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 polling of slave station
Configuring SDLC interface as half-duplex mode
Configuring
the maximum value of SDLC information frame
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. |
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 |
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. |
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. |
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 01712345(XID is configured, i.e. PU2.0)
sdlc partner 4000.1234.00C1 c1
sdlc address c2(The default configuration is PU2.1)
sdlc partner 4000.1234.00C2 c2
sdlc role primary
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 01712345(XID is configured, i.e. PU2.0)
sdlc partner 4000.5678.00c1 c1
sdlc address c2(default 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 01712345(XID is configured, i.e. PU2.0)
sdlc partner 4000.1234.00C1 c1
sdlc address c2(default configuration is PU2.1)
sdlc partner 4000.1234.00C2 c2
sdlc role primary