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In a large DLSw+ network with heavily populated branches sessions are sometimes dropped and performance is impacted because a DLSw+ router does not have enough memory and processing resources to relay all circuits between the branches and the data center. This problem is typically fixed by placing routers in the data center and peering a set of branch routers to each of them, creating a border peer design (Figure 1).
If, however, more than one router is connected to the same LAN within the same peer group to circumvent overloading one router (for example, member peer A "MPA" and member peer B "MPB"), then the explorers are duplicated when the border peer forwards an explorer within it's Peer Group. In Figure 1, BP2 forwards the explorer to all the routers in Peer Group 2 (including MPA and MPB even though they are serving the same LAN.) The DLSw+ Peer Clusters feature avoids these explorer replications and resolves some circuit connectivity issues that are the result of the explorer replication.
The DLSw+ Peer Clusters feature reduces explorer replication that typically occurs in a large DLSw+ peer group design where there are multiple routers connected to the same LAN (Figure 2).
In Figure 2, MPA and MPB are serving the same Token Ring LAN to share the circuit load between the branches (for example, workstations X through Y) and the data center (BP2). The problem arises when workstation X wants to communicate with workstation Y because the explorer is sent three times on the LAN. The explorer, which originated from MPA, follows these paths:
The border peer will not forward an explorer back to the peer from which it originated. For example, the X packet will not travel X---> MPA--->BP--->MPA--->Y. Although Peer Group Caching (a feature implemented in Cisco IOS 11.3) lessens the impact beyond the first explorer, there is still additional load on the internetwork that affects performance, bandwidth and CPU memory.
The DLSw+ Peer Clusters feature "clusters" DLSw+ peers (that are connected to the same LAN) into logical groups. Once the multiple peers are defined in the same peer group cluster, the DLSw+ border peer recognizes that it does not have to forward explorers to more than one member within the same peer group cluster.
Using Figure 2 again, but this time with the DLSw+ Peer Clusters feature configured, BP2 recognizes that MPA and MPB belong to peer cluster 5 and the explorer takes the following path:
Border peer---DLSw+ router that relays reachability information to other border and member peers.
Member peer---DLSw+ router is a member of a peer group that relies on the border peer to act as its proxy for exploring the network, rather than exploring the network itself.
Peer cluster---Virtual arrangement of peers that allows multiple peers to be connected to the same LAN without explorer replication.
Peer group---Predefined grouping of DLSw+ peers that allows meshed configurations to be broken into more scalable units. A peer group consists of a border peer with one or more member peer.s
This feature is supported on the following platforms:
No MIBs are supported by this feature.
This feature supports the following RFCs:
The DLSw+ Peer Clusters feature is configured locally on the member peer or on a border peer. Although both options can be configured, we recommend that the cluster-id of a particular peer is defined in either the border peer or on the member peer, but not both because of potential configuration confusion.
When the user defines the cluster option in the dlsw local-peer command on the member peer router, the cluster information is exchanged with the border peer during the capabilities exchange as the peers become active. The border peer uses this information to make explorer replication and forwarding decisions.
To enable the DLSw+ Peer Clusters feature on the member peer, use the following command in global configuration mode:
| Command | Purpose |
|---|---|
Defines the Member Peer as part of a particular cluster and enables the DLSw+ Peer Clusters feature locally. |
When the user configures the cluster option in the dlsw remote-peer command on a border peer, they enable the DLSw+ Peer Clusters feature without forcing every DLSw+ router in the network to upgrade their software.
To enable the DLSw+ Peer Clusters feature on a Border Peer, use the following command in global configuration mode:
| Command | Purpose |
|---|---|
Defines the border peer router as part of a particular cluster and enables the DLSw+ Peer Clusters feature.This feature is used only for the configuration of a border peer. |
Figure 3shows a DLSw+ network configured with the DLSw+ Peer Clusters feature.
Because BP2 is configured as the border peer with the DLSw+ Peer Clusters feature, it does not forward explorers to both MPA and MPB since they are part of the same peer cluster.
source-bridge ring-group 310 dlsw local-peer 10.1.1.3 border group 2 promiscuous
source-bridge ring-group 310 dlsw local-peer 10.1.1.1 group 2 promiscuous cluster 5 dlsw remote-peer 0 tcp 10.1.1.3
source-bridge ring-group 310 dlsw local-peer 10.1.1.2 group 2 promiscuous cluster 5 dlsw remote-peer tcp 0 10.1.1.3
dlsw local-peer 10.1.1.4 group 2 promiscuous dlsw remote-peer tcp 0 10.1.1.3
To verify that the DLSw+ Peer Clusters feature is enabled, issue the show dlsw capabilities command or the show dlsw capabilities local command on the border peer or member peer.
The following is output from the show dlsw capabilities command on BP1:
ibm-45k#show dlsw cap local DLSw:Capabilities for local peer 10.1.1.3 vendor id (OUI) :'00C' (cisco) version number :2 release number :0 init pacing window :20 unsupported saps :none num of tcp sessions :1 loop prevent support :no icanreach mac-exclusive :no icanreach netbios-excl. :no reachable mac addresses :none reachable netbios names :none V2 multicast capable :yes DLSw multicast address :none cisco version number :1 peer group number :2 peer cluster support :yes------>indicates peer cluster feature enabled border peer capable :yes peer cost :3 biu-segment configured :no UDP Unicast support :yes cisco RSVP support :no current border peer :local-peer version string : Cisco Internetwork Operating System Software IOS (tm) 4500 Software (C4500-AJS-M), Experimental Version 12.0(19981113:101717) [vtubati-120t_3_pi 110] Copyright (c) 1986-1998 by cisco Systems, Inc. Compiled Fri 13-Nov-98 10:33 by vtubati
The following is output from the show dlsw capabilities local command on MPB:
ibm-25kb#show dlsw cap local DLSw:Capabilities for local peer 10.1.1.2 vendor id (OUI) :'00C' (cisco) version number :2 release number :0 init pacing window :20 unsupported saps :none num of tcp sessions :1 loop prevent support :no icanreach mac-exclusive :no icanreach netbios-excl. :no reachable mac addresses :none reachable netbios names :none V2 multicast capable :yes DLSw multicast address :none cisco version number :1 peer group number :2 peer cluster support :yes peer cluster id :5------->Indicates the value configured for peer cluster id. border peer capable :no peer cost :3 biu-segment configured :no UDP Unicast support :yes cisco RSVP support :no current border peer :peer 10.8.218.61(2065) cost 3 version string : Cisco Internetwork Operating System Software IOS (tm) 2500 Software (C2500-AJS-L), Experimental Version 12.0(19981113:101717) [vtubati-120t_3_pi 114] Copyright (c) 1986-1998 by cisco Systems, Inc. Compiled Fri 13-Nov-98 15:49 by vtubati
This section documents new or modified commands. All other commands used with this feature are documented in the Cisco IOS Release 12.0 command references.
Use the dlsw local-peer global configuration command to define the parameters of the DLSw+ local peer. Use the no form of this command to cancel the definitions.
dlsw local-peer [cluster cluster-id] [peer-id ip-address] [group group] [border] [cost cost]
cluster cluster-id | (Optional) Implements the DLSw+ Peer Clusters feature and defines the router as part of a particular cluster. The valid range is 1 to 255. |
peer-id ip-address | (Optional) Local peer IP address. This address is required when Fast-Sequenced Transport (FST) or TCP is used. |
group group | (Optional) Peer group number for this router. The valid range is 1 to 255. |
border | (Optional) Enables the router as a border peer. The group option must be specified to use the border peer option. |
cost cost | (Optional) Peer cost advertised to remote peers in the capabilities exchange. The valid range is 1 to 5. |
lf size | (Optional) Largest frame size for this local peer. Valid maximum frame sizes are as follows: |
keepalive seconds | (Optional) Default remote peer keepalive interval in seconds. The valid range is 0 to 1200 seconds. The default is 30 seconds. The value 0 means no keepalives. |
passive | (Optional) Specifies that this router does not initiate remote peer connections to configured peers. |
promiscuous | (Optional) Accept connections from nonconfigured remote peers. |
biu-segment | (Optional) DLSw+ spoofs the maximum receivable I-frame size in XID so that each end station sends its largest frame. |
init-pacing-window size | (Optional) Size of the initial pacing window as defined in RFC 1795. The valid range is 1 to 2000. |
max-pacing-window size | (Optional) Maximum size of the pacing window as defined in RFC 1795. The valid range is 1 to 2000. |
No parameters are defined.
Global configuration
This command first appeared in Cisco IOS Release 10.3.
When there are multiple peers to a specific destination, use the cost keyword to determine which router is preferred and which is capable. The cost keyword only applies in fault tolerance mode.
The biu-segment option is a performance and utilization improvement. If a frame that arrives from a remote peer is too large for the destination station to handle, DLSw+ segments the frame. If you choose to implement this option, you must add the option to both DLSw peer partners.
The following command defines the local peer IP address and specifies the peer group number for this router:
dlsw local-peer peer-id 10.2.17.1 group 2
dlsw duplicate-path-bias
show dlsw capabilities
Use the dlsw remote-peer tcp global configuration command to identify the IP address of a peer with which to exchange traffic using TCP. Use the no form of this command to remove a remote peer.
dlsw remote-peer list-number tcp ip-address [backup-peer [ip-address | frame-relay interface
list-number | Remote peer ring group list number. This ring group list number default is 0. Otherwise, this value must match the number you specify with the dlsw ring-list, dlsw port-list or dlsw bgroup-list command. |
tcp ip-address | IP address of the remote peer with which the router is to communicate. |
backup-peer ip-address | (Optional) IP address of the existing TCP/FST peer for which this peer is the backup peer. |
backup-peer frame-relay interface serial number dlci-number | (Optional) Serial interface and DLCI number of the existing Direct/LLC2 Frame-Relay peer for which this peer is the backup peer. |
backup-peer interface name | (Optional) Interface name of the existing direct peer for which this peer is the backup peer. |
bytes-netbios-out bytes-list-name | (Optional) Configures NetBIOS bytes output filtering for this peer. The bytes-list-name argument is the name of the previously defined NetBIOS bytes access list filter. |
cluster cluster-id | (Optional) Used to indicate to a border peer that a particular remote-peer should be treated as part of a specific peer cluster. The valid Range is 1 to 255. |
cost cost | (Optional) Cost to reach this remote peer. The valid range is 1 to 5. |
dest-mac mac-address | (Optional) Establishes the TCP connection only when there is an explorer frame destined for the specified 48-bit MAC address written in dotted triplet form. |
dmac-output-list access-list-number | (Optional) Establishes the TCP connection only when the explorer frame passes the specified access list. The access-list-number is the list number specified in the access-list command. |
dynamic | (Optional) Establishes the TCP connection only when there is DLSw+ data to send. |
host-netbios-out host-list-name | (Optional) Configures NetBIOS host output filtering for this peer. The host-list-name is the name of the previously defined NetBIOS host access list filter. |
inactivity minutes | (Optional) Length of time a connection is idle before closing the dynamic remote peer connection. The valid range is 1 to 300 minutes. The default is 5 minutes. |
keepalive seconds | Keepalive interval for this remote peer. The range is 0 to 1200 seconds. |
lf size | (Optional) Largest frame size, in bytes, this local peer uses on a circuit to avoid segmented frames. Valid sizes are 516, 1470, 1500, 2052, 4472, 8144, 11407, 11454, and 17800 bytes. |
linger minutes | (Optional) Length of time the backup peer remains connected after the primary peer connection is reestablished. The valid range is 1 to 300 minutes. The default is 5 minutes. |
lsap-output-list list | (Optional) Filters output IEEE 802.5 encapsulated packets. Valid access list numbers are 200 to 299. |
no-llc minutes | (Optional) Length of time a remote peer remains connected after all LLC2 connections are gone. The valid range is 1 to 300 minutes. The default is 5 minutes. |
passive | (Optional) Designates this remote peer as passive. |
priority | (Optional) Enables prioritization features for this remote peer. Valid TCP port numbers are the following: · High: 2065 · Medium: 1981 · Normal: 1982 · Low: 1983 |
rif-passthru virtual-ring-number | (Optional) Configures the remote peer as RIF-Passthru. The virtual-ring-number value is the same number as the ring number value assigned in the source-bridge ring-group commands of the DLSw+ Passthru peers. |
tcp-queue-max size | (Optional) Maximum output TCP queue size for this remote peer. The valid maximum TCP queue size is 10 to 2000. |
timeout seconds | (Optional) Retransmit time limit for TCP. The valid range is 5 to 1200 seconds. The default is 90 seconds. |
No peer IP address is identified.
The linger option is inactive. If the linger option is added with no minutes specified, the default is 5 minutes.
The dynamic option is not on by default. If the dynamic option is added without either the inactivity or no-llc argument specified, the default is to terminate the TCP connection to the remote peer after 5 minutes of no active LLC2 connection.
Global configuration
This command first appeared in Cisco IOS Release 10.3. The following keywords and arguments first appeared in Cisco IOS Release 11.1: dynamic, inactivity minutes, linger minutes, no-llc minutes and timeout seconds. The following keywords and arguments first appeared in Cisco IOS Release 11.2: dest-mac mac-address, dmac-output-list access-list-number, linger minutes.
SNA Dial-on-Demand Routing allows switched links to be closed during idle periods. To enable this feature, set the keepalive option to 0 and configure the timeout option. When the dynamic option is configured, the keepalive option is automatically set to 0.
To enhance DDR cost savings, configure the TCP connection to a remote peer so it is dynamically established (that is, established only when there is DLSw data to send). You can also configure the TCP connection to terminate after a specified period of idle time on the peer or after a specified period of no active LLC sessions on the peer.
You cannot use both no-llc and inactivity in a command specifying a dynamic peer.
When you need to permit access to a single MAC address, the dest-mac option takes less time to configure than the dmac-output-list option.
Use the linger option to specify that a backup peer will remain connected for a specified period of time after the primary connection is gone.
When the priority option on the dlsw remote-peer command is configured, DLSw+ automatically activates four TCP ports to that remote peer (ports 2065, 1981, 1982 and 1983) and assigns traffic to specific ports. Furthermore, if APPN is running with DLSw+ and you specify the priority option on the dlsw remote-peer command, then the SNA TOS maps APPN COS to TCP TOS and preserves the APPN COS characteristics throughout the network.
The rif passthru option works only on Token Ring LANs via SRB. Other LAN types, such as SDLC and QLLC, are not supported. The RIF Passthru feature is supported with TCP encapsulation and it disables local acknowledgment.
The following features are not supported with the DLSw+ RIF Passthru feature:
The cluster keyword is available only on border peers.This option enables the DLSw+ Peer Clusters feature without forcing every DLSw+ router in the network to upgrade their software.
The following example specifies a TCP encapsulation connection for remote peer transport:
dlsw remote-peer 0 tcp 10.2.17.8
The following example specifies a TCP peer as backup to a primary FST peer:
dlsw remote-peer 0 fst 10.2.18.9 dlsw remote-peer 0 tcp 10.2.17.8 backup-peer 10.2.18.9
Posted: Fri Mar 12 15:28:18 PST 1999
Copyright 1989-1999©Cisco Systems Inc.