Subject: (NAT) DEMUXING Fragmented packets in RSIP

From: "Krishnan, Ganesh" <[email-masked]>
Date: Mon, 4 Oct 1999 17:53:40 -0700

Hi,

  None of the RSIP drafts currently talk about Demuxing fragmented IP
packets at the RSIP server.
There needs to be a section for this in the RSIP docs.

Points to be noted :

- RSIP port mapping can only be applied to a complete IP packet. Atleast one
needs the first fragment
to apply the port mapping!

- RSIP IP-IP tunnel can only be applied to a complete IP packet (at the
client?).. Seems ok. BITS/BITW
IPSEC implementations have to reassemble/fragment the packets to
apply/un-apply IPSEC anyway!

muxing outgoing fragmented flows - (packets going from inside the RSIP
domain to outside)
-------------------------------------------
   The usual muxing fields for fragmented flows are <src,dst,frag id, proto
field in the IP header>
   Any outgoing IP packet should be muxed based on these fields. 
The source address used here is the non-routable address/local address on
the client (e.g IP-IP tunnel
source address).

  Also, in general, this is useful and a good way of making sure that the
RSIP client indeed is making
use of the allocated ports only! and not something else. This should even be
checked for non-fragmented packets for all parameters cookies, ports (except
SPIs since we use the receiver's SPI on send!)

Demuxing incoming fragmented flows - (outside in)
---------------------------------------------
  Again use the demuxing fields <src,dst,frag id, proto field in the IP
header> fields to demux incoming packets
  
  need to store the fragments on receive until the first fragment arrives
and then forward the flow to the
appropriate client. This is needed since the port/SPI information is only
present in the first fragment.Once
the first fragment arrives, the RSIP server can stop reassembly/queueing and
forward the entire flow
to the client.

Note: - I can be bad and not send u the first fragment at all (so make sure
there are appropriate timeouts!)

- Also better have sufficient reassembly queue sizes for the receive on the
RSIP server side. One can have a frag/reassembly implementation that can
send the fragments in reverse order! and be receiver friendly (since the
last fragment first will tell the receiver how much space to allocate for
the entire packet!).

-
To unsubscribe, email [email-masked]' with
'unsubscribe nat' in the body of the message.

---

From: "Mike Borella" <[email-masked]>
Date: Tue, 5 Oct 1999 09:55:42 -0500

Thanks for the note on this.  Its something that we've taken for
granted that everyone would figure out.  In any case, we'll make
mention of it in an upcoming document.

-Mike

"Krishnan, Ganesh" <[email-masked]> on 10/04/99 07:53:40 PM

Please respond to "Krishnan, Ganesh" <[email-masked]>

Sent by:  "Krishnan, Ganesh" <[email-masked]>

To:   Mike Borella/MW/US/3Com, [email-masked]
cc:
Subject:  (NAT) DEMUXING Fragmented packets in RSIP

Hi,

Points to be noted :

-

-