INTERNET-DRAFT Mingui Zhang
Intended Status: Proposed Standard Huawei
Expires: April 24, 2014 Russ White
Verisign
Hongjun Zhai
ZTE
October 21, 2013
Control Plane Requirements for TRILL Active/Active Edge
draft-zhang-trill-active-active-cp-req-00.txt
Abstract
TRILL Active/Active Edge enables a Multi-Chassis Link Aggregation
Group to connect to multiple RBridges which can ingress and egress
data traffic for the same VLAN at the same time. The purpose of
introducing the TRILL Active/Active Edge is to increase the access
bandwidth and resilience. This new access type puts forward new
requirements for TRILL control plane. Current TRILL control plane
need be extended in order to make the TRILL Active/Active Edge
operational. Requirements are developed in this document as the
guidelines for designing those specific control plane functions.
Status of this Memo
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Copyright and License Notice
Copyright (c) 2013 IETF Trust and the persons identified as the
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document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Acronyms and Terminology . . . . . . . . . . . . . . . . . . . 3
2.1. Acronyms . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Control Plane Requirements . . . . . . . . . . . . . . . . . . 3
3.1. Discovery . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.2. Election . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.3. Forwarding Information Synchronization . . . . . . . . . . 4
3.4. Failure Detection and Notification . . . . . . . . . . . . 5
3.5. Communicating Configuration Information . . . . . . . . . . 5
4. Security Considerations . . . . . . . . . . . . . . . . . . . . 5
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6
6.1. Normative References . . . . . . . . . . . . . . . . . . . 6
6.2. Informative References . . . . . . . . . . . . . . . . . . 6
Author's Addresses . . . . . . . . . . . . . . . . . . . . . . . . 8
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1. Introduction
TRILL makes use of IS-IS link state routing to provide least-cost
forwarding between TRILL switches. At the edge, [RFC6349] already
defines an active-standby access for end-stations. An active-active
method is to be added in TRILL so that end stations are able to
increase the bandwidth and resilience of their access to a TRILL
campus using Multi-Chassis Link Aggregation Group (MC-LAG) [PS].
Unlike a LAN link, MC-LAG does not exchange TRILL IS-IS PDUs. The
TRILL switch ports attached to the MC-LAG demarcate the edge of TRILL
and no adjacency can be formed on top of the MC-LAG.
From the point of view of the end stations, the MC-LAG is treated as
if it were a single link and those RBridges connected to the other
end of the MC-LAG need operate as if they were a single TRILL switch.
Thus an Active/Active Edge (AAE) is set up. However, it doesn't mean
that RBridges in the AAE can be connected to only one MC-LAG. It's
possible that one port of an RBridge is connected to one MC-LAG and
the other port is connected to another.
To achieve the TRILL Active/Active Edge, some functions should be
added to the current TRILL control plane. There are several possible
places to host these functions. For example, the TRILL IS-IS, TRILL
BFD, ESADI protocol and TRILL Channel are potential choices [BFD]
[ESADI] [Channel]. This document describes the high-level
requirements for these new control plane functions. When specific
protocols are designed, these requirements should be followed.
2. Acronyms and Terminology
2.1. Acronyms
MC-LAG: Multi-Chassis Link Aggregation Group
IS-IS: Intermediate System to Intermediate System
TRILL: TRansparent Interconnection of Lots of Links
AAE: Active/Active Edge
2.2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
Familiarity with [RFC6325], [RFC6327], [6327bis] and [RFC6439] is
assumed in this document.
3. Control Plane Requirements
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This section specifies the requirements on the functions that the
TRILL control plane need to provide for the AAE.
3.1. Discovery
When an RBridge is attached to an MC-LAG, it need to recognize other
RBridges attached to this MC-LAG as in the same AAE. It also need to
notify other RBridges the fact that it joins or leaves the AAE.
The identification of the AAE is REQUIRED during the discovery. The
System Identifier of the MC-LAG is a choice. RBridges in an AAE MUST
include this ID in the Protocol Data Units of the control plane
protocol to achieve the discovery.
3.2. Election
RBridges per [RFC6325] run a protocol on the link to elect the
Designated RBridge (DRB). The DRB performs some common tasks for the
link. For example, the DRB gives the link a pseudonode nickname.
RBridges in an AAE need elect a master node to carry on common tasks
for the AAE as well. Since MC-LAG disables the delivery of TRILL IS-
IS PDUs. The TRILL IS-IS election protocol defined in Section 2.1 of
[RFC6325] is not applicable here.
A substitute election protocol SHOULD be set up. Such protocol should
reuse the decision process algorithm defined in [ISIS] to avoid
introducing too much complexity into TRILL.
3.3. Forwarding Information Synchronization
As an example, AAE members may learn MAC addresses through data plane
learning and ESADI protocol. MAC addresses learnt by one member
should be shared to other members in the same AAE in order to reduce
the unknown unicast traffic [PS]. As another example, the IGMP
(Internet Group Management Protocol) [RFC3376] snooping on those
ports attached to a MC-LAG has to be synchronized. A protocol is
needed to synchronize these forwarding information among AAE members
and keep the information updated in a timely manner.
MAC address may be frequently updated due to data plane learning. It
is REQUIRED that the CPU is not overloaded due to the control plane
MAC address update. Therefore the protocol should define a minimum
updating interval.
Due to the overhead that may be produced, this protocol SHOULD be
confined in the scope of the AAE members. Obviously, it SHOULD NOT be
realized though the extension of TRILL IS-IS, which may otherwise
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introduce a heavy burden to current TRILL's control plane. TRILL
ESADI or TRILL Channel are proper candidates to realize such
protocol.
3.4. Failure Detection and Notification
When a link of the MC-LAG to an AAE member RBridge or this RBridge
itself is failed, this failure should be detected and notified to
other AAE member RBridges through the control plane as soon as
possible. RBridges other than AAE member RBridges may need be
notified as well so that these RBridges can change their forwarding
paths to avoid the failure.
The failed AAE member RBridge leaves the AAE. It's possible that
there is less than two RBridges in the AAE due to the failure. Then
the AAE should be destroyed. If the AAE is not destroyed, the failure
notification will trigger a re-convergence of the AAE. It is optional
to establish a dedicated session such as BFD to detect the failure in
order to enable a fast convergence. All AAE members MUST run into a
consensus converge state just like the convergence in IGP routing
protocols. The control plane protocols need take the design of the
re-convergence algorithm into consideration.
3.5. Communicating Configuration Information
Configuration on RBridges to enable the operation of an AAE should be
minimized. Some of the configuration is local while the other is of
global sense and need be conveyed through the control plane to other
RBridges. An example is the Affinity Sub-TLV defined in [6326bis] and
used in [CMT].
The communication of the configuration information through the
control plane helps to settle mis-configuration. For example, enabled
VLANs of every port attached to the same MC-LAG MUST be the same. An
RBridge in an AAE can report the enabled VLANs to others through the
control plane so that a mis-configured VLAN can be rectified or
trigger an alarm to the management plane.
4. Security Considerations
Security issue should be considered when a specific extension is made
to the existing TRILL control plane.
Authenticity for contents transported in IS-IS PDUs is enforced using
regular IS-IS security mechanism [ISIS][RFC5310].
For security considerations pertain to extensions hosted by TRILL BFD
and ESADI, corresponding documents should refer to the Security
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Considerations in [BFD], [ESADI] and [Channel].
5. IANA Considerations
This document requires no IANA actions. RFC Editor: please remove
this section before publication.
6. References
6.1. Normative References
[RFC6325] Perlman, R., Eastlake 3rd, D., Dutt, D., Gai, S., and A.
Ghanwani, "Routing Bridges (RBridges): Base Protocol
Specification", RFC 6325, July 2011.
[RFC6327] Eastlake 3rd, D., Perlman, R., Ghanwani, A., Dutt, D., and
V. Manral, "Routing Bridges (RBridges): Adjacency", RFC
6327, July 2011.
[6327bis] D. Eastlake, R. Perlman, et al, "TRILL: Adjacency", draft-
ietf-trill-rfc6327bis-01.txt, July 2013, working in
progress.
[RFC6439] Perlman, R., Eastlake, D., Li, Y., Banerjee, A., and F. Hu,
"Routing Bridges (RBridges): Appointed Forwarders", RFC
6439, November 2011.
[BFD] V. Manral, D. Eastlake, et al, "TRILL (Transparent
Interconnetion of Lots of Links): Bidirectional Forwarding
Detection (BFD) Support", draft-ietf-trill-rbridge-bfd-
07.txt, July 2012, working in progress.
[ESADI] H. Zhai, F. Hu, et al, "TRILL (Transparent Interconnection
of Lots of Links): ESADI (End Station Address Distribution
Information) Protocol", draft-ietf-trill-esadi-03.txt, July
2013, working in progress.
[6326bis] D. Eastlake, T. Senevirathne, et al, "Transparent
Interconnection of Lots of Links (TRILL) Use of IS-IS",
draft-ietf-isis-rfc6326bis-01.txt, April 2013, working in
progress.
[Channel] D. Eastlake, V Manral, et al, "TRILL: RBridge Channel
Support", draft-ietf-trill-rbridge-channel-08.txt, July
2012, working in progress.
6.2. Informative References
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[PS] M. Zhang and D. Eastlake, "Problem Statement: TRILL
Active/Active Edge", draft-zhang-trill-aggregation-04.txt,
August 2013, working in progress.
[ISIS] ISO, "Intermediate system to Intermediate system routeing
information exchange protocol for use in conjunction with
the Protocol for providing the Connectionless-mode Network
Service (ISO 8473)", ISO/IEC 10589:2002.
[CMT] T. Senevirathne, J. Pathangi, et al, "Coordinated Multicast
Trees (CMT)for TRILL", draft-ietf-trill-cmt-02.txt,
November 2012, working in progress.
[RFC5310] Bhatia, M., Manral, V., Li, T., Atkinson, R., White, R.,
and M. Fanto, "IS-IS Generic Cryptographic Authentication",
RFC 5310, February 2009.
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Author's Addresses
Mingui Zhang
Huawei Technologies
No.156 Beiqing Rd. Haidian District,
Beijing 100095 P.R. China
Email: zhangmingui@huawei.com
Russ White
Verisign
12061 Bluemont Way
Reston, VA 20190
USA
Email: riwhite@verisign.com
Hongjun Zhai
ZTE
68 Zijinghua Road, Yuhuatai District
Nanjing, Jiangsu 210012
China
Phone: +86 25 52877345
Email: zhai.hongjun@zte.com.cn
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