🚀 go-pugleaf

> 
> 
> Mark,
> 
> Re : 802.2 Type 2 operation
> 
> 802.2 offers you Type 1 or Type 2 operation. Type 1 is pure datagram stuff with
> the ARPANET's "take your chance" approach while Type 2 goes the other extreme
> and do both flow control and error recovery. 
> 
> The general idea is that if you are going for a heavy weight Tranpsort Layer
> already such as TCP or TP-4, you should leave every thing to that layer and
> chose Type 1. If you are going to use light weight Tranpsort layer such as TP-0,
> then Type 2 is for you. (Interestingly, IBM is using Type 2 since under SNA,
> the link layer is the only level that will do error recovery). 
> 
> Hence unless we can get IEEE802.2 to create a Type 1.5, we don't think it is
> worth our while to spend the cycles required for Type 2. (Actually, having a
> Type 1.5 that will do low level acknowlegement but without flow control and
> error recovery procedure may be quite useful - particularly for network level
> gateway machines).
> 
> Leong

Your type "1.5" service is a proposed addendum to 802.2, called acknowledged
connectionless service. This service, actually called Type 3 service is a
"send one frame, receive one acknowledgement" service. If you are interested in
the details, the service is specified in ISA-S72.01-1985, the PROWAY Industrial
Data Highway standard from the Instrument Society of America. The goal was
to provide for reliable data transfer without the overhead of a connection
oriented service for real time, process control networks.
This service works best over a 802.4 token bus by the way,the "real time
extentions" in that standard are meant to support this service.
--jay

ihnp4!rosevax!jay