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Re: Check this out
by Dean Anderson 02 Sep '98

02 Sep '98

Well, the article also said that charging by the packet is "outrageous", which if I followed some of the BBN/GTE thread, was exactly what some were proposing. I think its only a matter of time before the PSTN and the Internet are one and the same, and regulated by PUC's. So I'd have to think also that either the concept of "long distance" will change, or perhaps something as crazy as per packet, long distance internet charges will come into existance. --Dean At 04:28 PM 9/1/98 -0400, you wrote: >I think the operative words in this article are "embarrassingly" >and "stupid". > >- paul > >At 10:32 AM 9/1/98 -0700, James B. Slayden Jr. wrote: > >>Something of interest! And may set some precedence?! >> >>----- Begin Included Message ----- >> >>http://www.mercurycenter.com/business/tech/docs/076951.htm >> >>----- End Included Message ----- >> >>James S. >> >> >> > > ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Plain Aviation, Inc dean(a)av8.com LAN/WAN/UNIX/NT/TCPIP http://www.av8.com ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

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56k modems/frame/ptp revisited (LONG) (fwd)
by MegaZone 01 Sep '98

01 Sep '98

I noticed several people reciting incorrect information in relation to PCM modems. For those who don't know, I worked for Livingston and then Lucent RABU up 'til February of this year. I was very involved with issues such as PCM modems on the PM-3. Simply put there is NO restriction on the SPEED of PCM modems aside from what the PSTN can carry. On a digital line end to end max theoretical is 64K, with RBS and the switch codecs and configurations in use today 56K in North America. The misconception is that there is a 53.3K cap on the speed. This is false. What the FCC limits is the power (db) level you can place on the line in the PSTN. This is to limit crosstalk in copper cable bundles. This power limitation does not equal a speed limitation. This seems to have arisen from the fact that the first PCM modems - USR X2 units - could not go faster than 53.3K without violating the FCC power limitations. All other things being equal, the more power you can use, the faster you can go. To cover their ass USR put the disclaimer on the boxes talking about how X2 was capable of 56K, but limited to 53.3K due to the FCC blah, blah. Many people read this as the FCC having some cap on allowed speed since they didn't explain that the trouble was with X2's inability to go faster in the allowed power band. Now, K56flex did NOT have this limitation. Users regularly reported connect speeds up to 54K, and a few even reported the magical 56K - but that was very rare indeed. How? K56flex was better at using the available power range (in most, but not all cases) and managed to squeeze out the additional throughput. X2 and K56flex both improved with time - X2 users eventually started seeing 54.6K connects, and K56flex saw higher numbers of 54K connects. But it doesn't appear that they removed the warnings from the packaging. And, now this baffles me, some K56flex modem vendors included the same language on their packaging. Which is nutty since 53K isn't a K56flex speed! It goes 52K -> 54K, 2K incriments. Anyway, now we have V.90. And, if you read user groups for the various server HW vendors, as well as USEnet groups, etc, you'll find some people reporting 54.6K connects with V.90. Off hand I don't recall seeing anyone in North America reporting 56K as of yet, which isn't surprising. Please, don't perpetuate the "FCC limits modem speeds to 53.3K" myth. -MZ -- <URL:mailto:megazone@megazone.org> Gweep, Discordian, Author, Engineer, me.. Join ISP/C Internet Service Providers' Consortium <URL:http://www.ispc.org/> "A little nonsense now and then, is relished by the wisest men" 781-788-0130 <URL:http://www.megazone.org/> <URL:http://www.gweep.net/> Hail Discordia! ==================================================================== ISPF, The Forum for ISPs by ISPs. October 26-28, 1998, Atlanta, GA. Three days of clues, news, and views from the industry's best and brightest. http://www.ispf.com/ for information and registration. ====================================================================

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peering@sprint.net
by Brian Horvitz 01 Sep '98

01 Sep '98

Anybody alive here? I've sent mail twice over the last week or so with no answer... Brian Horvitz Shore.Net Network Engineering

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56k modems/frame/ptp revisited (LONG)
by Tim Wolfe 01 Sep '98

01 Sep '98

13 people so far have asked me to post a summary to the list on this subject, so here it is. I have included all responses I received, with the name of the respondent at the top of their answer. Both questions are included at the top for continuity purposes. Question #1: Anyone have a nice layman's terms explanation of the throughput/latency differences between a 56k modem, a 56k leased line, and a 56k frame relay circuit? This is assuming a "perfect" lab enviroment, ie. the modem connects and sustains at maximum capability, the frame cloud is not overloaded etc.. Please reply off list. Question #2: I've gotten lot's of responses on my original question, but I'm finding perhaps I didn't ask the correct one. What I really need to know is what is the real world effect of latency on throughput? I know that frame relay has a higher latency than a point to point line, and that a point to point is generally regarded as faster. Would someone mind explaining the specifics of that relationship a little bit? Again, off list please, unless someone thinks it's an appropriate topic for this list.. **************************************** Here are the responses I received for both questions in no particular order. **************************************** David Newman wrote: "56K" modems really top out at 53.3 kbit/s because of an FCC regulation (I believe Canada has a similar rule). They theoretically can hit 56 kbit/s outside North America, though tests have showed 51-52 kbit/s to be the upper end for products shipping today. Absent congestion both a frame PVC and a leased line really do run at 56 kbit/s. David R. Dick wrote: "56K" modems take advantage of the digital nature of much of the present phone system. Unfortunately, they can only do this in one direction, so you get 56K down from the Internet to the user (actually only 53K, or so, because of electrical power limitations in the signalling method) and 33K from the user to the Internet. 56K leased lines are point-to-point connections. The data travels more or less directly (in electrical terms, anyway) between the user and the Internet -- 56K in each direction. 56K frame relay is a switched service and two point-to-point connections are involved: one from the user to the switch and one from the switch to the Internet. You get 56K in each direction, but there is some delay (latency) because of the diversion through the switch. In some places there may even be more than one switch involved, with extra latency, as you might expect. Paul G. Donner wrote: Basically, you'd need to look at the framing in each case as well as any Layer 2 acknowledgement mechanism that might be implemented. You can get this from a number of textbooks and put together an explanation yourself if you are so inclined. This would only consider up to the L2 overhead on the links (if applicable -> e.g. Frame Relay) which is probably what you are asking for. These link types are effectively in different categories and it would be sort of like comparing apples to oranges. Chris Cappuccio wrote: 56K is the low end of the leased line spectrum, with 56K leased line and 56K frame relay performing almost identically if you are using similar framing protocols. You will the top 56K performance from these... Lowest latency (20-40ms) 56K modem is at most 53K because of modem-enforced FCC limits, and because of the analog-digital conversion, you will get high latency (100-200ms) and lower throughput then a leased line. David R. Dick wrote: The simplest explanation involves the fact that most networking is TCP (not UDP) so packets travel in both directions, with acknowledgements, etc. When an ACK is delayed because of latency, the movement of the real data packets is also delayed. So it will just plain take longer to deliver the same data payload. Karl Auerbach wrote: As for so-called 56K modems -- they aren't. They are only 56K if the FCC allows, which they don't, so top speed is about 53K. And then it's only 56K in the direction from an ISP who has a digital ISDN based modem towards your "analog" 56K modem. The return path is 33Kbits (or worse.) If you take a couple of off the shelf "56K" modems and hook 'em up over a normal POTS line you'll end up with about 33Kbits (or worse) full duplex. I learned all this stuff a few weeks ago when I hooked a couple of routers together and found that my investment in 56K modems was wasted -- the best one can get is 33Kbits full duplex unless I invested in an ISDN link at one end and got the 56K ISP-end gear. As far as I know only 3COM makes a single BRI ISP-end 56K modem. It runs about $250. Usually they come in larger packs to hook to an ISDN PRI. Chris Cappuccio wrote: Latency and throughput are NOT related in this case! The speed of light itself puts a limit on how fast we can transfer data globally with fiber optics. Bigger pipes will simply ensure that you can get more data through at the same time. Once you have maxed out speed with the most efficient protocol, you are limited by the speed of light ;0 Anyways, the latency introduced with a modem connection is much larger then that of a dedicated line because of the two analog<->digital conversions. All-digital connections like ISDN, FR, and PTP connections are very low latency. Paul G. Donner wrote: FR is effectively frame/packet switched. PT-PT circuits do not have frame/packet structures (the transport may use T1 type framing but this is different). The major latency affect in FR is due to buffering of the packet/frames and and switching them. PT-PT don't go through this process. So effectively both types FR and PT-PT have propagation delay (e.g. speed of light limitations) but FR exhibits also processing delays which are neglible or non-existant with PT-PT circuits. Robert Gourley wrote: Given that there in no congestion in the frame relay network and that both the 56Kbps DDS line and the 56Kbpx frame relay PVC follow exactly the same route and have the same number of route miles, then the only difference in the latency of the two circuits is the effect of two serialization delays (one at the ingress and one at the egress) in the frame relay example. Serialization delay is = (packet size in bits)/(56,000 bits/sec). Blaine Christian wrote: Since you want to assume ideal conditions you will remove a significant difference between the 56k Modem and leased line. You will find that under ideal conditions both of these should perform equally well. Since a leased line/modem relies on less telco equipment it should peform better than the frame circuit. A 56k frame circuit will increase your latency by virtue of being processed by several frame switches. If the frame switches have to tag frames they may introduce more latency into your circuit (even if they do not tag your frames). The difference between all of these should be negligible (depending on switches and the amount of equipment traversed) and throughput should be equal depending on the equipment you are using (of course). --------------------------------------------------- Tim Wolfe, Network Administrator ClipperNet Internet Access Services tim(a)clipper.net 541.431.3360 voice 541.431.1176 fax ...Across the Desktop and around the World... ---------------------------------------------------

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open relays at Earthlink
by Adam D. McKenna 01 Sep '98

01 Sep '98

Earthlink has the following open mail relays: gull.prod.itd.earthlink.net snipe.prod.itd.earthlink.net (a couple of other earthlink hosts, I can't remember which now, they were all in the .prod.itd.earthlink.net subdomain.) I know this because I have been getting spammed by someone using them for the past week. I have tried e-mailing abuse(a)earthlink.net several times and have received no response. I'm hoping a clueful Earthlink admin will see this post and take the appropriate action. If not, then maybe Earthlink should be "nominated" for RBL. --Adam --- bash: syntax error near unexpected token `:)' Adam D. McKenna adam(a)flounder.net

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ISDN vs. Leased lines
by william＠pacific.net.ph 01 Sep '98

01 Sep '98

Hi! Just wondering if anyone knows of any comparative studies on ISDN 64K/128K vs. 64K/128K leased lines. I'd like to check the performance comparison, like throughput and errors. Thanks in advance! William

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Colo Space in Sprint
by Todd_R_Stroup/Fnsi/US＠fnsi.net 31 Aug '98

31 Aug '98

Any one have a small bit of colo space available at the Sprint NAP? Any other solutions besides going somewhere else will be accepted as well. We did have confirmed space at the NAP but I guess it vanishes after a few days or so... Words of wisdom in private please : tstroup(a)fnsi.net T..S _______________________________________________________________ From: "Steven Schnell, Sprint Corporation" <schnell(a)gsd.sprint.com> To: tstroup(a)fnsi.net Cc: nap-engr(a)cde1.gsd.sprint.com Subject: Sprint NAP Information Todd: Your equipment has been assigned to Bay 517. We will be supplying redundant DC power to your router only and UPS-backed AC to all other equipment. What will be your access line rate, DS3 or OC-3? If DS3, what CSU/DSU do you plan to use? If you desire dialup access to your equipment you will need to order your business line from Bell Atlantic. They can be reached at 800.755.1096. You will need to instruct them to terminate your business line in a modular jack in Bay 517. Please don't hesitate to contact me with any questions or comments. Regards, Steven

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MCI outage on 8/29?
by Dan Hollis 31 Aug '98

31 Aug '98

Anyone have details on the MCI outage 8/29? All routing to their seattle POP was down from 8:45a PST - 11:30a PST. More weekend warriors with backhoes? -Dan

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BGP Communities - almost an operational question
by Alex Bligh 31 Aug '98

31 Aug '98

I've been trying to find out any logical reason why Ciscos limit me to 16 communities per route. I'm not asking on cisco-nsp as I want to know whether other routers suffer this limitation. Having read and reread rfc1771 and rfc1997, I think the community attribute list is limited by (a) the message length (not really relevant) and (b) the attribute length. The latter appears to be mainly an issue of whether one can be bothered to use extended-length in lieu of non-extended length. Even without using extended-length you have 255 bytes to play with which my calculation gives you 61 or 62 community attributes to play with. So: a) Have I just read the RFC wrong? b) Does other s/w (GateD. Bay etc.) have the same limitation? c) What happens if I try and feed routes with lots of community attributes to a Cisco, (perhaps I feed routes with less than 16 communities on but have set community additive)? Does it drop some randomly? Given that some people use 666 style filtering to prevent advertisement of routes to peers, could this cause leaks? (yes, I have an application for more than 16 communities per route). -- Alex Bligh GX Networks (formerly Xara Networks)

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Question2
by Tim Wolfe 31 Aug '98

31 Aug '98

I've gotten lot's of responses on my original question, but I'm finding perhaps I didn't ask the correct one. What I really need to know is what is the real world effect of latency on throughput? I know that frame relay has a higher latency than a point to point line, and that a point to point is generally regarded as faster. Would someone mind explaining the specifics of that relationship a little bit? Again, off list please, unless someone thinks it's an appropriate topic for this list.. Thanks again, Tim --------------------------------------------------- Tim Wolfe, Network Administrator ClipperNet Internet Access Services tim(a)clipper.net 541.431.3360 voice 541.431.1176 fax ...Across the Desktop and around the World... ---------------------------------------------------

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