hi koojana
thanks for ur reply and time...
>2. The RFC says: "Once created,
the RREP is unicast to the next hop toward the originator of the RREQ, as
>indicated by the route table entry for that originator. As the RREP is
forwarded back towards the node >>>>which originated the RREQ
message, the Hop Count field is incremented by one at each hop. Thus, when
>>>the RREP reaches the originator, the Hop Count represents the
distance, in hops, of the destination from >the originator." Is the Hop
Count field in the RREP not supposed to contain the number of hops from
the >>>source to the destination, rather than from the
destination to the source ?
Why do you think this way? Anyway, Hop
counts from source to the destination is known while processing the
RREQ.
Section 5.2 of the RFC: the Hop Count field in the RREP is
supposed to contain "The number of hops from the Originator IP Address to
the Destination IP Address.".
Section 6.6 (also quoted above as Point 2): "Thus, when the RREP
reaches the originator, the Hop Count represents the distance, in hops, of
the destination from the originator."
Are these two statements not mutually contradictory ? This is because
the processing of the RREP (as mentioned in Section 6.6 and quoted above)
seems to be such that the Hop Count field of the RREP, when it
will finally reach the Originator, will contain the number of hops from
the Destination to the Originator, and not vice-versa. This is in
direct contradiction with what is specified about the Hop Count
field in the format of the RREP in Section 5.2.
Also, as you rightly said, when a RREQ reaches the node which issues
the RREP (whether the final Destination or an intermediate node), its Hop
Count field contains the number of hops from the Originator to the
Destination. This is precisely the information that the Source (and not
the Destination) needs, so as to enter it in the Hop Count field
of its Route Entry for the particular Destination. However, if the
RREP contains the number of hops from the Destination to the Source (and
not vice-versa), the Originator will never learn of this information. This
is why I think that the Hop Count field of the RREP MUST contain the
number of hops from the Originator to the Destination, and not vice-versa.
Please correct me if I am wrong with this.
thanks for ur time
varnit
----- Original Message -----
Sent: Monday, July 12,
2004 1:01 PM
Subject: RE: [manet]
RREP generation in AODV
Hi Varnit,
>This is a query regarding
the RREP generation in AODV, from Section 6.6 of its Internet Draft,
>RFC 3561. >1. The RFC says: "When generating a RREP message, a
node copies the Destination IP >>Address and the Originator
Sequence Number from the RREQ message into the corresponding fields
>in the RREP message."
>To which field in the RREP
does the Originator Sequence Number from the RREQ go ? There is
only >Destination Sequence Number field in the RREP.
This was discussed in the ML.
This should read Orginator IP address instead of orginator Sequence
number.
>2. The RFC says: "Once created,
the RREP is unicast to the next hop toward the originator of the RREQ,
as >indicated by the route table entry for that originator. As the
RREP is forwarded back towards the node >>>>which originated
the RREQ message, the Hop Count field is incremented by one at each hop.
Thus, when >>>the RREP reaches the originator, the Hop Count
represents the distance, in hops, of the destination from >the
originator." Is the Hop Count field in the RREP not supposed to contain
the number of hops from the >>>source to the destination,
rather than from the destination to the source ?
Why do you think this way? Anyway,
Hop counts from source to the destination is known while processing the
RREQ.
>3. The RREP is supposed to be
Route Reply, ie it is supposed to carry routing information that the
source >can use to send packets to the destibation. However it does
not have any field that tells the source about >such a route or the
next-hop it should choose for a route to the destination. Is it that the
source will >>simply take the node from which it first received
the RREP as the next-hop for a route to the destination
>?
When propagating RREQ, each
node creates (source and intermediate) the route towards the source.
AODV works to find a minimum hops path between the S (Source) and D
(Destination). Therefore, D will only process the RREQ with minimum hops
in case if it gets more than one RREQs for an unique discovery. Then D
will send RREP over this minimum hops paths that are found during the
route discovery process. When receiving RREP over minimum hops path, S
will create a route towards the D over this path via next hop. In this
way, RREP does not require any other fields. What you asked is needed
for DSR (I guess).
Regards
Koojana
Koojana Kuladinithi BSc, MSc
University of Bremen, FB 1 -
IKOM/ComNets
Otto-Hahn-Allee NW 1,
28359 Bremen - Germany
Tel.: +49
421 218 8264, Fax: +49 421 218 3601,
Email: koo at comnets.uni-bremen.de
WWW: http://www.comnets.uni-bremen.de/~koo