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North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical RE: redundancy [was: something about arrogance]
That is even worse than what we have been talking about. You should be running a P2P T1 back to yourself, and distributing the access from a POP, or have the carrier you're reselling the T1 for allocate a /24. There is no reason to run BGP for a single /24 whatsoever, it should be announced in Carrier address space. Using your AS for another company totally violates the whole idea of an "Autonomous System". Derek -----Original Message----- From: Manolo Hernandez [mailto:[email protected]] Sent: Tuesday, July 30, 2002 1:30 PM To: Derek Samford Cc: [email protected]; 'Pedro R Marques'; [email protected]; [email protected] Subject: RE: redundancy [was: something about arrogance] Yes their is a reason to some /24s advertised to the world. If this a class on BGP they would tell you that was a nono, but since this is the real world it happens and is sometimes required. It is required when you need to give a customer T-1 access at a location seperate from yours and has a seperate connection to the net and you are using your AS on the access router. A /24 is a solution that works nicely and still works with your aggregated /20 address. On Tue, 2002-07-30 at 13:23, Derek Samford wrote: > > I couldn't possibly agree more. In fact, my approach has been to create > a mesh between different Colo centers, and keep it at about 3 Transit > carriers. Because of the different methods of interconnection, I haven't > ever had a long-term outage. Also, I've been able to filter any issues > that are beyond my carrier's immediate reach (i.e. congested peering > points.) At the same time, I've been able to maintain aggregation of all > of my routes, and maintain true stability in my network. There is > absolutely no excuse to fill up the routing tables with nonsense. > > Derek > > -----Original Message----- > From: [email protected] [mailto:[email protected]] On Behalf Of > Phil Rosenthal > Sent: Tuesday, July 30, 2002 12:52 PM > To: 'Pedro R Marques'; [email protected] > Cc: [email protected] > Subject: RE: redundancy [was: something about arrogance] > > > I have in the past single-homed to Level(3) and Verio, each in their own > facility in NC. > In that time, both carriers had about 1 solid hour a month of solid > downtime (some months were worse, some were better). Some of the outages > were on the order of 8 solid hours (verio) or 4 hours (level3). > > We did not run HSRP with Level3, so it may be difficult to guarantee the > uptime of one gige handoff... But we ran HSRP with verio, and of all the > outages (about 20 of them) -- Maybe two of them were avoided because of > HSRP. > > Other than that, it was all downtime. > > At this point, I couldn't conceive single-homing to any uplink anymore. > > --Phil > > -----Original Message----- > From: [email protected] [mailto:[email protected]] On Behalf Of > Pedro R Marques > Sent: Tuesday, July 30, 2002 6:23 AM > To: [email protected] > Cc: [email protected] > Subject: redundancy [was: something about arrogance] > > > > Brad writes: > > I'm probably demonstrating my ignorance here (and my stupidity > > in > > stepping into a long-standing highly charged argument), but I'm > > completely missing something. For reasons of redundancy & > > reliability, even if you were to buy bandwidth in only one location, > > wouldn't you want to buy it from at least two different providers? > > > If you buy bandwidth from two different providers at two > > different locations, this would seem to me to be a good way to > > provide backup in case on provider or one location goes > > Tango-Uniform, and you could always backhaul the bandwidth for the > > site/provider that is down. > > Several other posters have mentioned reasons why redundancy between 2 > different connections to separate providers are not, in most situations, > > the preferable aproach but i would like to add another point/question... > > When considering redudancy/reliability/etc it is important to think > about what kind of failures do you want to protect against vs cost of > doing so. > > It is my impression, from reading this list and tidbits of gossip, that > the most common causes of failure are: > - link failure > - equipment failure (routers mostly), both software and hardware > - configuration errors > > All of those are much more frequent than the failure of an entire ISP (a > > transit provider). It is expected, i believe, of a competent ISP to > provide redudancy both within a POP and intra-POP links/equipment and > its connections to upstreams/peers. > > As such, probably the first level of redundancy that a origin AS > (non-transit) would look at would be with the intent to protect from > failures of its external connectivity link and termination equipment > (routers on both ends). > > To do so, one can look at: > - 2 external links to distinct providers > - 2 external links to the same provider > > While i can't speak to the economics part of the equation (although i > would expect it to be cheaper to buy an additional link than connect to > a different provider) from a point of view of restoration, protecting a > path with an alternate path from the same provider is certainly an > aproach that gives you much better convengence times. > > This comes from the fact that in terms of network topology, the distance > > between 2 links to the same upstream is much shorter than 2 links to > different upstreams. While, if you protect a path with an alternate path > > to the same ISP you can expect convergence to occur within the IGP > convergence times of your provider, with 2 different providers you need > global BGP convergence to occur. > > This gets to be longer dependent on how topologically distant your 2 > upstreams are... for instance attempting to protect a path to an ISP > with very wide connectivity with a protection path from one with very > limited connectivity would be a particularly bad case as you would have > to wait for the path announced by the larger ISP to be withdrawn n times > > from all its peering points and the protection path to make its way > through in replacement. > > It is counter-intuitive to me what i perceive to be the standard > practice of attempting to multi-home to 2 distinct providers by > origin-only ASes... from several points of view: convergence times, load > > on the global routing system, complexity of management, etc, dual > connectivity to different routers of the same provider (using distinct > physical paths) would seem to me to make more sense. > > Unless the main concern is that the upstream ISP fails entirely... which > > given the fact that it tends to have frontpage honors on the NYTimes > this days does not apear to be an all to common occurence (i mean > operationally, not financially - clarification added to dispel potential > > humorous remarks). > > So, my question to the list is, why is multi-homing to 2 different > providers such a desirable thing ? What is the motivation and why is it > prefered over multiple connections to the same upstream ? > > Is the main motivation not so much reliability but having a shorter > as-path to more destinations ? This would apear to me to be a clear > advantage since that doesn't necessarily reflect in better qualitify of > interconnection. > > My apologies in advance if these seem to be stupid questions... > > thanks, > Pedro. > > > >
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