Cisco Systems BC-281 DLSw+ Features, UDP Unicast, Enhanced Peer-on-Demand Routing Feature, BC-283

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Configuring Data-Link Switching Plus

Technology Overview

UDP Unicast

DLSw Version 2 uses UDP unicast in response to an IP multicast. When address resolution packets (CANUREACH_EX, NETBIOS_NQ_ex, NETBIOS_ANQ, and DATAFRAME) are sent to multiple destinations (IP multicast service), DLSw Version 2 sends the response frames (ICANREACH_ex and NAME_RECOGNIZED_ex) via UDP unicast.

UDP unicast uses UDP source port 0. However, some firewall products treat packets that use UDP source port 0 as security violations, discarding the packets and preventing DLSw connections. To avoid this situation, use one of the following procedures:

•Configure the firewall to allow UDP packets to use UDP source port 0.

•Use the dlsw udp-disablecommand to disable UDP unicast and send address resolution packets in the existing TCP session.

Enhanced Peer-on-Demand Routing Feature

DLSw Version 2 establishes TCP connections only when necessary and the TCP connections are brought down when there are no circuits to a DLSw peer for a specified amount of time. This method, known as peer-on-demand routing, was recently introduced in DLSw Version 2, but has been implemented in Cisco DLSw+ border peer technology since Cisco IOS Release 10.3.

Expedited TCP Connection

DLSw Version 2 efficiently establishes TCP connections. Previously, DLSw created two unidirectional TCP connections and then disconnected one after the capabilities exchange took place. With DLSw Version 2, a single bidirectional TCP connection establishes if the peer is brought up as a result of an IP multicast/UDP unicast information exchange.

DLSw+ Features

DLSw+ is Cisco’s version of DLSw and it supports several additional features and enhancements. DLSw+ is a means of transporting SNA and NetBIOS traffic over a campus or WAN. The end systems can attach to the network over Token Ring, Ethernet, Synchronous Data Link Control (SDLC) Protocol, Qualified Logical Link Control (QLLC), or Fiber Distributed Data Interface (FDDI). See the DLSw+ Design and Implementation Guide Appendix B, “DLSw+ Support Matrix,” for details. DLSw+ switches between diverse media and locally terminates the data links, keeping acknowledgments, keepalives, and polling off the WAN. Local termination of data links also eliminates data-link control timeouts that can occur during transient network congestion or when rerouting around failed links. Finally, DLSw+ provides a mechanism for dynamically searching a network for SNA or NetBIOS resources and includes caching algorithms that minimize broadcast traffic.

DLSw+ is fully compatible with any vendor’s RFC 1795 implementation and the following features are available when both peers are using DLSw+:

•Peer groups and border peers

•Backup peers

•Promiscuous and on-demand peers

•Explorer firewalls and location learning

•NetBIOS dial-on-demand routing feature support

 

 

Cisco IOS Bridging and IBM Networking Configuration Guide

 

 

 

 

 

 

 

78-11737-02

 

 

BC-283

 

 

 

 

 

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Contents BC-281 Configuring Data-Link Switching PlusBC-282 DLSw StandardDLSw Version 2 Standard IP MulticastExpedited TCP Connection DLSw+ FeaturesEnhanced Peer-on-Demand Routing Feature UDP UnicastBC-284 Local AcknowledgmentLLC2 Session without Local Acknowledgment BC-285BC-286 BC-287 DLSw+ Support for Other SNA FeaturesFollowing is a sample dlsw local peer statement Command PurposeDefining a DLSw+ Local Peer for the Router Defines the DLSw+ local peerDefining a DLSw+ Remote Peer TCP EncapsulationBC-289 BC-290 TCP/IP with RIF Passthrough EncapsulationFST Encapsulation Defines a remote peer with FST encapsulationDefines a remote peer with DLSw Lite encapsulation Direct EncapsulationDLSw Lite Encapsulation Defines a remote peer with direct encapsulationMapping DLSw+ to a Local Data-Link Control Token RingBC-292 BC-293 EthernetEnables DLSw+ on an Sdlc interface Associated with this serial interfaceBC-294 BC-295 Configuring Advanced FeaturesScalability Peer Groups and Border PeersBC-296 BC-297 BC-298 Enables peer groups and border peersConfigures peer-on-demand defaults Local, remote, and group cachesBC-299 Explorer Firewalls Displays content of group, local and remote cachesNetBIOS Dial-on-Demand Routing Following command enables NetBIOS DDRBC-301 Following command configures the SNA DDR featureUDP Unicast Feature SNA Dial-on-Demand RoutingDynamic Peers Configures a dynamic peerPromiscuous Peer Defaults LLC1 CircuitsBC-303 Configures promiscuous peer defaultsAvailability Load BalancingBC-304 Local routerAddresses on a transparent bridged are mapped Configures transparent redundancyBackup Peers Ethernet RedundancyConfigures a backup peer Modes of OperationBC-306 BC-307 Access ControlNetwork Management Traffic Bandwidth and Queueing ManagementDefines a port list DLSw+ Bridge Group ListBC-308 BC-309 Filter Lists in the Remote-Peer CommandStatic Paths Static Resources Capabilities ExchangeBC-310 Configuring DLSw+ TimersBC-311 BC-312 Following sections provide DLSw+ configuration examplesRouter a Router BBC-313 DLSw+ with Peer Groups Specified Example BC-314BC-315 Router CFEP BC-316BC-317 Router DBC-318 DLSw+ with Sdlc Multidrop Support Configuration ExamplesRouter E Following example, all devices are type PUBC-319 Following example, all devices are type PU 2.1 MethodHostname Router a BC-320DLSw+ Translation Between Fddi and Token Ring BC-321BC-322 DLSw+ Translation Between Sdlc and Token Ring Media ExampleSdlc partner 1000.5aed.1f53 d2 sdlc dlsw d2 BC-323DLSw+ over Frame Relay Configuration Example RingBC-324 BC-325 DLSw+ over Qllc Configuration ExamplesFollowing three examples describe Qllc support for DLSw+ ExampleBC-326 DLSw+ with RIF Passthrough Configuration ExampleBC-327 DLSw+ with Enhanced Load Balancing Configuration ExampleBC-328 DLSw+ Peer Cluster Feature Configuration ExampleBC-329 DLSWRTR2BC-330 Shows a DLSw+ border peer network configured with DLSw+ RsvpBC-331 DLSw+ with Ethernet Redundancy Configuration ExampleBC-332 DLSw+ with Ethernet Redundancy in a Switched EnvironmentBC-333 BC-334
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