Using SDLC Relay
This document describes OpenROUTE Networks implementation of Synchronous Data Link Control Relay (SRLY). It includes the following sections:
About SDLC Relay
How SDLC Relay Works
Setting Up SDLC Relay
Sample SDLC Relay Configuration
About SDLC Relay Configuration and Monitoring Commands
Accessing the SDLC Relay Configuration Environment
Accessing the SDLC Relay Monitoring Environment
SDLC Relay Commands
About SDLC Relay
Like DLSw, SRLY is a method for consolidating SDLC traffic onto the corporate multiprotocol backbone.
Unlike DLSw, SDLC Relay does not terminate the SDLC data link to reduce the likelihood of session timeouts, and does nothing to help reduce congestion on the WAN link. What SRLY provides is a serviceable method for shipping HDLC-formatted frames across WAN links.
How SDLC Relay Works
Despite its name, the SDLC Relay protocol (SRLY) is designed to handle other protocols besides SDLC. The protocol works by encapsulating SDLC or any bit-oriented protocol (HDLC, LAPB) in UDP packets, and transmitting them through the IP cloud on a point-to-point connection to another SRLY device.
These connections are established by matching SRLY traffic to specific ports and groups. During configuration, each group has a unique group number assigned, and exactly two ports: one SDLC primary port, and one SDLC secondary. Matching SRLY traffic to group numbers and ports ensures that attached end stations can only send packets to the end stations for which they are intended.
Once the router receives packets, it strips them of their UDP/IP header and transmits them to their destination address in their original protocol format.
Figure 1 SDLC Primary/Secondary Stations and Local/Remote Ports
Encapsulation in UDP/IP packets allows for SDLC frames to be handled via IP routing techniques. And since each SDLC frame is encapsulated unchanged, SRLY is transparent to sending and receiving stations. This transparency allows SRLY to support all SNA PU Types.
SDLC Primary and Secondary Stations
When configuring SRLY, you must connect a router's primary port to its primary end station, and connect its secondary port to its secondary end station. Within the primary-secondary communication process, the primary end station is responsible for initiating, scheduling, and terminating the session. The secondary station does not initiate communication, but responds to commands from its primary partner.
When running balanced protocols like LAP-B or HDLC, you can assign roles arbitrarily as long as one device is Primary, and its connected counterpart is Secondary.
When to Use SDLC Relay
Generally, you would use SRLY instead of DLSw when you need to exchange any bit-oriented protocol, such as LAPB, HDLC, or SDLC primary over the wide area, between SNA or non-SNA devices.
DLSw can be configured for Host 1 and end station C in Figure 2: other wide-area connections would have to be accomplished using SDLC Relay.
Figure 2 SDLC Relay Configurations
Setting Up SDLC Relay
Configuring SDLC Relay (SRLY) involves performing these steps on each of two routers.
- 1. Set the data link on the serial line using the set data-link command and the appropriate interface number.
- 2. Assign a group number using the add group command. The group number must be the same on each SRLY router. Group number 1 is the default.
- 3. At the SDLC Config> prompt, add a local port with the add local command. Be sure you add this port to the group defined in Step 2.
- 4. This port's data link type must be SDLC Relay (SRLY). Use the set data link command at the Config> prompt to set the data link type for the port.
- 5. At the SDLC Config> prompt, add a remote port with the add remote command. The IP address of the remote port is that of the cooperating SRLY router.
- 6. Repeat these steps for the second SRLY router. When prompted for the IP address of the remote port, provide the address of the first router.
SRLY Interface Requirements
When configuring SRLY, you must consider the following requirements.
Depending on the type of serial card that you are using, dual-port or quad-port, the SRLY interface may be either DTE or DCE. If you are using a dual-port, the SRLY interface is DTE. For DTE interfaces, you must use modems or modem eliminators between the primary and secondary devices and the router, if connecting to another DTE device (or, you can connect directly to a DCE device). The modem eliminator must be compatible with the interface, such as RS-232 or V.35. The interface may be DCE or DTE if you are using the quad-port and you are not using modem eliminators.
The serial line supports NRZ. The Quad Serial line supports NRZ and NRZI.
Sample SDLC Relay Configuration
Following is a complete SDLC Relay configuration. The example assumes that the router has not been configured for any other protocols or data links.
Context Diagram
The example is based on the information shown in Figure 3. The IP connection between the two routers is over Proteon Serial Line.
Configuring R1 for SDLC Relay requires all of the information shown. This information includes the following:
The example indicates where this information is provided in the course of the configuration procedure.
Figure 3 Context Diagram for SRLY Configuration
This example explains how to configure two routers for SRLY traffic. Router 1 (R1) is connected to a PU Type 2.0 node. Router 2 (R2) is connected to a front end processor (FEP).
Configuring SDLC Relay
On R1, set the data link of interface 2 to an SDLC Relay device. Use the set data-link command shown here.
Config>set data srly 2
You can list the devices to confirm that an SDLC Relay device has been added.
Config>list dev
Ifc 0 (Token Ring): CSR 6000000, vector 28
Ifc 1 (WAN Proteon Serial): CSR 81620, CSR2 80D00, vector 93
Ifc 2 (WAN SDLC Relay): CSR 81640, CSR2 80E00, vector 92
Set Serial Line Parameters
Next, set the line speed and clocking type parameters for the SRLY line. Note that the prompt for the SRLY configuration module is SRLY # Config>, where # is the number of the SRLY interface.
Config>network 2
SDLC relay interface user configuration
SRLY 2 Config>set clock internal
Must also SET SPEED for internal or mixed clocking
SLC Config>set speed
Internal Clock Speed [0]? 56000
For RBX Series routers, you must also set the cable type.
SRLY 2 Config>set cable rs-232 dce
After setting the line speed, clocking, and cable type, you can check the configuration with the list command.
SRLY 2 Config>list
Synchronous serial line interface configuration Maximum frame size in bytes = 2048
Encoding: NRZ
Idle State: Flag
Clocking: Internal
Cable type: RS-232 DCE
Internal Clock Speed: 56000
Transmit Delay Counter: 0
SLC Config>exit
Configuring the SDLC Relay Protocol
Configure the SDLC Relay protocol as shown:
Config>protocol sdlc
SDLC relay protocol user configuration
SDLC config>
As this example shows, the prompt for the SDLC Relay (SRLY) area is SDLC config>. Commands entered at this prompt only affect the SDLC Relay protocol. They have nothing to do with, and do not affect, SDLC data links or devices.
Exit the SDLC Relay configuration procedure at any time by entering exit.
Assign a Group Number
First, assign a group number with the add group command. This number is assigned to the primary and secondary ports on the router you are configuring for SRLY. The group number you designate must be the same for each router.
SDLC config>add group
Group number: [1]?
Notice that the list group command shows that no ports have yet been configured for group 1.
SDLC config>list group
Group number: [1]? 1 SDLC Relay ConfigurationGroup Number Port Status Net SDLC Station IP Address
Number address(hex)
---------- ---------- ----- ----------- -----------
No ports configured for group 1
Add a Local Port
Next, add a local port to group 1. The port you add is the SRLY line defined earlier.
SDLC config>add local
Group number: [1]?
Interface number: [0]? 2
(P)rimary or (S)econdary: [P]?
Notice that the list all command shows that a local secondary port is configured for group 1.
SDLC config>list all SDLC Relay Configuration
Group Number Port Status Net SDLC Station IP Address
Number address(hex)
---------- ---------- ----- ----------- -----------
1 (E) Local PRIMRY (E) 2
The (E) shown within the Port Status column stands for Enabled. By default, SRLY ports are enabled; SRLY ports must remain enabled in order to use the feature.
Add a Remote Port
Next add a remote port for group 1. This is the port that leads to the IP cloud. Each group must consist of a pair of ports, one primary, the other secondary. The remote port added here must be secondary since the local port attached to it is primary.
The IP address provided is that of the router on the other side of the IP cloud, R2.
SDLC config>add remote
Group number: [1]?
IP address of remote router: [0.0.0.0]? 10.2.50.30
(P)rimary or (S)econdary: [S]? p
SDLC config>list all SDLC Relay Configuration
Group Number Port Status Net SDLC Station IP Address
Number address(hex)
---------- ---------- ----- ----------- -----------
1 (E) Local PRMRY (E) 2 10.2.50.30
1 (E) Remote SCNDRY (E)
Configuring the Neighbor Router
Up to this point, this example has shown how to configure R1 in Figure 3. SRLY requires two routers, one on either side of the IP cloud. You must configure SRLY on each of them.
Set Data Link, Add Group, and Add Port
First, set up an SRLY data link for R2. Do this in the same manner as shown earlier for R1.
Next, add a group for R2, assigning the same group number (1, in this case) as that assigned on R1. Add a local port for the assigned group. This is the SRLY line you have already defined. In this case, the port type is secondary since a front end processor (FEP) (which, like a host, is always primary) is on the line.
SDLC config>add local
Group number: [1]?
Interface number: [0]?
(P)rimary or (S)econdary: [S]?
SDLC config>list all SDLC Relay Configuration
Group Number Port Status Net SDLC Station IP Address
Number address(hex)
---------- ---------- ----- ----------- -----------
1 (E) Local SCNDRY (E) 0 10.2.50.30
Add a Remote Port
Finally, add a remote port for group 1. This is the port that leads to the IP cloud. Since the FEP is primary, this port is secondary. As mentioned earlier, each group must consist of a primary and secondary station.
Since we are configuring R2, the IP address of the remote router belongs to R1. See Figure 3 for the addresses of R1 and R2, and their roles in the overall SRLY configuration.
SDLC config>add remote
Group number: [1]?
IP address of remote router: [0.0.0.0]? 10.1.50.7
(P)rimary or (S)econdary: [S]? pSDLC config>list all SDLC Relay Configuration
Group Number Port Status Net SDLC Station IP Address
Number address(hex)
---------- ---------- ----- ----------- -----------
1 (E) Remote PRMRY (E) 10.1.50.7
1 (E) Local SCNDRY (E) 0
About SDLC Relay Configuration and Monitoring Commands
Enter SDLC Relay configuration commands at the SDLC Config> prompt. Changes made to the router's configuration do not take effect immediately. They only become part of the router's non-volatile configuration memory when it restarts.
Conversely, you enter SDLC Relay monitoring commands at the SDLC> prompt. These commands take effect immediately, but do not become part of router's non-volatile configuration memory. Thus, while monitoring commands allow you to make real-time changes to the router's configuration, these changes are temporary. The router's configuration memory overwrites them when the router restarts.
Monitoring consists of these actions:
Accessing the SDLC Relay Configuration Environment
Use the SDLC Relay configuration process to change the configuration of the router. The new configuration takes effect when you restart the router.
To enter the configuration process, enter config at the * prompt. This brings you to the Config> prompt as shown:
MOS Operator Control
* config
Gateway user configuration
Config>
If the Config> prompt does not appear immediately, press Return again.
Enter SDLC Relay configuration commands at the SDLC config> prompt. To access this prompt, enter protocol sdlc as shown:
Config>protocol sdlc
SDLC Relay user configuration
SDLC config>
Accessing the SDLC Relay Monitoring Environment
To enter the monitoring environment, enter monitor at the * prompt. This brings you to the monitoring environment as shown:
MOS Operator Control
*monitor
+
Enter SDLC Relay monitoring commands at the SDLC> prompt. To access this prompt, enter protocol sdlc at the + prompt as shown:
+ protocol sdlc
SDLC>
SDLC Relay Commands
Table 1 lists the SDLC Relay configuration and monitoring commands.
Press Space twice after you type a command to display the available options for each command. Enter help for information about using the command line interface.
[C] means the command is available at the SDLC Config> prompt.
[M] means the command is available at the SDLC> prompt.
Add [C]
Adds group numbers, local ports, and remote ports.
Syntax: add
- group
- local-port
- remote-port
group
Assigns a number to a group of primary or secondary ports added to the router.
Example: add group
Group number: [1]? 1
Point to Point connection: (Yes of No)? Y
local-port
Identifies the interface that you are using for the local port.
Example: add local-port
Group number: [1]?1
Interface number: [0]? 0
(P)rimary or (S)econdary:[S}? p
remote-port
Identifies the IP address of the port directly connected to the serial line on the remote router.
Example: add remote-port
Group number: [1]? 1
IP address of remote router:[0.0.0.0]? 128.185.121.97
(P)rimary or (S)econdary:[S]? s
Clear-Port-Statistics [M]
Resets the SDLC Relay statistics for all ports. The statistics include counters for packets forwarded and packets discarded.
Syntax: clear-port-statistics
Example: clear-port-statistics
Clear all port statistics? (Yes or No): Y
Delete [M]
Removes group numbers, local ports, and remote ports.
Syntax: delete
- group
- local-port
- remote-port
group group#
Removes a group (group#) of SDLC Relay configured ports.
Example: delete group 1
local-port interface#
Removes the local port for the specified interface (interface#).
Example: delete local-port 0
remote-port
Removes the remote port for the specified group.
Example: delete remote-port
Group number: [1]? 1
(P)rimary or (S)econdary:[S}? S
Disable [C] [M]
Suppresses forwarding for an entire relay group or a specific relay port.
When you use this command within the monitoring process, its effects are not stored in the router's non-volatile configuration memory.
Syntax: disable
- group
- port
group group#
Suppresses transfer of SDLC Relay frames to or from a specific group (group#).
Example: disable group 1
port
Suppresses transfer of SDLC Relay frames to or from a specific local port.
Example: disable port
Interface number: [0]? 0
(P)rimary or (S)econdary:[S]? s
Enable [C] [M]
Enables data transfer for an entire group or a specific local interface port.
When you use this command within the monitoring process, its effects are not stored in the router's non-volatile configuration memory.
Syntax: enable
- group
- port
group group#
Allows transfer of SDLC Relay frames to or from the specified group.
Example: enable group 1
port
Allows transfer of SDLC Relay frames to or from the specified local port.
Example: enable port
Interface number: [0]? 0
(P)rimary or (S)econdary:[S]? s
List [C] [M]
Displays the configuration or status of a specific group or of all groups.
Syntax: list
- all
- group
all
Displays the configurations of all local ports.
Example: list all
SDLC Relay Configuration
Group Number Port Status Net Number IP Address
-----------------------------------------------------------------
1 (E) Local PRMRY (D) 2
1 (E) Remote SCNDRY (E) 128.185.452.11
2 (D) Local PRMRY (D) 0
2 (D) Remote SCNDRY (D) 128.185.450.31
group group#
Displays the configuration of a specified group.
Example: list group 1
SDLC Relay Configuration
Group Number Port Status Net Number IP Address
-----------------------------------------------------------------
1 (E) Local PRMRY (D) 2
1 (E) Remote SCNDRY (E) 128.185.452.11
Exit [C] [M]
Exits the SDLC Relay configuration or monitoring process.
Syntax: exit
Example: exit
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