PPPoA w/ Compression Service Adapter

[msuter]

Have 7206/NPE225 (recent 12.3-mainline) w/ a SA-COMP/4 compression card and PA-IMA-8T1 ATM card.

Using aal5snap and ppp virtual templates to achieve PPPoA, with compression enabled in the virtual templates.

The PPPoA virtual interfaces won't do hardware compression (only software - as told by "show compress"), but the other PPP interfaces (ISDN) do.

I can't seem to dig up any information on why this might be the case.

Any suggestions/thoughts?

Thanks!

[carenas123]

The reason for the limitation is that PPP compression is not stateless and maintains a compression history over the data stream to optimize the compression ratios. The compressed packets must be kept in order to maintain compression history. If packets are compressed before queueing, they must be put in a single queue. Putting them in different queues, as custom and priority queueing do, may lead to the packets arriving out of sequence, which breaks compression. Alternative solutions are sub-optimal and have not been implemented.