Thank you Tom for your suggestion. Do you think that GUE has some advantages against GTP-U? When it comes to foo over UDP capsulation, does GUE benefit user plane beyond GTP-U?
Best regards, --satoru > 2018/03/27 9:16、Tom Herbert <[email protected]>のメール: > > On Wed, Mar 21, 2018 at 9:27 AM, Sri Gundavelli (sgundave) > <[email protected]> wrote: >> FYI. This is the notes that Carlos captured. Thank you Carlos!! >> >> We are also waiting for Lyle to share his notes. Please review and >> comment, if you see any mistakes. >> > > With regards to SR encapsulation: "this is using IP-in-IP as default. > Why not using UDP encapsulation?" > > There is some rationale for UDP encapsulation here to maximize > compatibility with the network and potentially intermediate nodes like > firewalls. For example, in the performance numbers that Kalyani > posted, the TPS for SR over IPIP routing was lower than other > encapsulations. The reason for this is that the particular NIC (ixgbe) > is not parsing over IPIP or using flow label to get a good hash for > RSS. This is symptomatic of network devices that don't provide as good > support for protocols outside of TCP and UDP. There are likely routers > that would not be able to provide flow specific ECMP for similar > reasons. There was a comment in dmm meeting that ECMP for IPIP was > expected to by solved by using flow label in the hash. This is a great > idea, but unfortunately there is significant resistance to using flow > label for this purpose since it is not guaranteed to be persistent for > a flow and that can cause problems for stateful devices like > firewalls. > > UDP encapsulation is the typical answer to network protocol > compatibility. Several UDP encapsulation techniques have been defined > as well as some foo over UDP to run existing encapsulations over UDP > (e.g. MPLS/UDP, GRE/UDP). draft-ietf-rtgwg-dt-encap gives a nice > overview of considerations for UDP encap protocols. > > If a UDP encapsulation is considered for use with SR, I would suggest > GUE is an option. GUE has some unique features: > > - It's extensible (both common extensions are defined and allows > custom extensions per use case) > - It's generic (can encapsulate any IP protocol) > - It allows directly encapsulating IPv4 and IPv6 in UDP (to minimize > encapsulation overhead) > - It allows encapsulation of extension headers > > The last point may be of particular interest to SR. SR over IPIP might > be more precarious compared to other encapsulations since it > introduces two "atypical" (i.e. not TCP or UDP) protocols. GUE could > be used to normalize SR packets to look like UDP to the network. This > might look something like: > > IP|UDP|GUE|Routing_hdr|IP|payload > > The UDP and GUE header are effectively treated as routing shim at each > segment hop so SR is processed as without regard to the encapsulation. > To intermediate nodes these packets looks like any other UDP packet so > there's no compatibility issue. > > Tom > > _______________________________________________ > dmm mailing list > [email protected] > https://www.ietf.org/mailman/listinfo/dmm _______________________________________________ dmm mailing list [email protected] https://www.ietf.org/mailman/listinfo/dmm
