Internet DRAFT - draft-adam-gsmp-service
draft-adam-gsmp-service
GSMP Working Group Constantin M. Adam
Internet Draft Aurel A. Lazar
Document: <draft-adam-gsmp-service-00.txt> Mahesan Nandikesan
Xbind, Inc.
October 21, 1999
An ATM Switch Service Model for GSMP
<draft-adam-gsmp-service-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.
Internet-Drafts are working documents of the Internet
Engineering Task Force (IETF), its areas, and its working
groups. Note that other groups may also distribute working
documents as Internet- Drafts.
Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other
documents at any time. It is inappropriate to use Internet-
Drafts as reference material or to cite them other than as "work
in progress."
The list of current Internet-Drafts can be accessed at:
http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed
at: http://www.ietf.org/shadow.html.
Distribution of this memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (1999). All Rights Reserved.
Abstract
The basic set of ATM switch services useful for streaming media such
as video and audio are virtual circuit segments, virtual path
segments, and multicast segments with quality of service support.
These services are specified using the concept of traffic classes. A
definition of traffic classes different from that used by other bodies
is provided here. The present Internet Draft is based on the
corresponding set of services that are being considered by the IEEE
P1520 working group.
Table of Contents
1. Introduction .................................................. 2
Adam, Lazar, Nandikesan Expires March 2000 1
An ATM Switch Service Model for GSMP October 1999
2. Service model ................................................. 2
2.1 Traffic classes ........................................... 2
2.2 ATM switch services ....................................... 3
2.2.1 Virtual circuit segments ............................ 3
2.2.2 Multicast segments .................................. 3
2.2.3 Virtual path segments ............................... 4
2.2.4 Virtual path originations and terminations .......... 4
3. Message set ................................................... 5
3.1 Traffic classes and quality of service .................... 5
3.1.1 Get list of supported traffic class parameters ...... 5
3.1.2 Traffic class characterization messages ............. 6
3.3 Connection management messages ............................ 8
3.1.1 Virtual circuit segments ........................... 9
3.1.2 Multicast segments .................................. 10
3.1.3 Virtual path segments ............................... 10
3.1.4 Virtual path originations and terminations .......... 10
1. Introduction
The present Internet Draft lays down a set of ATM switch services that
are useful for supporting streaming media. It is based on the
corresponding set of services that are being considered by the IEEE
PIN working group [5]. While the IEEE PIN addresses API's,
the present Internet Draft addresses a protocol, namely GSMP, to
support these services.
2. Service Model
The basic set of ATM switch services useful for stream media such as
video and audio are virtual circuit segments, virtual path segments,
and multicast segments with quality of service support. (The term
"segment" is used here to distinguish the end-to-end concepts from
their local counterparts. For example, a three-hop virtual circuit
consists of three virtual circuit segments.) This section specifies
these services using the concept of traffic classes. Attention is
drawn to the fact that the definition of traffic classes provided here
is different from that used by other bodies.
2.1 Traffic classes and Quality of Service
In the context of the present service model, a traffic class is a
statistical model for the bit rate of an information stream. For
practical purposes it is characterized by two types of parameters:
(i) A qualitative parameter describing the type of the traffic,
e.g., video, voice, audio.
(ii) A quantitative parameter giving a bound on the peak cell rate -
PCR (as defined in [5]). This description may optionally be
Adam, Lazar, Nandikesan Expires March 2000 2
An ATM Switch Service Model for GSMP October 1999
complemented with bounds on additional quantitative parameters
such as the maximum burst size (MBS).
With each traffic class, a set of quality of service constraints is
attached. The quality of service constraints take the form of bounds
on quantitative parameters such as the maximum cell transfer delay
(defined in [5]). A list of presently used qualitative traffic
characterizations is given below:
o CBR Arbitrary statistics
o Video Real-time video statistics
o Voice Real-time voice statistics
o Audio Real-time audio statistics
A traffic class with a qualitative characterization of "CBR" means
that calls of this traffic class may have arbitrary traffic
characteristics. Unlike the others, such traffic classes do not have
peak cell rate specified. Instead, each call of such a traffic class
has a peak cell rate specified, and may be different for each of such
a traffic class. Such traffic classes will be referred to as CBR
traffic classes.
2.2 ATM Switch Services
2.2.1 Virtual circuit segments
A virtual circuit segment provides connectivity for a cell stream from
an input port to an output port of the switch. Each cell stream is
required to fall under one of a set of traffic classes supported by
the switch. In other words, the bit-rate of the cell stream should
follow the bounds specified in the traffic class. In return, the
switch is required to provide the cell stream with QOS associated with
the traffic class. The exception is calls of CBR traffic classes. For
these calls, the peak cell rate bound is specified per call during the
connection request; the switch is required to provide these calls
with virtual zero cell transfer delay and no loss.
The following requests are supported:
Request to create a virtual circuit segment:
Parameters: input port, input VPI, input VCI, output port,
output VPI, output VCI, traffic class number,
bandwidth.
Request to remove a virtual circuit segment:
Parameters: input port, input VPI, input VCI; output port,
output VPI, output VCI.
2.2.2 Multicast segments
Adam, Lazar, Nandikesan Expires March 2000 3
An ATM Switch Service Model for GSMP October 1999
A multicast segment provides connectivity for a cell stream from a
single input port to multiple output ports of the switch: Each
arriving cell is replicated and sent to each of the output ports. The
cell stream is required to fall under one of a set of traffic classes
supported by the switch. In other words, the bit rate of the cell
stream should follow the bounds specified in the traffic class. In
return, the switch is required to provide each of the replicated
output cell stream with QOS associated with the traffic class. The
same exception noted in Section 2.2.1 for CBR traffic classes applies
here as well. Each of the above replications is called a branch of the
multicast segment.
The following requests are supported. The parameter "Bandwidth" is
used only in conjunction with CBR traffic classes.
Request to add a branch.
Parameters: as for request to create a virtual circuit segment.
Request to remove a branch
Parameters: as for request to remove a virtual circuit segment.
Request to remove a multicast tree,
Parameters: input port, input VPI, input VCI.
2.2.3 Virtual path segments
A virtual path segment provides connectivity for a group of cell
streams from an input port to an output port of the switch. The sum of
the instantaneous bit-rates of all the streams in the group shall not
exceed at any given moment the bandwidth assigned to the virtual path
segment. In return, the ATM switch is required to transmit every cell
of every stream in the group with virtually zero delay and no loss.
The following requests are supported:
Request to create a virtual path segment:
Parameters: input port, input VPI, output port, output VPI,
bandwidth.
Request to remove a virtual path segment:
Parameters: input port, input VPI, output port, output VPI.
2.2.4 Virtual path originations and terminations
A virtual path origination is a logical subset of a port. It is
assigned a name space (VPI) and bandwidth. A virtual path termination
is a logical subset of a port. It is assigned a name space (VPI).
Adam, Lazar, Nandikesan Expires March 2000 4
An ATM Switch Service Model for GSMP October 1999
The following requests are supported:
Request to create a virtual path origination:
Parameters: port, VPI, bandwidth
Request to remove a virtual path origination:
Parameters: port, VPI
Request to create a virtual path termination:
Parameters: port, VPI
Request to remove a virtual path termination:
Parameters: port, VPI
3. Message Set
The messages that allow to set the traffic class characteristics and
the QOS constraints associated with these classes on the switch must
be issued immediately after the adjacency protocol has been
established, and before any connections are set up on the switch.
These features cannot be changed on the fly, as this would require an
operation similar to rebooting the switch in order for the new
settings to take effect.
3.1 Traffic Classes and Quality of Service
3.1.1 Get List of Supported Traffic Class Parameters Message
The set of supported traffic class parameters can be retrieved from
the service capability sets returned by the GSMP Get Service
Configuration message. The service capability set for the service
model presented in this Internet Draft is changed as follows:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Cap. Set ID | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| QOS Mask | Quantitative Mask |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | Qualitative Mask |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Field Descriptions
Cap. Set ID
The capability set ID for the present service model.
The following fields are bit masks parameterizing the traffic
class and QOS descriptors available on the port. The mask items
are given codes equal to their bit-position in the mask. For
Adam, Lazar, Nandikesan Expires March 2000 5
An ATM Switch Service Model for GSMP October 1999
example, maximum burst size is given code 2, since it is
represented by bit position 2.
Qualitative
Mask of supported qualitative traffic class characterizations.
Bit 0: Constant bit-rate (CBR)
Bit 1: Video
Bit 2: Voice
Bit 3: Audio
Bit 4 - 15: Reserved
Quantitative
Mask of supported traffic classes on the port.
Bit 0: Peak Cell Rate (PCR)
Bit 1: Sustained Cell Rate (SCR)
Bit 2: Maximum Burst Size (MBS)
Bit 3: Cell Delay Variation Tolerance (CDVT)
Bit 4 - 15: Reserved
QOS mask
Mask of supported QOS parameters on the port.
Bit 0: Maximum Cell Transfer Delay (Max CTD)
Bit 1: Average Cell Transfer Delay (Ave CTD)
Bit 2: Cell Loss Ratio (CLR)
Bit 3: Average Gap Loss [citation]
Bit 4: Cell Delay Variation (CDV)
Bit 5 - 15: Reserved
3.1.2 Set Traffic Class Characterization Message
In order to characterize the traffic classes, the traffic parameters
and QOS parameters for each class must be set. The present model
achieves this by placing the traffic and QOS parameters in a special
Add Branch Message in which the Input and Output Labels are set to
zero.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | Classes |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Traffic Class 1 Block ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Traffic Class 2 Block ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
Adam, Lazar, Nandikesan Expires March 2000 6
An ATM Switch Service Model for GSMP October 1999
~ ... ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The traffic class block has the following structure:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |Qualitat.| Quantitative Mask |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| QOS Mask | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Traffic Parameter 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Traffic Parameter 2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ... ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| QOS Parameter 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| QOS Parameter 2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ... ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Parameter Description
Classes Number of traffic classes.
Qualitat.
Code for the qualitative traffic description (See
Section 3.1)
Quantitative Mask
Mask of quantitative traffic class characteristics.
Every Quantitative Traffic Characteristic selected
in the mask is specified using 2 bytes. The
following list specifies the unit for
each parameter that is listed in Section 3.1:
Parameter unit
----------------------
PCR cells/s
SCR cells/s
MBS cell
CDVT microsecond
Exactly one bit of the field 'Qualitative' shall be
set to 1 for a given traffic class. The peak cell
rate field is a mandatory quantitative parameter,
i.e., bit 0 of the field 'Quantitative' must always
be set to 1.
Adam, Lazar, Nandikesan Expires March 2000 7
An ATM Switch Service Model for GSMP October 1999
QOS Mask mask of QOS parameters. Every QOS parameter
selected in the mask is specified using 2
bytes. The following list specifies the unit and
the range of each parameter:
Parameter unit
----------------------
Max CTD: microsecond
Ave CTD: microsecond
CLR ---
Ave Gap 10^-6 cells
CDV microsecond
The parameter CLR is represented as an order of
magnitude. Thus, a value of n represents a CLR of
10^n.
Notes: This message must be issued by the GSMP controller to the
switch after adjacency has been established but before any connections
are set up on the switch.
3.3 Connection Management Messages
The general structure of a connection management message is the
following:
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 | Message Type | Result | Code |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Partition ID | Transaction Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Port Session Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Input Port |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|M|B|T|R| |
+-+-+-+-+ Input Label ~
~ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Output Port |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|QMS|T|R| |
+-+-+-+-+ Output Label ~
~ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Service Selector |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The following fields need to be interpreted in a specific manner.
Adam, Lazar, Nandikesan Expires March 2000 8
An ATM Switch Service Model for GSMP October 1999
The QOS Model Selector (QMS) will be set to the value 0b11 (ARM
Specification) in connection management messages.
The Service Selector field contains three sub-fields. The first byte
is the service identifier assigned to the IEEE PIN Service model. The
second byte contains the traffic class identifier, to which the
connection belongs. The last two bytes contain a bandwidth.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|IEEE PIN SID | Traffic class | Bandwidth |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The bandwidth field is given the following floating point structure,
taken from the ATM Forum Traffic Management, Version 4.0. The Bit "R"
is reserved.
0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|R|N| Exponent | Mantissa |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The number represented by this structure is
N * (1 + Mantissa/512) * 2^Exponent.
The Service Selector field is only used in the Add Branch message. In
all other connection management messages, the Service Selector field
should be set to zero by senders and ignored by receivers.
3.3.1 Virtual Circuit Segments
Request to add a virtual circuit segment:
Implemented as an Add Branch VCC message with the
Service Selector field present. The 'Bandwidth' sub-field
of the Service Selector field is used only for calls of
a CBR traffic class.
Request to remove a virtual circuit segment:
Implemented as a Delete Branches message.
3.3.2 Multicast Segments
Adam, Lazar, Nandikesan Expires March 2000 9
An ATM Switch Service Model for GSMP October 1999
Request to add a branch:
Implemented as an Add Branch VCC message with the Service
Selector field present. The 'Bandwidth' sub-field of the
Service Selector field is used only for branches of
a multicast segment that is of a CBR traffic class.
Request to remove a branch:
Implemented as a Delete Branches message.
3.3.3 Virtual Path Segments
Request to Add a virtual path segment:
Is implemented as an Add Branch VPC message. The Service
Selector field is present, the 'Traffic Class' sub-field is
not used. The 'Bandwidth' sub-field of the Service Selector
field represents the bandwidth of the virtual path segment.
Request to remove a virtual path segment:
Implemented as a Delete Branches Message (with the VCIs set
to zero).
3.3.4 Virtual Path Originations and Terminations
Request to create a virtual path origination:
Is implemented as an Add Branch VPC message with the Input
VPI, Input VCI and output VCI fields set to zero. The
output VPI is set to the VPI of the virtual path
origination. The Service Selector field is present, the
'Traffic Class' sub-field is not used. The 'Bandwidth'
sub-field of the Service Selector field represents the
bandwidth of the virtual path origination.
Request to remove a virtual path origination:
Implemented as a Delete Branches message. The VCIs and
the Input VPI are set to zero. The Output VPI is set to
the VPI of the virtual path origination.
Request to create a virtual path termination:
Is implemented as an Add Branch VPC message with the
Adam, Lazar, Nandikesan Expires March 2000 10
An ATM Switch Service Model for GSMP October 1999
Output VPI, Output VCI and Input are set to zero. The
Service Selector field is present, but the 'Traffic Class'
and the 'Bandwidth' sub-fields of the Service Selector
field are not used.
Request to remove a virtual path termination:
Implemented as a Delete Branches message. The VCIs and
the Output VPI are set to zero. The Input VPI is set to
the VPI of the virtual path termination.
References
[1] GSMP Working Group, "General Switch Management Protocol V3",
draft-ietf-gsmp-02.txt, October 1999.
[2] GSMP Working Group, T. Worster, F. Hellstrand, A. Doria, "A QOS
Model for GSMP", draft-worster-gsmp-qos-00.txt, August 1999.
[3] IEEE/WG 1520, C. Adam, A. A. Lazar, M. Nandikesan, "Proposal for
Standaridizing the qGSMP protocol", P1520/TS/ATM-002,
http://comet.columbia.edu/pin-atm/docs/P1520-TS-ATM-002R1.pdf,
Jan 1999.
[4] IEEE/WG 1520, C. Adam, A. A. Lazar, M. Nandikesan, "Switch
abstractions for designing open interfaces", P1520/TS/ATM-016,
http://comet.columbia.edu/pin-atm/docs/P1520-TS-ATM-016R1.pdf,
March 1999.
[5] IEEE/WG 1520, C. Adam, A. A. Lazar, M. Nandikesan, "ATM switch
service interface", P1520/TS/ATM-018,
http://comet.columbia.edu/pin-atm/docs/P1520-TS-ATM-018R1.pdf,
March 1999.
Authors' Address
Constantin M. Adam
Xbind, Inc.
55 Broad Street, 23C
New York, NY 10004
USA
Telephone: 212-809-3303, ext. 102
email: ctin@xbind.com
Aurel A. Lazar
Xbind, Inc.
55 Broad Street, 23C
New York, NY 10004
Adam, Lazar, Nandikesan Expires March 2000 11
An ATM Switch Service Model for GSMP October 1999
USA
Telephone: 212-809-3303, ext. 101
email: aurel@xbind.com
Mahesan Nandikesan
Xbind, Inc.
55 Broad Street, 23C
New York, NY 10004
USA
Telephone: 212-809-3303, ext. 106
email: mahesan@xbind.com
Adam, Lazar, Nandikesan Expires March 2000 12
