Subject: Padding for OSPF packets in the OSPF implementations

From: "Singh, Gurpreet" <[email-masked]>
Date: Wed, 9 Oct 2002 12:18:20 -1000

Hi

OSPF spec RFC 2328 does not allow any padding field for extra bytes for the
OSPF pakcets.

Consider the following situation.

________________________________________________________________________
|   IP Header     |        OSPF Header        |    OSPF Payload
|  Junk bytes |
|                        |                                      |
|                   |
________________________________________________________________________

|-----------------------------------------IP Header
Length-----------------------------------|
                        |-----------------------OSPF Packet Length
---------------------------------|

The IP packet length in the IP header covers the Junk bytes. But the OSPF
header does not.

If such a OSPF packet is received should the implementations accept this
packet as a valid packet or ignore it ?

I know this is a implementation specific question but what would be the
correct implementation according to the protocol specification.

Thanks

Gurpreet

---

From: Acee Lindem <[email-masked]>
Date: Wed, 9 Oct 2002 18:26:57 -0400

Gurpreet,

How does one find the start of the OSPF header if there
are junk bytes between the IPv4 header and the OSPF header?
This doesn't seem valid to me.

On a related topic, I feel packets with padding on the end should
be accepted. This is in the spirit of RFC 1958 suggesting
to be tolerant when accepting and conservative when sending (I believe this
comes from an earliar Jon Postal quote). Note that draft-nguyen-ospf-lls-01.txt
depends on packets with a longer IP length being accepted for backward
compatibility.

--
Acee