IPv6 Multi-homing (was IPv6 /64 links)

Douglas Otis dotis at mail-abuse.org
Wed Jun 27 01:15:31 UTC 2012


On 6/25/12 10:33 PM, Mikael Abrahamsson wrote:
> On Mon, 25 Jun 2012, Cameron Byrne wrote:
> 
>> SCTP is coming along, and it has a lot of promise.
> 
> Doesn't SCTP "suffer" from the same problem as SHIM6 was said to be
> suffering from, ie that now all of a sudden end systems control where
> packets go and there is going to be a bunch of people on this list
> complaining that they no longer can do "traffic engineering"?

Dear Mikael,

SCTP permits multiple provider support of specific hosts where instant
fail-over is needed.  When DNS returns multiple IP addresses, an
application calls sctp_connectx() with this list combined into an
association endpoint belonging to a single host.  This eliminates a need
for PI addresses and related router table growth when high availability
service becomes popular.

Rather than having multi-homing implemented at the router, SCTP
fail-over does not require 20 second delays nor will fail-over cause a
sizable shift in traffic that might introduce other instabilities.
Although not all details related to multi-homing remain hidden, SCTP
offers several significant advantages related to performance and
reliability.

SCTP can isolate applications over fewer ports.  Unlike TCP, SCTP can
combine thousands of independent streams into a single association and
port.  SCTP offers faster setup and can eliminate head-of-queue blocking
and the associated buffering involved.  SCTP also compensates for
reduced Ethernet error detection rates when Jumbo frames are used.

Providers able to control multiple routers will likely prefer router
based methods.  A router approach will not always offer a superior
solution nor will it limit router table growth, but traffic engineering
should remain feasible when SCTP is used instead.

> I don't mind. I wish more would use SCTP so it would get wider use. I
> also wish <http://mosh.mit.edu/> would have used SCTP instead of trying
> to invent that part again (the transport part of it at least).

Perhaps MIT could have implemented SCTP over UDP as a starting point.
An adoption impediment has been desktop OS vendors.  This may change
once SCTP's advantages become increasingly apparent with the rise of
data rates and desires for greater resiliency and security.

Regards,
Douglas Otis












More information about the NANOG mailing list