INTERNET DRAFT Georg Kullgren
GSMP Working Group Stephen Shew
Nortel Networks
Hormuzd Khosravi
Intel
Jonathan Sadler
Tellabs
Satoru Okamoto
Kohei Shiomoto
Atsushi Watanabe
NTT
Expires August 2002
Requirements for adding optical support to GSMPv3
<draft-ietf-gsmp-reqs-01.txt>
Status of this Memo
This document is an Internet-Draft and is subject to
all provisions of Section 10 of RFC2026 except that the right to
produce derivative works is not granted.
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Abstract
This memo provides an overview of additional requirements on the GSMP
protocol.
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Table of Contents
1. Overview .......................................................... 3
2. Requirements for Optical Support .................................. 3
2.1. Label Types .................................................... 3
2.2. Port and Label Management Issues ............................... 4
2.3. Statistics messages ............................................ 4
2.4. Configuration Issues ........................................... 4
2.4.1. Switch Configuration ........................................ 4
2.4.2. Port Configuration .......................................... 4
2.4.3. Service Configuration ....................................... 5
2.5. Service Model Issues ........................................... 5
2.6. Encapsulation issues ........................................... 5
2.7. MIB Issues ..................................................... 6
2.8. OXC Transaction Model .......................................... 6
2.8.1 Serial Transactions .......................................... 6
2.8.2. Bulk Transactions ........................................... 6
2.9. OXC Restoration Capabilities ................................... 6
2.9.1. Non-Reserved Protection Links ............................... 7
2.9.2. Dedicated Protection Links .................................. 7
2.9.3. Protection Triggers ......................................... 8
2.9.4. Protection Link Capabilities ................................ 8
2.10 GSMP support to optical cross-connect system ................... 9
3. Requirements from Implementors ................................... 10
3.1. GSMP Packet Format ............................................ 10
3.1.1. Message segmentation ....................................... 10
3.1.1.1. "More" Result Flag ...................................... 10
3.1.1.2. SubMessage Number ....................................... 10
3.1.1.3. I flag .................................................. 10
3.1.1.4. Updated Messages ........................................ 10
3.1.1.5. Message Segmentation example ............................ 11
3.1.2. Transaction Identifier ..................................... 11
3.2. Window Size ................................................... 11
3.3. Retransmission ................................................ 11
3.4. Delete Branches Message ....................................... 12
3.5. Adjacency ..................................................... 12
3.5.1. Loss of Synchronisation .................................... 12
3.6. ReturnReceipt Result value in Events .......................... 12
4. Additional Requirements .......................................... 13
5. Security Considerations .......................................... 14
6. Acknowledgements ................................................. 14
7. References ....................................................... 15
8. Author's Addresses ............................................... 17
9. Full Copyright Statement ......................................... 18
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1. Overview
This draft is intended to describe the required updates to GSMP
requested by implementors and the required changes for support of
optical (non-transparent and all optical), SONET/SDH, and spatial
switching of IP packets, L2 frames and TDM data. The mix of possible
instantiations include GSMP controllers connected to: photonic cross-
connects (optical-optical), transparent optical cross connects
(optical-electrical-optical, frame independent), opaque cross
connects (optical-electrical-optical, SONET/SDH frames), and
traditional TDM switches (all electrical). These could form IP based
optical routers, optical label switches, wavelength routers, and
dynamic optical cross connects.
There are also several different generic models that might be applied
to running IP over WDM [1][2][11]. This document defines the
requirements for the separation of control functions from data
functions in order to provide a more flexible network
architecture.[3]
In this draft, no position will be taken about the eventual
architectural model that will be most appropriate (e.g., single or
multiple routing plane instances). The only assumption is that the
ability to separate the control mechanisms from the data switching is
as useful for the signaling of optical paths (e.g., GMPLS) as it is
for the signaling of L2 paths (e.g., MPLS).
GSMPv3[6] is well suited for providing the control mechanisms
necessary for allowing an IP based controller to direct the
activities of an optical switch. In order for GSMP to operate between
IP controllers and optical switches and cross connects, support for
optical labels and service and resource abstractions must be added to
GSMP.
2. Requirements for Optical Support
2.1. Label Types
New labels are needed to identify the entities that are to be
switched in the optical fabric. These are longer than GSMPv3 labels
as they have physical and structural context. As GMPLS[1][2] has had
very similar requirements for label formats alignment with GMPLS is
proposed. This includes support for:
- Digital Carrier Hierarchy (e.g., DS-1, E1)
- SONET and SDH Hierarchy (e.g., OC-3, STM-1, VT1.5, VC-12)
- PDH labels [12]
- OTN G.709 labels
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- Lambdas
- Fibers
GSMP MUST include support for all label types as well as for label
hierarchies and label lists as defined by GMPLS. Bundles of the
above labels SHOULD also be supported (e.g., 5 OC- 3s, contiguous
wavebands)
2.2. Port and Label Management Issues
As with routers, it may be useful to recognize bundles of links [13]
between optical cross-connects. This goes beyond knowledge of
separate independent ports. If so, changes to the port management
message MAY be needed to describe ports which are part of a link
bundle.
An updated label range message MUST be provided. There MUST also be
support of multiplexing (e.g. no multiplexing, SONET, Gigabit
Ethernet multiplexing etc).
2.3. Statistics messages
No changes are currently proposed for the statistics messages to
support optical switching.
2.4. Configuration Issues
2.4.1. Switch Configuration
No changes are currently proposed for the switch configuration
messages to support optical switching.
2.4.2. Port Configuration
The port configuration message supplies the controller with the
configuration information related to a single port. In order to
handle the specific port types in an optical switch, extensive
additions will need to be made to this command.
Port types MUST be added to support the mix of SONET/SDH signals that
can operate over a single fiber. Information that MAY need to be
conveyed includes[8]:
- wavelengths available per interface
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- bit rate per wavelength
- type of fiber
Again, it MAY be useful to recognize bundles of links [13] between
optical cross-connects. If so, changes to the port configuration
message would be needed to describe ports which are part of a link
bundle.
2.4.3. Service Configuration
While new capability sets MUST be added to support quality parameters
in optical switches, no changes are foreseen to the service
configuration message as its role to carry the service information as
defined in the applicable service model. The changes related to the
service model will be discussed in section 0.
2.5. Service Model Issues
While one assumption of using optical media is that bandwidth is
plentiful, it should be expected that traffic engineering will be
necessary in any case[3]. GSMP provides the means for each
connection, or in this each light trail, to be created with specific
quality attributes. Capability to control re-timing and re-shaping
MUST be added.
Currently, the default set of service models in GSMP are all based on
the services models defined elsewhere, e.g. the Intserv model[5][7],
the Diffserv[4] model, ATM QoS models and the Frame relay forum QoS
models. A determination needs to be made of the applicable quality
models for optical channel trails. These models MUST then be mapped
to the GSMP capability set mechanism.
2.6. Encapsulation issues
The working group needs to decide whether a new encapsulation is
required. In other words, will all optical switches used in either
the MPLS over Optics and the IP over optics applications require that
IP be implemented on the control channel connecting the GSMP
controller and Optical switch (the GSMP target). If a raw wavelength
control connection is to be allowed, a new encapsulation SHOULD be
defined.
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2.7. MIB Issues
If a new encapsulation is defined, then the encapsulation group
SHOULD be updated. No other changes should be required.
2.8. OXC Transaction Model
2.8.1 Serial Transactions
Many existing OXCs use a command interface which assumes a serial
transaction model. That is, a new command cannot be issued or
processed until the existing command is completed. Under
provisioning control via a network management application, and with
non-dynamic path setup, this model has been adequate.
Moving to a dynamic path setup capability with a distributed control
plane, a parallel transaction model is likely required for
performance. This is particularly helpful when the performance of
setting up a TDM style connection is much slower than setting up an
L2 connection table. If the OXC is not able to support a parallel
transaction model, a GSMP controller MUST be informed of this and
adopt serial transaction behaviour.
2.8.2. Bulk Transactions
Again due to the time it may take some OXCs to setup TDM connections
relative to L2 fabrics (e.g., VC-4/STS-1 SPE fabric in an HOVC/STS
switch), support for sending multiple transactions in the same
message is a useful optimization. When an OXC receives a bulk
message, the individual transactions are acted upon and a single
reply is sent. If parallel transactions are not supported, bulk
messages can improve performance by reducing transaction overhead.
Bulk transactions SHOULD be supported.
2.9. OXC Restoration Capabilities
To achieve fast link protection performance (e.g., 50 ms after
failure detection), SONET/SDH and some OXC systems use hardware based
protection schemes (e.g., ring protection). Achieving this level of
performance solely using a data control plane such as GMPLS is a
serious challenge. An alternate approach is to utilize fast
restoration capabilities of an OXC with a dynamic control plane. An
implication of this hybrid approach is that extensions are needed to
GSMP to provision the behaviour of an OXC in anticipation of a link
failure.
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This differs from the strict master-slave relationship in GSMP for
Layer 2 switches in that here the OXC is capable of taking an action
independent of the GSMP controller and then informing the controller
afterwards.
2.9.1. Non-Reserved Protection Links
An example of protection OXC behaviour is that when a link fails, a
backup link may be used to protect traffic on. This backup link
could be selected from a set of links, none of which are pre-
reserved. A backup link could be shared with one or more "working"
links which is a form of 1:n shared protection. Specifying the set
of possible backup links SHOULD be done as an option to the Add-
Branch message.
When a backup link is used or the OXC reverts back to the original
link, the control plane (i.e., signalling) may need to know about the
new path state in order to notify the operator, or take some other
OAM action (e.g., billing, SLA monitoring). An additional GSMP
message to inform the controller SHOULD be added to do this.
2.9.2. Dedicated Protection Links
A more specialized form of restoration called "1+1" defines a
(usually node disjoint) protection path in a transport/optical
network for a given working path. At the ingress node to the path,
the traffic signal is sent simultaneously along both working and
protection paths. Under non-failure conditions at the egress node,
only the last link of the working path is connected to the client.
When any link in the working path fails, traffic on the working path
ceases to be received at end of the path. The egress OXC detects
this condition and then switches to use the last link of the
protection path without the controller having to issue a Move-Input-
Branch message. At no time is the ingress node aware which link the
egress node is using. Selection of the protection path and all of
its links is outside the scope of GSMP.
Specification of the two output branches at the ingress node can be
done with the usual Add-Branch semantics. The ingress node protection
link is not shared with any other working link.
Specification of the two input branches at the egress node should be
done when the Add-Branch message is sent. This SHOULD be an option
to that message. The egress node protection link is not shared with
any other working link.
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When a protection link is used or the OXC reverts back to the working
link, the control plane (i.e., signalling) may need to know about the
new path state in order to notify the operator, or take some other
OAM action (e.g., billing, SLA monitoring). An additional GSMP
message to inform the controller SHOULD be added to do this.
If an alternate input port is not specified with an original Add-
Branch message, it MAY be specified in a subsequent Add-Branch
message. In this case, it is useful to include information about
existing users of the output port in that Add-Branch message. This
helps the OXC immediately learn of the association between the new
input port and an existing one. The association is used to enable
OXC protection procedures. This capability MUST be added to the add-
branch message.
Similar contextual information is needed for a Delete-Branch message
so that the OXC can determine if a path becomes unprotected. This
capability MUST be added to the Delete-branch message.
2.9.3. Protection Triggers
Aside from link or equipment failures, there are a variety of
maintenance conditions that could cause the backup/protection link(s)
to be used. These may include:
-
Scheduled maintenance of the working link. Here the network
operator deliberately takes a link out of service to perform
maintenance.
-
Reconfiguration of fiber/node/network which causes temporary need
to use backup links.
It may be useful to specify these triggers when the backup/protection
links are defined with the Add-Branch message. This depends on how
the OXC is implemented to be aware of such triggers. This is for
further study.
2.9.4. Protection Link Capabilities
When an OXC has the capability to perform protection switching
independently from the OCC, it may be useful for the OCC to be
informed of these capabilities at switch and/or port configuration.
Applications in the GSMP controller could use this information. For
example, signalling clients could define a path protection scheme
over multiple GSMP enabled OXCs. This is for further study.
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2.10 GSMP support to optical cross-connect system
The cross-connect system such as photonic cross-connect, transparent
optical cross-connect, opaque cross-connect and traditional TDM
switch can be consist of not only cross-connect (/switch) function,
but also multiplexing function (including transmission function),
path termination function (including client signal termination
function). In the optical cross-connect (OXC) system, the
multiplexing function corresponds to the wavelength division
multiplexing (WDM). The optical regenerator and wavelength converter
may be necessary in order to realize long-haul transmission and to
use effectively the wavelength resource respectively. Figure 1 shows
the generalized OXC functional block. The OXC system shown in Fig.1
should be controlled / managed by GSMP. The advantage of this
concept is that the GSMP can control the OXC system, without other
control protocols. This will reduce the cost and time of OXC control
application development. To control the OXC system, the control
concept of both connection termination and trail termination for each
optical label switched path or WDM sections (defined in G.872; OMS
and OTS) should be introduced in the GSMP. The GSMP for optical
switch can be located as subset of that for optical cross-connect.
+-------------+-------------------+-----------+
-->| | | |
WDM | Wavelength | Opt. regenerator/ | Opt. | signals |
demultiplex/| Wavelength | switch |
| multiplex | converter | |
<--| | | |
+-------------+-------------------+-----------+
|| ||
Client +-----------+
signals (In) -->| Path |
Client | terminator|
signalis(Out) <--| |
+-----------+
Figure 1 General OXC functional block
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3. Requirements from Implementors
3.1. GSMP Packet Format
The Basic GSMP Message Format in chapter 3.1.1 in [6] describes the
common fields present in all GSMP messages except for the Adjacency
protocol.
3.1.1. Message segmentation
If a message exceeds the MTU of the link layer it has to be
segmented. This was originally done with the "More" flag in the
Result field. The addition of the I flag and the SubMessage Number
to the header has made the "More" flag in the Result field obsolete.
A clarification of the I flag and SubMessage Number is also needed.
3.1.1.1. "More" Result Flag
The "More" flag should not be used in GSMP. A request message with
the Result field set to "More" SHOULD be answered with a failure
response with a Code field indicating the type of failure.
3.1.1.2. SubMessage Number
The definition of the SubMessage field should indicate if the
submessages are numbered starting with 0 or 1.
3.1.1.3. I flag
The value of the I flag for messages which are not segmented is
unspecified.
3.1.1.4. Updated Messages
The "Report Connection State Reply Message" and "All Ports
Configuration Message" shoud be rewritten to use the I flag instead
of the More flag.
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3.1.1.5. Message Segmentation example
A description of how to segment a message should be provided. The
definition of the Length field should state if each segment should
contain the total GSMP message length or the length of the segment.
3.1.2. Transaction Identifier
The Transaction Identifier in [6] does not distinguish between
replies from a request with "AckAll" and "NoSuccessAck". It also
does not provide any information about how to handle replies where
the Transaction ID doesn't match a Transaction ID from a previously
sent request.
If multiple controllers are connected to a single switch and the
switch send an event message with "ReturnReceipt" set to all of them,
there is no way for the switch to identify which controller the
receipt is coming from.
3.2. Window Size
The Switch Configuration Message defined in chapter 8.1 in [6]
defines a Window size to be used by the controller when sending
messages to the switch. It is not stated if this window should apply
to all messages or only to messages that will always generate a
reply.
If messages that may not generate a reply should be counted against
the window a time-out period when they are to be removed from the
window should be defined.
It is not defined if the the window should be cleared when the
adjacency is lost and later recovered.
3.2.2. Retransmission
A retransmission policy should be used if no reply is received for a
message with "AckAll" set.
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3.3. Delete Branches Message
The "Delete Branch Element" has a 4 bit Error field that should be
redefined to match the size of the "Failure Response Codes".
3.4. Adjacency
The chapter about how to handle a new adjacency and re-established
adjacencies should be clarified.
3.4.1. Loss of Synchronisation
If a controller looses synchronisation, the draft requires the switch
to reset the connection state This should be redefined since more
than one controller may be synchronised to a switch partition.
This change will affect the definition of the PFlag.
3.5. ReturnReceipt Result value in Events
When the GSMP V3 initially was defined the events was supposed to be
generated in a similar fashion as SNMP Traps. When an event was sent
it was a uni-direction message and there was no requirement of the
switch to verify that a controller received the message. Since event
messages never expected a reply of a sent message there where no need
of a Transaction Identifier. In the case of Event Messages the
Transaction Identifier was decided it SHOULD be set to zero.
Later on, a new Result Value of ReturnReceipt was introduced.
ReturnReceipt is a results field used in Events to indicate that a
switch requires an acknowledgment for the message.
Introduced at the same time was the allowance of Multiple Controllers
jointly controlling the same partition.
Since all Transaction Identifiers is set to zero in the case of Event
Messages the following problem can occur.
1. A switch has multiple controllers jointly controlling a partition.
2. The switch is configured to require acknowledgment of sent events.
3. For some reason one or more controller can not send the acknowledgment.
4. The switch has no ability to find out which controller that did
not respond.
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4. Additional Requirements
1. Better Slot/Port definition (Bay/Shelf also needed)
2. Better Bidirectional support
Use in Move branch, Delete branch -- need atomic behavior
3. Better Port Capability identification (needed to find stack of
supported TTP/CTPs)
Should be consistent with Neighbor Capability Exchange approaches
(i.e. LMP)
Should be consistent with Link attributes used in Routing
4. Need to identify how to number points in the potential
sub-multiplex tree
Use convention in iftable?
Or should points be refered to via root-ifindex:label,
and partitioning instantiates new root-ifindexes?
5. Better Node Capability identification
Support for LCAS?
6. Need to allow minimal Port configuration in addition to Matrix
Connection configuration
7. How should blocking switch fabrics be handled?
8. Better Path Switching support
Need to allow preconfiguration of selector allowing actions
independant of controller
9. Rectify how B and R flags interact, since Bidirectional links are a
fundamental unit in TDM nets
10.Remove "Layer specific" messages, i.e. ATM VPC Add/Move*/Delete Branch
11.Partitioning at "any layer" (not just port specific partitioning)
12.Generalize Statistics Messages (ie ATM vs Frame)
13.Clarify use of Port/Line Status so it corresponds w/ TDM
Administrative/Operational state
Clarify interaction with Port Up/Down Events
14.Support for transport over OSI TP1 or TP3, and SCTP
15.Need to correlate Events and only send root cause Event messages
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5. Security Considerations
The security of GSMP's TCP/IP control channel has been addressed in
[10]. Any potential remaining security considerations are not
addressed in the current revision of this draft.
6. Acknowledgements
The list of authors provided with this document is a reduction of the
original list. Currently listed authors wish to acknowledge that a
substantial amount was also contributed to this work by: Avri Doria
and Kenneth Sundell
The authors would like to acknowledge the careful review and comments
of Dimitri Papadimitriou and Torbjorn Hedqvist.
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7. References
[1] Ashwood-Smith, D., et. al.,
"Generalized MPLS - Signaling Functional Description",
Internet Draft draft-ietf-mpls-generalized-signaling-07.txt,
November 2001. Work in Progress.
[2] Mannie, E., et. al.,
"Generalized Multi-Protocol Label Switching (GMPLS)
Architecture",
draft-ietf-ccamp-gmpls-architecture-01.txt (work in
progress), November 2001
[3] Awduche, D, Rekhter, Y, et. al., "Multi-Protocol Lambda
Switching: Combining MPLS Traffic Engineering
Control with Optical Crossconnects," draft-
awduche-mpls-te-optical-03.txt (work in
progress), April, 2001
[4] Blake, S., et. al., _An Architecture for
Differentiated Services_, RFC2475, December 1998
[5] Braden, R., _Integrated Services in the Internet
Architecture: An Overview_, RFC1633, June 1994
[6] Doria, A, Sundell, K, Hellstrand, F, Worster, T, "General
Switch Management Protocol V3," Internet Draft
draft-ietf-gsmp-11.txt (work in progress),
December 2001
[7] J. Wroclawski, "Specification of the Controlled-Load
Network Element Service," RFC2211, Sep 1997.
[8] Rajagopalan, B., et. al., _IP over Optical Networks: A
Framework_, draft-many-ip-optical-framework-
03.txt (work in progress), March 2001
[9] Sjostrand, H, et al, Definitions of Managed Objects for the
General Switch Management Protocol (GSMP),"
Internet-Draft draft-ietf-gsmp-mib-07 (work in
progress), November 2001.
[10] Worster, T, et al, "GSMP Packet Encapsulations for ATM,
Ethernet and TCP," Internet-Draft draft-ietf-
gsmp-encaps-05 (work in progress), December 2001.
[11] G.ASON _Architecture for the Automatic Switched Optical
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Network_, Draft v0.5.1, June 2001
[12] Sadler, J., Mack-Crane, B., "Generalized Switch Management
Protocol", draft-sadler-gsmp-tdm-labels-00.txt
work in progress), February 2001
[13] Kompella, K., et. al., _Link Bundling in MPLS Traffic
Engineering_, draft-ietf-mpls-bundle-01.txt
(work in progress), November 2001
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8. Author's Addresses
Hormuzd Khosravi
Intel
2111 NE 25th Avenue
Hillsboro, OR 97124 USA
Phone: +1 503 264 0334
hormuzd.m.khosravi@intel.com
Georg Kullgren
Nortel Networks AB
S:t Eriksgatan 115 A
P.O. Box 6701
SE-113 85 Stockholm Sweden
geku@nortelnetworks.com
Jonathan Sadler
Tellabs Operations, Inc.
1000 Remington Blvd
Bolingbrook, IL 60440
Phone: +1 630-848-7741
Email: Jonathan.Sadler@tellabs.com
Stephen Shew
Nortel Networks
PO Box 3511 Station C
Ottawa, ON
K1Y 4H7
sdshew@nortelnetworks.com
Kohei Shiomoto
Shiomoto.Kohei@lab.ntt.co.jp
Atsushi Watanabe
Nippon Telegraph and Telephone Corporation
807A 1-1 Hikari-no-oka, Yokosuka-shi
Kanagawa 239-0847, Japan
atsushi@exa.onlab.ntt.co.jp
Satoru Okamoto
Nippon Telegraph and Telephone Corporation
9-11 Midori-cho 3-chome, Musashino-shi
Tokyo 180-8585, Japan
okamoto@exa.onlab.ntt.co.jp
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9. Full Copyright Statement
"Copyright (C) The Internet Society 2001. All Rights Reserved. This
document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implmentation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph
are included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into
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