>Hi,
> Does anyone have a link for a definitive comparison
>between cnnection oriented versus connectionless WAN
>Protocols ?
>
>e.g SDLC, HDLC, HDLC (Cisco), LAPB, PPP.
>
>I realise that SDLC, HDLC, LAPB, PPP are all in effect
>the same frame format and I´m thinking they should all
>be connectionless allowing higher level protocols like
>TCP to provide the reliability.
If I read between the lines above, it sounds as if you believe
transport should always provide the reliability. Why? Why not?
Are there legitimate applications for unreliable transport and for
reliable data links?
>
>I have some confusion though with the similarity with
>IEEE 802.2, i.e I´ve read that PPP contains a control
>field of 03 making it connectionless.
There are additional cases of 802.2. Class 1 is indeed
connectionless and unreliable. Class 2, which essentially is SDLC
over LAN, is connection-oriented and reliable.
Additionally, the Manufacturing Automation Protocol suite has a
variant, 802.2 class 3, which is connectionless but reliable (i.e.,
acknowledged datagram). This is a very special application intended
for real-time robot control, an application in which it would make no
sense to route the traffic.
>
>However, if an application used 02 in the control
>field it could presumably be connection orientated.
>i.e it has the ability to support both.
Yes, it could be connection-oriented. But what limitations would
there be on windowing, given the current frame format?
>
>Any thoughts ?
>
>Regards,
>
>Phil.
_
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