IBM BC-203 manual RFC 1490 Routed Format for LLC2 BNN, BC-226

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Overview of IBM Networking

SNA FRAS

SNA FRAS

Using Frame Relay Access Support (FRAS), the Cisco IOS software allows branch SNA devices to connect directly to a central site front-end processor over a Frame Relay network. FRAS converts LAN or Synchronous Data-Link Control (SDLC) protocols to a Frame Relay format understood by the Network Control Program (NCP) that runs in an FEP. The Cisco IOS software and the NCP support two frame formats:

•RFC 1490 routed format for LLC2, specified in the FRF.3 Agreement from the Frame Relay Forum and known in NCP literature as Frame Relay Boundary Network Node (BNN) support. Support for this feature requires NCP 7.1 or higher.

•RFC 1490 802.5 source-route bridged format, known in NCP literature as Frame Relay Boundary Access Node (BAN) support. Support for this feature requires NCP 7.3 or higher.

Management service point support in FRAS allows the SNA network management application, NetView, to manage Cisco routers over the Frame Relay network as if it were an SNA downstream PU.

FRAS provides dial backup over RSRB in case the Frame Relay network is down. While the backup Public Switched Telephone Network (PSTN) is being used, the Frame Relay connection is tried periodically. As soon as the Frame Relay network is up, it will be used.

This section contains a brief overview of SNA FRAS which is described in the following topics:

•RFC 1490 Routed Format for LLC2 (BNN), page 226

•RFC 1490 Bridged Format for LLC2 (BAN), page 227

RFC 1490 Routed Format for LLC2 (BNN)

RFC 1490 specifies a standard method of encapsulating multiprotocol traffic with data link (Level 2 of the OSI model) framing. The encapsulation for SNA data is specified in the FRF.3 Agreement.

The Frame Relay encapsulation method is based on the RFC 1490 frame format for “user-defined” protocols using Q.933 NLPID, as illustrated in Figure 98.

Figure 98 Frame Relay Encapsulation Based on RFC 1490

DLCI

Control

NLPID

L2

L3

DSAP

Control

F

S3217

Q.922

0x30

Q.933

Protocol ID

Protocol ID

SSAP

 

C

Address

 

0x08

0x4c (802.2) 0x08

 

 

 

S

 

 

 

 

 

 

 

 

 

 

Note The protocol ID for SNA subarea FID4 is 0x81. The protocol ID for SNA subarea FID2 is 0x82. The protocol ID for APPN FID2 is 0x83.

FRAS allows the router acting as a FRAD to take advantage of the SNA BNN support for Frame Relay provided by ACF/NCP 7.1 and OS/400 V2R3. Downstream PU 2.0 and PU 2.1 devices can be attached to the router through SDLC, Token Ring, or Ethernet links. The router acting as a FRAD is connected to the Network Control Program (NCP) or AS/400 through a public or private Frame Relay network, as illustrated in Figure 99.

Cisco IOS Bridging and IBM Networking Configuration Guide

BC-226

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Contents Overview of IBM Networking BC-203Rsrb BC-204Configuration Considerations BC-205DLSw+ BC-206DLSw Standard DLSw Version 2 StandardBC-207 DLSw+ Features Enhanced Peer-on-Demand Routing FeatureIP Multicast UDP UnicastLocal Acknowledgment BC-209BC-210 LLC2 Session Without Local AcknowledgmentBC-211 DLSw+ Support for Other SNA Features BC-212Stun and Bstun Stun NetworksBC-213 Stun Features BC-214BC-215 BC-216 StunBstun Features LLC2 and Sdlc ParametersBstun Networks BC-217Cisco’s Implementation of LLC2 BC-218IBM Network Media Translation Cisco’s Implementation of SdlcBC-219 Sdllc Media Translation Features Virtual Token Ring ConceptBC-220 Resolving Differences in LLC2 and Sdlc Frame Size Maintaining a Dynamic RIF CacheOther Considerations BC-221Qllc Conversion BC-222Cisco’s Implementation of Qllc Conversion BC-223Comparing Qllc Conversion to Sdllc BC-224Other Implementation Considerations BC-225RFC 1490 Routed Format for LLC2 BNN BC-226RFC 1490 Bridged Format for LLC2 BAN BC-227BC-228 NciaNcia Server Ncia Client/Server ModelBC-229 BC-230 Ncia Server Client/Server ModelAdvantages of the Client/Server Model Extended ScalabilityMigration Support BC-231BC-232 AlpsDspu and SNA Service Point BC-233BC-234 Router Acting as a Dspu ConcentratorSNA Switching Services Benefits of SNASwBC-235 Reduced Configuration Requirements Scalable Appn NetworksIP Infrastructure Support Network Design SimplicityHPR Capable SNA Routing Services Branch ExtenderBC-237 Enterprise Extender HPR/IP BC-238Usability Features Dynamic CP Name Generation SupportDynamic SNA BTU Size Dlur Connect-OutManagement Enhancements LAN and IP-Focused Connection Types Trap MIB Support for Advanced Network Management AwarenessToken Ring, Ethernet, and Fddi Virtual Token RingDLC Switching Support for Access to Sdlc and Qllc Cisco Transaction ConnectionVirtual Data-Link Control Native IP Data-Link Control HPR/IPCtrc and Cics BC-243Ctrc and DB2 BC-244Cmcc Adapter Hardware Benefits of CtrcBC-245 Channel Interface Processor Channel Port AdapterBC-246 Differences between the CIP and CPA Escon Channel Port AdapterParallel Channel Port Adapter BC-247Cmcc Adapter Features for TCP/IP Environments Common Link Access to WorkstationSupported Environments TCP/IP OffloadIP Host Backup Cisco Multipath Channel+BC-249 Cmcc Adapter Features for SNA Environments Cisco SNABC-250 Cisco Multipath Channel TN3270 ServerBC-251 SNA Functions Telnet Server FunctionsBC-252 BC-253 BC-254
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