Internet DRAFT - draft-bouwen-sigtran-il1a
draft-bouwen-sigtran-il1a
Sigtran WG J. Bouwen
Internet Draft Alcatel
Document:<draft-bouwen-sigtran-il1a-00.txt> K. Morneault
Category: Informational Cisco
February 2001
Layer 1 Activation Management for
ISDN Q.931 User Adaptation Layer (IUA):
ISDN Layer 1 Activation Adaptation Layer (IL1A)
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering
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1. Abstract
ISDN Basic Access terminations require an explicit activation/de-
activation of layer 1. In a decomposed gateway architecture with an
Access Gateway and a Media Gateway Controller, it is the Media
Gateway Controller who controls the activation process. This draft
describes the use of an SCTP adaptation layer for the exchange of
the activation/de-activation messages. The defined messages can be
considered as an extension for IUA [1] when layer 1 control of Basic
Access interfaces is required.
2. 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 RFC-2119 [1].
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3. Introduction: layer 1 activation for ISDN
In ISDN access gateway architectures, the layer 1 functionality for
Basic Interfaces is split between the access gateway (access node)
and the entity containing call control (the local exchange).
When VoIP Access Gateways are deployed that support ISDN
terminations, a similar functionality is required. Two sub-functions
are necessary:
1. The Media Gateway Controller has to know if layer 1 of a
particular ISDN Basic Access termination is permanently
activated, or if activation/de-activation procedures are
required. This information is a property of the ISDN
termination, and is covered by a new Megaco termination
property defined in [4]
2. The activation/de-activation procedure itself, which
requires the exchange of a limited set of signalling messages
between the Media Gateway Controller and the Access Gateway.
The activation/deactivation procedure for Basic Interfaces is
defined in ITU Recommendation I.430 [2]. Remark that the procedure
is only valid for Basic Access interfaces, Primary Rate Interfaces
are permanently activated.
This document describes the use of an SCTP adaptation layer for the
exchange of the activation/de-activation messages. The defined
messages can be considered as an extension for IUA [1] when layer 1
control of Basic Access interfaces is required.
Because IUA already contains layer 2 activation/de-activation
messages, the use of IUA mechanisms for layer 1 activation/de-
activation is preferred to implementing layer 1 functionality in
Megaco events and signals. Co-ordination between layer 1 and layer 2
activation will be simplified.
4. Layer 1 Messages
Table 1 shows the messages defined in G.964 [3] for layer 1
activation/de-activation, and the direction in which they are
exchanged.
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+======================================================+
!Message ! MG û direction û MGC !
+======================================================+
! Activation Initiated by User ! ----> !
+------------------------------------------------------+
! DS Activated ! ----> !
+------------------------------------------------------+
! Access Activated ! ----> !
+------------------------------------------------------+
! Access Deactivated ! ----> !
+------------------------------------------------------+
! Activate Access ! <---- !
+------------------------------------------------------+
! Deactivate Access ! <---- !
+=======================================================
Table 1 û G.964 Activation/de-activation Messages
5. ISDN Layer 1 Activation Adaptation Layer (IL1A) Messages)
The ISDN Layer 1 Activation Adaptation Layer uses the message format
as it is defined for IUA. The messages consist of the common header
and the IUA message header defined for QPTM and TEI status messages.
No additional variable-length parameters are required.
Figure 1 shows the message format when integer based interface
identifier are used, Figure 2 shows the format for text based
interface identifiers.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Version | Reserved | Message Class | Message Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tag (0x1) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Interface Identifier (integer) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tag (0x5) | Length=8 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| DLCI | Spare |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1 IL1A Message Format for integer I/F ids
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Version | Reserved | Message Class | Message Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tag (0x3) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Interface Identifier (text) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tag (0x5) | Length=8 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| DLCI | Spare |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2 IL1A Message Format for text I/F ids
The fields have the following values:
Version
1 : Release 1.0
Message Class
9 : IL1A messages
Message types
0 : Reserved
1 : Activate Access
2 : Activation Initiated by User
3 : DS Activated
4 : Access Activated
5 : Deactivate Access
6 : Access Deactivated
The values of the other fields are defined in the IUA specification
6. IL1A Support
When one of the communicating parties (Access Gateway or Media
Gateway Controller) does not support the IL1A message class, it will
respond with the ôUnsupported Msg Classö error on receipt of an IL1A
message. Error recovery procedures for this case are for further
study.
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7. Security Considerations
Security considerations for IUA apply.
8. IANA Considerations
The IL1A Message Class has to be registered with IANA.
9. References
[1] ISDN Q.921-User Adaptation Layer (IUA)
RFC 3057, November 2000
[2] ITU-T Recommendation I.430 (1995), Basic user-network interface
- layer 1 specification
[3] ITU-T Recommendation G.964 (1994), V-interfaces at the digital
local exchange (le) û V5.1-interface (based on 2048 kbit/s) for the
support of access network (AN)
[4] ISDN Package for Megaco
draft-bouwen-megaco-isdn-pack-01.txt, February 2001
10. Author's Addresses
Jan Bouwen
Alcatel
F. Wellesplein 1
B-2000 Antwerpen
Belgium
Email: jan.bouwen@alcatel.be
Ken Morneault
13615 Dulles Technology Drive
Herndon, VA 20171
USA
Email: kmorneau@cisco.com
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