Re: RTP under EIGRP

No...you see the first router just sends an mcast. There is no seq # involved there. When the recv gets the packen THEN it unicasts back with the seq #, etc

Regards,

Joe Astorino CCIE #24347 (R&S)
Sr. Technical Instructor - IPexpert
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-----Original Message-----
From: Charles.Henson_at_Regions.com
Date: Tue, 9 Feb 2010 09:43:35
To: <jastorino_at_ipexpert.com>
Cc: CCIE Groupstudy<ccielab_at_groupstudy.com>
Subject: Re: RTP under EIGRP

Thanks Joe. But the sending router continues to MCast. So he sends his
first MCast with only a source seq number? And then he gets an ACK with a
seq number from router B and an ACK with a seq number from router B. So he
has a seq number from both downstream routers. Yet he still sends MCast and
not unicast so which sequence number does he plug in along with his own so
the downstream router(s) know it's a reliable transmission and nothing has
been missed? Or does he send out two MCasts (redundant) to the network?
That's what I'm confused on....

Charles Henson

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They are two separate streams. Think about it like TCP SYN/ACK. The sending
router keeps track of thing with multiple recipients and has multiple sets
of seq numbers

------Original Message------
From: Charles.Henson_at_regions.com
Sender: nobody_at_groupstudy.com
To: CCIE Groupstudy
ReplyTo: Charles.Henson_at_regions.com
Subject: RTP under EIGRP
Sent: Feb 9, 2010 10:31 AM

I may be reading too much into this. Reading the Doyle books for fun.
Routing TCP/IP Vol 1 Second Edition:

####################################################################################################################

Page 264 Operation of EIGRP
Reliable Transport Protocol
The Reliable Transport Protocol (RTP) manages the delivery and reception of
EIGRP
packets. Reliable delivery means that delivery is guaranteed and that
packets will be
delivered in order.
Guaranteed delivery is accomplished by means of a Cisco-proprietary
algorithm known as
reliable multicast, using the reserved class D address 224.0.0.10. Each
neighbor receiving
a reliably multicast packet unicasts an acknowledgment.
Ordered delivery is ensured by including two sequence numbers in the
packet. Each packet
includes a sequence number assigned by the sending router. This sequence
number is
incremented by one each time the router sends a new packet. In addition,
the sending router
places in the packet the sequence number of the last packet received from
the destination
router.
####################################################################################################################

If I have a segment with three routers on it and Router A sends an MCast to
router B and C, then he should get an acknowledgement back from both. That
makes sense. But then it says that Router A sends his own sequence number
as well as the sequence number from the destination router to guarantee
delivery. If there are multiple receiving routers (hence using multicast in
the first place) then how is router A using a sequence number of a
destination router to guarantee delivery. His own sequence number I
understand. But the downstream router?

Any help would be appreciated.

Charles Henson

Blogs and organic groups at http://www.ccie.net
Received on Tue Feb 09 2010 - 15:48:58 ART