When designing source-route bridging (SRB) networks featuring routers and IBM Systems Network Architecture (SNA) entities, you must carefully consider the configuration of SNA nodes as well as routing nodes. This appendix provides examples that focus on three specific SNA devices:
Figure C-1 illustrates a typical environment. Tables C-1 through C-6 present the definition parameters for the devices shown in Figure C-1.
The parameters listed in Tables C-1 through C-6 illustrate input to the Network Control Program (NCP) system generation process that runs in the host processor using the Network Definition Facility (NDF). The NDF is part of the ACF/NCP/System Support Program utility. The output produced by the generation process is a load module that runs in an FEP. Its typical size can be slightly under 1 MB to more than 3 MB. The ACF/NCP/System Support Program utility is also used for loading and dumping an FEP.
The following tables outline relevant parameters for generating Token Ring resources.
Table C-1. BUILD Definition Parameters
The LUDRPOOL definition shown in Table C-2 specifies the number of peripheral resources required for the correct amount of control block storage to be reserved for new connections.
The GROUP definition shown in Table C-3 specifies group definition parameters.
Table C-3. GROUP Definition Parameters
The LINE definition shown in Table C-4 specifies line definition parameters.
Table C-4. LINE Definition Parameters
| Parameter | Example, Parameter Value, or Range | ParameterDescription and Implementation Notes |
|---|---|---|
| ADAPTER | TIC1 | 4 MB Token Ring interface. |
| TIC2 | 4 or 16 MB Token Ring interface. | |
| ADDRESS | 1088 to1095 | Range of valid addresses for TICs; only one specified per LINE definition. |
| BEACTO | 52 | Time in seconds the ring can beacon before TIC considers it down; maximum is 600. |
| LOCADD | 4000abbbbbbb | Locally administered TIC address, where a is any value from 0 to 7, and b is any integer value from 0 to 9. |
| LOCALTO | 1.5 | V5R4; same as in BUILD (see Table C-1), but only for PU 4 (LOGICAL, SUBAREA) devices; allows granularity for individual TICs for SUBAREA connections. |
| REMOTTO | 2.5 | V5R4 parameter; same as LOCALTO; see BUILD parameters in Table C-1. |
| T2TIMER | localt2, remott2, N3 | V5.4 parameter; see BUILD parameters in Table C-1; can be defined in LINE definition only if a subarea node was defined in GROUP definition. |
| MAXTSL | 2044 to 16732 | Specifies maximum data in bytes that NTRI can transmit; TIC1 maximum is 2044; TIC2 maximum at TRSPEED16 is 16732. |
| PORTADD | Number | For association of physical to logical ECLTYPEs; matches physical or logical ECLTYPE specification. |
| RETRIES | m, t, n, ml | Where m = number of retries for remote ring sessions, t = pause between retry sequence, n = number of retry sequences, and ml = number of retries in a sequence for local ring sessions. |
| TRSPEED | 4 or 16 | TIC speed. |
Table C-5 specifies physical unit (PU) definition parameters.
Table C-5. FEP Physical Unit (PU) Definition Parameters
Table C-6 specifies logical unit (LU) definition parameters.
Devices that are attached to Token Ring and communicate with an IBM host application must be defined via the VTAM access method associated with the host. These devices are seen as dial-in resources from the host side and are defined in a configuration component named Switched Major Node. Some common definitions used in network configurations are outlined in Table C-7 through Table C-9
Table C-8. VTAM PU Definition Parameters
The following configuration was taken from a 3174-13R cluster controller serial number 45362 connected to a Token Ring. These entries were used with a specific 3174 running on a 4 Mbps Token Ring. The configuration of this 3174-13R involved three specific configuration screens. Tables C-10 through C-12 list the configuration line numbers,entries used, and descriptions of the configuration line. When applicable, extended descriptions are included for configuration entries that are relevant to the requirements of the routed network.
Note
Of particular interest when configuring 3174 devices for a router-based SRB environment are configuration line items 106, 107, and 384 in configuration screen 2 (refer to Table C-11). These specify the required addresses and relevant Token Ring type for the cluster controller.
Table C-10. 3174-13R Screen 1 Configuration Details
| Configuration Line Number | Sample Value | Parameter Description and Implementation Notes |
|---|---|---|
| 98 | Online test password. | |
| 99 | TKNRNG | Description field. |
| 100 | 13R | Model number. |
| 101 | 7 | Host attachment type. |
Table C-11. 3174-13R Screen 2 Configuration Details
Table C-12. 3174-13R Screen 3 Configuration Details
| Configuration Line Number | Sample Value | Parameter Description and Implementation Notes |
|---|---|---|
| 500 | 0 | CSCM unique. |
| 501 | TOSFNID | Network identifier. |
| 503 | TOSFCTLR | LU name. |
SNA end stations implement Logical Link Control type 2 (LLC2) when attached to a local-area network (LAN). LLC2 implements the following:
Timers
Sequencing
Error recovery
Windowing
Guaranteed delivery
Guaranteed connection
Figure C-2 illustrates how the T1 reply timer and error recovery operates for a 3174. Assume that the link between the two routers just failed. The following sequence characterizes the error recovery process illustrated in Figure C-2:
The 3174 sends a data frame and starts its T1 timer.
The T1 timer expires after 1.6 seconds.
The 3174 goes into error recovery.
The 3174 sends an LLC request (a receiver ready with the poll bit on), which requests the 3745 to immediately acknowledge this frame.
The 3174 starts its T1 timer.
The T1 timer expires after 1.6 seconds.
This operation is retried a total of seven times. The total elapsed time to disconnect the session is calculated as follows:
The first attempt plus seven retries multiplied by 1.6 seconds:
= 8 × 1.6 seconds
= 12.8 seconds
