HP Advanced Communications Controllers (ACC) manual Interface Table

ZCOM Tables and Data Structures

Interface Table

The list headers in this array function identically to ITXLSTA only for the low priority transmit requests. A terminal may be linked to ITXLSTX, ITXLSTA and ITXLSTB all at the same time, if it has express, high, and low priority transmit requests in progress.

IPLIMIT - Port unacknowledged transmit limit (in bytes)

This array contains the limit (in bytes) of all unacknowledged transmit messages to terminals belonging to the same port or subchannel of this interface. This array contains one element, one for each port or subchannel of the Mux card. If the DAM issues a transmit request to the Mux card and the Mux card does not have enough free buffers to hold the request data, the Mux will reject the request with an “out of buffers” error. The DAM will retry the request after an unacknowledged transmit request completes. This field is used to minimize the number of retries (and thereby increase overall performance) by imposing a limit on the size of unacknowledged transmit requests. This array is initialized by TTGEN from the default value hpiplim in the ZCOM header. This value is configured through the Port-Limit or E1T1-Port-Limitparameter in the TTGEN configuration file.

IPBYTES - Port unack TX size (in bytes)

This array is maintained by the DAM and keeps track of the number of 256-byte buffers currently in use by all unacknowledged transmit messages to a port of this interface card. The ipbytes array contains one element for each port/subchannel on the Mux card. The DAM compares the iplimit value for a port with the ipbytes value times 256 to determine whether it should issue a transmit request immediately or wait until a previously issued transmit request completes. The DAM uses this method to predict when the Mux card will reject a request with an “out of buffers” error and can thereby avoid sending a request now which has a high probability of needing to be retransmitted later.

IPENDG_BUFS - Total pending transmit size (in # of buffers)

This field is used internally by the ZCOM drivers.

IPSTAT - Port/Subchannel status

Depending on the card type this interface table is for, this ipstat field either contains the status of each subchannel in a 4-port E1/T1 ACC card, or the status of each port in a non-4-port E1/T1 ACC card (e.g., 2-port card or 8-port ACC card).

The individual ipstat bits are handled as follows:

Chapter 3 89