What is the difference between SAP and SNAP?

Tricon7

Different books only give me tidbits of information, and none of them give good explanations. I've seen enough practice questions on these to know that I'd better know the difference and what each is before I get ready to take the 801 again.

bighornsheep

If I remember correctly, SAP provides layer 2 access for upper layer (Transport/session/presentation/application) protocol whereas SNAP provides layer 2 access for Network layer.

For example, Port numbers in the TCP/IP protocol uses SAP, but CDP or other layer 1-3 protocols will use SNAP.

rjbarlow

I remember that SNAP part in the 802.3 header would have to have the same purpose of the (Destination)SAP, just it was an expansion of the original DSAP field created to support more layer 3 protocols, it was created 2 bytes long instead 1 byte, think and remember so.