eli@spdcc.COM (Steve Elias) (09/19/89)
In article <19661@mimsy.UUCP> chris@mimsy.UUCP (Chris Torek) writes:
!i wrote:
!!i'm not sure if 4 out of 5 networking cats would agree with
!
!I think they would---certainly so if they had experience with both
!broadband and fiber:
!
! a) broadband is slow.
wrong. 10 Mbits/sec is not "slow", by today's standards.
!You can get 10 MB/s by using three broadband channels (TV channel
!bandwidth is ~4.5 MB/s), as in DEC's product(s?). You can buy
!80 MB/s off the shelf from Proteon. (18 TV channels anyone? :-) )
all of Chipcom's broadband products run at 10 Mbits/sec,
though forward and reverse channels are required.
other broadband vendors also sell full speed products.
it is rare to see a network which pushes the limits of
a 10 Mbits/sec ethernet, you know!
! b) broadband requires maintenance.
yes. and a large up-front fixed cost.
!I am not up on the current costs for new installations of each. It
!does seem obvious (which does not make it necessarily true) that it
!should cost less to use existing broadband facilities than to run new
!fiber optic lines, at least initially (maintenance costs add up fast).
!But fiber is much nicer, and should be cheaper in the long run.
surely, the market is moving towards FIBER FIBER FIBER!
but we've yet to see standardized Ethernet/Fiber products.
even the FDDI spec is incomplete...
--
... 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... */rsmith@vms.macc.wisc.edu (Rusty Smith, MACC) (09/19/89)
In article <4616@ursa-major.SPDCC.COM>, eli@spdcc.COM (Steve Elias) writes... >In article <19661@mimsy.UUCP> chris@mimsy.UUCP (Chris Torek) writes: >!i wrote: >!!i'm not sure if 4 out of 5 networking cats would agree with >! >!I think they would---certainly so if they had experience with both >!broadband and fiber: >! >! a) broadband is slow. > > wrong. 10 Mbits/sec is not "slow", by today's standards. > >! b) broadband requires maintenance. > > yes. and a large up-front fixed cost. > > > surely, the market is moving towards FIBER FIBER FIBER! > but we've yet to see standardized Ethernet/Fiber products. > even the FDDI spec is incomplete... > We have a large broadband system here. There are four trunks and the longest is a cascade of 15 amplifiers. We have approxiamately 40 Chipcom ethermodems on our network. The use 18 MHz of bandwidth, which is 3 t.v. channels. This is not much bandwidth for a cable t.v. system. The problem with the Chipcoms is that they are "dumb" devices with no way to manage or find when they drift and go into high errors. We couple them with Dec LanBridges and manage the network through statistics of the LanBridges performance. With a campus of 40k plus students and multiple services the broadband system was the only one that could meet our requirements at the time. To go between 2 buildings it would much easier to install 2 Dec LanBridges with a fiber interface on one side. There are 3 of these here on the Engineering campus to extend "backbone" presence to their other buildings. They are reliable and easy to install. Broadband is not slow, but it does require maintenance and high installation costs. The fiber has low installation costs and no real maintenance. That's my 2 cents worth. Hope it helps. Rusty Smith Internet: rsmith@vms.macc.wisc.edu MACC Data Communications Bitnet: rsmith@wiscmacc (608) 263-6307 Univ. of Wisconsin @ Madison
eli@spdcc.COM (Steve Elias) (09/20/89)
(Rusty Smith, MACC) writes: >We have a large broadband system here. There are four trunks and the >longest is a cascade of 15 amplifiers. We have approxiamately 40 >Chipcom ethermodems on our network. The use 18 MHz of bandwidth, which >is 3 t.v. channels. This is not much bandwidth for a cable t.v. >system. The problem with the Chipcoms is that they are "dumb" devices >with no way to manage or find when they drift and go into high errors. i can't comment on future products. as for current products: our Marathon bridge is manageable and can couple distant ethernets via broadband cable -- though it uses MAP channel allocations, which overlap other commonly used frequencies... as for the 18 MHz for Ethermodems -- i believe Chipcom offers a 12 MHz version. -- ... 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... */
chris@mimsy.UUCP (Chris Torek) (09/20/89)
>In article <19661@mimsy.UUCP> I wrote: >>broadband is slow. In article <4616@ursa-major.SPDCC.COM> eli@spdcc.COM (Steve Elias) writes: >wrong. 10 Mbits/sec is not "slow", by today's standards. By *whose* standards? >... it is rare to see a network which pushes the limits of >a 10 Mbits/sec ethernet, you know! Rare for you, perhaps. 10 Mb/s is only 1.25 MB/s. That is slow. If you have 100 hosts sharing the network, and each is 1% busy, your available bandwidth is at best 1.25 MB/s. (Since network traffic tends to be bursty, it actually varies.) In any case, old workstations (Sun 3s) with current software (Jacobson's header-prediction tcp) already use 1 MB/s (8 Mbits/s) on Ethernet. Tomorrow's workstations, which (with the exception of a few places) will be running yesterday's software, should be able to do the same. Once you put today's software on them. . . . Look at it another way: today's small computer disk drives will move more than 3 MB/s (on synchronous SCSI). Today's file systems cut this in half (alas!). But this means your file server should be able to `want' 1.5 MB/s when talking to a single host. 10 Mb/s is thus a recipe for bottlenecks: today, when fusing two LANs into one, and tomorrow, as a LAN itself. (Good thing FDDI still looks promising.) -- In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7163) Domain: chris@mimsy.umd.edu Path: uunet!mimsy!chris
eli@spdcc.COM (Steve Elias) (09/20/89)
In article <19691@mimsy.UUCP> chris@mimsy.UUCP (Chris Torek) writes: >>In article <19661@mimsy.UUCP> I wrote: >>>broadband is slow. > >In article <4616@ursa-major.SPDCC.COM> eli@spdcc.COM (Steve Elias) writes: >>wrong. 10 Mbits/sec is not "slow", by today's standards. > >By *whose* standards? 99 44/100 % of networks out there are 10 Mbps or slower. that's my criterion for saying that 10 Mbps is not slow by today's standards. >>... it is rare to see a network which pushes the limits of >>a 10 Mbits/sec ethernet, you know! > >Rare for you, perhaps. i contend it is rare among that 99 44/100 % of networks that i mention above. please pardon mon affaire if you think my concept of "rarity" doesn't match yours. >10 Mbps is thus a recipe for bottlenecks: today, when fusing two LANs into >one, and tomorrow, as a LAN itself. (Good thing FDDI still looks >promising.) i agree that we are cooking a recipe for bottlenecks -- in that sense, 10 Mbps is slow. by the same token (should i plug token bus as a backbone network, here?), you will be able to call FDDI "slow" in a few years, when processing and data xfer requirements advance to the point where FDDI backbones are overtaxed... you can always call current technology "slow", but if everyone's running at the same "slowness", then they aren't "slow" relatively. semantics, right? -- ... 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... */
haas%basset.utah.edu@cs.utah.edu (Walt Haas) (09/23/89)
Well, to add my $0.02 worth to this debate,... We have both broadband and fiber and are expanding both. If *all* you want is Ethernet connectivity over moderate distances by all means put in fiber. Where broadband has the advantage is that it lets us distribute eight or so instructional TV channels, four kinds of data channel, and controllable security cameras for the University police, everywhere on campus with one installation. The down side is the substantial cost of adding an Ethernet onto the broadband. Even in buildings where we have broadband already we frequently pull fiber for Ethernet if there is a relatively short hop to an existing Ethernet. The cost of the fiber extension runs around $4k, the broadband approach probably at least twice that. -- Walt Haas haas@cs.utah.edu utah-cs!haas