Hi Robin, > > Adding ISP uplinks to single-homed edge networks can be very > beneficial. > > But it requires some kind of scheme to make them useful. Currently, > the only way to multihome like this is to get PI space and advertise > it into the DFZ through one ISP or the other. As more and more > end-user networks do this, so we have the routing scaling problem. Multi-homing with PA is possible. See RFC3704 section 4 on suggested solutions. My BRDP Based Routing proposal is an enhancement, it eliminates careful planning and configuration and the need for tunnels.
> > Taking an existing ISP uplink out of service would need more > attention, but > > don't say this is impossible or not cost-effective. Let's say: it > depends. > > More important: it can be decided site by site. > > I haven't been able to understand this clearly, or why you think it a > host-based routing scaling solution could pass either set of > critiques I (and others) have made: > > 1 - It would be impossible to deploy it widely enough (in any > reasonable time frame) that there were such a proportion of > all hosts (such as 95%, 99% or whatever) that the resulting > multihoming would actually be useful to anyone who deployed it - > this is because a host-based solution only works when both > hosts are upgraded. This is especially so if the scheme involves > rewriting applications, as well as host stacks. > > As Brian Carpenter wrote recently: > > It's clear that once you ask for action by application > programmers or non-routine action by end users, the costs > become unthinkable. > > > 2 - As I wrote here: > > Fundamental objections to a host-based scalable routing solution > http://www.irtf.org/pipermail/rrg/2008-November/000233.html > > It would be undesirable to push this functionality out to hosts, > compared to handling it with some new architectural structures > in the network (that is, the routing and addressing system in > the core of the Net and in ISP and end-user networks). I prefer a step-by-step approach. The first step would upgrade edge networks for multi-homing, this enables multi-homing for hosts that can make use of it. In a second step, hosts are updated. It depends on the gain for users how fast a transition takes place. Keep in mind that many end-user hosts use dynamic addresses already (single address, IPv4, lots of NAT). Day-to-day renumbering is no problem at all. Upgrading server farms requires special attention. I would not say servers MUST have static unique addresses, there are examples of hosted servers based on DNS names. For those, multi-homing is not that difficult to implement. I think the subject line has some negative judgment. And I would call it the edge-based solution. Keep in mind that I do not prefer edge-based over core-based. I think they are orthogonal. Teco. _______________________________________________ rrg mailing list [email protected] https://www.irtf.org/mailman/listinfo/rrg
