On Fri, Jan 23, 2015 at 10:12 AM, Nicholas Weaver
<[email protected]> wrote:
>
>> On Jan 23, 2015, at 10:01 AM, Paul Hoffman <[email protected]> wrote:
>>
>> What is the problem with #2? IP fragmentation happens, and The Internet is 
>> expected to work with it. That is, of what possible value is "inform their 
>> customers"?
>
> The Internet has unfortunately decreed that Fragmentation Does Not Work with 
> IPv4, and Really Does Not Work with IPv6.
>
> This will cause timeouts until the resolver realizes it should use a smaller 
> EDNS0 MTU and in that case, the resolver will failover to TCP for that query, 
> which some in the DNS community view as anathema...
>

Besides the additional latency caused by loss recovery, as Nicholas
said, fragments may also bring problem of fragmentation attack
described in:
A. Herzberg and H. Shulmanz. Fragmentation considered poisonous. In
Proc. of IEEE Conference on Communications and NetworkSecurity (CNS),
Oct. 2013.

-Liang Zhu

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