernet over MPLS or PPP over MPLS but PPP over MPLS is recommended
because it saves 16 bytes per frame. The pseudo wire between two
RBridge ports can be auto-configured [RFC4447] or manually
configured; the two RBridges then appear directly interconnected with
a transparent link.
(Technically speaking, it is possible to create a specially
designated TRILL encapsulated pseudo wire for point-to-point TRILL
over MPLS. However, the authors think that this is not worth the
effort in this case because of available technologies, particularly
the highly-efficient PPP link technology.)
From a customer/provider point of view, this can also be though of as
shown in the following diagram:
*---------* *---------*
| TRILL |<---- TRILL Link------->| TRILL |
| Site A | (Customer Layer) | Site B |
| | | |
| +-------+ +---+ +-------+ |
| | RB/PE |-----| P |------| PE/RB | |
| +-------+ +---+ +-------+ |
| |<---------PW ---------->| |
| | (Provider Layer) | |
*---------* *---------*
{ MPLS Network }
{ One RBridge Campus }
The interworking between the RBridge network and the MPLS network is
within the combined TRILL/MPLS device. This has a similar
architecture to MPLS/VPLS [RFC4762].
2.1.2 Provider Point-to-Point Service
Two RBridge ports may also be connected by attachment circuits (ACs)
to Provider Edge (PE) devices that are part of a typically separately
managed provider network. The provider network then provides a
transparent path between these attachment circuits, connecting the
RBridge ports. The following diagram illustrates this arrangement:
D. Eastlake, et al [Page 5]
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<-------------TRILL Link------------>
*--------* <----------PW----------> *--------*
| TRILL | | TRILL |
| Site A | | Site B |
| +--+ AC +----+ +---+ +----+ AC +--+ |
| |RB|------| PE |---| P |---| PE |------|RB| |
| +--+ +----+ +---+ +----+ +--+ |
| | { Provider Network } | |
*--------* *--------*
{ One RBridge Campus }
If the attachment circuits are Ethernet, the two PEs would be
configured to form a pseudo wire with Ethernet encapsulation
[RFC4448]. This pseudo wire can be auto-configured [RFC4447] or
manually configured; the two RBridges then appear directly
interconnected with an Ethernet link. The provider edge devices
SHOULD use the Raw mode and non-service-delimiting, which provides a
transparent Ethernet transport.
If the attachment circuits are PPP link type, the two PEs must be
configured to form a PW with PPP encapsulation [RFC4618]. After the
pseudo wire is established between two PEs, the two RBridges then
appear directly connected with a PPP link. The PPP link configuration
will be more efficient than the Ethernet point-to-point
configuration; it saves about 16 bytes per frame by replacing the
TRILL Outer.MacDA, Outer.MacSA, Outer.VLAN, and outer Ethertype with
a PPP code point [RFC6361].
In both case, the pseudo wire provides transparent transport between
attachment circuits. The TRILL link and the connectivity over that
link is automatically discovered and established through TRILL IS-IS
control messages.
2.2 Multi-Access Link Interconnection
Multiple RBridges may interconnect via an [802.1Q] Bridged LAN that
acts as a hub. The bridged LAN simply forwards on the outer Ethernet
header of the TRILL over Ethernet frames. This configuration creates
what appears to each connected RBridge as a multi-access link. In
other words, each RBridge connecting to a bridged LAN normally has
connectivity to every other RBridge connecting to the same bridged
LAN.
MPLS/VPLS can provide the same capability when multiple parts of an
RBridge campus are interconnected over an IP/MPLS network and make
each RBridge attaching to the VPLS appear as having a multi-access
TRILL link. The diagram below shows one RBridge campus is split
between three different sites and the use of MPLS/VPLS for RBridge
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interconnection. Ethernet attachment circuits and pseudo wires are
assumed.
*-------* ........................... *-------*
| | . MPLS/VPLS . | |
| TRILL |AC +----+ PW +----+ AC| TRILL |
| Site 1+---|VSI ********************** VSI|---+ Site 2|
| | | PE ***** ***** PE | | |
| | +----+ **** **** +----+ | |
| | . +*--*+ . *-------*
*-------* ..........|VSI |...........
| PE |
+----+
|AC
|
*---------*
| TRILL |
| Site 3 |
| |
*---------*
One VPLS instance is configured on three Provider Edge (PE) devices
and the pseudo wires are configured for the VPLS instance. Each
RBridge Site connects to the VSI on a PE via an attachment circuit.
The VSI on a PE forwards TRILL frames based on the outer Ethernet
header of the frames [RFC6325]. Either BGP [RFC4761] or LDP [RFC4762]
protocol can be used to automatically construct the VPLS instance on
the PEs.
The choice of three VSIs and three singly connected sites was for
illustrative purposes. There could be two or more than three.
Furthermore, each TRILL site could have multiple connections to the
VPLS network and/or direct connection via other technologies or VPLS
networks to one or more of the other sites. TRILL sorts all this out
and router properly.
A PE may connect to several different RBridge campuses that belong to
different customers. Separated VPLS instances are configured for
individual customers and customer traffic is isolated by VPLS
instance. The PE treats an RBridge as a generic Ethernet customer
devices and has no awareness of TRILL. The outer Ethernet MAC of
TRILL frames may be either a next-hop RBridge MAC address (for
unicast frames) or one of TRILL defined multicast addresses (ALL-IS-
IS-RBridges and All-RBridges) [RFC6325]. The VSI at each PE learns
the source MAC addresses on each VSI interface and forward the frame
based on the destination MAC. For the multicast frames, the VSI
replicates the frames to all pseudo wires it associates. If a VPLS is
configured with some optimization capability [VPLS-BCAST], the
multicast frames can be delivered over a point-to-multipoint pseudo
wire while unicast frames are carried over a point-to-point pseudo
D. Eastlake, et al [Page 7]
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wire.
The scenario above can also be extended to multiple RBridge
interconnections when a device serves both the RBridge and PE
functions, similarly to the case in Section 2.1.2 and 2.1.1 above.
Note: If the customer devices associated with one VPLS instances
happen to include some RBridges and some end stations or IEEE 802.1Q
bridges providing paths to end stations, TRILL will, by default, be
able to handle this by providing both through service and end station
service. However, the end station addresses will be visible to the
VPLS instance. If, in such a case, all the RBridge ports connected to
the VPLS are configured as trunk ports (see Section 4.9.2 of
[RFC6325]), then they will not provide any end station service.
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3. RBridge Behavior for MPLS Pseudo Wire
This section describes RBridge behaviors for TRILL Ethernet or TRILL
PPP links over MPLS pseudo wire (PW) as described in Sections 2.1.
1. For two RBridge ports connecting via a PPP pseudo wire, the ports
MUST be configured as IS-IS point-to-point because there are no
subnetwork point of attachment (SNPA/MAC) addresses of the end
points at the PPP protocol layer. Thus TRILL will use IS-IS P2P
Hellos that, as described in "Point-to-Point IS to IS Hello PDU"
(section 9.7 of [IS-IS]), do not use Neighbor TLVs or require
SNPAs. However, as described section 4.2.4.1 of [RFC6325], three-
way IS-IS handshake using extended circuit IDs is required.
2. Any MPLS forwarder within an MPLS label switched path does not
change the TRILL Header Hop Count. RBridges are not aware of the
packet forwarders in with the MPLS network.
3. If it is desired for MPLS label switched routers to perform QoS in
the same way as RBridges do, an Ethernet path MUST be used and
RBridges MUST be configured to send an Outer.VLAN tag on the
RBridge port leading to the pseudo wire. The PE can then copy the
priority value from the Outer.VLAN tag to the COS field of the
pseudo wire label prior to the forwarding [RFC5462].
4. TRILL MTU-probe and TRILL MTU-ack messages (section 4.3.2 of
[RFC6325]) are not needed on a pseudo wire link. Implementations
MUST NOT send MTU-probe and SHOULD NOT reply to these messages.
The MTU pseudo wire interface parameter SHOULD be used instead.
PE MUST configure the MTU size as the originating RBridges Size
specified in Section 4.3.1 of [RFC6325].
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4. IANA Considerations
No IANA action is required by this document. RFC Editor: Please
remove this section before publication.
5. Security Considerations
The IS-IS authentication mechanism [RFC5304] [RFC5310], at the TRILL
IS-IS layer, can be used to prevent fabrication of link-state control
messages over TRILL links including those discussed in this document.
For general TRILL protocol security considerations, see [RFC6325].
Use cases in which the path between RBridges transits a provider
network under separate administration may represent a substantial
increase in the threat of observation, deletion, modification, or
insertion of data or control information. Under such circumstances
consideration should be give to the use of security at the TRILL link
level, such as [802.1AE] if the path between the RBridge ports is
Ethernet or security as suggested in [RFC6361] if that path is PPP.
6. Acknowledgements
The authors sincerely acknowledge the contributions of Ben Mack-Crane
and Sue Hares.
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7. Normative References
[RFC2119] - Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4446] Martini, L., "IANA Allocations for Pseudowire Edge to
EdgeEmulation (PWE3)", BCP 116, RFC 4446, April 2006.
[RFC4447] Martini, L., Ed., Rosen, E., El-Aawar, N., Smith, T., and
G. Heron, "Pseudowire Setup and Maintenance Using the Label
Distribution Protocol (LDP)", RFC 4447, April 2006.
[RFC4448] Martini, L., Ed., Rosen, E., El-Aawar, N., and G. Heron,
"Encapsulation Methods for Transport of Ethernet over MPLS
Networks", RFC 4448, April 2006.
[RFC4618] Martini, L., "Encapsulation Methods for Transport of
PPP/High-Level Data Link Control (HDLC) over MPLS Networks",
BCP 116, RFC 4618, September 2006.
[RFC4761] Kompella, K. and Y. Rekhter, "Virtual Private LAN Service
(VPLS) Using BGP for Auto-Discovery and Signaling", RFC4761,
January 2007.
[RFC4762] Lasserre, M. and Kompella, V, "Virtual Private LAN
Service(VPLS) Using Label Distribution Protocol (LDP)
Signaling",RFC4762, January 2007
[RFC2119] S. Bradner, "Key words for use in RFCs to Indicate
Requirement Levels," BCP 14 and RFC 2119, March 1997
[RFC5304] Li, T. and Atkinson, R, "IS-IS Cryptographic
Authentication," RFC 5304, October 2008
[RFC5310] Bhatia, M., Manral, V., Li, T., Atkinson, R., White, R.,
and M. Fanto, "IS-IS Generic Cryptographic Authentication", RFC
5310, February 2009
[RFC5462] Andersson, L. and Asati, R., "Multiprotocol Label Switching
(MPLS) Label Stack entry: "Exp" Field Rename to "Traffic Class"
Field", RFC5462, February 2009
[RFC5659] Bocci, M and Bryant, S, "An Architecture for Multi-Segment
Pseudowire Emulation Edge-to-Edge", RFC 5659, October2009.
[RFC6325] Perlman, R., Eastlake 3rd, D., Dutt, D., Gai, S., and A.
Ghanwani, "Routing Bridges (RBridges): Base Protocol
Specification", RFC6325, July 2011.
[RFC6326] Eastlake 3rd, D., Banerjee, A., Dutt, D., Perlman, R.,
D. Eastlake, et al [Page 11]
INTERNET-DRAFT TRILL over MPLS PW
andGhanwani, A. "Transparent Interconnection of Lots of
Links(TRILL) Use of IS-IS", RFC6326, July 2011.
[RFC6361] Carlson, J., and D. Eastlake, "PPP Transparent
Interconnection of Lots of Links (TRILL) Protocol Control
Protocol", RFC6361, August 2011.
8. Informative References
[802.1AE] "IEEE Standard for Local and metropolitan area networks /
Media Access Control (MAC) Security", 802.1AE-2006, 18 August
2006.
[802.1Q] IEEE 802.1, "IEEE Standard for Local and metropolitan area
networks - Virtual Bridged Local Area Networks", IEEE Std
802.1Q-2011, May 2011.
[IS-IS] International Organization for Standardization, "Intermediate
system to Intermediate system intra-domain routing information
exchange protocol for use in conjunction with the protocol for
providing the connectionless-mode Network Service (ISO 8473)",
ISO/IEC10589:2002, Second Edition, Nov 2002
[VPLS-BCAST] Delord, S, and Key, R., "Extension to LDP-VPLS for
Ethernet Broadcast and Multicast", draft-ietf-l2vpn-ldp-vpls-
broadcast-exten-02, work in progress, 2011.
D. Eastlake, et al [Page 12]
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Authors' Addresses
Lucy Yong
Huawei R&D USA
5340 Legacy Drive
Plano, TX 75025
Phone: +1-469-227-5837
Email: lucy.yong@huawei.com
Donald E. Eastlake, 3rd
Huawei R&D USA
155 Beaver Street
Milford, MA 01757 USA
Phone: +1-508-333-2270
Email: d3e3e3@gmail.com
Sam Aldrin
Huawei R&D USA
2330 Central Expressway
Santa Clara, CA 95050
Phone: +1-408-330-4517
Email: sam.aldrin@huawei.com
Jon Hudson
Brocade
130 Holger Way
San Jose, CA 95134
Phone: +1-408-333-4062
jon.hudson@brocade.com
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D. Eastlake, et al [Page 14]
