- Bronze, 100 points or more
Hi every body!
I hope you guys are doing great. It has been a while since i posted on forum.
I was reading about LLc layer defined by 802.2.
According to my book, LLC provides following functions:
1) multiplexing ( identify data by type)
2) acts as interface between between mac layer and network layer.
3) flow control.
In LLC header, one of the field is control field which is one byte long.
What does this control do? is there any sub field in control field?
Thanks a lot and have a nice weekend!
Just to add to Giuseppe's post.
TCP and UDP work across routed networks. LLC by definition doesn't and can't because it works at L2.
So TCP has it's own flow control and congestion mechanisms for end to end delivery of packets eg. sequence numbers, windiw sizes, acknowledgements etc and it does this by using a connection oriented service.
UDP as you say does not provide a connection oriented service so if the developer of a UDP application wants to guarantee delivery etc. they have to write the code for that in their application.
I agree TCP/IP does not use connection oriented LLC services.
But connection oriented LLC services exist and are used by non IP stacks like Source Route Bridging, IBM networking.
Actually, DLSW+ with TCP encapsulation emulates an end-to-end LLC connection-oriented session to allow transport of non routable connection-oriented protocols over IP networks.
In the banks there are still a lot of routers used for DLSW+ for example.
Also in big enterprises to interface with mainframes there is still some of them.
Hope to help
try again the answer is another one but this is probably the only values to take care of unless you want to know the values used by
STP IEEE 802.1D
(hint: SNAP follows and then eventually IP)
Hope to help
Good to see you back, how is the studying going ?
Rather than me write it all out attached is a link to a Cisco doc on LLC that covers the control field and what it does -