In the discussion of error correction, I think an error on my part has been
missed. I was thinking about it and I wonder if this is entirely accurate:
(concerning what happens after a frame is discarded on WAN link)
"The end station will respond by acking the next packet it recieves with the
appriopriate (lower numbered) sequence number (of the missed packet). The
originating station will
get this ack (with the lower sequence number) see that the end station is
requesting a packet out of sequence and the originating station will begin
it's next transmission with the data from that particular sequence number."
Is this correct?
-----Original Message-----
From: Christopher Larson [mailto:[EMAIL PROTECTED]]
Sent: Thursday, February 08, 2001 3:22 PM
To: 'Jeremy Dumoit'; Brant Stevens; Dennis Laganiere;
[EMAIL PROTECTED]
Subject: RE: not quite sure...
HDLC will not retransmit as there is only error detection in HDLC, but no
error correction. This is the same with Frame-relay. Frame-relay, and HDLC
will detect and discard errored frames but will not retransmit those frames.
They depend on upper layers (like TCP for TCP/IP) to recognize there is a
missing packet and correct that error.
-----Original Message-----
From: Jeremy Dumoit [mailto:[EMAIL PROTECTED]]
Sent: Thursday, February 08, 2001 2:19 PM
To: Brant Stevens; Dennis Laganiere; [EMAIL PROTECTED]
Subject: RE: not quite sure...
I actually think it depends on what encapsulation
is running accross the serial link. If you're using
HDLC then it's a connection oriented, reliable
protocol... meaning if a packet is lost in transit
accross the serial link, the router will knw it when
it receives a response from the destination router.
It'll then resend the frame. If you're using a
datagram protocol, like ppp, however, it will rely on
the upper layer protocols to detect missing data..
--- Brant Stevens <[EMAIL PROTECTED]> wrote:
> The question is if Router B and Router C are
> routing, or if they are
> bridging... If they are routing, then Router B
> would re-transmit a packet.
> If bridging is happening, then Host A would
> retransmit...
>
> Hope this helps...
>
> Brant I. Stevens
> Internetwork Solutions Engineer
> Thrupoint, Inc.
> 545 Fifth Avenue, 14th Floor
> New York, NY. 10017
> 646-562-6540
>
> -----Original Message-----
> From: [EMAIL PROTECTED]
> [mailto:[EMAIL PROTECTED]]On Behalf Of
> Dennis Laganiere
> Sent: Wednesday, February 07, 2001 11:32 PM
> To: '[EMAIL PROTECTED]'
> Subject: not quite sure...
>
>
> I've tried to diagram this question to make it
> clear...
>
> Host A is sending to Host D...
>
> A line error occurs on the serial link between
> Router-B and Router-C while
> passing a packet from Host-A to Host-B
>
> Devices - Host A---------ROUTER B---------ROUTER
> C--------HOST D
> Interfaces - (A1) (B1) (B2) (C1)
> (C2) (D1)
>
> What device would rebroadcast?
>
> I think that router-B (port B2) would realize an
> error had occured, and
> would resend, so the answer should be port B2, but
> I've been through all my
> books and can't find anything to confirm or deny my
> conclusion...
>
> Any thoughts?
>
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