[e2e] TCP Loss Differentiation

David P. Reed dpreed at reed.com
Mon Feb 23 17:34:54 PST 2009

The routers don't break.  The routers and middleboxes (by interfering 
with delivery) break communications between endpoints.

They are not supposed to be blocking packets with IP and TCP options, 
for example.  When they do, the rationale is some kind of silly 
paternalistic argument.  But the IP and TCP options are there for a 
reason.  If they are bad ideas, don't block them unilaterally, get the 
IETF to decide that they should be removed from the standard.

The original "firewall" idea was introduced by Bellovin and Cheswick, 
etc. because Unix folks had a bad attitude about security (accept 
traffic on as many ports as possible and don't use secure root passwords).

Detlef Bosau wrote:
> Lars Eggert wrote:
>> On 2009-2-23, at 18:01, David P. Reed wrote:
>>> Is the Internet ecology so broken that good things that are pretty
>>> simple just cannot be deployed at all?
>> Yes, pretty much, if they could end up causing a significant number 
>> of support hotline calls ("Vista broke my router").
> I can't help to quote a common signature in German news:
> "User help desk, good morning, how may I help you?"
> "I installed ***** on my computer."
> "And what's your problem?"
> "My computer doesn't work any more."
> "Thank you, but you already told so...."
> Sorry, but a end point hardly can break a router or "the Internet". 
> (Hopefully....)
> When did Cerf and Kahn deploy IP and TCP? And how many computers are 
> obviously able to work with these? 500 millions? One billion?
> Or even more?
> So, I tend to say: When some device cannot work with the Internet and 
> appears to "break a router", the device is somewhat flawed...

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