Cisco Systems BC-281 - page 5

Configuring Data-Link Switching Plus Technology Overview

BC-285

Cisco IOS Bridging and IBM Networking Configuration Guide

78-11737-02

Figure127 LLC2 Session without Local Acknowledgment

On backbone networks consisting of slow serial links, the T1 timer on end hosts could expire before the

frames reach the remote hosts, causing the end host to resend. Resending results in duplicate frames

reaching the remote host at the same time as the first frame reaches the remote host. Such frame

duplication breaks the LLC2 protocol, resulting in the loss of sessions between the two IBM machines.

One way to solve this time delay is to increase the timeout value on the end nodes to account for the

maximum transit time between the two end machines. However, in networks consisting of hundreds or

even thousands of nodes, every machine would need to be reconfigured with new values. With local

acknowledgment for LLC2 enabled, the LLC2 session between the two end nodes would not be not

end-to-end, but instead, would terminate at two local routers. Figure128 shows the LLC2 session with

the 37x5 ending at Router A and the LLC2 session with the 3x74 ending at Router B. Both Router A and

Router B execute the full LLC2 protocol as part of local acknowledgment for LLC2.

Figure128 LLC2 Session with Local Acknowledgment

With local acknowledgment for LLC2 enabled in both routers, Router A acknowledges frames received

from the 37x5. The 37x5 still operates as if the acknowledgments it receives are from the 3x74. Router

A looks like the 3x74 to the 37x5. Similarly, Router B acknowledges frames received from the 3x74. The

3x74 operates as if the acknowledgments it receives are from the 37x5. RouterB looks like the 3x74 to

37x5. Because the frames do not have to travel the WAN backbone networks to be acknowledged, but

are locally acknowledged by routers, the end machines do not time out, resulting in no loss of sessions.

3x74

S1106a

WAN

SNA session

Token

Ring

Token

Ring

Router A Router B

LLC2 session

37x5

Router A Router B

S1107a

WAN

SNA session

Token

Ring

Token

Ring

LLC2 session LLC2 session

TCP session

3x74

3

7x5

Contents

Main Configuring Data-Link Switching Plus Technology Overview DLSw Standard DLSw Version 2 Standard IP Multicast UDP Unicast Enhanced Peer-on-Demand Routing Feature DLSw+ Features Local Acknowledgment Page Notes on Using LLC2 Local Acknowledgment DLSw+ Support for Other SNA Features DLSw+ Configuration Task List Defining a DLSw+ Local Peer for the Router Defining a DLSw+ Remote Peer TCP Encapsulation TCP/IP with RIF Passthrough Encapsulation FST Encapsulation Direct Encapsulation DLSw Lite Encapsulation Mapping DLSw+ to a Local Data-Link Control Token Ring Ethernet SDLC QLLC FDDI Configuring Advanced Features Scalability Page Page Page Page Page Page Availability Page Page Modes of Operation Network Management Traffic Bandwidth and Queueing Management Access Control DLSw+ Ring List or Port List Page Page Configuring DLSw+ Timers Verifying DLSw+ Monitoring and Maintaining the DLSw+ Network DLSw+ Configuration Examples DLSw+ Using TCP Encapsulation and LLC2 Local AcknowledgmentBasic Configuration Example BC-313 12 Router A Router B 10.2.25.1 10.2.5.2 Figure131 DLSw+ with Local AcknowledgmentSimple Configuration DLSw+ Using TCP Encapsulation with Local AcknowledgmentPeer Group Configuration Example 1 Router A Router C Figure132 DLSw+ with Peer Groups Specified (Example 1) BC-315 BC-316 DLSw+ Using TCP Encapsulation with Local AcknowledgmentPeer Group Configuration Example 2 Figure133 DLSw+ with Peer Groups Specified (Example 2) SDLC 01 controller Router C Router A Router B Router D Router E BC-317 Router D BC-318 Router E DLSw+ with SDLC Multidrop Support Configuration Examples In the following example, all devices are type PU2.0: BC-319 In the following example, all devices are type PU2.1 (Method 1): In the following example, all devices are type PU2.1 (Method 2): DLSw+ with LLC2-to-SDLC Conversion Between PU 4-to-PU 4 Communication Figure134 LLC2-to-SDLC Conversion for PU 4-to-PU 4 Communication BC-320 DLSw+ Translation Between Ethernet and Token Ring Configuration Example Router A Router B Figure135 DLSw+ Translation Between Ethernet and Token Ring AS/400 128.207.111.1 DLSw+ Translation Between FDDI and Token Ring Configuration Example Figure136 DLSw+ Translation Between FDDI and Token Ring Router A Router B DLSw+ BC-322 DLSw+ Translation Between SDLC and Token Ring Media Example AS/400 Figure137 DLSw+ Translation Between SDLC and Token Ring Media BC-323 BC-324 DLSw+ over Frame Relay Configuration Example Router A Router B n Session Figure138 DLSw+ over Frame Relay DLSw+ over QLLC Configuration Examples BC-326 Example 3 3745 B10.1.14.2 DLSw+ with RIF Passthrough Configuration Example Figure 139 is a sample configuration for DLSw+ using the RIF Passthrough feature. Figure139 Network Configuration with RIF Passthrough A10.1.12.1 25 3745 DLSw+ with Enhanced Load Balancing Configuration Example RTR D Figure 140 shows DLSw+ with the Enhanced Load Balancing feature. Figure140 DLSw+ with Enhanced Load Balancing Router D DLSw+ Peer Cluster Feature Configuration Example Figure 141 shows a DLSw+ network configured with the DLSw+ Peer Clusters feature. BP2 MPA MPB DLSW+ RSVP Bandwidth Reservation Feature Configuration Example BC-330 DLSw+ RSVP Bandwidth Reservation Feature with Border Peers Configuration Figure 143 shows a DLSw+ border peer network configured with DLSw+ RSVP. Figure143 DLSw+ RSVP Bandwidth Reservation Feature in a Border Peer Network DLSWRTR1 IPRTR1 DLSw+ with Ethernet Redundancy Configuration Example DLSw+ with Ethernet Redundancy Enabled for Switch Support Configuration BC-333