Motorola's CyberSURFR Cablemodem: Motorola has a a large marketshare
of the current deployed enduser cablemodems. @Home uses them. Time
Warner uses them.
The state of the
Cablemodem industry: This excellent
article from USA Today sheds light on the state of cablemodems and why the industry
barely exists today (if ever). [An older article but still relivant]
Check out Bob's web page with bookmarks
to other Cablemodem vendors.
Check out a new
vendor to the cablemodem ranks: Terayon with
funding from Cisco Systems
Comparison of ISDN to ADSL to Cablemodems and my initial thoughts of
@Home's service
I recently moved to an area where ISDN, ADSL and cablemodems are
available (yes, I'm, spoiled!). Being technically experienced with
all three of these technologies, the decision was going to be based
on price. The rational for my cost justification is based upon the
fact that I have my machine configured at home to poll POP3 mail
about every 15 minutes, poll news, etc 24 hours a day, 7 days a week.
So.. usage cost comes into play for dial-up connections. Check out
the numbers:
Pro: cheaper, 2 voice lines, dedicated bandwidth, static IP, can choose
your ISP
Con: Dial-up circuit, only 128Kb/s of bandwidth, only 140hrs left out of
160hrs per month (free), usage billed during business hours, no free local
voice calls, if someone hogs your line from the Internet, your
monthly bill will go through the roof!
Pro: 384Kb/s dedicated link, Always up, static IP address, voice
service over same copper pair, can choose your ISP
Con: High cost, ADSL is in trial and service might go away or become
more expensive
Pro: 2Mb/s down -- 500Kb/s up, Always up, static IP address, setup
fee includes on-site setup, ISA or PCI 3Com NIC, and patch cable.
Con: No ISP choice, shared cable plant, single source for ISP
So.. As you can tell, it really is a no brainer in terms of cost and performance
on paper. How does the @Home experience really work? Good. Not great though.
@Home is the cablemodem and networking arm of several different CableTV vendors
including: CableVision, ComCast, COX, InterMedia, Marcus, and TCI. The @Home service
in my area uses the
Motorola CyberSURFR Cablemodem at the enduser's home and a HFC or Hybrid Fiber-Coax
system for data connectivity back to the main node.
So far, connectivity has been pretty good but I've noticed a few things:
Once the connection is running, the performance is impressive: As a test,
I downloaded Netscape Communicator (Enterprise version) which is an ~18MB
file at roughly 400KB/s. I imagine this speed is due to @Home's massive caching
server but that is still awesome.
Latency (PING times) vary widely: I have noticed that this system has ping times
at ~18ms within the local cablemodem system but usually the ping times to the
Internet skyrockets up towards 200ms (Alter.net [BBN]). This SUCKS for any on-line
gaming situations!
Connectivity pauses: Since getting the service, I have noticed that
connectivity is initially slow. It seems that the Motorola hardware has
two network queues:
Active: These connections are serviced immediately
Idle: These connections are checked for any queued traffic
every so often. I have found that I will lose 5-8 seconds worth
of PINGs before connectivity resumes.
All in all.. the @Home service seems to be initially great. Always up.. decent
performance in BOTH directions.. etc. I'll add more to this area when I can.
Chambers Cable is trying again..
12/6/97
Chambers Cable of Chico, CA is starting a commercially available cablemodem service
for a relatively low cost. Though the system may seem initially like a good deal,
there are several problems with their design that will make it ultimately fail until
they upgrade their coax cable plant. Here are the facts as of November 1st, 1997:
Why should you be
weary of Chamber's second attempt?
Chambers
choose to go with a split cablemodem / modem design because they realized that their
cable plant is less than optimum:
1) Their coax backbone network in Chico, CA is not clean distortion-free)
enough to handle cablemodem traffic.
2) As usual, the Chico plant is a low priority for Chambers. See this
press release on how Chambers is upgrading
their other two coax plants but not Chico.
3)Chambers is not interested in upgrading all of their in-line coax amplifiers
to handle bi-directional signals.
4) Most of all their system's in-line amplifiers are running at their maximum
bandwidth (no room for more channels)
5) Chambers does not have enough network bandwidth to back haul the traffic
Chamber's coax
backbone system doesn't have any redundancy nor the backbone capacity to handle more
channels.
With the system I originally deployed, we were using a full 6Mhz channel
for each direction yielding 10Mb/s for user's transmitted and received traffic. Their
new system utilizes (2) 3Mhz channels [probably the same spectrum I was using before]
for a maximum transmit rate of 6Mb/s per channel UNI-DIRECTIONAL ONLY.
How many users do you think it will take to saturate the (2)6Mb/s links when each
enduser's machine is connected at 10Mb/s Ethernet speeds?
Last time I checked,
Chamber's connection to the Internet was only a 384Kb/s Fractional T1 connection. Also,
remember, this link is for their existing analog modem dial-up service too!
Ok, so lets be generous and say they have a upgraded it to a FULL T1. Still,
a connection like this will be a major bottleneck for their new cablemodem customers.
If you figure that Chambers will have (50) concurrent cablemodem customers trying
to download at 6Mb/s each, that's 300Mb/s of traffic trying to be serviced by a
1.5Mb/s circuit!! To be honest, today's Internet isn't that fast nor can most
enduser's computers handle such a data rate. Also, it will be seldom that every
cablemodem user will be downloading simultaneously but Chambers will definitely
sign up more than (50) people.
Ok.. lets try: 300 users * 100Kb/s = 30Mb/s
Still not a pretty thought huh?
For Chambers to offer a decent service level to their customers, they will need to
implement at least (1) DS3 (45Mb/s) connection today and be prepared to get a
a OC-3 (155Mb/s) or fractional OC-12 (622Mb/s) connection in the future.
Don't count on Chambers even ordering a T3 (DS3) anytime soon!
Chamber's existing
Cable service is known for crappy TV signal quality in Chico and their existing
analog Dial-in modem Internet service has had it's problems too.
Lots of busy signals..
Lost e-mail.. etc.
This style of
cablemodem design is only good for the occasional internet surfer that downloads far
more data than they upload. The reason for this is because the speed of this system
limited to the cablemodem's analog modem port. Currently, this cablemodem's modem
port supports v.34+ which can yield 33.6k in the best cases. I haven't heard any
news of a 56k modem port (or upgrade) for the Scientific Atlanta cablemodem nor if
Chambers will upgrade their modem pools to support 56Kb/s connections.
I haven't
confirmed this yet but I'm pretty sure that since this system is modem-based, once
you are off-line, you CANNOT contact your machine at home unless someone initiates a
connect from your house. Most bi-directional cablemodems are on-line 100% of the
time. Most likely, this is purely a firmware issue that could be implemented
by Scientific Atlanta but I doubt Chambers would be inclined to enable this feature.
You will still
need an extra modem line if you are going to be on-line all the time (~$16/month + $30
install)
You are required
to purchase the Scientific Atlanta cablemodem before you can even get on-line. Since
there are still NO standards for cablemodem systems and if you move away from Chico,
you need to either sell the modem or become proud of your new $300 pet rock!
Beyond all of
these issues, the real sad part of this new system is that doesn't come even close to
the same performance and availability levels that my original system did. Why? Read
the next section.
So should you
buy it? Hmmm... that depends. When the system works properly, it should be
significantly faster than 33.6 / 56Kb/s modems or ISDN. The issues will be about
how well they manage the system and whether or not they will upgrade their coax backbone
to deal with the new demand. If you can get lease a cablemodem from Chambers and you
are willing to deal with slow to dead network performance on occasion.. go for it.
Try it.
Chambers Cable and CSU Chico's original Cablemodem venture..
Chambers Cable and California State University, Chico conducted a preliminary
test of sending/receiving TCP/IP over existing Cable TV system at 10Mb/s
(Ethernet speeds). This pilot lasted about 8-10 months and Chico State wanted to
deploy the system on a city-wide basis but Chambers Cable was not interested in
investing the necessary money to bring their existing system up to
1990's specs. Ultimately, to make a long story short, Chambers dropped
the project since they didn't feel that Cablemodems would be a profitable
venture. This is very unfortunate for the power users of Chico since the
only other high speed alternative to cablemodems is
ADSL.
How does it work:
In Chico, Chambers Cable provides various television programming from channel 2
to, currently, channel 36. Cablemodems and other hardware made by LanCity
Corporation, receive Internet traffic on an unused channel (37) and send Internet
traffic back on channel (-2). If you would have tuned your TV to channel (37)
when the pilot was active, you would have noticed the slightly moving horizontal
lines. Between those two lines was network data traffic!
A little Background:
Each non-compressed television channel uses typically about 6Mhz [6 million signals
per second] of bandwidth for both the video and audio signals. In contrast, a
common analog telephone line uses only about 3.2Khz of bandwidth. So if you think
your 28.8k modem is fast.. you haven't seen anything yet! Putting it very
generically, the cablemodem is just like an analog modem using a MUCH larger
bandwidth to transmit and receive data over a different connection.
This how my test network was configured. This screen capture was taken from the
Win95 application 'Ws_Watch' now called What's UP from
IpSwitch [very cool]
You are graphical user
(for this main page) since 8/28/99
Rolf Ostergaard's Cablemodem site: A great site for
research docs, standards, etc!
GTE's WorldWind: The real truth about their
service and how they do system-wide bandwidth throttling!
Motorola's CyberSURFR Cablemodem: Motorola has a a large marketshare
of the current deployed enduser cablemodems. @Home uses them. Time
Warner uses them.
Chambers
choose to go with a split cablemodem / modem design because they realized that their
cable plant is less than optimum:
So should you
buy it? Hmmm... that depends. When the system works properly, it should be
significantly faster than 33.6 / 56Kb/s modems or ISDN. The issues will be about
how well they manage the system and whether or not they will upgrade their coax backbone
to deal with the new demand. If you can get lease a cablemodem from Chambers and you
are willing to deal with slow to dead network performance on occasion.. go for it.
Try it.
