On Thu, May 25, 2017 at 12:44 PM, Templin, Fred L <[email protected]> wrote: > If you are talking about the GUE direct encapsulation of IPv4 and IPv6, I > agree > > with the current spec and that direct encapsulation (i.e., with no > additional > > encapsulations between the IP/UDP and inner IP headers) is desirable and > > should remain as part of the spec. I think we may be over-thinking this. > +1. I think a little too much has been inferred beyond the what is actually in draft. Versions are straightforward:
- There is a two bit version number field that begins GUE header. The format of the rest of the header depends on the version. - Version 0 defines an encapsulation header that encapsulates by IP protocol number. - Version 1 defined a means for direct encapsulation of select protocols as an optimization. Formats for IPv4 and IPv6 are defined. - Version 2 and 3 are reserved Rather Version 1 constitutes a new version or a different format seems to be a matter of terminology, however semantically and implementation wise the intent is clear. If it's necessary the field could be renamed "version/format" Tom > > > Fred > > > > From: Int-area [mailto:[email protected]] On Behalf Of Joe Touch > Sent: Thursday, May 25, 2017 12:08 PM > To: Tom Herbert <[email protected]> > Cc: [email protected] > Subject: Re: [Int-area] 答复: 答复: 答复: 答复: Is the UDP destination port number > resource running out?// re: I-D Action: draft-ietf-intarea-gue-04.txt > > > > > > > > On 5/25/2017 11:47 AM, Tom Herbert wrote: > > You can't put bare Ethernet inside GUE. You need to use EtherIP - > > exactly because it has a 16-bit field, of which only the first 4 bits > > are (already) defined. > > > > My point is that EtherIP burns 16 bits vs bare Ethernet, but those 16 > > bits allow it to be mapped to one of the IP versions (you picked IPv5). > > The same trick works for UDP and TCP - just pick a different 16 bit > > pattern for each one. > > > > Inserting two bytes before the TCP header breaks four byte alignment > > of the header which is a bigger hit than the benefit of saving two > > bytes. A nice side effect of the two byte header in EtherIP is that it > > aligns the Ethernet payload (e.g. an IP header) to four bytes. > > Maintaining this four byte alignment is still important to some CPU > > architectures most notably Sparc, but can even be problematic to x86 > > under certain circumstances. > > > > Tom > > Sure - I'm not sure the 4-byte penalty is worth avoiding any nearly any > case, frankly -- even for IP. > > Joe _______________________________________________ Int-area mailing list [email protected] https://www.ietf.org/mailman/listinfo/int-area
