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Cable Modems: Myths and Reality: 

Cable Modems: Myths and Reality Presentation by Richard Wiggins System Architect, NEM Online Michigan State University Author, The Internet for Everyone: A Guide for Users & Providers Co-host, Nothin’ But Net television show wiggins@msu.edu

At a Watering Hole in East Lansing: 

At a Watering Hole in East Lansing … an imponderable question...

Your Speaker and Cable Modems: 

Your Speaker and Cable Modems Cable modem at home since August 1995 One of first 50 people on the planet with cable modem service? (Unprovable assertion) TCI-MET service of TCI of Mid-Michigan Predates TCI’s national roll-out of @Home Applications: FTP and Web access to files from university, publishers High-speed download of new software releases Some Internet phone, CU-SeeMe Visited a family reunion in Alabama in 1996 via CU-SeeMe Running personal Web server at home since early 1997 Launched @Home service for TCI Chicago (June 1997)

Illustration: A Cable Modem Addict: 

Illustration: A Cable Modem Addict ...Since summer 1995

Reactions of Californians Visiting East Lansing in 1995 When Told “I Have a Cable Modem at Home”: 

Reactions of Californians Visiting East Lansing in 1995 When Told “I Have a Cable Modem at Home” “No you don’t!” “You must be confused; don’t you mean ISDN?” “It really runs at 10 megabits / second? No!” “It can’t be 10 meg for the upstream link can it??” “Gee, we don’t have this in Silicon Valley yet!”

The Perils of Speaking Before Librarians: 

The Perils of Speaking Before Librarians “The Web in the Blink of an Eye”


AGENDA What is a Cable modem? Who makes cable modems? Where are they in use? What do they cost? The myth of infinite speed Challenges and opportunities: Advantages Standardization Competition Reliability Solution for ubiquitous Internet?

LANcity (Bay Networks) LCP Cable Modem: 

LANcity (Bay Networks) LCP Cable Modem 10 megabits / second Bidirectional Symmetrical Suitable for cable plants with fiber to neighborhood, coax to home

Typical Cable Modem Configuration: 

Typical Cable Modem Configuration Ethernet Connection (Thin or Twisted Pair) to PC with Ethernet Card Conventional Co-axial Cable (the same cable you plug into your TV)

Typical Cable Modem Configuration in the Home: 

Typical Cable Modem Configuration in the Home Television Set(s) Cable Modem PC with Ethernet Card Ethernet (Thin or Twisted Pair) …to Cable System’s Head End Coax TV Cable

Typical Cable System with Internet Access: 

Typical Cable System with Internet Access Cable System Head End High-speed Internet Backbone Link Fiber Optic Links to Neighbor- hoods Conventional Copper Co-ax Cable to Homes

Possible Cable Modem Configuration: Multiple Computers in the Home: 

Possible Cable Modem Configuration: Multiple Computers in the Home Cable Modem PC with Ethernet Card

A Typical Cable Modem ...: 

A Typical Cable Modem ... …Connects 1 single host computer Though some can connect dozens of hosts Has its own IP address Though some share an IP address with the single connected host Operates at speeds from 1 megabit / second to 10 megabits / second Though some claim up to 30 megabits / sec Is bidirectional Though some use “telco return”

“Telco Return” Configuration: 

“Telco Return” Configuration Hybrid Cable / Telephone Modem PC with Ethernet Card Downstream Via Cable Co. Head End Upstream via POTS

General Instrument’s Cable Modem on a Card (“Surfboard”): 

General Instrument’s Cable Modem on a Card (“Surfboard”) Half-ISA slot card Cable “F” connector directly on card 27 Mbps data throughput over a 6 MHz channel Phone modem used for return channel (URLs, uploaded email, etc.)

Who Makes Cable Modems?: 

Who Makes Cable Modems? Bay Networks -- LANcity Motorola Zenith General Instruments Hewlett-Packard Scientific Atlanta Phasecom

Who Doesn’t Make Cable Modems?: 

Who Doesn’t Make Cable Modems? Intel Announced, then backed out in 1996 DEC Resold LANcity modems in 1995, left business soon thereafter

Relative Speed Comparisons: 

Relative Speed Comparisons Cable modems run up to 10 megabits / sec ISDN = 128 kilobits / sec Dialup modem = 28.8 kbps (or 33.6 or 56)

Deployment of Cable Modems: 

Deployment of Cable Modems Many companies @Home service in US (TCI, Comcast, etc) Media One, Time Warner in several US locations Cox Cable in Phoenix Shaw cable in Alberta Helsinki TV in Finland Marubeni cable in Tokyo Television Internacional in Monterey, Mexico Many others around the developed world Numerous trials beginning in 1995 Hype exceeded deployment rate in 1996, early 1997


Pricing Typically starts at ~ $30 / month Probably slow speed 1 IP address No Web server allowed Perhaps $70 per month for 1 IP address and 10 megabit service Perhaps $300 to $1000 per month for multiple IP addresses serving a business Some systems charge fees if you exceed monthly bandwidth quota

Sneaky Cable Modem Configuration: Multiple Computers in the Home: 

Sneaky Cable Modem Configuration: Multiple Computers in the Home Cable Modem PC running Transparent IP Gateway Software House-wide Ethernet

Rent vs Buy: 

Rent vs Buy Generally cable modems are not interoperable Not like buying a 28.8 dialup modem! Generally you rent the modem as part of the service fee Fundy Cable in Moncton, New Brunswick selling Scientific-Atlanta cable modem for $299 CDN Price includes installation

The World Wide Wait: 

The World Wide Wait The Web is terribly slow Easily can take 30 seconds to paint a screen Sometimes can take one minute What will we say about the Web in 2007? Do you remember when …. ? Are cable modems the answer?

Quotes from Computing Industry Czars: 

Quotes from Computing Industry Czars “There’s one big problem -- telecommunications bandwidth” -- Andy Grove, CEO, Intel “Bandwidth bottleneck. No question, that’s the biggest obstacle.” -- Bill Gates …but these two sell processors and software, not bandwidth! (but Bill Gates is investing in satellites)

What is Bandwidth, Anyhow?: 

What is Bandwidth, Anyhow? Technically, the theoretical carrying capacity of a communications medium Practically, the capacity that we expect from a particular medium E.g. a 33.6 modem moves 33,600 bits per second We also speak of the cumulative bandwidth of a network Bandwidth is important …but it isn’t the only consideration

Amdahl’s Law -- Simplified: 

Amdahl’s Law -- Simplified Gene Amdahl -- one of creators if IBM System 360 Architecture Each component of a computer system contributes delay to the system If you make a single component of the system infinitely fast… …system throughput will still exhibit the combined delays of the other components

Example: Travel to a Conference in Calgary: 

Example: Travel to a Conference in Calgary Drive to Lansing airport Wait for a plane, fly to Detroit Wait for a plane, fly to Minneapolis Wait for a plane, fly to Calgary Wait for a bus (a long time!) and ride to every hotel in Seattle Arrive at hotel, wait in line, check in Wait for slow elevator, head to room

Travel Example cont’d: 

Travel Example cont’d Total trip time was 7 hours Suppose we made the plane from Minneapolis to Calgary infinitely fast This removes about 2.5 hours of the flight time This does not eliminate the other components of delay Trip still requires 3.5 hours, even though one of the links was infinitely fast

Trying to Make Part of the Internet Infinitely Fast: 

Trying to Make Part of the Internet Infinitely Fast ….Isn’t possible Involves huge expense for diminishing payoff Doesn’t address all the components of delay

The Role of Routing: 

The Role of Routing The Internet is a packet-switched network Each data transfer is broken into chunks called packets Your URL request may fit in a packet or two The Web page you download may take dozens or hundreds of packets Overall this enhances the efficiency of Internet link utilization But for any one transaction it may slow things down

Links Between You and That Web Page: 

Links Between You and That Web Page Very common to have a dozen links -- or more Sometimes inscrutable From East Lansing to Ann Arbor is 60 miles with a 45 megabit/second link But data may visit Ann Arbor, then Chicago, then Cleveland, then Ann Arbor ... or worse Try the command TRACEROUTE (aka TRACERT) sometime


Congestion You “own” your 33.6 dialup connection You share: A campus Ethernet link A cable modem link to your cable system’s head end Your campus or corporate link to the greater Internet But in all cases you share every path between you ISP (or organization) and any other server anywhere on the planet

Congestion Varies: 

Congestion Varies By what everyone else is doing on the various paths you’re using By your own activity E.g. if you’re downloading software while surfing the Web Most campuses and ISPs experience “two hump” effect At 10:30 am or so and at 2:00 pm or so Eastern US feels effect as West coast surfers start using the Net

Bandwidth Isn’t the Only Issue: 

Bandwidth Isn’t the Only Issue There are many components to delay Delay, once added, can never be recovered Components of delay include:

Server Delays: 

Server Delays Routine delivery of a static Web page usually takes very little time But increasingly Web pages are delivered from databases Database lookups tend to be slower than file system lookups Also some database lookups tend to degrade dramatically with multiple users

The Cost of a Clickthrough: 

The Cost of a Clickthrough Many Web pages now feature banner ads Those ads are often on different servers, located remotely from the server where your page is The advertising servers are often very busy, thus slow Can add a second or more to delay

HTTP/HTML Handling of Images: 

HTTP/HTML Handling of Images As designed by Marc Andreessen: A page with 20 inline images …costs 21 transactions to download That’s 21 separate TCP connections That means “setting up” and “tearing down” each of those 21 TCP connections Total cost to you, and to the network, is tremendous One estimate: 40% of Web traffic

The Cost of Images: 

The Cost of Images Images, by far, are the biggest cost of Web pages They can be huge -- individual complex image might be 100K Smart Web designers keep image sizes very small But few Web designers are that smart

Cost of Images Will Only Increase: 

Cost of Images Will Only Increase Graphics-rich presentation is demanded A text-only Web site would be ridiculed “Hired guns” design for what looks good... ... not for what’s bandwidth friendly

Web-Page Animation: 

Web-Page Animation Animated GIFs can be much bigger More sophisticated forms of animation take even more If you leave an animation running in a browser window it consumes your CPU

Real Time Data Feeds: 

Real Time Data Feeds RealAudio Audionet plays dozens of radio stations on demand MSU broadcast its graduation last year Doobie Brothers concert as well www.policescanner.com Dallas, LA police scanners I am not making this up! Archival as well as real time NPR programs all archived

Real Time Video: 

Real Time Video Big growth area C-Span, Fox News are pioneers Tremendous bandwidth hog Equivalent of a T1 line for one feed That’s 1.5 megabits / second Many organizations’ entire Internet feed Audio, by contrast, might require only 28K of bandwidth

Java Applets: 

Java Applets Can be terribly slow to load and start Java assumes a “virtual machine” which is implemented in software Inherently slow Can take a second, or several seconds, to start executing A frustrating form of delay Often unexpected Often useless

The Cable Modem Example: 

The Cable Modem Example Even if cable modems were infinitely fast …they only account for the local loop How congested is the local segment your cable modem is connected to? How fast is the cable company’s connection to national backbones? How congested is that connection? How congested is the rest of the Internet? How fast is the remote server?

Cable Modem Reality and Illusions: 

Cable Modem Reality and Illusions Some people think they are infinitely fast They need to hear this presentation Example: TV producer When they work, they are great Downloads of next version of Netscape go real fast Internet is always available without overhead of dialup But -- there are periodic outages And it is a shared medium

Internet Speeds: 

T1=1.544 Mb/sec DS-3 = 45 Mb/sec OC-12 = 622 Mb/s Internet Speeds

The Tragedy of the Commons: 

The Tragedy of the Commons Economists believe a shared public good will always be oversubscribed Give people very fast local links, … and they’ll consume all the bandwidth on your long-haul link There are some schemes to help...


Caching Storing a local copy of data near the consumer In the PC’s memory or disk space for browsers Earliest versions of Mosaic didn’t do this Need was apparent At a “proxy” server near the user On a campus At an ISP


Mirroring Decision to replicate an entire Web site or database at various disparate locations E.g. AltaVista has a European mirror site Entire database is moved periodically Or, provisions for staged updating When links from “mother lode” are uncongested Archie experience: many mirrored databases need not be in perfect sync

Mirroring Benefits: 

Mirroring Benefits Not only helpful, but crucial, to success of some services Improves performance, offers backup sites Also saves bandwidth for transoceanic links Market niche: build a popular service convince the owners of transoceanic links to pay for a copy on their side of the pond

Offline Viewers : 

Offline Viewers E.g. Webwhacker Ultimate extreme of prefetching You point the offline viewer at a Web site Tell it to fetch the New York Times once a day Why can’t the browser learn routine behavior and do this automatically?

Switching versus Routing: 

Switching versus Routing Every packet is individually addressed and routed That’s a LOT of work for the routers Proposals for “tunneling”, “wormholing” and “switched IP” Make some Internet links behave more like the phone network You make a connection at beginning of session, and the route between server and user is fixed

The Gigapop: 

The Gigapop Internet2 calls for much faster backbone links: At least OC-3 (155 megabits/second) Soon, OC-12 (622 megabits) Then OC-24 (1244 megabits) The Gigapop = a routing/switching station capable of handling these speeds Requires the fastest of routers A prototype gigapop is in place at Research Triangle in North Carolina


Multicasting Proven concept, deployed years ago with the Mbone Mbone required special routers and special software on end-user desktop Without multicasting, if 1000 people in Seattle tune into a RealVideo lecture from East Lansing… There are 1000 separate redundant connections Tremendously wasteful of network capacity

Benefit of Multicasting: 

Benefit of Multicasting Multicasting has 1 connection cross country To each local ISP or campus at which there are listeners Then data is routed to each sub-network as needed Big winners: Audionet and other net casters TV and radio broadcasters don’t worry about number of listeners

Limits of Bandwidth Conservation: 

Limits of Bandwidth Conservation You can only cache what doesn’t change Mirroring is currently mostly manual Real time data can be neither cached nor mirrored …but… @Home is implementing caching, mirroring, and their own national high-speed backbone

Competition for Cable Modems: 

Competition for Cable Modems

Faster Modems: 

Faster Modems 33.6K modem is about 16% faster than 28.8 56K modem would be about twice as fast …whenever it’s real Even fast modems are only a fraction of speed of Ethernet Factor of several hundred Only in theory! Ethernet is shared

Faster Metropolitan Links: ISDN: 

Faster Metropolitan Links: ISDN An old digital technology Provides about 128 kilobits / second Costs about $30 to $70 per month Rapidly being overshadowed by newer schemes

Faster Metropolitan Links: ADSL: 

Faster Metropolitan Links: ADSL Moving 1.5 to 6.1 megabits/second Over existing copper phone wires Requires improvements to parts of phone network Asymmetric: megabits to user, only kilobits from user URLs are small Web pages are big Don’t install a Web server on your ADSL link

ADSL: The Big Lie: 

ADSL: The Big Lie

Challenges and Opportunities: 

Challenges and Opportunities

Advantages for Consumers: 

Advantages for Consumers Web pages paint much faster ...although not infinitely fast Streaming media can withstand higher sampling rates ...limiting factor tends to be long-haul Internet links Bulk file downloads are much faster You can download the next version of Netscape Navigator in minutes instead of hours

All the Net, All Day Long: 

All the Net, All Day Long Overhead of modem dialin is more than you think Having the Internet always available changes your approach Switchboard replaces 911 Also replaces your address book Weather Channel home page replaces Weather Channel on TV Your loved ones file missing person reports Put it in the basement

Remote File Access: 

Remote File Access Michigan State University has deployed Andrew File System (AFS) campus-wide Every faculty / staff / student has AFS space Cable modem users in East Lansing area can mount their AFS space as a virtual drive on home PC File access time is same as on campus Sometimes better!


Standardization Most cable modems are not interoperable Industry is working on standards MCNS: Multimedia Cable Network Systems standard Developed by industry group CableLabs, modem vendors

Competition Summary: 

Competition Summary X2 dialup modems ISDN Slow deployment in North America Still meets many needs ADSL Ad for ADSL service on way from Calgary airport Satellite (ie DirectPC) Very asymmetric, telco return

Reliability Challenges: 

Reliability Challenges Weather Copper changes characteristics when it’s -10 degrees F Cable cuts Power outages Other users’ Ill-behaved equipment Server, router outages

Cable Companies’ Service Level Commitment: 

Cable Companies’ Service Level Commitment A 24 X 7 network demands 24 X 7 service staff Multi-hour outages of phone service would never be tolerated Some applications are critical E.g. teleradiology project in mid-Michigan If radiologist doesn’t get the image, quality of health service diminished Cable companies have had PR problems Please: at least state your service commitment

Challenge: Where is the Back Office?: 

Challenge: Where is the Back Office? Some local tech support essential to keep network running But where is the help desk? Other value-added service points? Who helps you configure Eudora or install a helper app? Where is the person who fixes your account if something is wrong?

The Promise of Broadband: 

The Promise of Broadband Media One (formerly Continental Cablevision) slogan: “This is broadband. This is the way” Will cable companies actually enter the telephone business? ...before phone companies enter the cable business?

What About Mobile Access?: 

What About Mobile Access? Every Ethernet card on the planet carries a unique ID number Thanks to DHCP, my laptop works anywhere on MSU campus Why can’t I plug it into the wall at the International Hotel? And get high-speed access to all my e-mail, Word documents in progress, etc? The cell phone industry figured it out Will the phone companies offer this on ADSL?

Solution for Ubiquitous Internet?: 

Solution for Ubiquitous Internet? Network Computer hype: Oracle, Sun, IBM, others Easy to extend cable modem into complete network terminal Set-top box from Scientific Atlanta, HP, LANcity? Game-system based Web surfer from Sega New cable-ready version of Web TV? Box could talk Ethernet or CATV

Related Web Sites: 

Related Web Sites Cable modem facts summary: http://www.teleport.com/~samc/cable5.html General Instrument Surfboard NIC: http://www.gi.com/vware/sb1000.htm LanCity cable modem specs: http://www.baynetworks.com/Products/Modems/2688.html#tec Zenith cable modem specs: http://www.zenith.com/main/network_systems/data.html

Related Web Sites: 

Related Web Sites Cable modem consortium site: http://www.cablemodem.com/ Motorola CyberSURFR modem specs: http://www.mot.com/MIMS/Multimedia/prod/specs/modemSpec.html

The Slides for this Talk...: 

The Slides for this Talk... Will appear at this location: www.nemonline.org/present/rww Speaker’s email address: wiggins@msu.edu

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