Re: [tcpm] WG Last Call for ICMP Attacks

[Carlos Pignataro <cpignata at cisco.com>]

On 9/9/2009 11:00 AM, Joe Touch wrote:
> 
> 
> Carlos Pignataro wrote:
> ...
>> The document says the following; would s/discarded/discarded or delayed/
>> cover it?
> 
>>    It is important to note that ICMP error messages are unreliable, and
>>    may be discarded due to data corruption, network congestion or rate-
>>    limiting.  Thus, while they provide useful information, upper layer
>>    protocols cannot depend on ICMP for correct operation.
> 
> That would help there, but it is also useful in other places to indicate
> what happens when a legitimate ICMP is delayed, i.e., how that affects
> what your algorithm would do.
> 
> It's OK to qualify it with "this is unlikely", but IMO it needs to be
> discussed with more than a single word in a single paragraph.

I think that "this is unlikely" or "this is highly unlikely" would still
be understating the probability (I am curious to see any experienced
example of ICMP being delayed minutes). Redundancy architectures of
routers typically cover the planned upgrade (or even unexpected reload)
scenarios you presented.

Perhaps a separate sentence in that paragraph before the "Thus, " with
some variation of "rate-limiting can delay ICMPs, and some other highly
unlikely theoretical scenarios can compound the delay"?

Thanks,

-- Carlos.

> 
> Joe