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 3:42 AM
> To: Tom Herbert; Templin, Fred L
> Cc: Xuxiaohu; Donald Eastlake; [e-mail]; [e-mail]; [e-mail];
> [e-mail]
> Subject: Re: [trill] Fwd: Mail regarding draft-ietf-trill-over-ip
> 
> 
> 
> On 5/5/2015 12:34 PM, Joe Touch wrote:
> >> Or just define a simple version translation as part of encapsulation.
> >> > So for IPv8:
> >> >
> >> > 0x1000->0x0101 on encapsulation
> >> > 0x0101->0x1000 on decapsualtion
> > And what happens to 0x0101 WHEN it shows up?
> >
> > You need more patterns than you have because IP is allowed to use any
> > of them.
> 
> FWIW, you're essentially arguing for bit-stuffing, i.e., if a pattern you think will
> be common shows up, don't stuff, and if something else shows up, then do.
> 
> That works only if you do true stuffing, e.g.,:
> 
> 	0x01** = uncompressed
> (might as well add 0x11** and 0x10** to that)
> 	0x00** = compressed
> 
> But then if 0x0000, 0x0001, 0x0010 or 0x0011 show up, you need to decide
> how to represent them - they CANNOT be uncompressed without at least two
> more bits somewhere else that indicates they're uncompressed and their value.
> 
> So now your GUE methods are very sensitive to IP version numbers, which IMO
> defeats the "G" in the name. Never mind how this complicates hardware when

Agree. As I had mentioned to Tom in private, I do believe the additional capability of GUE (e.g., fragmentation) would be much useful in some network environments. However, since GUE is intended to be a generic UDP encapsulation approach, we'd better design it as generic and future-proof as possible from the beginning, specifically speaking, without being deeply influenced by a particular GUE payload type. If both foo-in-GUE (foo could be NSH, TRILL...) and foo-in-UDP (i.e., a compact version of foo-in-GUE) are needed someday, could you still achieve the same effect as that for IP-in-UDP (as a compact IP-in-GUE) and IP-in-GUE?

Best regards,
Xiaohu

> (not if) other IP versions are used (for whatever reason).
> 
> Joe
> 
>