Internet DRAFT - draft-adam-gsmp-sr

draft-adam-gsmp-sr





GSMP Working Group                                   Constantin M. Adam 
Internet Draft                                           Aurel A. Lazar 
Document: <draft-adam-gsmp-sr-00.txt>                Mahesan Nandikesan 
                                                            Xbind, Inc. 
                                                       October 21, 1999 
 
 
       A Quality of Service Extension to the Minimal Resource Set 
                       <draft-adam-gsmp-sr-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 
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      Internet-Drafts are draft documents valid for a maximum of six 
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      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 present document introduces an extension to the minimal resource 
set [1] for guaranteeing quality of service based on the concept of a 
schedulable region. The schedulable region is an abstraction that 
captures the capacity of a multiplexer. The draft also provides GSMP 
messages to support the extension. 
 
 
Table of Contents 
 
1. Introduction .................................................. 2
 
2. Admission control model ....................................... 2
 
3. Realizing the admission control model ......................... 3
  
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4. Message set ...................................................  4
   4.1 Traffic classes and QOS messages ..........................  5
   4.2 Schedulable region estimation policy messages .............  9
   4.3 Schedulable region estimate messages ...................... 11
 
A. Schedulable region representation ............................. 12
 
B. Measure of change of schedulable region ....................... 13
 
 
1. Introduction 
 
In reference [1], a minimal resource model of an ATM switch was
presented along with a message set for exposing and controlling those
resources. The basic feature captured by that model was cell switching
from the input to the output ports. The present document introduces an
extension for guaranteeing quality of service while switching cells,
and provides GSMP messages to support the extension.
 
2. Admission control model 
 
The present section lays down the foundations for a quality of service 
extension to the minimal resource model. The extension is based on a 
capacity concept known as the schedulable region, which characterizes 
the capacity of a multiplexer, the same way the capacity characterizes 
the capacity of a link. The concept is based on the auxiliary concept 
of traffic classes, which is used here with a different meaning than 
that used by the ATM Forum. 
 
In the context of the present quality of 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 its type, 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 
       complemented with bounds on additional quantitative parameters 
       such as the maximum burst size - MBS. 
 
 
 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 
 
With each traffic class, a set of quality of service constraints is 
  
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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 set of traffic classes is associated with each output port 
multiplexer of an ATM switch. Given such a set of traffic 
classes and a multiplexer, the operating point is defined as the 
vector consisting of the number of calls of each class that the 
multiplexer currently accommodates. An operating point is said to be 
admissible if the multiplexer can provide the requisite quality of 
service guarantees to all the calls. The set of all admissible 
operating points is said to be the schedulable region of the 
multiplexer. Figure 1 gives an illustration of a schedulable region 
with two traffic classes. 
 
 
       Number of class II calls 
                 ^ 
                 | 
                 | 
                 | 
                 |\ 
                 |.\ 
                 |..- 
                 |...\ 
                 |....--  
                 |.......\ 
                 |........\ 
                 |.........---- 
                 |.............\ 
                 --------------------------> 
                        Number of class I calls 
 
 
          Figure 1: A schedulable region of a multiplexer supporting 
                    two traffic classes. 
 
 
3. Realizing the Admission Control Model 
 
The main task in realizing the admission control model is to determine 
the boundaries of the schedulable region. Once this has been 
determined, the admission control procedure reduces to checking 
whether the operating point of the multiplexer lies within the 
schedulable region.  This can be performed easily by an external 
switch controller. Thus, the present section focuses on the definition 
and the representation of the schedulable region. A trivial 
approximation of the schedulable region is given by (See Appendix A)
 
       A = (C/p_1, C/p_2, ..., C/p_n)  (i.e., k = 1), 
 
       B = Null matrix (i.e., m = 0), 
 
  
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where C is the capacity of the output line and p_1,p_2,...,p_n are the 
peak cell rate bounds of the n traffic classes. The 
above will be referred to as the "peak-rate-based estimator". This 
schedulable region approximation can be evaluated directly on the 
switch hardware or by an external switch controller. But some other 
estimation methods, including those based on real-time measurements, 
cannot be realized on the external switch controller. Thus, these must 
be implemented on the switch itself, just as with scheduling and 
buffer management policies. As a result, the minimal resource model 
shown in Figure 2 must be extended to include schedulable region 
estimators as shown in Figure 3.  Although only one estimator is shown 
in the figure, there is one estimator per multiplexer. 
 
 
                 +---------------+ 
                 |Switching Table| 
                 +---------------+ 
      Input                                           Output 
      Ports   +=====================+  +-----------+  Ports 
     -------->|                     |--|Multiplexer|---------> 
              |    Switch Fabric    |  +-----------+ 
       ...    |                     |  +-----------+ 
     -------->|                     |--|Multiplexer|---------> 
              +=====================+  +-----------+ 
 
                  Figure 2: Minimal resource model 
 
 
 
                 +---------------+      
                 |Switching Table|     +---------+ 
                 +---------------+     |Estimator| 
      Input                            +---------+    Output 
      Ports   +=====================+  +-----------+  Ports 
     -------->|                     |--|Multiplexer|---------> 
              |                     |  +-----------+ 
              |                     |   
              |                     |       ... 
              |   Switch Fabric     |   
       ...    |                     |  +---------+ 
              |                     |  |Estimator| 
              |                     |  +---------+ 
              |                     |  +-----------+ 
     -------->|                     |--|Multiplexer|---------> 
              +=====================+  +-----------+ 
 
                  Figure 3: Extended resource model 
 
 
 
4. Message Set 
 
This section presents a set of messages to realize the QOS extension 
  
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presented above. These messages are intended to be used in conjunction 
with the messages provided with the minimal resource model in [1]. 
 
The message set has been subdivided into three logical groups. 
However, the order in which they are supposed to be executed is not 
reflected by the order in which they are listed. The typical order of 
execution of these messages is as follows: 
 
At initialization (after adjacency, but before any connections are 
setup): 
 
   1. Get estimation policy support message 
   2. Get traffic and QOS parameter support message 
   3. Set traffic classes and QOS message 
   4. Set schedulable region estimator message 
 
After initialization: 
 
   1. Get schedulable region estimate message 
 
The message to set the schedulable region may be used at any time 
to re-initialize the schedulable region estimate.  
 
The messages that allow to set the traffic classes, the QOS parameters 
and schedulable region estimation policies on the switch must be 
issued after the adjacency protocol has been established, and before 
any connections are set up on the switch. 
 
 
4.1 Traffic classes and Quality of Service 
 
4.1.1 Get Traffic and QOS Parameter Support Message 
 
Message Format    
 
    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            | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |  SR-E |      Reserved         |    Qualitative Traffic Mask   | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |   Quantitative Traffic Mask   |          QOS Mask             | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
 
Purpose           Query the set of traffic and QOS parameter types 
                  supported by a given schedulable region estimation 
                  policy.  
 
Message Type      220 
 
  
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Request Fields    SR-E. 
 
Response Fields   Qualitative Traffic Mask, Quantitative Traffic Mask, 
                  QOS Mask. 
 
Field Descriptions  
 
     SR-E         Code for the schedulable region estimation policy. 
 
     Qualitative Traffic Mask 
 
                  Mask of supported qualitative traffic 
                  characterizations.  Definitions are given in 
                  Section 2. 
 
                  Bit 0:       Constant bit-rate (CBR) 
                  Bit 1:       Video 
                  Bit 2:       Voice 
                  Bit 3:       Audio 
                  Bit 4 - 15:  Reserved 
 
    Quantitative Traffic Mask 
 
                  Mask of supported quantitative traffic 
                  parameters. All parameters that are given 
                  abbreviations are defined in [5]. 
 
                  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. All parameters 
                  that are given abbreviations are defined in [5]. 
 
                  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 
 
 
 
4.1.2 Set Traffic Classes and QOS Message 
 
Message Format 
 
    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  
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
  
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   |    Version    | Message Type  |    Result     |     Code      | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   | Partition ID  |          Transaction Identifier               | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |                              Port                             | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |                        Port Session Number                    | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |A|                  Reserved                           |Classes| 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |                                                               |  
   ~                    Traffic Class 1 Block                      ~ 
   |                                                               |  
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |                                                               |  
   ~                    Traffic Class 2 Block                      ~ 
   |                                                               |  
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |                                                               |  
   ~                             ...                               ~ 
   |                                                               |  
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
 
 
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  
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |     Buffer ID       |Qualitat.|         Quantitative  Mask    | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |           QOS Mask            |           Reserved            | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |                       Traffic Parameter 1                     | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |                       Traffic Parameter 2                     | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   ~                              ...                              ~ 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |                         QOS Parameter 1                       | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |                         QOS Parameter 2                       | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   ~                              ...                              ~ 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
 
Purpose            Set the number of traffic classes and the traffic 
                   and quality of service parameters for each traffic 
                   class. 
 
Message Type       221 
 
Request Fields     Port, Port Session Number, classes, 
  
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                   Traffic Class Blocks. 
 
Response Fields    None 
 
Field Description 
 
    A              1 = Set all the other ports with the same set of 
                       traffic and quality of service parameters (in 
                       addition to the port given in the field Port). 
 
                   0 = Set the traffic and quality of service   
                       parameters only for the specified Port. 
 
 
    Classes        Number of traffic classes. 
 
    Buffer ID 
                   The buffer of the multiplexer to which the 
                   the traffic class is mapped. Only one traffic class 
                   may be mapped to a buffer. 
 
    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 4.1.1: 
 
                   Parameter      unit 
                   ----------------------              
                   PCR            cells/s       
                   SCR            cells/s 
                   MBS            cell 
                   CDVT           microsecond 
 
                   The peak cell rate is a mandatory 
                   quantitative parameter, i.e., bit 0 of the field 
                   'Quantitative' must always be set to 1. 
 
     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            --- 
  
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                   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. 
 
 
4.1.3 Get Traffic Classes and QOS Message 
 
Message Format     Same as in Section 4.1.3. 
 
Purpose            Get the number of traffic classes and the traffic 
                   and quality of service parameters for each traffic 
                   class. 
 
Message Type       222 
 
Request Fields     Port, Port Session Number. 
 
Response Fields    A, Classes, Traffic Class Blocks 
 
 
4.2 Schedulable Region Estimation Policies 
 
4.2.1 Get Schedulable Region Estimation Policy Support Message 
 
Message Format    
 
    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               | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |         SR Estimator Mask     | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
 
Purpose           Query schedulable region estimation support 
                  available on a port. 
 
Message Type      223 
 
Request Fields    None 
 
Response Fields   SR Estimator Mask 
 
Field Descriptions 
  
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    SR Estimator Mask 
                  Mask of supported schedulable region estimators. 
                  Bit 0:       Peak rate based estimator 
                  Bit 1 - 14:  Reserved 
                  Bit 15:      Proprietary 
 
 
4.2.2 Set Schedulable Region Estimation Policy Message 
 
Message Format   
 
    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                              | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |                      Port Session Number                      | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |A|      Reserved       |  SR-E |  Res  |  SR Update Threshold  | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   ~                    Estimator Parameters ...                   ~ 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
 
Purpose         Select a schedulable region estimation algorithm and 
                update threshold on a specific port. 
 
Message Type    224 
 
Request Fields  A, SR-E, SR Update Threshold, Parameters. 
 
Response Fields None. 
 
   A          1 = Set all the other ports with the same schedulable 
                  region estimator code, update threshold, and 
                  parameters (in addition to the port given in 
                  the field Port). 
 
              0 = Set the parameters only for the specified Port. 
 
 
   SR Update Threshold 
              specified in units of 0.01%, resulting in a maximum 
              possible value of 20%. See Chapter 3 for definition. 
 
   SR-E 
              Code of the estimator. (See section 4.2.1.)  
 
   Estimator Parameters 
  
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              specific to each estimator. The proprietary estimation 
              policy and the peak rate based estimation policy do not 
              take any parameters. 
 
Notes: This message is 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. 
 
 
4.2.3 Get Schedulable Region Estimation Policy Message 
 
Message Format  Same as in Section 4.2.2. 
 
Purpose         Retrieve the schedulable region estimator code,  
                parameters, and update threshold on a specific port. 
 
Message Type    225 
 
Request Fields  None. 
 
Response Fields A, SR-E, SR Update Threshold, Estimator Parameters. 
 
 
4.3 Schedulable Region Estimates 
 
4.3.1 Set Schedulable Region Message 
 
Message Format    
 
    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                             | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |                      Port Session Number                      | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |       Reserved        | Dimen |   Planes-A    |   Planes-B    | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   ~                          Coefficients a_ij                    ~ 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   ~                          Coefficients b_ij                    ~ 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
 
Purpose         Set the schedulable region on a specific port. This 
                message can be used to give the schedulable region 
                estimator an initial estimate. The estimator is not 
                required to use this initial estimate. 
 
Message Type    226 
  
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Request Fields  Dimen, Planes-A, Planes-B, Coefficients a_ij, 
                Coefficients b_ij. 
 
Response Fields None. 
 
   Dimen 
                The dimension of the Schedulable Region (the number of 
                columns of the matrix A - see Appendix A). 
 
   Planes-A 
                The number of rows of the matrix A (See Appendix A). 
 
   Planes-B 
                The number of rows of the matrix B (See Appendix A). 
 
   Coefficients a_ij 
                The elements of the matrix A = (a_ij), listed row by 
                row and represented using four bytes per element. 
                (see Appendix A). 
 
   Coefficients b_ij 
                The elements of the matrix B = (b_ij), listed row by 
                row and represented using four bytes per element. 
                (see Appendix A). 
 
 
4.3.2 Get Schedulable Region Message 
 
Message Format  Same as the Set Schedulable Region Message. 
 
Purpose         Query the present schedulable region estimate on a 
                specific port. 
 
Message Type    227 
 
Request Fields  None. 
 
Response Fields Dimen, Planes-A, Planes-B, Coefficients a_ij, 
                Coefficients b_ij. 
 
 
Appendices 
 
A. Schedulable Region Representation 
 
A n-dimensional schedulable region is represented using two matrices  
A = (a_ij) and B = (b_ij), each with n columns and an arbitrary number 
of rows. The entries of A and B are non-negative. Denote the number of 
columns of A and B by k and m, respectively. Each row of A represents 
a region 
 
       H_i = { x in N^n| x_1/a_i1 + x_2/a_i2 + ... + x_n/a_in <= 1}, 
  
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where N is the set of non-negative integers. In other words, H_i is 
the region bound by the coordinate axes (in the n-dimensional space 
N^n), and the hyper-plane whose intercepts are a_i1, a_i2, ..., a_in. 
 
Similarly, each row of the matrix B defines a region G_i in the 
n-dimensional space N^n. 
 
The schedulable region represented by the pair of matrices A, B is 
then given by 
 
     S = S1 union S2, 
 
where 
 
     S1 = union of H_1, H_2,..., H_k,

     S2 = intersection of G_1, G_2,..., G_m. 
 
 
B. Measure of Change of a Schedulable Region 
 
Suppose that the schedulable region of a multiplexer changes from S to 
S' (but both have the same dimension n).  Let t_i be the largest 
number of calls of traffic class i that schedulable region S can 
accommodate if there are no calls of any other traffic class. 
Similarly, let t'_i be the largest number of calls of traffic class i 
that schedulable region S' can accommodate if there are no calls of 
any other traffic class. Then, the percentage change from S to S' is 
defined as 
 
          max { |t_1 - t'_1|/t_1, ..., |t_n - t'_n|/t_n }. 
 
 
References 
 
[1]  GSMP Working Group, T. Worster Editor, "General Switch 
     Management Protocol V3", draft-ietf-gsmp-00.txt, June, 1999 
 
[2]  GSMP Working Group, A. Doria, F. Hellstrand, C. Adam, "Support 
     Structure for Optional Abstract or Resource Models", 
     draft-doria-gsmp-option-arm-00.txt, Feb 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. 
 
  
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[5]  ATM Forum, "Traffic Management Specification, Version 4.0", 
     April 1996. 
 
 
Authors' Address 
 
Constantin M. Adam 
Xbind, Inc. 
55 Broad Street, 23C 
New York, NY 10004 
USA 
Telephone: 212-809-3303, ext. 102 
email: 

 
Aurel A. Lazar 
Xbind, Inc. 
55 Broad Street, 23C 
New York, NY 10004 m
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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