At 04:58 PM 4/14/01, Up_and_Up wrote:
>Hi All,
>
>HostA----------Router1-----------Router2-----------HostB
> Ether Serial Ether
>
>If a packet is sent from HostA to HostB and the packet is lost between R1
>and R2 - who resends?
>
>I've seen this question before and thought the generally agreed upon answer
>was that Host A would resend with the reason being "The data-link layer
>protocols in use today on serial lines, including PPP, Frame Relay, and
>Cisco HDLC, detect errors but are not responsible for error correction or
>retransmission."
Yes, that's the agreed-upon answer and the best way to think about it. What
you say is usually true. There are some exceptions, for example, if Router
1 and 2 were running X.25. X.25 does retransmit.
I skimmed the cram session. It looks pretty good, but be sure to use
something more than this to study. (I'm sure you know that.) The cram
session has the usual misconceptions, such as claiming that SRB and SRT are
in 802.5, which they aren't, and that HSRP is a routing protocol that is
standing by, (it's a router standing by), and AppleTalk is "chatty."
Then it has a few unique misconceptions like the one you asked about, and
the overuse of the term "broadcast," and the indication that SNA is
non-routable because it existed before WANs, and the following really awful
statement:
"TCP and LLC Type 2 are reliable protocols because they are layer four
protocols
IP, UDP, and Frame Relay are NOT reliable protocols because they are layer
three protocols."
But the CCIE wouldn't be worth the paper it's written on if you could pass
by reading one over-simplified document! ;-) As long as you are studying
with other materials also, I think the cram session is a nice wrap-up of
what you need to know, and if you know your stuff, you'll recognize the
misconceptions.
Priscilla
>The reason I post this is I have found a contradictoring document and wanted
>some 2nd and 3rd opinions. The document in questions is the cramsession
>from BrainBuzz.com at the link:
>
>http://cramsession.brainbuzz.com/cramsession/cisco/ccie_written/
>
>The statement in question is at the top of Page 13. It states the the
>packet would be resent (actually rebroadcast) from Router B.
>
>I'm not using this guide to learn from as much to reinforce what I have
>learned and this statement is bringing up an old question.
>
>Thanks to all who answer,
>Sean
>FAQ, list archives, and subscription info:
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________________________
Priscilla Oppenheimer
http://www.priscilla.com
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