eli@spdcc.COM (Steve Elias) (10/10/89)
dyer@ursa-major.spdcc.COM (Steve Dyer) writes: >Has anyone ever investigated using a couple of channels from a town's >cable TV system as the basis of a metropolitan-area network? look no further, Steve! the cities of Springfield, Mass and St. Paul, Minnesota have linked their respective ethernets over their local cable systems -- the result for each is a full speed ethernet that spans many buildings, many miles apart. a large company local to the Boston area is also looking into linking their building ethernets this way. >like this *might* work with broadband modems and the right link-level hardware. >For connection to a regional network also located in the same town >(e.g., NEARnet), it might be preferable to lots of relatively low speed >leased lines. indeed. we at Chipcom are exploring the possibilities of attaching to NEARnet via broadband cable technology (yes, folks: 802.4!). our Marathon bridge is a very zippy .3 to .4 learning bridge. i'd call it a transparent bridge, but after BOFing at Interop, let's just call it a translucent bridge. the bridge runs at nearly 9000 packets per second at short distance, and drops to about 4000 pps at ten miles.... naturally, latency increases with long distance as well. (you knew that!) naturally, there are some gotchas with this technology. the local cable system has to be fairly high quality stuff. some cable companies are fairly lax about attenuations and other nifty RF stuff; such conditions would cause many physical layer 802.4 errors. >I'd appreciate hearing from people who know a little bit more about >the issues and whether or not this is completely unrealistic. it's being done already. the major reason Chipcom has not hooked to internet or NEARnet via broadband is that we will be moving to Southboro next year... (by the way, i work for Chipcom and worked on the Marathon bridge software and systems for most of the last 18 months. ok?) -- ... Steve Elias (eli@spdcc.com);6178906844;6179325598; {} /* free email to fax gateway for destinations in metro Boston area. */ /* send email and the destination fax number... */
boomer@athena.mit.edu (Don Alvarez) (10/10/89)
In article <164@ursa-major.SPDCC.COM> eli@ursa-major.spdcc.COM (Steve Elias) writes: dyer@ursa-major.spdcc.COM (Steve Dyer) writes: >>[anybody every run ethernet over local cable-tv through a city?] >[yes, Springfield, mass and St. Paul, Minnesota have] > > naturally, there are some gotchas with this technology. the local > cable system has to be fairly high quality stuff. some cable > companies are fairly lax about attenuations and other nifty RF stuff; > such conditions would cause many physical layer 802.4 errors. > how about the problem of having every character you type sent ito the home of every phreak and hacker in a 100 square mile area? -don boomer@athena.Princeton.edu -- + -------------------------------------------------------------------------- + | Don Alvarez M.I.T. Center For Space Research (617) 253-7457 | | boomer@SPACE.MIT.EDU Moving Soon: Princeton University Gravity Lab 8/89 | + -------------------------------------------------------------------------- +
dglo@zodiac.ADS.COM (Dave Glowacki) (10/11/89)
In article <164@ursa-major.SPDCC.COM> eli@ursa-major.spdcc.COM (Steve Elias) writes: > dyer@ursa-major.spdcc.COM (Steve Dyer) writes: >>Has anyone ever investigated using a couple of channels from a town's >>cable TV system as the basis of a metropolitan-area network? > > look no further, Steve! the cities of Springfield, Mass and > St. Paul, Minnesota have linked their respective ethernets > over their local cable systems -- the result for each is a > full speed ethernet that spans many buildings, many miles apart. St. Paul's broadband link is half-speed, but full speed links are doable (if you can get 'em past the politicians :-) Unfortunately, this link is only used as a glorified Appletalk network link (or was when I left the city 8 months ago.) In its infinite wisdom, the rest of the city is "networked" up over another chunk of broadband via a bunch of glorified terminal servers. >>like this *might* work with broadband modems and the right link-level hardware. > naturally, there are some gotchas with this technology. the local > cable system has to be fairly high quality stuff. some cable > companies are fairly lax about attenuations and other nifty RF stuff; > such conditions would cause many physical layer 802.4 errors. The BIGGEST gotcha when I worked at St. Paul was the problems caused by the cable company searching for cable pirates. The network would go down without warning about once a month because of that. >>I'd appreciate hearing from people who know a little bit more about >>the issues and whether or not this is completely unrealistic. Send mail to pwcs.StPaul.GOV and they can probably answer some of your questions or give you pointers to the right people. -- Dave Glowacki dglo@ads.com Advanced Decision Systems
eli@spdcc.COM (Steve Elias) (10/11/89)
In article <9456@zodiac.ADS.COM> dglo@ads.com (Dave Glowacki) writes: ! eli@ursa-major.spdcc.COM (Steve Elias) writes: !! ...St. Paul, Minnesota have linked their respective ethernets !! over their local cable systems -- the result for each is a !! full speed ethernet that spans many buildings, many miles apart. ! !St. Paul's broadband link is half-speed, but full speed links are doable !(if you can get 'em past the politicians :-) Unfortunately, this link !is only used as a glorified Appletalk network link (or was when I left the !city 8 months ago.) In its infinite wisdom, the rest of the city is !"networked" up over another chunk of broadband via a bunch of glorified !terminal servers. the network i refer to was installed just a few months ago... actually, i think St. Paul is referring to it as a 'beta test'. -- ... Steve Elias (eli@spdcc.com);6178906844;6179325598; {} /* free email to fax gateway for destinations in metro Boston area. */ /* send email and the destination fax number... */