15 Aug
2013
15 Aug
'13
12:01 p.m.
On Thu, Aug 15, 2013 at 10:59:55AM -0400, Charles Hargrove wrote:
No least cost path routing for IP like MX records?
No, because of a fundamental difference. The SMTP protocol is a
higher-level one which uses TCP connections which of course have a status
of succeeded or not, so if a connection specified by an MX record does
not succeed (is refused, etc) the mailer can try an alternate.
IP is much lower level and has no such status: packets are not
acknowledged at the IP level so there may be no notification that a packet
has not reached its destination. There is no way at the IP level to
tell that a particular route isn't working and to therefore try another.
There are proposed mechanisms to allow a choice of routes (RSPF, OSPF,
etc), but none of them have been implemented on AMPRNet and the existing
encap scheme doesn't allow for them (yet).
- Brian