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 
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      Internet-Drafts are draft documents valid for a maximum of six 
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      The list of current Internet-Drafts can be accessed at: 
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      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
  
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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 
  
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       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 
  
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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). 
 
  
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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 
  
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     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                      ~ 
   |                                                               |  
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |                                                               |  
  
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   ~                             ...                               ~ 
   |                                                               |  
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
 
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. 
  
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     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.  
  
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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  
 
  
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       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 
  
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            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 
  
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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 










































  
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