Re: [Int-area] draft-bonica-intarea-frag-fragile-01

[Joe Touch <[e-mail]>]

> On May 31, 2018, at 12:07 PM, Ron Bonica <[e-mail]> wrote:
> 
> Joe,
> 
> draft-ietf-tsvwg-udp-options is exactly the kind of work that the current draft encourages. If IP fragmentation is fragile, it makes sense for upper-layer protocols to manage fragmentation/mtu issues on their own, without relying on IP fragmentation.

I disagree.

UDP fragmentation has its benefits and uses, but should not be required when a transport layer isn’t needed - e.g., for IP tunneling.

Fundamentally, IP fragmentation is fragile for only a few reasons:
1) the ID space is small (which shouldn’t matter unless there is a very large amount of reordering)
2) loss of fragments creates inefficiencies (true, but routers can fate-share fragments they drop sometimes, just as was eventually done for ATM AAL5)
3) in-network devices can’t find transport ports in some fragments, causing problems for NATs, policy filters and firewalls, etc.

Of these, my view is that #3 is the only reason actually driving a claim of fragility - and all it tells me is that “the Internet is fragile when devices don’t follow the rules”.

I do not think it is appropriate to validate that conclusion.

Joe