byte_t
byte_t cs_this; /* connection id number (xmit) */
byte_t tslot_limit; /* highest transmit slot id (0-l)*/
byte_t rslot_limit; /* highest receive slot id (0-l)*/
byte_t xmit_oldest; /* oldest xmit in ring */
byte_t xmit_current; /* most recent xmit id */
byte_t recv_current; /* most recent rcvd id */
byte_t flags;