GSMP Working Group Constantin M. Adam Internet Draft Aurel A. Lazar Document: Mahesan Nandikesan Xbind, Inc. October 21, 1999 An ATM Switch Service Model for GSMP 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