International Technical Support Organization

Transcription

1 International Technical Support Organization GG IBM Frame Relay Guide February 1995

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3 IBML International Technical Support Organization IBM Frame Relay Guide February 1995 GG

4 Take Note! Before using this information and the product it supports, be sure to read the general information under Special Notices on page xvii. First Edition (February 1995) Order publications through your IBM representative or the IBM branch office serving your locality. are not stocked at the address given below. Publications An ITSO Technical Bulletin Evaluation Form for reader s feedback appears facing Chapter 1. removed, comments may be addressed to: If the form has been IBM Corporation, International Technical Support Organization Dept. 545 Building 657 P.O. Box Research Triangle Park, NC When you send information to IBM, you grant IBM a non-exclusive right to use or distribute the information in any way it believes appropriate without incurring any obligation to you. Copyright International Business Machines Corporation All rights reserved. Note to U.S. Government Users Documentation related to restricted rights Use, duplication or disclosure is subject to restrictions set forth in GSA ADP Schedule Contract with IBM Corp.

5 Abstract This document is unique in its detailed coverage of frame relay. It provides extensive information about frame relay standards and the functions implemented by IBM products. Focus is on the frame relay implementation of the relevant products. Basic knowledge of the products discussed is assumed. This document was written for network personnel who either support, implement, and design frame relay networks, or are responsible for installing and maintaining equipment using frame relay networking facilities. (311 pages) Copyright IBM Corp iii

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7 Contents Abstract iii Special Notices xvii Preface xix How This Document is Organized xix Related Publications xx IBM RouteXpander/ xx IBM 3172 Interconnect Controller xx IBM 3174 Establishment Controller xx IBM 2220 Nways BroadBand Switch xx IBM 6611 Network Processor xx Frame Relay Token-Ring Bridge Program/DOS xxi NCP, SSP, EP Publications xxi VTAM Publications xxi IBM AS/ xxi NPM Publications xxi NTune Publications xxii TCP/IP for MVS/VM xxii International Technical Support Organization Publications xxii Non-IBM Publications xxiii Acknowledgments xxiii Chapter 1. Introduction to Frame Relay Fast Packet Switching Frame Relay, an International Standard The Physical Layer The Data Link Control Layer Congestion Control Local Management Interface (LMI) LMI and the Group of Four Network to Network Interface (NNI) Multiprotocol Interconnect over Frame Relay IBM Frame Relay Extension Bridged and Routed Protocol Data Units IEEE Logical Link Control Dynamic Window Algorithm Frame Relay Access Device (FRAD) Frame Relay Access Devices and SNA Private versus Public Frame Relay Network Service IBM Product Support Chapter 2. IBM RouteXpander/ Functional Overview Standards and Protocols Local Management Interface (LMI) Congestion Management Attachment Details Installation Details Frame Relay Device Driver DLCIs and MAC Address Copyright IBM Corp v

8 2.4 Routing and Bridging SNA over Frame Relay TCP/IP Routing IPX Routing Source Route Bridging Transparent Bridging System Management Local System Management SNMP Management NetView for MVS Problem Determination RXR/2 Test Configuration LAPS Configuration for the RXR/ SNA Routing Observations NCP V Chapter 3. IBM 3174 Establishment Controller Functional Overview Standards and Protocols Local Management Interface (LMI) LMI Timers and Counters Congestion Management Installation Details Routing and Bridging SNA over Frame Relay TCP/IP over Frame Relay Configuration Customization Panel Flow Configure Frame Relay for SNA Multi-Host, APPN and Gateway Getting Started Model / Attach Gateway Definitions for Host-1B System Management Local Management NetView Management SNMP Management Problem Determination New Error Logs for the Frame Relay Feature Chapter 4. IBM 3172 Interconnect Controller Functional Overview SNA Communications Program (SNA\Comm) MultiProtocol Extensions (MPE) Standards and Protocols SNA\Comm Frame Relay Attachment Details MPE Frame Relay Attachment Details Local Management Interface (LMI) Congestion Management MultiProtocol Extension Routing and Bridging MPE IP Routing MPE Bridging SNA Communications Routing and Bridging SNA\Comm SNA Connectivity SNA\Comm IP Routing vi IBM Frame Relay Guide

9 SNA\Comm Bridging MPE System Management MPE Problem Determination SNA\Comm System Management Local Management NetView SNMP Problem Determination Configuration Example LAPS Configuration LAPS Configuration Details TCP/IP SNA Communications Program Fragmentation Issues Chapter 5. IBM 2220 Nways BroadBand Switch Introduction IBM s Network BroadBand Services Frame Relay Standard Mode Frame Relay IBM Value Add Mode Transfer Modes Quality of Service Bandwidth Adaptation Frame Relay Standards and Protocols Local Management Interface Attachment Details Implementation Details Frame Relay Access Agent Congestion Management: Overview Congestion Management: Details Adapter Congestion Port Level Congestion Installation Details Existing Parallel SNA and Multiprotocol Environments Frame Relay Connections Standard Mode Parameters Frame Relay Virtual Connection (VCO) Configuration IBM Nways Broadband Switch Manager For AIX Nways Configuration Tool (NCT) Management Management Categories Management Objects Chapter 6. IBM 6611 Network Processor Functional Overview Standards and Protocols Frame Relay Attachment Details Local Management Interface (LMI) LMI Timers and Counters Congestion Management Installation Details Configuration Details Configuring Serial Ports for Frame Relay Serial Ports Frame Relay Configuration Contents vii

10 6.3.3 Source Route Bridging Transparent Bridging Translational Bridging IP over Frame Relay Banyan Vines over Frame Relay Xerox Network Systems (XNS) over Frame Relay AppleTalk over Frame Relay DECNET over Frame Relay IPX over Frame Relay System Management Problem Determination Chapter 7. Frame Relay Token-Ring Bridge Program/DOS Functional Overview Standards Attachment Details Local Management Interface Congestion Management Installation Details Implementation Details Management Problem Determination Chapter 8. ACF/NCP and IBM 3746 Model 900 Frame Relay Support Introduction NCP Releases and Frame Relay Standards and Protocols NCP LMI Implementation Supported LMI Procedure NCP Echo Detection LMI Timers and Counters IBM 3745/NCP Frame Relay Description NCP FRFH Support NCP FRTE Support FRTE Subarea Connections FRTE Peripheral Node Support NCP Frame Relay Support for the IBM 3746 Model ACF/NCP and IBM 3746 Model 900 Implementation Details Frame Relay Definition Structure Frame Handler Substitute Subports Timers and Counters Configuration Recommendations Line Quality FRFH Performance when Using IBM 3746 Model Maximum Frame Size Maximum Number of DLCIs LMI T391 and T392 Timers IEEE Timers LMI Timers and Counters: Example NCP Congestion Control FRTE Frames and Discard Eligible (DE) NCP Dynamic Window Algorithm NCP Communications Rate Relative PVC Priority Example Communications Rate and Congestion viii IBM Frame Relay Guide

11 8.12 Management Support NCP Dynamic Reconfiguration NTune Use for Frame Relay Resources NetView Performance Monitor Frame Relay Problem Determination Chapter 9. IBM AS/ Functional Overview Standards and Protocols AS/400 Frame Relay Attachment Details Local Management Interface (LMI) Congestion Management System Management Problem Determination Installation Details Configuration Details Network Interface Description Point-to-Point Frame Relay Line Description LAN Frame Relay Line Description SNA TCP/IP Appendix A. RFC Information and Frame Format A.1 RFC 1293 Inverse Address Resolution Protocol A.2 RFC Multiprotocol Interconnect over Frame Relay A.3 RFC 1315 Management Information Base for Frame Relay DTEs List of Abbreviations Index Contents ix

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13 Figures 1. Packet Switching Circuit Switching Fast Packet Switching Using Frame Relay Frame Relay Reference Model Frame Format In-Band Congestion Signaling Link Integrity Verification Procedure ANSI and ITU-T LMI Message Format ITU-T Information Element Format Status Enquiry Message Format Status Message Format User and Network to Network Interface RFC 1490 Encapsulation Subnetwork Access Protocol (SNAP) IBM Frame Relay Extensions Bridged Frames Using a Virtual LAN IEEE LLC Protocol Data Unit Encapsulation Frame Relay Access Devices SDLC Frame Relay Access Device IBM Frame Relay Access Devices LMI Parameters Set in the RXR/2 WAN Access Protocol in LAPS RXR/2 Bridging or Routing over Frame Relay RXR/2 Frame Relay Device Driver Configuration for Bridging SNA Packets Configuration for Bridging IP Packets RXR/2 Source Route Bridging RXR/2 Transparent Bridging RXR/2 Message Log RXR/2 FRNOTEBK Output RXR/2 Output from WACSTAT -A Command RXR/2 Scenario 1 Physical Configuration RXR/2 Scenario 1 Logical Configuration RXR/2 Token-Ring Adapter Configuration RXR/2 WAC Adapter and Selected Protocols RXR/2 WAC Adapter Parameter Details RXR/2 WAN Access for the Network Adapter Protocol RXR/2 WAN Access for the Network Adapter Details of the RXR/2 WAN Access for the Network Adapter CM/2 HOST001 Link Details CM/2 LINK001 Link Details for APPN Connection Using 3174 in Frame Relay Networks SNA over Frame Relay Configurations TCP/IP Connectivity Using 3174 for SRB over Frame Relay Connections Example Scenario Customization Panel Flow Model and Attachment Selection Panel Multi-Host Definition Panel for Primary Host-1A Frame Relay Host-1A Panel Common SNA Panel LAN Description Panel Copyright IBM Corp xi

14 52. Frame Relay Index Assignment Panel LAN Address Assignment Panel Frame Relay Definition Panel Definition Panel for 2nd Host-1B Frame Relay Panel for Host-1B Common Network Panel for Host-1B Frame Relay Index Assignment for Host-1B APPN Node Definition Panel Network Resources Panel Frame Relay Optional DLCI Specification Panel Test Menu 2nd Page Frame Relay Test Menu Panel Display Frame Relay Port Summary Information Panel Update Frame Relay Parameters List all DLCI Status and Data Types Panel List Specific DLCI Status Summary Panel Link Status Summary Panel SSC Sequence in the Log when the 3174 Comes Up LMI Parameters Set in the 3172 WAN Access Protocol in LAPS MPE IP Support TCP/IP Statements in TCPIP.Profile Data Set as a Bridge SNA\Comm and TCP/IP Offload Connectivity in the SNA Monitor Display SNA Monitor LAN Adapter 0 Display Link Station Detail Display Adapters Required for Each Frame Relay Port RXR/2 WAN Access for Network Adapter and Protocols TCPIPCFG Setup for Frame Relay Ports Frame Relay Service: LMI Interfaces Frame Relay Network Using the Nways Switch Frame Relay Connection Nways Switch Network Management - Overview Fully and Partially Meshed Topologies Serial Port Configuration Selection Serial Port Physical Configuration Serial Port Physical Configuration IP Port Configuration Panel IP Destinations per DLCI Window IP Point-to-Point Addresses per DLCI Window Vines Destinations per DLCI Window XNS Destinations per DLCI Window List DLCIs to Be Used by AppleTalk DECnet Destinations per DLCI Panel IPX Destination Address to DLCI Mapping Frame Relay Token-Ring Bridge Program/DOS in a Bridged Network Frame Relay Token-Ring Bridge Program/DOS Installation Options Frame Relay Token-Ring Bridge Program/DOS WAC Device Driver Configuration Device Driver Parameters for Frame Relay Device Driver Parameters for Frame Relay Basic NCP Frame Relay Terminology Frame Relay NCP Frame Relay Frame Switching NCP FRFH Support xii IBM Frame Relay Guide

15 106. Connecting NCPs with Frame Relay Hybrid Frame Relay Network Options for Interconnecting NCPs Fast Frame Relay Subarea Paths Fast Subarea Routing with NCP Frame Relay Support Frame Relay Boundary Node Support Frame Relay Peripheral Node Support IBM 3746 Model 900 CLP Throughput Dynamically Defined PU and LUs NTune Peripheral FRTE Substitute Subports Substitute Subports Substitute Subport Substitute Subport Substitute Subport PVC Using Primary Path PVC Using Backup Path IBM 3746 Model 900 CLP Throughput Timers and Counters Test Configuration NTune - Comrate and Buffers NTune - Terminating Equipment Details NTune - Terminating Equipment Details (ODLC) Changing MLTGPRI with NTune NTune - Physical Line Details Display NTune - Physical Line Details Display NTune - Physical Line Details Display NTune - Physical Line Details Display NPM Display Using NPM Desk/ The AS/400 in a Frame Relay Network The AS/400 Network Interface Description The AS/400 Line Description for Frame Relay The Frame Relay Token-Ring Line Description The Frame Relay Ethernet Line Description The Frame Relay Host Controller Description Figures xiii

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17 Tables 1. Frame Relay Standards Length of Data Link Connection Identifier (DLCI) DLCI Values Measurement Interval Calculation LMI System Parameter - Timers LMI System Parameter - Counters IE Value Differences Network Level Protocol ID (NLPID) IEEE Protocol Identifiers (PID) IEEE LLC PDUs and Control Field(s) Encoding IEEE LLC Timers IEEE LLC Counters Device Frame Relay Function Cross-Reference Frame Relay Terminating Equipment (FRTE) Functions Frame Relay Frame Handler (FRFH) Functions IBM RouteXpander/2 Frame Relay Inter-Operability Matrix IBM 3174 Establishment Controller Frame Relay Interoperability Matrix LMI Counters (Hard Coded) LMI Timers Models and Protocols Supported New Error Logs IBM 3172 Interconnect Controller SNA\Comm Frame Relay Interoperability Matrix IBM 3172 Interconnect Controller MPE Frame Relay Interoperability Matrix Some Connection Quality-of-Service Parameters Frame Relay Physical Interfaces Connection Parameters for Frame Relay Standard Mode (PCO) Connection Parameters for Frame Relay Network BroadBand Services Mode (PCO) Connection Parameters for Frame Relay Network BroadBand Services Mode and Limits (PCO) Connection Parameters in the Target Node (VCO) IBM 6611 Network Processor Frame Relay Interoperability Matrix NCP LMI Definitions - Timers NCP LMI Definitions - Counters NCP IEEE LLC Definitions, Timers NCP IEEE LLC Definitions, Counters Setting of Congestion Indicators Communications Rates on a 9600 bps Line Fields which Can Be Modified Using NTune AS/400 Frame Relay Interoperability Matrix Copyright IBM Corp xv

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19 Special Notices This publication is intended to help networking personnel to support, design and implement frame relay networks. The information in this publication is not intended as the specification of any programming interfaces that are provided by the products covered in this publication. See the PUBLICATIONS section of the IBM Programming Announcement for: IBM RouteXpander/2 IBM 3174 Establishment Controller IBM 3172 Interconnect Controller IBM 2220 Nways BroadBand Switch IBM 6611 Network Processor Frame Relay Token-Ring Bridge Program/DOS ACF/NCP and 3746 Model 900 IBM AS/400 for more information about what publications are considered to be product documentation. References in this publication to IBM products, programs or services do not imply that IBM intends to make these available in all countries in which IBM operates. Any reference to an IBM product, program, or service is not intended to state or imply that only IBM s product, program, or service may be used. Any functionally equivalent program that does not infringe any of IBM s intellectual property rights may be used instead of the IBM product, program or service. Information in this book was developed in conjunction with use of the equipment specified, and is limited in application to those specific hardware and software products and levels. IBM may have patents or pending patent applications covering subject matter in this document. The furnishing of this document does not give you any license to these patents. You can send license inquiries, in writing, to the IBM Director of Licensing, IBM Corporation, 500 Columbus Avenue, Thornwood, NY USA. The information contained in this document has not been submitted to any formal IBM test and is distributed AS IS. The information about non-ibm (VENDOR) products in this manual has been supplied by the vendor and IBM assumes no responsibility for its accuracy or completeness. The use of this information or the implementation of any of these techniques is a customer responsibility and depends on the customer s ability to evaluate and integrate them into the customer s operational environment. While each item may have been reviewed by IBM for accuracy in a specific situation, there is no guarantee that the same or similar results will be obtained elsewhere. Customers attempting to adapt these techniques to their own environments do so at their own risk. Any performance data contained in this document was determined in a controlled environment, and therefore, the results that may be obtained in other operating environments may vary significantly. Users of this document should verify the applicable data for their specific environment. Copyright IBM Corp xvii

20 Reference to PTF numbers that have not been released through the normal distribution process does not imply general availability. The purpose of including these reference numbers is to alert IBM customers to specific information relative to the implementation of the PTF when it becomes available to each customer according to the normal IBM PTF distribution process. The following terms are trademarks of the International Business Machines Corporation in the United States and/or other countries: ACF/VTAM Advanced Peer-to-Peer Networking AIX APPN AS/400 BBNS ESCON IBM NetView NTune NTuneMON NTuneNCP Nways OS/2 OS/400 PerfDesk Personal System/2 Presentation Manager PS/2 RS/6000 S/370 S/390 SystemView VTAM The following terms are trademarks of other companies: Windows is a trademark of Microsoft Corporation. PC Direct is a trademark of Ziff Communications Company and is used by IBM Corporation under license. UNIX is a registered trademark in the United States and other countries licensed exclusively through X/Open Company Limited. DEC, DECnet IPX IDNX AppleTalk NDIS DCE Banyan, VINES Xerox VT100 AT&T Digital Equipment Corporation Novell, Incorporated Network Equipment Technologies, Incorporated Apple Computer, Incorporated 3Com Corporation and Microsoft Corporation The Open Software Foundation Banyan Systems, Incorporated Xerox Corporation Digital Equipment Corporation American Telephone and Telegraph Company Other trademarks are trademarks of their respective companies. xviii IBM Frame Relay Guide

21 Preface This document gives a detailed introduction to frame relay, its standards, formats and procedures, and provides an overview of the frame relay implementation within a variety of IBM networking products. This document is intended for system engineers, network administrators and network planners responsible for planning, building and maintaining networks using frame relay facilities. A basic knowledge of networking concepts and terminology is assumed. How This Document is Organized The document is organized as follows: Chapter 1, Introduction to Frame Relay This chapter gives an extensive introduction to frame relay. relevant standards, messages formats and procedures. It describes the Chapter 2, IBM RouteXpander/2 This chapter gives an overview of the frame relay support within IBM RouteXpander/2. Implementations details and configuration examples are given. Note: Reading this chapter may be useful to ease the understanding of the chapters on the IBM 3174 Establishment Controller, IBM 3172 Interconnect Controller, IBM AS/400 and Frame Relay Token-Ring Bridge Program/DOS. Chapter 3, IBM 3174 Establishment Controller This chapter gives an overview of the frame relay support within the IBM 3174 Establishment Controller. Implementation details and configuration examples are given. Chapter 4, IBM 3172 Interconnect Controller This chapter gives an overview of the frame relay support within the IBM 3172 Interconnect Controller. Implementation details and configuration examples are given. Chapter 5, IBM 2220 Nways BroadBand Switch This chapter gives an extensive overview of the frame relay support within the IBM 2220 Nways BroadBand Switch. Implementation details are given. Chapter 6, IBM 6611 Network Processor This chapter gives an overview of the frame relay support within the IBM 6611 Network Processor. Implementation details and configuration examples are given. Chapter 7, Frame Relay Token-Ring Bridge Program/DOS This chapter gives an extensive overview of the frame relay support within the Frame Relay Token-Ring Bridge Program/DOS. Implementation details and configuration examples are given. Chapter 8, ACF/NCP and IBM 3746 Model 900 Frame Relay Support Copyright IBM Corp xix

22 This chapter gives an extensive overview of the frame relay support available with ACF/NCP. In addition the frame relay support on the IBM 3746 Model 900 is detailed. Implementation details and configuration examples are given. Chapter 9, IBM AS/400 This chapter gives an overview of the frame relay support within the IBM AS/400. Implementation details and configuration examples are given. Related Publications IBM RouteXpander/2 IBM 3172 Interconnect Controller The publications listed in this section are considered particularly suitable for a more detailed discussion of the topics covered in this document. IBM RouteXpander/2 User s Guide and Reference (Version 2), SC IBM 3172 Systems Network Architecture (SNA) Communications Program and TCP/IP Offload Feature User s Guide, GC IBM 3172 Interconnect Controller Model 3 Hardware Planning Guide, GA IBM 3172 Interconnect Controller Status Codes, GA IBM 3174 Establishment Controller IBM 2220 Nways BroadBand Switch IBM 6611 Network Processor 3174 Establishment Controller Utilities Guide, GA Establishment Controller Planning Guide for Configuration Support-C Release 5, GA Central Site Customizing User s Guide, GA Models 81R,82R,90R,91R and 92R User s Guide, GA Models 51R,52R,53R,61R,62R,63R and 64R User s Guide, GA Models 1L, 1R,2R,3R,11L,11R,12L,12R,13R and 14R User s Guide, GA At a Glance, an Overview,GA IBM Multiprotocol Network Program Configuration Guide, SC IBM Multiprotocol Network Program Operations and Problem Management, SC IBM 6611 Network Processor Network Management Reference, GC xx IBM Frame Relay Guide

23 Frame Relay Token-Ring Bridge Program/DOS NCP, SSP, EP Publications VTAM Publications Frame Relay Token-Ring Bridge/DOS User s Guide NCP V7R2 Library Directory, SC NCP V7R2 Migration Guide, SC NCP V7R2 Resource Definition Guide, SC NCP V7R2 Resource Definition Reference, SC NCP V7R2 Generation and Loading Guide, SC NCP V7R2 Customization Guide, LY (available to IBM-licensed customers only) NCP V7R2 Customization Reference, LY (available to IBM-licensed customers only) NCP V7R2 Messages and Codes, SC NCP V7R2 Trace Analysis, LY (available to IBM-licensed customers only) NCP V7R2 Diagnosis Guide, LY (available to IBM-licensed customers only) NCP V7R2 Reference, LY (available to IBM-licensed customers only) NCP V7R2 Reference Summary and Data Areas, LY (available to IBM-licensed customers only) VTAM V4R2 Resource Definition Reference, SC VTAM V4R2 Customization, LY (available to IBM-licensed customers only) VTAM V4R2 Operation, SC VTAM V4R2 Messages and Codes, SC VTAM V4R2 Programming, SC IBM AS/400 Local Area Network Support, SC Communication Management, SC Network and Systems Management, SC TCP/IP Configuration and Reference, SC NPM Publications NetView Performance Monitor User s Guide, SH NetView Performance Monitor Desk/2 User s Guide, SH Preface xxi

24 NTune Publications NTune User s Guide, SC NTuneNCP Reference, LY (available to IBM-licensed customers only) TCP/IP for MVS/VM IBM TCP/IP Version 2 Release 2.1 for MVS: Offload of TCP/IP Processing, SC IBM TCP/IP Version 2 Release 2.1 for MVS: Planning and Customization, SC IBM TCP/IP Version 2 Release 2 for VM: Offload of TCP/IP Processing, SC International Technical Support Organization Publications High-Speed Networking Technology: An Introductory Survey, GG Multiprotocol Networking with the 3172 Model 3, GG RouteXpander/2 Introduction and Configuration Examples, GG in Higher Speed WAN and Multiprotocol Networks, GG (available 2nd quarter 95) IBM and NCP Version 7 Release 2, GG (available 2nd quarter 95) A complete list of International Technical Support Organization publications, with a brief description of each, may be found in: Bibliography of International Technical Support Organization Technical Bulletins, GG To get a catalog of ITSO technical publications (known as redbooks ), VNET users may type: TOOLS SENDTO WTSCPOK TOOLS REDBOOKS GET REDBOOKS CATALOG How to Order ITSO Technical Publications IBM employees in the USA may order ITSO books and CD-ROMs using PUBORDER. Customers in the USA may order by calling or by faxing Visa and Master Cards are accepted. Outside the USA, customers should contact their local IBM office. Customers may order hardcopy ITSO books individually or in customized sets, called GBOFs, which relate to specific functions of interest. IBM employees and customers may also order ITSO books in online format on CD-ROM collections, which contain books on a variety of products. xxii IBM Frame Relay Guide

25 Non-IBM Publications ITU-T Recommendation I Framework for Frame Mode Bearer Services ITU-T Recommendation I ISDN General Structure and Service Capabilities: Frame Mode Bearer Service ITU-T Recommendation Q Digital Subscriber Signaling System No. 1: Data Link Layer ITU-T Recommendation Q Digital Subscriber Signaling System No. 1: Network Layer ITU-T Recommendation I ISDN Overall Network Aspects and Functions: Congestion Management for the ISDN Frame relaying Bearer Service Frame Relay Principles and Applications by Philip Smith, Addison-Wesley, ISBN Acknowledgments This project was designed and managed by: Volkert Kreuk International Technical Support Organization, Raleigh Center The author of this document is: Ben Naude IBM South-Africa This publication is the result of a residency conducted at the International Technical Support Organization, Raleigh Center. Thanks to the following people for the invaluable advice and guidance provided in the production of this document: Jim Ashton IBM Research Triangle Park Pepe Boo International Technical Support Organization, Raleigh Center Mark DeCain International Technical Support Organization, Raleigh Center Mick Lugton International Technical Support Organization, Raleigh Center Jean-Pierre Marce IBM France Larry Rosenfeld IBM Research Triangle Park Mohammad Shabani International Technical Support Organization, Raleigh Center Preface xxiii

26 Shawn Walsh International Technical Support Organization, Raleigh Center xxiv IBM Frame Relay Guide

27 Chapter 1. Introduction to Frame Relay At the end of the eighties and beginning in the nineties important technological changes were taking place which played a major role in the development of frame relay. The introduction of, usually LAN attached, intelligent workstations changed the data processing paradigm from centralized host computing to distributed processing. The growth of distributed processing, the need for LAN interconnection, and the growing use of graphics and images has lead to exponentially increasing network traffic. In addition to the larger data volumes, traffic patterns are also changing. Traditional networking coped with certain amounts of host interactive traffic that was relatively constant during business hours and used bandwidth offshift for batch file transfer. Due to distributed processing and LAN interconnection today s networks are confronted with traffic patterns which are more unpredictable. Not only the demand for connectivity has changed, but also the technology to provide networking facilities has been subject to important changes. The introduction of digital and fiber technologies provides faster and more reliable communication but requires networking techniques which are able to efficiently operate at higher speeds. In order to meet this requirement the concept of fast packet switching has been developed. 1.1 Fast Packet Switching Before discussing what fast packet switching is we will first elaborate on the differences between packet switching with circuit switching and/or traditional time division multiplexing. Figure 1. Packet Switching Copyright IBM Corp

28 Packet Switching networks allocates capacity only when stations have packets to send, rather than dedicating a portion of their capacity to each active station on the network. Examples of packet switching architectures are X.25, SNA and IP. X.25 and SNA use connection oriented network protocols meaning that data transfer between end stations requires an end-to-end relationship to be established first. IP uses a connectionless network protocol, and end stations may send data without a prior connection establishment. Packet switching architectures make packet forwarding decisions based on (network layer) addresses imbedded in the data. The packet switch, therefore, has to understand the addressing structure and routing information contained within the data it is forwarding. Because the packet switch understands the addressing, it can accept data over a single link and forward it to multiple destinations. Figure 1 on page 1 depicts how the concept of packet switching allows an end station to multiplex data destined for multiple destinations on a single network attachment. Station X is exchanging data with both Y and Z simultaneously. To allow the network switches S to route traffic to the appropriate destination routing identifiers, shown as 1 and a for data transport between X and Y and 2 and b for traffic between X and Z, is appended to the data. These routing identifiers either have global significance, meaning the same routing identifier (a=1 and b=2 in above example) is used on either end of the network or have local significance, meaning that values are assigned independently on either end. If the routing identifiers are not the same then the network packet switches are responsible for changing these identifiers when data packets progress through the network. As mentioned, X.25 requires a connection, called virtual circuit (VC), to be established before end stations can communicate. The connections are dynamically established for switched virtual circuits (SVCs) or defined at subscription time for permanent virtual circuits (PVCs). The routing identifiers, or logical channel numbers (LCNs), are assigned during connection establishment. The LCNs for a PVC are fixed numbers. The LCNs for a SVC are dynamically allocated. Traditional packet switches do error checking, acknowledgement and possible retransmission on a hop by hop basis rather than end-to-end. These architectures therefore, not only provide efficient utilization of bandwidth, but also provide relatively error free transmission of data. Circuit Switching, unlike packet switching, dedicates a fixed amount of bandwidth to each attached (active) station, regardless of the actual traffic from that station. The circuit switches (for example time division multiplexors) are entirely protocol independent and do not know or care what the bits they are forwarding represent. Figure 2 on page 3 depicts the concept of circuit switching. Station X is able to transfer data to Y and Z at the same time. When multiplexing techniques are employed X requires only a single physical network attachment which appears as two distinct connections. Circuit switching does not acknowledge packets and provides no error checking and correcting. These functions are supposed to be handled by the end stations. Due to the limited processing high throughput rates can be achieved and circuit switching provides the best choice when traffic is steady and predictable. 2 IBM Frame Relay Guide

29 The primary weakness of circuit switching is that fixed blocks of bandwidth are reserved for the duration of a connection. Since data connections, like voice connections, do not come and go and the bandwidth required for a data connection can vary significantly over time. This can be very inefficient. In addition, to provide connections to multiple destinations at the same time requires multiple network attachments which can be expensive. Figure 2. Circuit Switching Fast Packet Switching is a generic term that refers to packet switching technologies that omit most of OSI model 1 layer two processing and all of layer 3-7 processing to achieve higher data throughput. The error correction and acknowledgment is performed by the end points. Fast packet switching provides the best of both worlds. It uses packet transfer mode to more efficiently allocate bandwidth to bursty traffic, but it does less per packet processing, which translates into improved throughput. Because it operates below layer 3 of the OSI model it is easy to run multiple protocols over it. Figure 3 on page 4 depicts the concept of fast packet switching using frame relay. Fast packet switching is usually used to refer to both frame relay and cell relay. Cell relay allows the transport of data, voice and images, and although people experiment with voice transport, frame relay is considered to be restricted to data transport. Examples of cell based transfer mechanisms are Asynchronous Transfer Mode (ATM), broadband ISDN and the IEEE standard for Metropolitan Area Subnetwork. For an excellent overview of these, and high-speed networking in general, see High Speed Networking Technology: An Introductory Survey. The technique of frame relay will be explained in more detail in the following sections. 1 The OSI reference model for networking (or simply OSI model) has been created by the International Standards Organization (ISO). It is assumed that the readers are familiar with the OSI model, if not, readers are referred to one of the many publications on this subject. Chapter 1. Introduction to Frame Relay 3

30 Figure 3. Fast Packet Switching Using Frame Relay 1.2 Frame Relay, an International Standard The two organizations which have been the main driving forcing in defining frame relay as an international standard are ITU-T and ANSI. ITU-T is one of the organizations of the International Telecommunication Union (ITU), a United Nations organization for maintaining and extending international cooperation for the improvement and use of telecommunications. The ITU-T has replaced the former CCITT. ANSI, American National Standards Institute, is a non-governmental organization coordinating standards developing activities and representing the USA in international standards bodies. Note: Several manufacturers of communications equipment started developing their first frame relay implementations before the standards committees had finalized the frame relay standards. At the end of the eighties a number of vendors joined in the Group of Four, which later became the Frame Relay Forum. In 1990 the Group of Four examined the proposed ANSI and the existing ITU-T standard from 1988 (I.122), extended them to suit the purpose of the vendors and produced a document called Frame Relay Specifications with Extensions - Based on Proposed T1S1 Standards. Incompatibilities (see for example 1.2.5, LMI and the Group of Four on page 21) exist between the early implementations based on this document and more recent implementations based on the ANSI and ITU-T standards. Table 1 (Page 1 of 2). Frame Relay Standards Description ITU-T ANSI Standard Status Standard Status Architectural Framework I.233 Approved T1.606 Approved Data Link Layer Signaling Q.922 Approved T1.602 Approved Network Layer Signaling Q.933 Approved T1.617 Approved Congestion Management I.370 Approved T1.606 Addendum Approved 4 IBM Frame Relay Guide

31 Table 1 (Page 2 of 2). Frame Relay Standards Description ITU-T ANSI Standard Status Standard Status Network to Network Interface I.372 Approved T1.617 Approved Note: 1. The first version (Blue Books, Melbourne 88) of the frame relay standard was documented in ITU-T I.122. I.122 still exist (and is often referred to) but merely points to the newer standards. Table 1 on page 4 gives an overview of the ITU-T and ANSI publications relevant to frame relay. The remainder of this section will focus on the ITU-T standards although it is important to remember that ITU-T and ANSI frame relay standards have been developed in parallel and are closely aligned. The ITU-T frame relay standards originated within the framework of ISDN. However, there is nothing in the standard that precludes it from being implemented in a non-isdn environment. Actually, few if any frame relay implementations are based on ISDN physical level interfaces. The architectural framework defined in ITU-T I.233 makes a distinction between the frame relaying and frame switching packet mode bearer services. ITU-T I describes the frame relaying bearer services, and ITU-T I describes the frame switching bearer services. It is beyond the scope of this document to elaborate on their differences. For details, refer to the appropriate publications. The remainder of this document limits itself to the frame relaying service (the most basic of the packet mode bearer services). Figure 4. Frame Relay Reference Model The ITU-T frame relay standard encompasses both the frame relaying service description and the user-network interface protocol architecture. To understand these concepts, the reference model shown in Figure 4 is used. Depicted are user equipment attached via a user-network interface to a network providing the frame relaying function. Chapter 1. Introduction to Frame Relay 5