tep@tots.UUCP (Tom Perrine) (07/13/90)
In article <9007121800.AA01850@xap> stewart@xyplex.com (Bob Stewart) writes: >Paul Tsuchiya writes: >Seems to me that imbedding topological meaning in an address is not >necessarily a good idea. That implies that as I move my portable around the >network (from hotel to hotel, or, worse yet, on a cross country trip with a >mobile phone), its address has to change. We have that problem now with SLIP >connections. A name service could track the change so you could always reach >me by name, but the more I move the more I have to change the name mapping, >and such mappings usually don't appreciate being changed very much. > >*I*n *M*y *H*umble *O*pinion, hierarchical administration for initial address >assignment works nicely, such as with Domain Name Service or Ethernet global >addresses, but should really be independent of routing. Of course, flat >addresses don't offer any built-in efficiencies for finding the right >neighborhood, like IP addresses do now... > >Tradeoffs, tradeoffs, always tradeoffs. Why can't there just be a right >answer? > > Bob But there is a right answer! Everyone will now use PPP over... cellular telephone dial-ups!! :-) I hate to admit it, but the cell-phone (phone system) model of addressing does have many advantages for the *user*. No matter where you go, your logical address (phone number) follows you. Of course, this puts all of the burden on the switching system, and the routing can often be far from optimal for a roaming cell phone user. I imagine that the main reason that this works for cell phones is that there is enough "excess" capacity in the switching system to handle the (hopefully) relatively rare, inefficient cases of roaming cell phones, which are a very small part of the switching load. Is there anything that we can learn (read "steal") from this example? Tom Perrine (tep) |Internet: tep@tots.Logicon.COM Logicon |UUCP: nosc!hamachi!tots!tep Tactical and Training Systems Division |-or- sun!suntan!tots!tep San Diego CA |GENIE: T.PERRINE "Harried: with preschoolers" |+1 619 455 1330 Home of the _Tower Operator Training System_ as seen in the SunTech Journal.
amanda@mermaid.intercon.com (Amanda Walker) (07/14/90)
In article <153@tots.UUCP>, tep@tots.UUCP (Tom Perrine) writes: > I hate to admit it, but the cell-phone (phone system) model of > addressing does have many advantages for the *user*. No matter where > you go, your logical address (phone number) follows you. In all of the cellular systems I've used so far, roaming is only half automatic. In particular, to place a call to a roamer, you have to dial the roamer access number for the area where they are, and then dial their phone number. This amounts to source routing, which is even more of a pain for mobile destinations than it is for "static" ones. Bleah. Maybe Motorola's proposed satellite-based cellular system will be better. That's it! We put the core gateways into geosynchronous orbit... :-) -- Amanda Walker <amanda@intercon.com> Postmaster With An Attitude InterCon Systems Corporation
karn@envy.bellcore.com (Phil R. Karn) (07/14/90)
In article <269E07C3.604D@intercon.com>, amanda@mermaid.intercon.com (Amanda Walker) writes: |> Maybe Motorola's proposed satellite-based cellular system will be better. |> |> That's it! We put the core gateways into geosynchronous orbit... :-) The satellites in Motorola's proposed "Iridium" system would NOT be in geosynchronous orbit, they would be in low altitude polar orbits. As such, the system is much more like the Multiple Satellite System (MSS) that DARPA looked at a few years ago. Dave Mills was one of the investigators. Satellites in low altitude orbits move quite rapidly, so this will present a very interesting problem in routing. On the other hand, orbits are quite predictable, so at least you can compute your connectivity matrix at any desired time in the future. Back in the early days of communications satellites, it was not yet clear that geostationary was the way to go at that time. Many paper proposals for fleets of satellites in low earth orbit were made, but they never went very far because of the limits of the ground station technology in those days. Phil
newbery@rata.vuw.ac.nz (Michael Newbery) (07/17/90)
In article <269E07C3.604D@intercon.com> amanda@mermaid.intercon.com (Amanda Walker) writes: >In all of the cellular systems I've used so far, roaming is only half >automatic. In particular, to place a call to a roamer, you have to dial >the roamer access number for the area where they are, and then dial their Not in New Zealand. Cell phones have their own area code which covers the country. All cell calls cost the same per minute regardless of distance (which is cheaper than the most expensive 'normal' toll step.) As part of testing they placed a call, got in a plane and flew the length of the country, keeping the circuit up during the entire journey. (OK, so NZ is small, but it is bigger in area than the U.K. which does require area access numbers). -- Michael Newbery<newbery@rata.vuw.ac.nz> Q: What do you do with a wombat? A: Play wom with it!
rpw3@rigden.wpd.sgi.com (Rob Warnock) (07/17/90)
In article <269E07C3.604D@intercon.com> amanda@mermaid.intercon.com (Amanda Walker) writes: +--------------- | In article <153@tots.UUCP>, tep@tots.UUCP (Tom Perrine) writes: | > I hate to admit it, but the cell-phone (phone system) model of | > addressing does have many advantages for the *user*. No matter where | > you go, your logical address (phone number) follows you. | | In all of the cellular systems I've used so far, roaming is only half | automatic. In particular, to place a call to a roamer, you have to dial | the roamer access number for the area where they are, and then dial their | phone number. This amounts to source routing, which is even more of a | pain for mobile destinations than it is for "static" ones. Bleah. +--------------- In fact, most of the current cellular romaing systems are 3/4-automatic... ;-} Automatic for the roamer dialing out; that's half. But now many (most?) cellular companies offer a hack such that if you dial a person's cellular number in their home area *and* they're currently known to be roaming somewhere (they've placed a roming call within the last 24 hours), the home area system will give you an intercept recording which tells you they're out of area... *and* gives you the roamer access number where they are. Sort of an ICMP Redirect... ;-} ;-} -Rob ----- Rob Warnock, MS-9U/510 rpw3@sgi.com rpw3@pei.com Silicon Graphics, Inc. (415)335-1673 Protocol Engines, Inc. 2011 N. Shoreline Blvd. Mountain View, CA 94039-7311
grw@cabernet.Eng.Sun.COM (Gregory Whitehead) (07/17/90)
In article <64290@sgi.sgi.com> rpw3@sgi.com (Rob Warnock) writes: >In article <269E07C3.604D@intercon.com> amanda@mermaid.intercon.com >(Amanda Walker) writes: >+--------------- >| In article <153@tots.UUCP>, tep@tots.UUCP (Tom Perrine) writes: >| > I hate to admit it, but the cell-phone (phone system) model of >| > addressing does have many advantages for the *user*. No matter where >| > you go, your logical address (phone number) follows you. >| >| In all of the cellular systems I've used so far, roaming is only half >| automatic. In particular, to place a call to a roamer, you have to dial >| the roamer access number for the area where they are, and then dial their >| phone number. This amounts to source routing, which is even more of a >| pain for mobile destinations than it is for "static" ones. Bleah. >+--------------- > >In fact, most of the current cellular romaing systems are 3/4-automatic... ;-} >Automatic for the roamer dialing out; that's half. But now many (most?) >cellular companies offer a hack such that if you dial a person's cellular >number in their home area *and* they're currently known to be roaming >somewhere (they've placed a roming call within the last 24 hours), the >home area system will give you an intercept recording which tells you >they're out of area... *and* gives you the roamer access number where >they are. Sort of an ICMP Redirect... ;-} ;-} Actually, GTE offers "Follow Me" Roaming in many foreign areas now. The roamer simply registers in the foreign area (by dialing *18) and all calls are forwarded automagically. It's pretty neat, but it sure can surprise your friends... ;-) -Greg
obrien@aeroaero.org (Michael O'Brien) (07/17/90)
In article <139016@sun.Eng.Sun.COM>, grw@cabernet.Eng.Sun.COM (Gregory Whitehead) writes: |> In article <64290@sgi.sgi.com> rpw3@sgi.com (Rob Warnock) writes: |> >In article <269E07C3.604D@intercon.com> amanda@mermaid.intercon.com |> >(Amanda Walker) writes: |> >+--------------- |> >| In article <153@tots.UUCP>, tep@tots.UUCP (Tom Perrine) writes: |> >| > I hate to admit it, but the cell-phone (phone system) model of |> >| > addressing does have many advantages for the *user*. No matter where |> >| > you go, your logical address (phone number) follows you. |> >Automatic for the roamer dialing out; that's half. But now many (most?) |> >cellular companies offer a hack such that if you dial a person's cellular |> >number in their home area *and* they're currently known to be roaming |> >somewhere (they've placed a roming call within the last 24 hours), the |> >home area system will give you an intercept recording which tells you |> >they're out of area... *and* gives you the roamer access number where |> >they are. Sort of an ICMP Redirect... ;-} ;-} |> |> Actually, GTE offers "Follow Me" Roaming in many foreign areas now. |> The roamer simply registers in the foreign area (by dialing *18) and |> all calls are forwarded automagically. The non-wireline services in California have recently banded together to permit this in an even easier fashion, as I recall. As best I can figure out, they must all send any roamers who've acquired the system in to a central clearinghouse all the time; anyone who calls your number back in your home area gets forwarded to you ALL THE TIME, unless you SPECFICALLY send a code that turns the service OFF. The manual warns that you'd better cancel this (or it self-cancels at midnight) when you return home or you won't get any calls THERE, either. Now THAT'S an ICMP redirect. -- Mike O'Brien obrien@aerospace.aero.org
perry@MCL.UNISYS.COM (Dennis Perry) (07/17/90)
Date: 13 Jul 90 17:41:23 GMT From: intercon!news@uunet.uu.net (Amanda Walker) Organization: InterCon Systems Corporation, Herndon, VA . . In all of the cellular systems I've used so far, roaming is only half automatic. In particular, to place a call to a roamer, you have to dial the roamer access number for the area where they are, and then dial their phone number. This amounts to source routing, which is even more of a pain for mobile destinations than it is for "static" ones. Bleah. Maybe Motorola's proposed satellite-based cellular system will be better. That's it! We put the core gateways into geosynchronous orbit... :-) -- Amanda Walker <amanda@intercon.com> Postmaster With An Attitude InterCon Systems Corporation _________________ Actually, thought along this line exist, i.e. put the gateways in the satellite. We thought of doing this at DARPA when I was there and we also explored such issues with the Multiple Satellite Program, an upto 200 node packet switched global communications network. With the demise of MILSTAR perhaps the light satellite concept will gain momentum. dennis
davel@vision.UUCP (Dave Lockwood) (07/17/90)
In article <1990Jul16.234452.29721@comp.vuw.ac.nz> newbery@rata.vuw.ac.nz (Michael Newbery) writes: >Not in New Zealand. Cell phones have their own area code which covers the >country. All cell calls cost the same per minute regardless of distance >(which is cheaper than the most expensive 'normal' toll step.) >As part of testing they placed a call, got in a plane and flew the length >of the country, keeping the circuit up during the entire journey. >(OK, so NZ is small, but it is bigger in area than the U.K. which does >require area access numbers). Sorry, the UK does _NOT_ require area access numbers on celluar! As far as I know there are three "area" codes - 0860 (which is for phones on the Cellnet network) and 0836/0831 which are for phones on the Vodafone network. I have one of the latter, and can be called anywhere in the UK (where there is service) by dialling the _same_ code+number. This "network" code is often confused as an "area" code...it isn't. -- -------------------- I'm totally incommunicado, except for --------------------- Dave Lockwood ...!uunet!mcsun!ukc!vision!davel davel@vision.uucp Technical Consultant ...!uunet!bulus3!bungia!vware!davel davel@vware.MN.ORG VisionWare Ltd, G4CLI@GB7YHF.194.GBR.EU dave@g4cli.ampr.org 57 Cardigan Lane, D.LOCKWOOD@ICLX davel@vision.co.uk Leeds, LS4 2LE, +44-532-788858 +44-831-494088 United Kingdom +44-532-304676 "Hey, You!" ----------------------- VISIONWARE DOS/UNIX INTEGRATION ------------------------
Mills@udel (07/18/90)
Phil, MSS was to put up 240 satellites in 800-km orbits by flinging them from the Shuttle at odd moments. They were to have steerable antennas and operate at Etherspeeds. Assuming random (!) orbit inclinations, a ground station would see about five satellites at a time and a satellite would see about 35 other satellites at a time. The average crosslink between the satellites would be about ten minutes. For homework tonight, you get to design the crosslink acquisition and routing algorithm. You also get to figure out how a new satellite not knowing the orbit elements or ephemeris of the other satellites finds its friends with a 5-degree beamwidth antenna. There will be a test in the morning. Open book. Oh, I forgot. The system is power-limited. The best routing may be achieved with minimum-power routing, rather than minimum-distance. In other words, take the usual linear metric (like hop count or delay) and square it. Then construct the minimum path. Surprising things happen, like this can result in the MAX number of hops, rather than the usual MIN. I worked on the project for a short while, but have not seen the final report. However, my simulations showed that the degree of connectivity quickly blows away SPF algorithms and blows everything away with min-power routing. Iridium is a rare metal probably ill used to build satellites with. You may remember the ill-fated XTEN network that could be described as an Ethernet radio operating at 10 GHz for metro-area coverage. Are we now seeing XTENs in the sky? Dave
rpw3@rigden.wpd.sgi.com (Rob Warnock) (07/24/90)
In article <9007171938.aa18804@huey.udel.edu> Mills@udel writes: +--------------- | You may remember the ill-fated XTEN network that could be described as | an Ethernet radio operating at 10 GHz for metro-area coverage. Are we | now seeing XTENs in the sky? +--------------- Not exactly. The 10 GHz local radio was not so much an Ethernet as a whole bunch of Localtalks... ;-} ;-} XTEN was [supposed to be] closer to a "non-mobile digital cellular radio". While the carrier frequency used for local distribution was indeed 10 GHz, the data rate was a paltry 256 Kbits/sec, shared among all stations located in a "cell", a 6-mile (max.) radius quarter-circle from a "local node" (that is, an area of about 28 sq. mi.). [Cells could, of course, be smaller than that, with careful power budgeting and re-use planning, just like today's mobile cellular systems. But there were only four frequencies available for re-use planning.] The traffic from the four cells of each local node was to be gathered and sent to a "city node" (central office), via point-to-point links not part of the allocation at 10 GHz. City traffic was then to be TDMA'd via one or more satellite transponders at geo-sync. Thus, nothing moved around. The routers would have been virtually identical to today's IP routers, except maybe simpler since the physical plant was so much more hierarchically laid out -- everything not local to a city went up to a satellite and back. The total "peak-busy-hour" traffic for New York City in 1992 was estimated [in 1979] to be less than one FDDI's worth. And today a lot of people think FDDI is slow. (SONET, here we come! ;-} ) The only historically safe guess is that we'll continue to underestimate our networking bandwidth appetites... -Rob (p.s. Fall of 1979, my job at Xerox/XTEN was designing/evaluating multi-access protocols for the 10 GHz local radio...) ----- Rob Warnock, MS-9U/510 rpw3@sgi.com rpw3@pei.com Silicon Graphics, Inc. (415)335-1673 Protocol Engines, Inc. 2011 N. Shoreline Blvd. Mountain View, CA 94039-7311
Mills@udel.edu (07/25/90)
Rob, Thanks for the interesting info. The primary reason my antenna was up at the time you guys were fiddling was that I suspected you eventually would intend to lay paw on the juicy amatuer radio allocation 10.0-10.5 GHz. Fortunately, that push never came to shove. Now, about 220-222 MHz... Dave