Question on behave-tcp-02 and its implications for STUNbis

> -----Original Message-----
> From: Philip Matthews [mailto:philip_matthewsmagma.ca]

> Sent: Tuesday, November 21, 2006 3:33 PM
> To: Saikat Guha
> Cc: behaveietf.org
> Subject: [BEHAVE] Question on behave-tcp-02 and its 
> implications for STUNbis
> 
> Section 4.1 of behave-tcp-02 talks about the definition
of 
> "endpoint independent mapping" in the case of
TCP.
> The document says:
>        Consider an internal IP address and TCP port
(X) 
> that initiates a
>        TCP connection to an external (Y1:y1) tuple. 
Let the mapping
>        allocated by the NAT for this connection be
(X1'1'). 
Shortly
>        thereafter, the endpoint initiates a connection
from the same
> (X)
>        to an external address (Y2:y2) and gets the
mapping 
> (X2'2')
on the
>        NAT.  As per [BEHAVE-UDP], if (X1'1')
equals 
> (X2'2')
for all
>        values of (Y2:y2) then the NAT is defined to
have "Endpoint
>        Independent Mapping" behavior.
> 
> Say (X)
closes the first connection [to (Y1:y1)] before 
> opening the second connection [to (Y2:y2)]?
> How long must the NAT remember the binding allocated to
the 
> first (now closed) connection in order to be considered
to 
> have "Endpoint Independent Mapping"
> when (X)
opens the second connection?
> Or must (X;x) open the second connection before it
closes the 
> first connection?
> What do existing NATs do today?

The endpoint independent mapping applies only when you have
an active
connection from the same address & port. The time that a
NAT should
remember the mapping info is not defined, as far as I
recall. But in
case of TCP, I would think the FIN/RST would cause the
mapping to be
removed, probably immediately. Existing NATs that I know of
remove the
binding immediately or after a configured timeout to wait
after a
fin/rst.

> 
> This question arose when I was considering the
operation of 
> STUNbis over TCP.
> STUNbis currently says:
>        When using TCP or TLS over TCP, the client
SHOULD
>        close the connection as soon as it has received
the 
> STUN Response, if
>        it has no plans to send further requests.
> If a client opens a TCP connection to a STUN server,
sends a 
> Binding Request and receives a response, can it close
the 
> connection immediately, or does it need to keep the 
> connection open until it finishes establishing at least
one 
> TCP connection with a peer that uses the obtained
mapped address?
> 

If you want an endpoint independent mapping behavior, you
would have to
open the new connection and remove the existing connection.

Senthil
> - Philip
> 
> 
> 
> 
> 
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Question on behave-tcp-02 and its implications for STUNbis

Thread: Question on behave-tcp-02 and its implications for STUNbis