Subject: RE : [manet] RREQ aggregation in AODV

From: "HyunWook Cha" <[email-masked]>
Date: Mon, 16 Jun 2003 14:53:25 +0900

Hi He Huang,
I think that 'RREQ aggregation' that you mentioned has one important
issue to be addressed.
As you know, a MANET node replies only once for multiple duplicate RREQs
from same source in the route discovery in AODV.
So, a RREQ for same destination from different source may not be replied
in your scheme, otherwise it should have triggered RREP reply. 
As a result, it can not guarantee that originator of RREQ receives RREP
indicating the shortest path for the destination.
In 'route aggregation', gratuitous RREP should be sent for reverse paths
towards originators of RREQs for same destination. (These RREPs can be
merged into one extended RREP).
I recommend some simulation work for the assessment.
 
Regards,
Hyunwook Cha
ETRI, Korea

---

From: "He Huang" <[email-masked]>
Date: Mon, 16 Jun 2003 07:35:11 -0400

Hi, HyunWook,

See my comment below,

HyunWook Cha wrote:

> Hi He Huang,
>
> I think that `RREQ aggregation' that you mentioned has one important
> issue to be addressed.
>
> As you know, a MANET node replies only once for multiple
> duplicate RREQs from same source in the route discovery in AODV.
>
> Yes, it is true for the same source.
>
>
>
> So, a RREQ for same destination from different source may not be
> replied in your scheme, otherwise it should have triggered RREP
> reply.
>
>
> It is not true. An RREPs will be generated if one RREQ from different
> source is received. See section 6.5 in the draft.
>
>
>
> As a result, it can not guarantee that originator of RREQ receives
> RREP indicating the shortest path for the destination.
>
> In `route aggregation', gratuitous RREP should be sent for reverse
> paths towards originators of RREQs for same destination. (These RREPs
> can be merged into one extended RREP).
>
> If I understand correctly, gratuitous RREP is sent to the destination
> of RREQ from one intermediate node. No change in generating gratuitous
> reply .
> No merged RREP can be assumed at this point.  Anyway, RREQ aggregation
> doesnot affect the existing process of gratuitous RREP.
>
>
>
>
BR

---

From: "HyunWook Cha" <[email-masked]>
Date: Tue, 17 Jun 2003 08:04:09 +0900

Hi He Huang,

I think my explanation in previous mail is not sufficient. 
See my revised comments, below.

Hi, HyunWook, 
See my comment below, 

HyunWook Cha wrote: 
=>Hi He Huang,
=>I think that `RREQ aggregation' that you mentioned has one important
issue to be addressed. 
=>As you know, a MANET node replies only once for multiple duplicate
RREQs from same source in the route discovery in AODV. 

=>So, a RREQ for same destination from different source may not be
replied in your scheme, otherwise it should have triggered RREP reply.  

==>For example, let's assume multiple paths from one source to one
destination can be possilbe in current topology.
The source originates RREQ and then RREQ is forwarded to the destination
or intermediate nodes which knows route for the destination by flooding.
In any case, a MANET node replies only once for duplicate RREQs from the
source. So among multiple paths, only one path which is the shortest
from the source's point of view will be established. In the meanwhile,
another node does route discovery for the same destination. In your
scheme, an intermediate node which receives RREQ from the second source
and already received RREQ from the first source does not forward the
RREQ from the second source. 
Think about this case where this intermediate node is not on the
shortest path from the first source to the destination. Then, RREP from
the destination may not be received by this node. Thus, RREQ from the
first souce as well as the second source may not be replied at this
node. In this case, it is possilble that this node is on the shortest
path from the second source to the destination. If this node has
forwarded RREP from the second source, the second souce should have
received RREP with route information about the shortest path.  

=>As a result, it can not guarantee that originator of RREQ receives
RREP indicating the shortest path for the destination. 
=>In `route aggregation', gratuitous RREP should be sent for reverse
paths towards originators of RREQs for same destination. (These RREPs
can be merged into one extended RREP). 

If I understand correctly, gratuitous RREP is sent to the destination of
RREQ from one intermediate node. No change in generating gratuitous
reply . 
No merged RREP can be assumed at this point.  Anyway, RREQ aggregation
doesnot affect the existing process of gratuitous RREP.

==>I mentioned gratuitous RREP because you had not mentioned it. And I
mean by the extended gratuitous RREP that multiple unicast 
g-RREP towards the same destination(the originator of RREP) can be
merged into just one g-RREP for just optimization.

  
=>I recommend some simulation work for the assessment. 
=>Regards, 
=>Hyunwook Cha 
=>ETRI, Korea 
BR 

Regards,
HyunWook Cha

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---

From: "HyunWook Cha" <[email-masked]>
Date: Mon, 16 Jun 2003 23:17:38 +0900

Hi He Huang,

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] 
Sent: Monday, June 16, 2003 8:35 PM
To: [email-masked]
Cc: [email-masked]
Subject: Re: RE : [manet] RREQ aggregation in AODV

Hi, HyunWook, 

See my comment below, 

HyunWook Cha wrote: 

Hi He Huang,

  

  

For example, let's assume multiple paths from one source to one

In `route aggregation', gratuitous RREP should be sent for reverse paths
towards originators of RREQs for same destination. (These RREPs can be
merged into one extended RREP). 

 
I mentioned gratuitous RREP because you had not mentioned it. And I mean
by the extended gratuitous RREP that multiple unicast 
g-RREP towards the same destination(the originator of RREP) can be
merged into just one g-RREP for just optimization.

Regards, 

Hyunwook Cha 

ETRI, Korea 

BR