>Dear group,
>
>I find a confused question on an exam guide which is:
>select the connect-oriented protocols:
>1.ATM
>2.TOKEN RING
>3.FDDI
>4.Ethernet
>5.FrameRelay
>
>anyone can help me select the correct answer?
>
>thanks
>
>dean
I'll try to do as you ask, help you select the answer, rather than
give you the answer.
There is a subtle difference, which most exams don't observe, between
connection orientation and statefulness. In connection orientation,
there is a distinct setup phase, after which the receiver has
awareness of the sender. Resources are committed to that connection.
Stateful communications also describe a situation where the receiver
has prior knowledge of the sender, but don't necessarily have an
explicit setup function and don't necessarily commit resources. In
other words, all connection-oriented communications are stateful, but
not all stateful protocols are connection-oriented.
Which of the protocols you list will work if the sender decides to
send to a receiver that doesn't know about its existence? Hint: ATM
was developed by the telephone industry, and Frame Relay was a
specific ATM access protocol. Can you simply pick up the telephone
and start talking, or must you dial first?
You can just start sending on a LAN. There are a couple of subtle
points that involve Token Ring and FDDI. Ethernet receivers
definitely don't have prior awareness of the sender. Some people
might suggest, however, that a TR or FDDI receiver marking token bits
is connection-oriented, because there is a receiver action.
No, I don't argue that. What I will argue is that TR and FDDI
_senders_ are stateful but not connection-oriented, as they need to
be aware they have sent a frame in order to remove it from the ring.
They also need to maintain state about whether they have or do not
have the token.
Confusing things further, Logical Link Control type 2 (LLC2), which
is most commonly seen over TR, definitely is connection-oriented.
But "token ring" refers to the MAC and PHY protocols, not LLC.
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