Frame Relay Applications: Novell IPX & IBM SNA

Traditionally, four networking suites are deployed using Frame Relay as the Layer 2 transport mechanism. This time out, we provide in-depth coverage of the Novell IPX and IBM SNA suites.

 By Cisco Press
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Network Consultants Handbook - Frame Relay
by Matthew Castelli

Network Consultants Handbook -- Click here to go to publisher's site

Frame Relay and the Novell IPX Suite
Novell IPX implementations over Frame Relay are similar to IP network implementation. Whereas a TCP/IP implementation would require the mapping of Layer 3 IP addresses to a DLCI, Novell IPX implementations require the mapping of the Layer 3 IPX address to a DLCI. Special consideration needs to be made with IPX over Frame Relay implementations regarding the impact of Novell RIP (distance-vector algorithm) or NLSP (NetWare Link Services Protocol, link-state algorithm) and SAP (Service Advertising Protocol) message traffic to a Frame Relay internetwork.

Frame Relay IPX Bandwidth Guidelines
IPX can consume large amounts of bandwidth very quickly by virtue of its broadcast announcement-based design. Following are some considerations that demonstrate some methods to consider to manage the IPX traffic and minimize its impact on a Frame Relay WAN.

To reduce overhead in a Frame Relay network, implement the Burst Mode NetWare Loadable Module (NLM). Burst Mode opens the IPX window to avoid waiting for one acknowledgement (ACK) per IPX packet, and allows a maximum window of 128.

Another consideration is the implementation of the Large Internet Packet EXchange (LIPX) NLM if not version 4.X or higher. LIPX will allow for larger-sized packets between client and server. (Often in the case of Frame Relay WANs, the client and server will be connected via Frame Relay VC.) Native IPX without LIPX allows for a maximum payload frame size of 512 bytes; LIPX extends the packet size to 1000 to 4000 bytes. The larger packet size consumes less processing power from the Frame Relay access devices, in turn increasing throughput.

NOTE:   Because Ethernet and Token Ring LANs support higher frame sizes, the native IPX 512 byte frame limitation has an adverse effect on network throughput across WAN routers.

If you are working with an older version of Novell NetWare (v3.11), implement the NLSP NLM for network routing. NLSP only sends routing information when an event happens (link failure) or every two hours. The standard RIP [routing] protocol sends its entire routing table to all other routers every 30 seconds. NLSP uses less bandwidth over the WAN, ensuring more bandwidth is available for user data traffic.

NOTE:   SAP utilizes IPX packets to broadcast or advertise available services on a NetWare LAN. NetWare servers use these SAP packets to advertise their address, services available, and name to all clients every 60 seconds. All servers on a NetWare LAN listen for these SAP messages and store them in their own server information table. Because most Novell clients utilize local resources, the resources should be advertised on a local basis and not broadcast across the Frame Relay WAN.

This article was originally published on Feb 1, 2002
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