CL: yes you did, PO, and therefore you are entitled to ask the rest of us
>how we ever got such and such a certification without knowing this ;->
>Still wondering how many CCIE's are unable to duplicate your feat. :->
Many CCIEs can't tell you what's in an IP or TCP header and I find this
shocking. Knowing the order of fields in the header and the offsets is not
important. Knowing which fields are in the headers and what they do is
important.
We're probably all sick of analogies, but here goes anyway. I worked in the
shipping industry for a couple years many years ago (on automated cranes).
Usually it didn't matter one hoot what was being sent in the containers. We
just got the containers from one medium to another - boat, train, truck,
etc. - without any concern about the contents. But sometimes the contents
really mattered. When designing and troubleshooting the system, in
particular, we needed to know if the contents might blow up under some
conditions, might perish due to lack of refrigeration, might need to be
divided up for transport on smaller trucks, might require acknowledgement
of receipt, etc.
Ok, nuff said.
Priscilla
>At 03:59 AM 8/20/00, Derek CHUNG wrote:
> >Is a TCP packet (layer 4) encapsulated by a IP packet (layer 3) which is
> >inside a Layer 2 frame?
> >If so, why the headers of a IP packet and TCP packet look so similar and
> >redundant?
> >
>CL: I also believe that this premise remains untrue. While both IP and TCP
>headers are normally 20 bytes, I see very little else in common, as
>befitting the very different functions they perform. TCP has more
>reliability functions built in - acknowledgement, windowing, etc. whereas IP
>is more oriented towards best effort delivery across an internet.
> >___________________________________
><<snip>>
>
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Priscilla Oppenheimer
http://www.priscilla.com
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