Re: [trill] Fwd: Mail regarding draft-ietf-trill-over-ip

[Xuxiaohu <[e-mail]>]

> -----Original Message-----
> From: Joe Touch [mailto:[e-mail]]
> Sent: Wednesday, May 06, 2015 12:33 AM
> To: Xuxiaohu; Donald Eastlake; [e-mail]
> Cc: [e-mail]; [e-mail]; [e-mail]
> Subject: Re: [trill] Fwd: Mail regarding draft-ietf-trill-over-ip
> 
> 
> 
> On 5/4/2015 7:23 PM, Xuxiaohu wrote:
> > In a word, IP-in-UDP is just intended for those network environments
> > where fragmentation on the tunnel layer and strong checksums are not
> > desired.
> 
> That's insufficient. They are only applicable where fragmentation and a strong
> checksum are not *needed*.

Agree that "needed" is a more appropriate word.

> Once you run IP in IP (IP in UDP in IP qualifies as this), you have only two
> choices:
> 
> 	- support fragmentation
> 
> 	- use in networks that are engineered so that
> 	fragmentation is never needed
> 
> As to the strong checksum, similarly you have to either support one or deploy
> the result where that checksum isn't needed - either because you know that all
> apps will have strong enough checksums of their own or because you know
> enough about the kinds of errors that will occur that strong checksums aren't
> needed.
> 
> But the key there is to define a use case where these properties are true AND to
> limit the document solution to uses in those case ONLY.

The use case is the Softwire networks (including both mesh and hub-spoke modes) where IP-in-IP and IP-in-GRE are good enough to address the MTU and checksum issues.

Best regards,
Xiaohu

> > For those network environments where fragmentation on the tunnel layer
> > and stronger checksums are required, GUE should be considered instead.
> 
> Agreed.
> 
> Joe