rfc1695.txt

著名的RFC文档,其中有一些文档是已经翻译成中文的的.

Network Working Group                                           M. Ahmed
Request for Comments: 1695                                     K. Tesink
Category: Standards Track                                        Editors
                                            Bell Communications Research
                                                             August 1994


                     Definitions of Managed Objects
                     for ATM Management Version 8.0
                              using SMIv2

Status of this Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Table of Contents

   1. Introduction .............................................    2
   2. The SNMPv2 Network Management Framework ..................    2
   3. Object Definitions .......................................    2
   4. ATM Terminology ..........................................    3
   4.1 VCL/VPL and VCC/VPC .....................................    3
   4.2 PVC and SVC .............................................    5
   4.3 Traffic Management Parameters ...........................    5
   4.3.1 Traffic Policing and Traffic Shaping  Parameters ......    5
   4.3.2 Cell Loss Priority ....................................    6
   4.3.3 QoS Class .............................................    6
   5. Overview .................................................    7
   5.1 Background ..............................................    7
   5.2 Structure of the MIB ....................................    7
   5.3 ATM Interface Configuration Group .......................    7
   5.4 ATM Interface DS3 PLCP and TC Layer Groups ..............    8
   5.5 ATM Virtual Link and Cross-Connect Groups ...............    8
   6. Application of MIB II to ATM .............................    8
   6.1 The System Group ........................................    8
   6.2 The Interface Group .....................................    8
   6.2.1 Support of the ATM Cell Layer by ifTable ..............    9
   7. Support of the AAL3/4 Based Interfaces ...................   10
   8. Support of the AAL5 Managed Objects ......................   10
   8.1 Managing AAL5 in a Switch ...............................   11
   8.2 Managing AAL5 in a Host .................................   12
   8.3 Support of AAL5 by ifTable ..............................   13
   8.4 Support of Proprietary Virtual Interface  by  ifT-able ..   14
   8.5 AAL5 Connection Performance Statistics Group ............   15



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RFC 1695                 ATM Management Objects              August 1994


   9. ILMI MIB and the ATM Managed Objects .....................   15
   10. Definitions .............................................   18
   11. Acknowledgments .........................................   72
   12. References ..............................................   72
   13. Security Considerations .................................   73
   14. Authors' Addresses ......................................   73

1.  Introduction

   This memo defines a portion of the Management Information Base (MIB)
   for use with network management protocols in the Internet community.
   In particular, it describes objects used for managing ATM-based
   interfaces, devices, networks and services.

   This memo specifies a MIB module in a manner that is both compliant
   to the SNMPv2 SMI, and semantically identical to the peer SNMPv1
   definitions.

2.  The SNMPv2 Network Management Framework

   The SNMPv2 Network Management Framework consists of four major
   components.  They are:

      0    RFC 1442 [1] which defines the SMI, the mechanisms used
           for describing and naming objects for the purpose of
           management.

      0    STD 17, RFC 1213 [2] defines MIB-II, the core set of
           managed objects for the Internet suite of protocols.

      0    RFC 1445 [3] which defines the administrative and other
           architectural aspects of the framework.

      0    RFC 1448 [4] which defines the protocol used for network
           access to managed objects.

   The Framework permits new objects to be defined for the purpose of
   experimentation and evaluation.

3.  Object Definitions

   Managed objects are accessed via a virtual information store, termed
   the Management Information Base or MIB.  Objects in the MIB are
   defined using the subset of Abstract Syntax Notation One (ASN.1)
   defined in the SMI.  In particular, each object type is named by an
   OBJECT IDENTIFIER, an administratively assigned name.  The object
   type together with an object instance serves to uniquely identify a
   specific instantiation of the object.  For human convenience, we



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RFC 1695                 ATM Management Objects              August 1994


   often use a textual string, termed the descriptor, to also refer to
   the object type.

4.  ATM Terminology

   Some basic ATM terminologies are described in this section to
   facilitate defining the ATM managed objects.

4.1.  VCL/VPL and VCC/VPC

   There are two distinct types of ATM virtual connections: Virtual
   Channel Connections (VCCs) and Virtual Path Connection (VPCs).  As
   shown in Figures 1 and 2, ATM virtual connections consist of
   concatenated series of virtual links which forms a path between two
   end points, with each concatenation occurring at an ATM switch.
   Virtual links of VCCs are called Virtual Channel Links (VCLs).
   Virtual links of VPCs are called Virtual Path Links (VPLs). The VCI
   and VPI fields in the ATM cell header associate each cell of a VCC
   with a particular VCL over a given physical link.  The VPI field in
   the ATM cell header associates each cell of a VPC with a particular
   VPL over a given physical link.  Switches route cells between VCLs
   (or VPLs) via a cross-connect function according to the cells'
   VCI/VPI (or VPI) values.

            <-----------------------VCC-------------------------->
                      ------------             -----------
                      |ATM       |             |ATM       |
                      |X-Connect |             |X-Connect |
               VCL1   |Point     |    VCL2     |Point     |  VCL3
            O---------|----X-----|-------|-----|----X-----|-------O
                      |          |             |          |
                      ------------             ------------
                       ATM Switch               ATM Switch


            Figure 1: Virtual Channel Links and
                      Virtual Channel Connection














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RFC 1695                 ATM Management Objects              August 1994


            <-----------------------VPC-------------------------->
                      ------------             -----------
                      |ATM       |             |ATM       |
                      |X-Connect |             |X-Connect |
               VPL1   |Point     |    VPL2     |Point     |  VPL3
            O---------|----X-----|-------|-----|----X-----|-------O
                      |          |             |          |
                      ------------             ------------
                       ATM Switch               ATM Switch


            Figure 2: Virtual Path Links and
                      Virtual Path Connection

   A single ATM end-system or switch does not support the whole end-to-
   end span of a VCC (or VPC).  Rather, multiple ATM end- systems and/or
   switches each support one piece of the VCC (or VPC).   That is, each
   ATM end-system at one end of the VCC/VPC supports its end of the
   VCC/VPC  plus the VCLs or VPLs on its external interfaces, and each
   switch through which the VCC/VPC passes, supports the multiple
   VCLs/VPLs on that switch's external interfaces and the cross-
   connection of those VCLs/VPLs through that switch.  Thus, the end-
   to-end management of a VCC or VPC is achieved only by appropriate
   management of its individual pieces in combination.

   Note that for management purposes, an ATM network may be viewed as a
   large distributed switch by hiding all the network's internal
   connectivity as being internal to the distributed switch (as shown in
   Figure 2a).  This model may for example be used for Customer Network
   Management (CNM) purposes.





















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RFC 1695                 ATM Management Objects              August 1994


            <---------------------VCC--------------------------->
                    --------------------------------------
                    |                                    |
                    | ----------              ---------- |
                    | | ATM    |              | ATM    | |
               VCL1 | | Switch |              | Switch | | VCL3
            O-------|-|--------|------/-------|--------|-|------O
                    | |        |              |        | |
                    | ----------              ---------- |
                    |                                    |
                    |             ATM Network            |
                    --------------------------------------



            Figure 2a: ATM Network modeled as a large distributed
                       switch

   A VCC has a set of traffic characteristics (i.e., bandwidth
   parameters, QoS Class parameters, etc.).  VCLs inherit their traffic
   characteristics from the VCC of which they are a part.  VCCs are bi-
   directional by definition.  However, the traffic parameters in the
   two directions of a connection can be symmetric or asymmetric, i.e.,
   the two directions can have the same or different traffic flows.  A
   uni-directional traffic flow across a VCC is achieved by assigning a
   zero bandwidth in one direction.  Note that in addition to the
   bandwidth required by the user traffic flow, bandwidth is also
   required for OAM cell flows, even for the zero-bandwidth direction of
   a uni-directional connection.  These same principles apply to VPCs.

4.2.  PVC and SVC

   A Permanent Virtual Connection (PVC) is a provisioned VCC or VPC.  A
   Switched Virtual Connection (SVC) is a switched VCC or VPC that is
   set up in real-time via call set-up signaling procedures.  A PVC (or
   an SVC) can be a point-to-point, point-to-multipoint, or multipoint-
   to-multipoint VCC or VPC.

4.3.  Traffic Management Parameters

4.3.1.  Traffic Policing and Traffic Shaping Parameters

   In order to allocate resources fairly among different users, some
   networks police traffic at resource access points.  The traffic
   enforcement or policing taken at a UNI is called Usage Parameter
   Control (UPC) and is activated on an incoming VCL or VPL as shown in
   Figure 3.  The use of the traffic enforcer at the ingress of the
   connection is to make sure that the user traffic does not exceed the



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RFC 1695                 ATM Management Objects              August 1994


   negotiated traffic parameters such as the peak cell rate associated
   with a specific traffic descriptor type.


                     ----------             ----------
              UNI    |  ATM   |    NNI      |  ATM   |     UNI
               |     | switch |     |       | switch |      |
          O<---|---->X(UPC)   |<----|------>|   (UPC)X<-----|--->O
               | VCL |        |     | VCL   |        |  VCL |
                     ----------             ----------


                         Figure 3: An Example of a UPC

   In addition, traffic shaping may be performed on an outgoing VPL or
   VCL at a given ATM interface.  The function of the ATM traffic shaper
   either at the source or an egress point of the connection is to
   smooth the outgoing cell traffic inter-arrival time.  If policing or
   shaping is not performed then the policing or shaping algorithm is
   not activated.  ATM Forum has specified seven traffic descriptor
   types including one for the best effort traffic [9].

4.3.2.  Cell Loss Priority

   To prioritize traffic during resource congestion, ATM cells are
   assigned one of the two types of Cell Loss Priority (CLP), CLP=0 and