Leo is exactly right. The real reasons that folks multihome are: 1) Backbone and/or routing instability striking one upstream provider 2) Local loop/fiber cuts That's pretty much it. Although there might be a small element of fear that a provider might go out of business, there is normally plenty of notice that a provider is going down, provided you are using a reputable business ISP and service, as opposed to DSL. I don't think multhoming needs to be limited, currently. The size of the routing table is increasing at a more or less linear rate, now. Even at a higher than linear rate, modern core routers used by most carriers (i.e. Juniper M-series and Cisco GSRs) can certainly handle a much large routing table, even in base configurations, with no memory upgrades. The number of routing updates is certainly not taxing router CPUs, either. We may run into scalability problems with the algorithm at some point, but it hasn't hit us yet. And, for now, CPU speed has been growing faster than the processing requirements of the table. The fact is, bandwidth is really cheap now. It is a "best practice" to have multiple providers of any resource that has a long lead-in time and that some or all of your business functions are dependant on. This article in NW is part of a distressing genre of similar skreeds, which have themes like "we are running out of IP address space, and must switch to IPv6, right now" or "the routing table is too big and the internet will melt down tomorrow". These articles appear in places like NW, Boardwatch, and Interactive Week. A greybeard from IETF is almost always trotted out as part of these tabloid-esqe little dramas. The uninformed and the semi-informed have a moment (or longer) of panic, then resume their lives, occasionally internalizing the misinformation. Multihoming is good for almost everyone who needs it, and NW writers need to do better research. - Daniel Golding -----Original Message----- From: owner-nanog@merit.edu [mailto:owner-nanog@merit.edu]On Behalf Of Leo Bicknell Sent: Thursday, August 23, 2001 6:33 PM To: 'nanog@merit.edu' Subject: Re: multi-homing fixes On Thu, Aug 23, 2001 at 03:23:24PM -0700, Roeland Meyer wrote:
At $99US for 512MB of PC133 RAM (the point is, RAM is disgustingly cheap and getting cheaper), more RAM in the routers is a quick answer. Router clusters
You almost make some good arguments. I pick up on this one for two reasons: 1) You clearly haven't priced Cisco RAM lately. :-) 2) You've missed the issue completely. You dance around ISP's providing more reliable service (eg, by adding RAM to their routers), and then dismiss that in the face of poor service and cheap prices people will buy multiple links. Much like your $99 RAM argument, customers today can get two or three T1's for the same price as one just a year ago. More bandwidth, more reliability, often less cost. Who would say no? Clearly ISP's should offer better service, but at the current bandwidth prices even with an ISP that took every precaution I, as a customer, would always buy from two people. The price really is that cheap. Even if ISP's (from a backbone perspective) delivered real 100% uptime, many people would buy two circuits (to different CO's) to avoid localized fiber / cable cuts. Multi-homing is here to stay, in a big way. It will only become more popular, no matter how good the ISP's become, for a number of reasons. Any future protocol or policy discussions should take this as a given. -- Leo Bicknell - bicknell@ufp.org Systems Engineer - Internetworking Engineer - CCIE 3440 Read TMBG List - tmbg-list-request@tmbg.org, www.tmbg.org