Internet DRAFT - draft-aboulmagd-ccamp-crldp-ason-ext
draft-aboulmagd-ccamp-crldp-ason-ext
CCAMP O. ABoul-Magd
Internet Draft Nortel Networks
Document: draft-aboulmagd-ccamp-crldp-ason-ext-02.txt December 2002
Category: Informational
CR-LDP Extensions for ASON
Status of this Memo
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Abstract
Automatic Switched Optical Network (ASON) is an architecture for the
introduction of a control plane to optical networks. ASON
architecture defines a set of reference points that defines the
relationship between different network entities. Signaling across
those reference points can make use of protocols that are defined at
the IETF in the context of Generalized Multi-Protocol Label Switched
(GMPLS) work. This document describes Constraint Route Label
Distribution Protocol (CR-LDP) extensions for use across ASON
reference points.
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Table of Contents:
Page
Abstract 1
1. Introduction 3
2. Overview of CR-LDP Extensions for ASON 3
3. CR-LDP Messages for ASON 4
3.1 Call Setup Message 4
3.1.2 Call Setup Procedure 5
3.2 The Call Release Message 5
3.2.1 Call Release Procedure 6
4. CR-LDP TLV for ASON 6
4.1 Call ID TLV 6
4.1.1 Call ID Procedure 8
4.2 Call Capability TLV 8
4.3 Crankback TLV 8
5. Additional Error Codes 9
6. IANA Consideration 9
9. Security Consideration 10
10. References 10
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1. Introduction
Automatic Switched Optical Network (ASON) is an network architecture
for the introduction of control plane for optical networks. The
development and the standardization of ASON have been going on at
the ITU-T and its recommendation G.8080 [1]. The control plane
architecture introduces a set of reference points between the
different architectural components. ASON signaling that runs across
those interfaces are described in ITU-T recommendation G.7713 [2].
Constraint Route Label Distribution Protocol (CR-LDP) [3] is one of
the protocols under consideration at the ITU for the realization of
G.7713 and its dynamic connection management. The work specific to
CR-LDP extensions for ASON is documented in ITU-T recommendation
G.7713.3 (scheduled for consent in January 2003).
This draft introduces those CR-LDP extensions that are specific to
ASON. This draft should be considered in junction with RFC 3036 [4],
RFC 3212 [3], and CR-LDP extensions for GMPLS [5].
2. Overview of CR-LDP Extensions for ASON
This draft describes ASON specific CR-LDP extensions covering the
following ASON signaling requirements:
- Call and connection control separation
- Support of Soft Permanent Connections (SPC)
- Crankback
- Additional error codes
An important ASON architectural principle is the separation between
the call and the connection controllers as described in G.8080. Call
and connection control separation allows for a call with multiple
connections associated to it. It also allows for a call with no
connections (a temporary situation that might be useful during
recovery).
The separation of the call and the connection controllers could be
achieved using one of two models. The first model is a one where the
call set up request is always accompanied by a connection request.
The second model is a one in which call set up is done independent
from connection set up. The first model is usually referred to as
logical separation, while the second model is usually referred to as
complete separation. CR-LDP extensions for ASON support the two
separation models.
Two new messages are introduced for call operations (set up and
release). The Call Setup message is used for those cases where
complete separation is required. Otherwise the LDP Label Request
message is used for logical separation.
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A connection set up request must indicate the call to which the
connection needs to be associated. A Call ID TLV is introduced to
achieve this goal. The structure of the Call ID allows it to have a
global or an operator scope.
Call release is always achieved using the Call Release message. The
reception of the call Release messages signifies the intention to
remove all connections that are associated to the call. Connection
release is achieved using the CR-LDP label release procedure (using
LDP Label Release and Label Withdraw messages) as defined in [4].
A Call Capability TLV is also introduced to explicitly indicate the
capability of the requested call.
An SPC service assumes that both source and destination user-to-
network connection segments are provisioned while the network
connection segment is set up via the control plane. For example when
the initial request is received from an external source, e.g. from a
management system, there is an implicit assumption that the control
plane has adequate information to determine the specific destination
(network-to-user) link connection to use. Support for CR-LDP is
provided by the use of the Egress Label TLV as defined in OIF UNI
1.0 [6] and [7].
3. CR-LDP Messages for ASON
This section describes the formats and the procedures of the two
messages that are required for ASON call and connection control
separation. Those messages are the Call Setup messages and the Call
Release message.
3.1 Call Setup Message
The format of the Call Setup message is:
0 1 2 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0| Call Setup (TBD) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source ID TLV |
~ ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Dest ID TLV |
~ ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Call ID TLV |
~ ~
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| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Call Capability TLV |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Optional Parameters |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Message ID:
Is as defined in RFC3036 [4].
Source ID TLV:
Is as defined in UNI 1.0 [6] and in [7]
Dest ID TLV:
Is as defined in UNI 1.0 [6] and in [7]
Call ID TLV:
Is as defined in section 4.1 of this draft
Call Capability TLV:
Is as defined in section 4.2 of this draft
3.1.2 Call Setup Procedure
The Calling party sends the Call Setup message whenever a new call
needs to be set up with no connection associated to it. The Call
Setup message shall contain all the information required by the
network to process the call. In Particular the Call Setup message
shall include the calling and called party addresses as specified by
the Source ID and Dest ID TLV. The setup message must include Call
ID TLV. The call control entity shall identify the call using the
selected identifier for the lifetime of the call. The Call Setup
message shall progress through the network to the called party. The
called party may accept or reject the incoming call. An LDP
Notification message with the appropriate status code shall be used
to inform the calling party whether the setup is successful. The
call can be rejected by either the network, e.g. for policy reasons,
or by the called party.
3.2 The Call Release Message
This format of the Call Release message is:
0 1 2 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0| Call Release (TBD) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message ID |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source ID TLV |
~ ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Dest ID TLV |
~ ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Call ID TLV |
~ ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Optional Parameters |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3.2.1 Call Release Procedure
The Call Release message is sent by any entity of the network to
terminate an already established call. The Call Release message must
include the Call ID TLV of the call to be terminated. Confirmation
of call release is indicated to the request initiator using a
Notification message with the appropriate status code. Reception and
processing of the Call Release message must trigger the release of
all connections that are associated to that call. Connection release
follows the normal CR-LDP procedure using Label Release and Label
Withdraw messages.
4. CR-LDP TLV for ASON
This section describes the Call ID TLV and the Call Capability TLV
introduced for ASON.
4.1 Call ID TLV
An established call may be identified by a Call ID. The Call ID is a
globally unique identifier that is set by the source network. The
structure for the Call ID (to guarantee global uniqueness) is to
concatenate a globally unique fixed identifier (composed of country
code, carrier code, unique access point code) with an operator
specific identifier (where the operator specific identifier is
composed of ingress network element (NE) address and a local
Identifier).
Therefore, a generic CALL_ID with global uniqueness includes <global
Id> (composed of <country code> plus <carrier code> plus <unique
access point code>) and <operator specific Id> (composed of <NE
address> plus <local Identifier>). For a CALL_ID that requires only
operator specific uniqueness, only the <operator specific Id> is
needed, while for a CALL_ID that requires to be globally unique both
<global ID> and <operator specific Id> are needed.
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The <global Id> shall consist of a three-character International
Segment (the <country code>) and a twelve-character National Segment
(the <carrier code> plus <unique access point code>). These
characters shall be coded according to ITU-T Recommendation T.50.
The format of the operator specific (Op-Sp) CALL_ID TLV:
0 1 2 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U|F|Op-Sp Call ID (TBD) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NE Address (NEA Sub TLV) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
NEA Sub TLV:
The Source NE Address is an address of the transport network
element controlled by the source network. Its length can be 4,
6, 16, or 20 byte long. The NEA Sub TLV is TLV Type 1.
Local Identifier:
A 64-bit identifier that remains constant over the life of the
call.
The format of the globally unique (GU) Call ID TLV:
0 1 2 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U|F|GU Call ID (TBD) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | IS |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NS |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NE Address (NEA sub TLV) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
International Segment (IS):
To be coded according to ITU-T recommendation T.50. The
International Segment (IS) field provides a 3 character ISO
3166 Geographic/Political Country Code. The country code is
based on the three-character uppercase alphabetic ISO 3166
Country Code (e.g., USA, FRA)..
National Segment (NS):
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The National Segment (NS) field consists of two sub-fields: the
ITU Carrier Code followed by a Unique Access Point Code. The
ITU Carrier Code is a code assigned to a network
operator/service provider, maintained by the ITU-T
Telecommunication Service Bureau in association with
Recommendation M.1400. This code shall consist of 1-6 left-
justified characters, alphabetic, or leading alphabetic with
trailing numeric. The unique access point code is a matter for
the organization to which the country code and ITU carrier code
have been assigned, provided that uniqueness is guaranteed.
This code shall consist of 6-11 characters, with trailing NULL,
completing the 12-character National Segment.
4.1.1 Call ID Procedure
The following processing rules are applicable to the CALL ID TLV:
- For initial calls, the calling/originating party call controller
must set the CALL ID values to all-zeros
- For a new call request, the source networks call controller (SNCC)
sets the appropriate type and value for the CALL ID.
- For an existing call (in case Call ID is non zero) the SNCC
verifies existence of the call
- Intermediate nodes are not allowed to alter the Call ID TLV set by
the ingress node.
- The destination user/client receiving the request uses the CALL ID
values as reference to the requested call between the source user
and itself. Subsequent actions related to the call uses the CALL
ID as the reference identifier.
4.2 Call Capability TLV
The format of the Call Capability TLV is:
0 1 2 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U|F| Call Capabaility(TBD) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Call Capability |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The Call Capability TLV is used to explicitly indicate the
configuration potentiality of the call.
4.3 Crankback TLV
Crankback requires that when the Label Request message is blocked at
a particular node due to unavailable resources, the node will inform
the initiator of the Label Request message of the location of the
blockage. The initiator can then re-compute new explicit routes that
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avoid the area where resource shortage is detected. A new Label
Request message is sent that includes the new route.
The support of crankback in CR-LDP is facilitated by the
introduction of a Crankback TLV. An LDP Notification message is used
to inform the Label Request message initiator of the blocking
condition. The Notification message includes the Crankback TLV that
indicates the location of resource shortage. The location of the
resource shortage is identified using the ER-HOP TLV. The encoding
of the Crankbck TLV is:
0 1 2 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U|F| Crankback(TBD) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ER-HOP TLV |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
5. Additional Error Codes
G.7713 includes a number of error conditions that are currently
missing from CR-LDP related RFCs. The list of those error conditions
is given below. There is the need to assign status codes to them.
Invalid SNP ID
Calling Party busy
Unavailable SNP ID
Invalid SNPP ID
Unavailable SNPP ID
Failed to create SNC
Failed to establish LC
Invalid A End-User Name
Invalid Z End-User Name
Invalid CoS
Unavailable CoS
Invalid GoS
Unavailable GoS
Failed Security Check
TimeOut
Invalid Call Name
Failed to Release SNC
Failed to Free LC
6. IANA Consideration
This draft uses the LDP RFC 3036 [4] name spaces; see
http://www.iana.org/assignments/ldp-namespaces, which require
assignment for the following messages:
Call Setup
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Call Release
The assignment for the following TLVs
Op-Sp Call ID TLV
GU Call ID TLV
Call Capability TLV
Crankback TLV
The assignment for the new error codes as listed in section 5 of
this draft.
9. Security Consideration
This document doesnĘt introduce any new security concerns other than
those defined in RFC 3036 and RFC 3212.
10. References
1 M. Mayer, Architecture for Automatic Switched Optical Networks
(ASON), ITU G.8080/Y1304, V1.0, October 2001.
2 Z. Li, Distributed Call and Connection Management, ITU
G.7713/Y1704, October 2001.
3 B. Jamoussi, Ed., Constraint-Based LSP Setup Using LDP, RFC
3212, January 2002.
4 L. Andersson,et. al., LDP Specifications, RFC 3036, January
2001.
5 P. Ashwood-Smith, et. al., Generalized MPLS Signaling-CR-LDP
Extensions, draft-ietf-mpls-generalized-cr-ldp-07.txt, August
2002
6 B. Rajagopalan, User Network Interface (UNI) 1.0 Signaling
Specification, OIF-UNI-01.1, October 2001.
7 B. Rajagopalan, LDP and RSVP Extensions for Optical UNI
Signaling draft-bala-uni-ldp-rsvp-extensions-02.txt, work in
progress, 2002.
11. Author's Addresses
Osama Aboul-Magd
Nortel Networks
P.O. Box 3511, Station C
Ottawa, Ontario, Canada
K1Y 4H7
Phone: 613-599-9104
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Email: osama@nortelnetworks.com
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