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Re: ATM Wide-Area Networks
by salo＠msc.edu 30 Jul '96

30 Jul '96

>From: Sean Doran <smd(a)icp.net> >To: pferguso(a)cisco.com, salo(a)msc.edu >Subject: Re: sell shell accounts? >Cc: nanog(a)merit.edu >Date: Wed, 24 Jul 1996 01:43:30 +0100 > >| o Given that each link is rather expensive, it behooves the >| NSP to try to avoid needlessly moving a packet back and >| forth across a DS-3 local loop just because my ATM >| provider can't provide me with any more PVCs. >| (Which was my major point, by the way.) > >Interestingly enough, the NSPs I observe moving large amounts >of traffic around are set up in such a way that their routers >are generally colocated with carrier transmission gear, and >so there *is* no local loop to speak of, as an added cost to >an outside supplier. > [...] Hopefully, my thinking is clearer than my writing... What I originally called "local loop B," now relabeled "This Thing Here," is probably comprised of: o a port on the ATM switch/service o a connection between the router and the switch, (usually a wide-area link, given that most wide-area ATM services backhaul traffic to a few ATM switches) o a port on the router A short-cut VC would avoid needlessly passing packets back and forth across "This Thing Here." That would seem to be a good thing in most circumstances, inasmuch as some or all of the components of "This Thing Here" cost something and may potentially become a bottleneck. -tjs | ________ _______________________ ________ | | Router | loop A | | loop C | Router | | | A |=========| Wide-Area ATM Service |========| C | | |________| |_______________________| |________| | | | | <=== This Thing Here | | | ________ | | Router | | | B | | |________|

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Re: Ping triangulation
by Peter Lothberg 29 Jul '96

29 Jul '96

> They use the ping times to figure out which server would be closest. > All the servers are not located in the same place. The idea is that > european users may receive better service from a european server. > > Roy > > > The network topology and geography does not match very well, I would guess that the network center of Europe is likely to be somwhere on the US Eastcoast. Only Stockholm have multiple international E3 links.... --Peter

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Re: ATM Wide-Area Networks
by salo＠msc.edu 29 Jul '96

29 Jul '96

> > I am not quite sure how an ATM switch becomes a "packet shredder," or > > even what a "packet shredder" is... > > An ATM switch shreds a 1500 byte IP packet into 29 ATM cells of 53 bytes > each. At the risk of being excessively pedantic, the host ATM interface, not the switch, segments the SDU into cells. My point was that the term "packet shredder" doesn't seem to have any very precise meaning beyond perhaps the writer's desire to use a catchy phrase to indicate an attitude towards ATM. Some people use it to describe the segmentation function of ATM interfaces, other use it to describe switches which don't do packet discard. > If an ATM has a 5% loss, i.e. 1 in every 20 cells is lost, then 0% > of the IP traffic will get through. ... Most anything with 5% loss is broken. -tjs

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Re: Why aren't ISPs providing stratum 1 NTP service?
by dgaudet＠hotwired.com 29 Jul '96

29 Jul '96

In article <hot.mailing-lists.nanog-Pine.BSI.3.93.960719091042.14736C-100000(a)sidhe.memra.com>, Michael Dillon <michael(a)memra.com> wrote: >And heavily used WWW servers are another thing that could benefit from >aligning themselves with the topology. The protocols don't support this cleanly. So far nothing I've seen would allow a single URL to be used to access the "nearest" server. Until something like that exists (i.e. the end users don't need to know a thing about network topology) it seems pointless to align WWW servers with the topology. Your suggested use of redirects just complicates things -- consider how the URLs would end up looking in a search engine. Dean

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Re: ATM Wide-Area Networks (was: sell shell accounts?)
by Vincent J. Bono 27 Jul '96

27 Jul '96

<snip> > ATM can be used in two main modes: as a funny form of TDM > or as a means of overcommitting resources. > > The former is in use now in the land of InternetMCI, > ESNET, NSI and others, for better or for worse, and has > been for some time. As Tim and others have pointed out, > it works, given some tweaking here and there with things > like EPD. > > The latter has been observed in use as an offering by MFS, > and it had obvious problems. It has also been observed > from time to time at the ATM-using NAPs, and also had > obvious problems. These problems were arguably not > directly the fault of ATM, but of arguably broken > interface and adaptation devices like ADSUs, ethernet > framers and FRADs. I'd wonder if a large part of the problems are not avoidable, but that since most persons do not as yet have a "feel" for ATM, its harder to see and diagnose building problems, or predict failure points. ATM acting like TDM *still* isn't TDM. "Load" testing is fine and well (sorry DISA folks) but it's the field use that matures technology and turns proposed process into good technique. We've watched the ATM simulations (and even helped with the code for a few) but nothing came close to predicting what happened in real life when clients implemented it, especially in the multimedia (IP/TV/VOICE) applications. -v

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Re: Why aren't people changing their subject lines when threads drift?
by Justin W. Newton 26 Jul '96

26 Jul '96

At 11:42 PM 7/25/96 -0700, you wrote: >> Isn't IBM doing some sort of fancy load redistribution for the WWW >> servers its running for the 1996 Summer Olympics? I seem to recall they >> were determining the "closest" server via a technique called "ping >> triangulation", whatever that is. > >If so, that's pretty silly and is probably not leading to performance >that's very different from either purely random or strict round robin. > >Ping times only correlate to available bandwidth when congestion is bad. >Otherwise these two factors are militantly unrelated to each other. Well, I suppose all they have to do is buil a global OSPF network encompassing the entire internet and they'd be set. Justin "Yes I'm kidding" Newton Justin Newton Internet Architect Erol's Internet Services

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route servers
by Shifter 25 Jul '96

25 Jul '96

Are there any other routers that allow incoming telnet sessions without a password besides route-server.cerf.net? -John -- shifter(a)portal.stwing.upenn.edu -----BEGIN PGP PUBLIC KEY BLOCK----- Version: 2.6.2 mQCNAzF+qeMAAAEEALdaUpOTi8EtNjZMA9URTXGmQq1NPdyRSx2JXhQ7Q8Yz9qxU q3tqRtlydRqp37VPmygibGB8eS7RptqolTlYvrVMHXSDcZjKpgpZA9d+3rCKUaLM F9Hvltl2EafIEspVoNUYahpdXof4oMjs2sKGzJO8aDwyM34pRaicZR8SZJz9AAUR tClTaGlmdGVyIDxzaGlmdGVyQHBvcnRhbC5zdHdpbmcudXBlbm4uZWR1Pg== =Eucp -----END PGP PUBLIC KEY BLOCK-----

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None
by Alejandro Ortiz 25 Jul '96

25 Jul '96

suscribe ========================================================================= Alejandro Ortiz Herrera. Coordinador de Telecomunicaciones y Redes Ruteo Tel. (52)(8) 3 58 20 00 ext.4134 Direccion de Informatica (52)(8) 3 28 41 34 I.T.E.S.M Campus Monterrey Fax. (52)(8) 3 28 42 08 alortiz(a)campus.mty.itesm.mx ==========================================================================

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Re: ATM Wide-Area Networks (was: sell shell accounts?)
by reb＠ieng.com 24 Jul '96

24 Jul '96

> At 9:33 PM 7/23/96, Curtis Villamizar wrote: > > In message <199607232130.QAA20147(a)uh.msc.edu>, Tim Salo writes: > > > > "Good" ATM switches are doing Early Packet Discard and Partial Packet > > Discard. You can ask your favorite switch vendor for details, or look > > at the following for a nice summary: > > > > http://www.fore.com/html/atm-edu/whitep/FTBMWP.html > > Also in the "dead horse dept" (I hope) unless you are dealing with > boneheaded switch vendors. Some don't believe in EPD/PPD preferring > ABR. Are any of them still entirely clueless in this regard and not > doing either EPD/PPD or ABR? I think a better question is which switch vendors are supporting _any_ kind of xPD besides Fore? At my last recollection, though I am no switch expert, only Fore. Certainly other switch vendors were starting to throw large buffers at the problem. And still others said "ABR will solve this problem. Wait for ABR." (And I'll add that this was said even when it was clear ABR was a couple of years away.) As for ABR, ATM vendors have been forecasting '96 and '97 deliverables since at least '94. As such, I would expect most of them to be doing or at least working on bringing ABR to fruition. But in order for ABR to be useful in a router environment, routers need to understand ABR. Anyone know what routers do? There are also issues wrt telcos' sunk investment in switches -- switches built when switch vendors were nearly unanimously boneheaded. Given telcos' tendencies to depreciate equipment over long cycles, one can expect those switches to be in telcos' networks for some time. ISPs looking to deploy their own ATM switches needn't be concerned with this but those looking to buy ATM service from telcos most certainly do. All hoping aside, I'm not so sure these issues are in the "dead horse dept"... eric P.S. I took a stab at answering my own question and found that out of the two vendors I checked, at least Cascade now implements EPD. ---- R. Eric Bennett <reb(a)ieng.com> | Internet Engineering Group 313-669-8800 (v) 313-669-8661 (f) | 122 S. Main, Suite 280 http://www.ieng.com/ | Ann Arbor, MI 48104

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Re: sell shell accounts?
by salo＠msc.edu 24 Jul '96

24 Jul '96

> Date: Tue, 23 Jul 1996 19:03:08 -0400 > To: salo(a)msc.edu (Tim Salo) > From: Paul Ferguson <pferguso(a)cisco.com> > Subject: Re: sell shell accounts? > Cc: freedman(a)netaxs.com, nanog(a)merit.edu > > At 05:06 PM 7/23/96 -0500, Tim Salo wrote: > >The desire for a full mesh of VCs between routers becomes more compelling > >if you have more than three routers. The diagram is left as an exercise > >to the reader; I rather dislike having to draw in ASCII. > > > >Note that the two paths between A and C, (directly versus via B), seem > >to take distinctly different paths. (Perhaps, I missed your point). > > Perhaps I missed your point. > > Tim, I could've sworn that you had been following the IETF ION WG > mailing list, where this has been discussed on hundreds of occasions. > I hesitate to even mention this on NANOG (I really don't want to > re-hash this on this list), but I can't hold my tongue. > > The scalability of an ATM network where each end-point is fully meshed > to all other end-points decreases in direct proportion to the number > of end-points. This is not so much a layer 2 problem, per se, but rather > the ability to maintain functional routing (convergence, et al.) in a > fully meshed network topology. > > This does not scale. I believe that given my [secret] assumptions, (some of which are revealed below), it scales well beyond the financial abilities of most any NSP. I assumed that the wide-area ATM service supported only PVCs and PVPs. (I keep hearing promises of SVCs "next year" but I don't think anyone [domestically] has delivered them.) I believe this address your concern about maintaining functional routing, but I make no claims to being a routing expert, so I might not fully comprehend the issue. I also assumed that the going price for a DS-3 xwide-area ATM connection is, to more or less pull a number out of the air, $250,000/year. This has two implications: o Any one NSP isn't going to be able to afford all that many connections. A full mesh of 100 routers, (i.e., $25 millino/year in ATM services) would require 4,950 PVCs. That is a lot to configure, but... o Given that each link is rather expensive, it behooves the NSP to try to avoid needlessly moving a packet back and forth across a DS-3 local loop just because my ATM provider can't provide me with any more PVCs. (Which was my major point, by the way.) On the other hand, you are correct that this doesn't sale to thousands of routers. But, I didn't think that was the problem we were trying to solve here, (just yet). -tjs

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