

At 02:47 19/05/2006, Joe Touch wrote:

>>>Since the attacker needs to guess both ends of the TCP connection
>>>including IP addresses and TCP ports, I am not sure what the benefit
>>>of ICMP payload parsing is in this case.
>>>
>>>I am sure I missed something here.
>>The "benefit" is being a good network citizen. When you perform 
>>egress-filtering, you preventyour own users from performing 
>>ICMP-based attacks against systems that belong to other networks.
>
>What about errors based on loose source routes,

Loose source routes? Does anybody still use this? Or, well, even 
worse, does any body still process this?

>or just misdirected traffic? I.e., how do you know that it's not 
>appropriate to indicate that a host (especially) isn't in your net 
>when asked; that would cause certain ICMPs never to be issued (net 
>unreachable, host unreachable) if they reach a forwarding point in 
>your net that isn't a valid address for your net (which is entirely 
>reasonable).

With the same argument, you could never implement ingress/egress filtering.

Joe, the E in IETF stands for Engineering!

Kindest regards,

--
Fernando Gont
e-mail: [email-masked] || [email-masked]
PGP Fingerprint: 7809 84F5 322E 45C7 F1C9 3945 96EE A9EF D076 FFF1

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02BG-LH
	for [email-masked]; Sat, 20 May 2006 01:24:13 -0400
Date: Sat, 20 May 2006 02:19:00 -0300
To: "Bora Akyol" <[email-masked]>,
	"Templin, Fred L" <[email-masked]>, [email-masked]
From: Fernando Gont <[email-masked]>
Subject: RE: [tcpm] ICMP and TCP
Cc: 

At 18:19 19/05/2006, Bora Akyol wrote:

>The point is that TCP IMHO is powerless to secure ICMP messages.
>By making changes to TCP to declare ICMP errors as soft errors
>depending on the state and ignoring some errors altogether,
>we are trying to create a workaround for a problem with another layer
>in the protocol stack.

Engineering, maybe?

>This is all and well to solve a short term goal, but what is the long
>term answer?

Well, you are probably getting into "architecture" issues.

You would end up asking other questions such as:
Shouldn't multihoming be a network layer thing, rather than a 
transport protocol thing?
Where should we really be doing congestion control?

etc.

Kindest regards,

--
Fernando Gont
e-mail: [email-masked] || [email-masked]
PGP Fingerprint: 7809 84F5 322E 45C7 F1C9 3945 96EE A9EF D076 FFF1

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