Source routing (network drivers)

Token-ring and FDDI source routing is supported for MDI network drivers running on SVR5 and SCO OpenServer 5. It is implemented in the DLPI module rather than in a separate STREAMS module. The cet, tok, trps, and wwdw drivers provide this capability. The FDDI drivers skfp and dfx can be configured to use source routing although generally source routing is not used on FDDI networks.

The user can disable source routing, thus keeping all traffic confined to the local ring:

1. Run netcfg on SVR5 or netconfig on SCO OpenServer 5 go into Advanced Options.

2. Set the NETxSRSRMODE parameter to 0 (None) rather than the default 1 (Auto).

   This parameter can also be set through the system tuner application but netcfg and netconfig do not display the correct information if you do this.

Additional tunable parameters for source routing can be set in the same way. The full list of tunables is:

SRTXRESP

Timeout for responding to rx, in seconds. This is used with Spanning Tree Explorer frames.

SRRXARE

Window for rejecting more AREs, in seconds. This is used with All Routes Explorer (ARE) frames and Specifically Routed Frames (SRF).

SRRXSTEBCS

Number of Spanning Tree Explorer frames bcs before invalidating the route entry and finding new route. When this number of STE bcs and SRF tx pairs occur, the route is removed and an ARE is sent if AREs are enabled; otherwise, an STE is sent.

SRRXSTEUCS

Number of STE ucs sent before the route entry is invalidated and another route is found. If the count of STE ucs received with no intervening SRFs exceeds this value, the route is dropped.

SRMAXTX

Upper limit, in seconds, for tx ``recur'' window.

SRMINTX

Lower limit, in seconds, for tx ``recur'' window.

SRTXRECUR

Detected ``recurs'' before transmitting an STE . Note that this statistic is incremented only when the event is within the window bounded by the SRMINTX and SRTXRECUR values.

SRAREDISAB

If set to 0 (default), ARE frames are enabled. If set to 1, ARE frames are disabled. Disabling AREs can reduce network utilization.

SRSRMODE

Valid values are:

0

Disable source routing; all traffic is confined to the local ring.

1

(default) The routing information field is automatically interpreted and routing entries and frame headers are set up as needed.

2

The DLS user will manually provide the source routing information.

SRMAXROUTE

Maximum number of routes cached by the source routing subsystem.

The SCO implementation of source routing provides transparent routing even for protocols that are source routing unaware such as SCO's TCP/IP and IPX. It also enables protocol stacks to utilize their own stack-based source routing with an SRMODE_REQ message.