Subject: [manet] Doubtful areas in RFC 3561

From: "Koojana Kuladinithi" <[email-masked]>
Date: Mon, 4 Aug 2003 09:48:13 +0200

Hi Charlie, Elizabeth & Samir

We are working at implementing RFC 3561. Following paragraphs of RFC 3561
seem to be confusing. 

I would appreciate if you can have a look and give us your feedback.

---------------------------------
6.5 Processing & forwarding Route Requests

Second paragraph says 
"First, it first increments the hop count value in the RREQ by one,
   to account for the new hop through the intermediate node."

Later paragraph (3rd) says

"If a node does not generate a RREP (following the processing rules in
   section 6.6), and if the incoming IP header has TTL larger than 1,
   the node updates and broadcasts the RREQ to address 255.255.255.255
   on each of its configured interfaces (see section 6.14).  To update
   the RREQ, the TTL or hop limit field in the outgoing IP header
   is decreased by one, and the Hop Count field in the RREQ message
   is incremented by one, to account for the new hop through the
   intermediate node."

According to above explanations, hop count in RREQ is incremented 2 times 
by an intermediate node before broadcasting. Isn't this incorrect?

---------------------------------------

6.6 Generating Route Replies

"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."

There is no field in RREP to put Originator Sequence Number from the RREQ

--------------------------------------------------

6.6.1 Route Reply Generation by the Destination

"If the generating node is the destination itself, it MUST increment
   its own sequence number by one if the sequence number in the
   RREQ packet is equal to that incremented value.  Otherwise, the
   destination does not change its sequence number before generating
   the RREP message."

But, 6.1 says that destination node increments its own sequence number,

"   -  Immediately before a destination node originates a RREP in
       response to a RREQ, it MUST update its own sequence number to
       the maximum of its current sequence number and the destination
       sequence number in the RREQ packet."

These two statements seem contradictory.  For example, if RREQ has 
seq = 20 & Destination node has seq = 22.  

6.6.1 says that destination node should not increment its seq number

6.1 says that destination node should increment its seq number to 23

What is correct?
--------------------------------

Thanks in advance

Kind regards

Koojana

University of Bremen
FB 1 – IKOM/ComNets
Koojana Kuladinithi BSc, MSc
Otto-Hahn-Allee NW 1
28359 Bremen - Germany

Tel.: +49 421 218 8264, Fax: +49 421 218 3601, Mobile: +49 160 2690070
Email: [email-masked]  
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From: Ian Chakeres <[email-masked]>
Date: Mon, 4 Aug 2003 08:41:42 -0700

I'll do my best to answer your questions in-line.

We'll incorporate these changes into the next draft.

Ian Chakeres

>Koojana Kuladinithi wrote:

Hop count should only be incremented once.  

This should read Originator IP Address instead of Originator Sequence
Number.

This was discussed on the list recently.  It should read:

   - Immediately before a destination node issues a route reply in
     response to a RREQ, it MUST update its own sequence number to the
     maximum of its current sequence number and the destination
     sequence number in the RREQ packet plus one (1).

>Email: [email-masked],A (B 
>,A         (B [email-masked] 
>,A (B
>
>
>

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From: "Koojana Kuladinithi" <[email-masked]>
Date: Tue, 5 Aug 2003 11:38:11 +0200

Hi Ian,

Thanks and still to clarify the following.

>      sequence number in the RREQ packet plus one (1).

Even with this new text, I am not certain that I still can figure this 
out.  From this para, I can see 2 possibilities of updating the destination
sequence number,

1. ( Max ( current seq, RREQ seq )  )  +  1

2. Max ( current seq, ( RREQ seq + 1 )  )

What is right?

Kind regards
Koojana

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From: Ian Chakeres <[email-masked]>
Date: Tue, 5 Aug 2003 07:04:20 -0700

Number 2 is correct.  
Ian Chakeres

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From: "Koojana Kuladinithi" <[email-masked]>
Date: Wed, 6 Aug 2003 09:07:54 +0200

Hi Ian

> >>      sequence number in the RREQ packet plus one (1).

According to the new modification in section 6.1 (as mentioned above),
Destination sequence is updated as follows.

Seq num		Dest. Seq		new Dest. Seq
in RREQ     
  22				21			23
  21				21			22
  20				21			21
  19				21			21

But, in section 6.6.1 says,		

Shouldn't the above paragraph (for section 6.6.1) now be written as follows
(or similar manner)?

"If the generating node is the destination itself, it MUST update
its own sequence number to the sequence number in the RREQ packet plus one
(1), if the sequence number in the RREQ packet is greater than or equal to
the nodes own sequence number. Otherwise, the destination does not change 
its sequence number before generating the RREP message."

Kind regards

Koojana

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From: Ian Chakeres <[email-masked]>
Date: Wed, 6 Aug 2003 07:07:35 -0700

Both will be updated to read the same.

Ian Chakeres