Subject: [NAT] NAT Tables...

From: "Arumugam V" <[email-masked]>
Date: Mon, 6 May 2002 15:07:44 +0530

Hi,

I am Arumugam, new to this NAT area. I'm looking into the lattest draft
version of the NAT MIB.

Can anyone help me to understand the BIND and SESSION tables of the NAT.

1. when the BIND Table entries would be created and how it's different from
Session table.

Your help would be appreciated.

Thanks and Regards,
Arumugam

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From: Rajiv Raghunarayan <[email-masked]>
Date: Mon, 06 May 2002 22:32:40 +0530

Hi Arumugam,

Here's my take on your question:

One could separate NAT into two main classes - NAT and NAPT. The
former works only on an address translation level while the latter
addresses ports as well.

The Address Bind table maintains information about the address-only
binds. Note that in this case there could be more than one session
branched off this BIND (and the loss of a session does not 
necessarily indicate loss of a BIND) i.e. one entry in the address
bind table could map to zero or more entries in the session table.

The Address Port Bind table, on the other hand, maintains info
regarding napt. Typically one bind in this case would translate
to one session, but there could be cases (twice nat) where two
binds would combine to form one session entry.

Further, if you consider a static binds i.e. no timeouts, a bind 
would always exist, but there is no guarantee that there is a
session necessarily associated with the bind at all times.

Hope this answers your query.

-Rajiv.

---

From: Rajiv Raghunarayan <[email-masked]>
Date: Mon, 06 May 2002 22:32:40 +0530

Hi Arumugam,

-Rajiv.

---

From: "Christopher A. Martin" <[email-masked]>
Date: Mon, 06 May 2002 14:14:18 -0500

Comments inline....

-----Original Message-----
From: [email-masked] [mailto:[email-masked]]On Behalf Of Rajiv
Raghunarayan
Sent: Monday, May 06, 2002 12:03 PM
To: [email-masked]
Cc: [email-masked]
Subject: Re: [NAT] NAT Tables...

Hi Arumugam,

---------My comment------
Rajiv, could you calrify, I thought that NAT can work on both the network
and/or transport layer (may use a port other than the originating hosts
source port), whereas NAPT performs mapping totally at the transport layer,
with exception of the single address(es) used for specific NAPT pools. I
agree with your comment above except for my stated assumption, which I think
should be addressed.

Or is the standard for NAT to use the same transport layer address as the
originating host (have not seen this, yet, in draft or RFC format)
----end comment-----------

-Rajiv.

---

From: "Christopher A. Martin" <[email-masked]>
Date: Mon, 06 May 2002 14:14:18 -0500

Comments inline....

-----Original Message-----

Hi Arumugam,

----end comment-----------

-Rajiv.

---

From: Rajiv Raghunarayan <[email-masked]>
Date: Tue, 07 May 2002 15:36:17 +0530

Christopher,

Comments inline..

> originating host (have not seen this, yet, in draft or RFC format)

I guess I should've been more clear. What I meant to say was that
there are two main types of NAT - one which pertains to address
translation (basic NAT in its various forms) and the other including
transport level translation as well.

Yes, by definition NAT covers both covers both address as well as 
transport level translations (section 4.0, RFC 2663).

Thanks for the correction.

-Rajiv.

---

From: Rajiv Raghunarayan <[email-masked]>
Date: Tue, 07 May 2002 15:36:17 +0530

Christopher,

Comments inline..

-Rajiv.