draft-rao-sigtran-v5ua-00

Internet Engineering Task Force			  Sanjay Rao
INTERNET DRAFT				 Neeraj Khanchandani
					      Fahir Ergincan
					     Nortel Networks

Expires in six months				   July 2000

	    V5.2 extensions to the IUA protocol
	      <draft-rao-sigtran-v5ua-00.txt>

Status of this Memo

This document is an Internet-Draft and is in full
conformance with all provisions of Section 10 of  RFC2026.

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Abstract

This document defines a mechanism for backhauling of V5.2
messages over IP by extending the ISDN User Adaptation Layer
Protocol (<draft-ietf-sigtran-iua-03.txt>). The document
aims to become an Appendix to IUA and to be the base for a
V5.2 implementation.

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		     Table of Contents

1.Introduction ........................................	   3

1.1.Scope .............................................	   3

1.2.Terminology .......................................	   3

2.Overview ............................................	   4

2.1.Proposed V5.2 Backhaul Architecture ...............	   5

2.2.IUA Message Header ................................	   6

2.3.New IUA Message Header for V5.2 implementations

2.4. References .......................................	   7

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1.  Introduction

This document describes a method of implementing V5.2 back-
haul messaging over IP using a modified version of the ISDN
User Adapation Layer Protocol (IUAP). The document aims to
become an Appendix to IUA and to be the base for the "appli-
cation guide".

1.1.  Scope

There is a need for a V5.2 backhaul to meet the following
access types:
	  - Analog telephone access
	  - ISDN Basic rate access
	  - ISDN Primary Rate access (V5.2)
	  - Other analog or digital accesses for semi-
	  permanent connections without associated outband
	  signaling information

1.2.  Terminology

Bearer Channel Connection (BCC) protocol - A protocol which
allows the LE to instruct the AN to allocate bearer chan-
nels, either singly or in multiples, on demand.

Communication channel (C-channel) - A 64 kbit/s time slot on
a V5.2 interface provisioned to carry communication paths.

Communication path (C-path) - Any one of the following
information types:
	  - The layer 2 data link carrying the Control pro-
	  tocol
	  - The layer 2 data link carrying the Link Control
	  protocol
	  - The layer 2 data link carrying the PSTN signal-
	  ling
	  - Each of the layer 2 data links carrying the pro-
	  tection protocol
	  - The layer 2 data link carrying the BCC protocol
	  - All the ISDN Ds-type data from one or more user
	  ports
	  - All the ISDN p-type data from one or more user
	  ports
	  - All the ISDN t-type data from one or more user
	  ports

Note: This definition includes the possibility that there is
more than one C-path of the same information type, each
allocated to a different logical C-channel.

Logical Communication channel (Logical C-channel) - A group
of one or more C-paths, all of different types, but exclud-
ing the C-path for the protection protocol.

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Multi-link - A collection of more than one 2.048 kbit/s link
which together make up a V5.2 interface.

Multi-Slot - A group of more than one 64kbit/s channels pro-
viding 8Khz and time slot sequence integrity, generally used
together within an ISDN Primary Rate Access (ISDN-PRA) user
port, in order to supply a higher bit-rate service.

Physical Communication Channel (Physical C-channel) - A
64kbit/s time slot on a V5.2 interface which has been
assigned for carrying logical C-channels. A physical C-
channel may not be used for carrying bearer channels.

Primary Link - A 2.048 kbit/s link in a multi-link V5.2
interface whose physical C-channel in time slot 16 carries a
C-path for the protection protocol and, on V5.2 initializa-
tion, also the C-path for the control protocol, link control
protocol, and the BCC protocol. Other C-paths may also be
carried in the time slot 16.

Secondary Link	- A 2.048 kbit/s link in a multi-link V5.2
interface whose time slot 16 carries a C-path for the pro-
tection protocol, and, on V5.2 initialization, acts as the
standby C-channel for the control protocol, link control
protocol, and BCC protocol and any other C-paths initially
carried in time slot 16 of the primary link.

2.  V5.2 Overview

V5.2 is an industry standard ETSI interface (reference ETS
300 347-1) defined between a Local Exchange (LE) and an
Access Network (AN) providing access to the following types:
	  - Analog telephone access
	  - ISDN Basic rate access
	  - ISDN Primary Rate access (V5.2)
	  - Other analog or digital accesses for semi-
	  permanent connections without associated outband
	  signaling information

The original V5 specification uses 2048 kbps links, V5.2 may
use upto 16 such interface links.

	----------		----------	  o--o
	|	 |	E1	|	 |-------  /\
	|	 |--------------|	 |	   --
	|   LE	 |	E1	|  AN	 |
	|	 |--------------|	 |	  o--o
	|	 |		|	 |-------  /\
	----------		----------	   --

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LE and AN are connected with up to 16 E1 (PCM30) links.
Channels 16, 15 and 31 on any E1 link can be reserved for
data communication between LE and AN. The channels reserved
for data are called "Communication Channels" or "C-
Channels."

The C-Channels are the physical media to exchange data
between the V5.2 protocol peer entities, as well as to
transfer the ISDN BRI D-Ch messages between the terminals
and the LE. A logical communication path between two peer
entities is called a "C-path".

The signaling information in V5.2 are defined as:
	  - Analog signals are carried by means of the V5
	  PSTN protocol (L3)
	  - ISDN/analog ports are controlled by the V5 Con-
	  trol protocol (L3)
	  - ISDN protocol messages are mapped to LAPD
	  frames, which are carried by means of LAPV5-EF
	  sublayer (L2)
	  - V5 protocol messages are mapped to LAPV5-DL
	  frames, which are carried by means of LAPV5-EF
	  sublayer (L2)

In order to support more traffic and dynamic allocation of
links, the V5.2 protocol has several additions:
	  - A bearer channel connection protocol establishes
	  and de-establishes bearer connections required on
	  demand, identified by the signalling information,
	  under the control of the Local Exchange.
	  - A link control protocol is defined for the
	  multi-link management to control link identifica-
	  tion, link blocking and link failure conditions.
	  - A protection protocol, operated on two separate
	  data links for security reasons, is defined to
	  manage the protection switching of communication
	  channels in case of link failures.

The following protocols are defined for the various protocol
layers:
	  - LAPV5-EF
	  - LAPV5-DL
	  - V5-Link Control
	  - V5-BCC
	  - V5-PSTN
	  - V5-Control
	  - V5-Protection

2.1.  Proposed V5.2 Backhaul Architecture

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	******	 V5.2	     ******	 IP	 *******
	* AN *---------------* SG *--------------* MGC *
	******		     ******		 *******

	+-----+					 +-----+
	|V5.2 |		     (NIF)		 |V5.2 |
	+-----+		  +----------+		 +-----+
	|     |		  |	| IUA|		 | IUA |
	|     |		  |	+----+		 +-----+
	|LAPV5|		  |LAPV5|SCTP|		 |SCTP |
	|     |		  |	+----+		 +-----+
	|     |		  |	| IP +		 | IP  |
	+-----+		  +-----+----+		 +-----+

NIF  - Nodal Interworking function EP	- End Point SCTP -
Stream Control Transmission Protocol IUA  - ISDN User Adap-
tation Layer Protocol

2.2.  IUA Message Header

	0	  1	    2	      3
	0 2 4 6 8 0 2 4 6 8 0 2 4 6 8 0 2
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	|  Tag (0x01)  |  Length	|
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	|   Interface Identifier	|
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	|  DLCI	       |  Spare		|
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

	Figure 2 IUA Message Header

2.3.  New IUA Message Header for V5.2 implementations

Spare field is now the Envelope Function Address (EFA)
field.

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	0	  1	    2	      3
	0 2 4 6 8 0 2 4 6 8 0 2 4 6 8 0 2
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	|  Tag (0x01)  |  Length	|
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	|   Interface Identifier	|
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	|  DLCI	       |Spr|   EFA	|
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

	Figure 3 IUA Message Header for V5.2

The EFA identifies a  C-path, which is a 13-bit number,
ranging from 0 to 8191 (decimal). An EFA uniquely identifies
one of the five V5.2 protocols, or an ISDN agent attached to
an AN. The following list contains the possible values for
the EFA

	Definition		Value
	----------		------
	ISDN_PROTOCOL		0 - 8175
	PSTN_PROTOCOL		8176
	CC_PROTOCOL		8177
	BCC_PROTOCOL		8178
	PROT_PROTOCOL		8179
	LINK_CONTROL_PROTOCOL	8180
	RESERVED		8181 - 8191

2.4.  References

[1]  ISDN Q.921-User Adaptation Layer <draft-ietf-sigtran-
     iua-03.txt>

[2]  EN 300 347-1 (1999): V interfaces at the digital Local
     Exchange (LE); V5.2 interface for the support of Access
     Network (AN); Part 1: V5.2 interface specification.

[3]  EN 300 347-1 (1999): V interfaces at the digital Local
     Exchange (LE); V5.2 interface for the support of Access
     Network (AN); Part 1: V5.2 interface specification.

[4]  ETS 300 125 (1991) : DSS1 protocol; User-Network inter-
     face data link layer specification; (Standard is based
     on : ITU Q.920, Q.921).

[5]  ETS 300 166 (08/1993) : Transmission and Multiplexing;
     Physical and electrical characteristic of hierarchical
     digital interfaces (Standard is based on G.703).

[6]  ETS 300 167 (08/1993) : Transmission and Multiplexing;

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     Functional characteristic of 2048 kbits/s interfaces
     (Standard is based on G.704, G.706).

2.5.  Author's Addresses

Sanjay Rao				 Tel +1-919-991-2251
Nortel Networks		    Email rsanjay@nortelnetworks.com
35 Davis Drive
Research Triangle Park, NC 27709
USA

Neeraj Khanchandani			 Tel +1-919-991-2274
Nortel Networks		    Email neerajk@nortelnetworks.com
35 Davis Drive
Research Triangle Park, NC 27709
USA

Dr. Fahir Ergincan			Tel +49 7545 96 8844
Nortel-Dasa Network Systems   Email fahir@nortelnetworks.com
88039 Friedrichshafen
Germany

	  This Draft Expires in 6 months from July,2000

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