see also throughput issues
This is a subscription time option which enables the following:
- packet size negotiation
- window size negotiation
- call accept packet extended from 3 bytes to include facilities and addresses.
Increasing the packet size or the window size allows the throughput of a call
to be increased.
Extended format lines must transmit an extended format call accept packet that includes in its format both address and facility fields (can be zero length), must be prepared to receive an extended call connected packet.
