Configure SDLC Directory

SDLC task in this chapter describes how to configure the router into a SDLC workstation (it is different from configuring the router into SDLC sender whose equipment is not a SDLC workstation. SDLC sender transmit SDLC frame between two SDLC workstations through a multi-media and multi-protocol environment). The first task is necessary. In order to meet the network needs, the appropriate command can be used for completing its configuration. Other tasks are optional. When it is necessary to advance the performance of SDLC, these tasks can be executed.

Configuring the router as SDLC master station or SDLC slave station

Setting up SDLC workstation supportive of DLSW+

Configuring SDLC as two-way and concurrent mode

Configuring SDLC timer and re-send times

Configuring the number of SDLC frame and information frame

Controlling the size of cache

Controlling the polling of slave station

Configuring SDLC interface as half-duplex mode

Configuring XID Value

Configuring the maximum value of SDLC information frame

Monitoring SDLC workstation

Example of Configuration

 

Configuring the router as SDLC master station or SDLC slave station

SDLC defines two type network nodes: master node and slave node. In a preset sequence, the master node polls the slave node. When the data is exported, the data will be forwarded from slave node to master node. When our router is configured into the master node and slave node, it is called SDLC workstation.

Setting up SDLC workstation supportive of DLSW+

Setting the equipment into SDLC workstation. When the property of DLSW+ needs to be configured, the command below can be used under interface configuration mode:

Steps

Command

Purpose

1

encapsulation sdlc

Configuring serial port encapsulation type as SDLC.

2.

sdlc role { primary | secondary }

Configuring interface role

3.

sdlc vmac mac-address

Configuring MAC address of serial port.

4.

sdlc partner mac-address sdlc-address

Designating destination address and setting up a LLC protocol interactive connection.

Configuring a SDLC multi-point link. The default configured SDLC role is primary. The physical unit without xid value in SDLC address command is PU 2.1 type equipment; it is also the default configuration.

Other DLSw+ configuration commands can be referred to the chapter of “DLSw+ Configuration”.

Configuring SDLC as two-way and concurrent mode

SDLC two-way and concurrent mode allows master SDLC link station to use a full duplex serial circuit. When an outstanding polling occurs, the master SDLC link station is able to send the data to the slave station. The two-way and concurrent mode works only on the side of SDLC master station. In the slave link station, it response to the polling sent from the master station.

SDLC two-way and concurrent mode runs in the multi-branch link environment or point-to-point link environment.

In the multi-branch link environment, a two-way and concurrent master station is able to poll a slave station and receive the data from the slave station and send the data (information frame) to other slave stations.

In the point-to-point link environment, so long as no maximum limit on reaching the window, a two-way and concurrent master station is able to send the data (information frame) to the slave station even if there is an outstanding polling.

Any one of the commands can be used under interface configuration mode for activating the two-way and concurrent mode:

Command

Purpose

sdlc simultaneous full-datamode    or

sdlc simultaneous half-datamode

Setting the send of data from master station to the polled slave station and receive of data from it.

Shutting down the master station sending the data to the slave station.

 

Configuring SDLC timer and re-send times

When SDLC workstation sends frame, it will wait for the response of receive end. The response indicates the frame has been received. The response time allowed by the router before re-sending frame can be amended. The times of re-sending the frame by the software can be set before terminating SDLC session process. Through controlling these values, by controlling these values, the network overhead can be reduced in continuing to detect the transmitted frame.

One or two commands below can be used under interface configuration mode for configuring SDLC timer and retransmission times:

Command

Purpose

sdlc t1 milliseconds

Controlling the total time of software of waiting for response

sdlc n2 retry-count

Configuring the times of software of retrying a timeout operation.

 

 

Configuring the number of SDLC frame and information frame

The maximum length of input frame and the maximum number of the information frame (or the size of window) received before router sends response to the receive end can be configured. When the configured value is relative big, the network overhead can be reduced.

The command below can be used under interface configuration mode for configuring SDLC frame and number of information frame.

Command

Purpose

sdlc n1 bit-count

Configuring the maximum length of input frame

sdlc k window-size

Configuring the size of local window of router

sdlc poll-limit-value count

Configuring the times of master station’s polling to the slave station.

 


 

Controlling the size of cache

The size of cache can be controlled. The cache is used for storing the data that is not decided to be sent to remote SDLC station. The command is especially useful in SDLC protocol convert equipment that implements the communication between SNA workstation whose link layer protocol is LLC2 in token-ring local area network (LAN) and SNA workstation whose link layer protocol is SDLC on serial link. The frame length and the size of window on the token-ring are usually much bigger than the acceptable ones on the serial link. What’s more, the serial link is slower than token-ring.

In order to control the accumulation problem produced in the high-speed data transmission from token-ring to serial link, the command below can be used on the basis of each address under interface configuration mode:

Command

Purpose

sdlc holdqueue address queue-size

Setting the maximum quantity of the data packets stored in the sequence before transmission.

Controlling the polling of slave station

The interval of router’s polling to the slave station, the length of time of sending data from master station to slave station and how long the software polls a slave station before moving to the next station can be controlled.

The following points should be noted in using these commands:

Only when the slave station is polled by the master station, the data can be transmitted. When the polling terminates and the value of timer is too big, the response time of slave station will add. When the value of the timer is reduced too small, it will lead to the congestion of serial link and data flood due to the excessive and unnecessary polling frames sent from the slave station, which takes the extra CPU time for dealing with them.

The communication efficiency between master station and single slave station can be improved by increasing the limit value of polling, but it may delay the polling to other slave stations.

One or more commands below can be used under interface configuration mode for controlling the polling of slave station:

Command

Purpose

sdlc poll-pause-timer milliseconds

Configuring the waiting time interval of router’s polling to two slave stations on some single serial port.

sdlc poll-limit-value count

Configuring the times of a master station’s polling to slave station.

The “def” format of these commands can be used for restoring to the default polling value.

Configuring SDLC interface as half-duplex mode

Under default state, SDLC interface runs under full duplex mode. The command below can be used under interface configuration mode for configuring SDLC interface as half-duplex mode.

 

Command

Purpose

half-duplex

Configuring SDLC interface as half-duplex mode

Configuring XID Value

XID value set in the router shall be consistent with the corresponding parameter set on token-ring host with which SDLC equipment will communicate and shall match with the corresponding system parameter in IDBLK and IDNUM defined in VTAM of token ring host.

Notes: Configuring XID value will affect the attribute of the interface. If XID value is configured, it means that the equipment connected with the interface is Pu2.0. XID value can be configured after the port is shut down.

The command below can be used under interface configuration mode for configuring XID value.

Command

Purpose

sdlc xid address xid

Designating XID value related to SDLC station.


 

Configuring the maximum value of SDLC information frame

Normally, the router and SDLC equipment that interacts with router protocol shall support the same and maximum length of SDLC information frame. The bigger the value is, the more efficient the link is used and the performance will be better.

After SDLC equipment is configured with the maximum possible information frame to be sent, the router shall be configured for supporting the same maximum length of information frame. The default value is 265 bytes. The maximum value supported by the software must be smaller than the maximum frame value of LLC2 defined at the time of configuring the maximum length of LLC2 information frame.

The command below can be used under interface configuration mode for configuring the maximum value of SDLC information frame:

Command

Purpose

sdlc sdlc-largest-frame address size

Configuring the maximum length of information frame that can be sent or received by the designated SDLC station.

 

 

 

 

Monitoring SDLC workstation

The command below can be used under management mode for monitoring the configuration of SDLC workstation and deciding which SDLC parameter needs to be adjusted.

Command

Purpose

show interfaces

Showing configuration information of SDLC workstation.

 

Example of Configuration

The following are the examples of SDLC configuration:

Example of SDLC two-way and concurrent mode configuration

Example of SDLC’s configuring DLSw+ 

Example of configuring half-duplex

Example 1-1 of sdlc configuration

Example 1-2 sdlc Configuration

Example of SDLC two-way and concurrent mode configuration

 

The following configuration defines serial interface 1/0 as SDLC master station. Two slave stations of C1 and C2 are connected with the master station through sharable device of modem.

Two-way and concurrent mode is activated.

interface serial 1/0
  encapsulation sdlc-primary
  sdlc address c1
  sdlc address c2
  sdlc simultaneous full-datamode

The network with above configuration is shown in the chart below:

Two slave stations are connected with an independent serial port through the sharable device of modem.

 

Example of SDLC’s configuring DLSw+ 

The example below describes SDLC configuration that can be implemented and supported by DLSw+.

Router is used as remote slave station and master station of c1 and c2.  c1 and c2 are reserved by DLSw+ and cannot be used by any other data link user.

interface serial  1/0
  encapsulation sdlc
  sdlc vmac 4000.3174.0000
  sdlc address c1
  sdlc xid c1 01712345
  sdlc partner 4000.3745.0001 c1
  sdlc address c2
  sdlc xid c2 01767890
  sdlc partner 4000.3745.0001 c2
  sdlc role primary

 

Example of configuring half-duplex

In the example below, SDLC interface is configured into half-duplex mode

encapsulation sdlc 
sdlc simultaneous half-duplex

 

Example 1-1 of sdlc configuration

The example describes SDLC configuration that can be implanted and supported by DLSw+. In this example, 4000.1111.0001 is MAC address of HOST A.

 Router A is used as short range, SDLC configuration is as follows:

interface fastethernet 0/0

  bridge-group 10

Router B is used as remote slave station and master station of c1 and c2. c1 and c2 are reserved by DLSw+ and cannot be used by any other data link user. C1 is PU2.0, c2 is PU2.1, SDLC configuration is as follows:

interface serial  1/0

  encapsulation sdlc

  sdlc vmac 4000.1111.0001

  sdlc address c1

  sdlc xid c1 01712345XID is configured, i.e. PU2.0

  sdlc partner 4000.1234.00C1 c1

  sdlc address c2The default configuration is PU2.1

  sdlc partner 4000.1234.00C2 c2

  sdlc role primary

 

Example 1-2 sdlc Configuration

 

The example describes SDLC configuration implemented and supported by DLSw+

Router A is used as short-range slave station, SDLC configuration is as follows:

interface serial  1/0

  encapsulation sdlc

  sdlc vmac 4000.1234.0000

  sdlc address c1

  sdlc xid c1 01712345XID is configured, i.e. PU2.0)

  sdlc partner 4000.5678.00c1 c1

  sdlc address c2default configuration is PU2.1

  sdlc partner 4000.5678.00c2 c2

  sdlc role secondary

 

Router B is used as remote slave station and master station of c1 and c2. c1 and c2 are reserved by DLSw+ and cannot be used by any other data link user. C1 is PU2.0, c2 is PU2.1, SDLC configuration is as follows:

interface serial  1/0

  encapsulation sdlc

  sdlc vmac 4000.5678.0000

  sdlc address c1

  sdlc xid c1 01712345XID is configured, i.e. PU2.0

  sdlc partner 4000.1234.00C1 c1

  sdlc address c2default configuration is PU2.1

  sdlc partner 4000.1234.00C2 c2

  sdlc role primary