Activity light on my cable modem ...?

Yea, I notice the same thing. Even with the computer off the activity light is going crazy. I guess it means nothing now.
Reply to
Nog
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Exactly. What you're seeing is all your neighbors traffic. However, only the traffic that's destined for your cable modems MAC address, and gets decrypted, appears at the ethernet port. Therefore, you can't put a sniffer on the ethernet port and either decrypt the traffic, or try to measure it. (There are other ways of measuring traffic such as through the JTAG port).
A good clue is the netmask of your cable connection. You'll find it on the status screen of your router or wireless router. Depending upon your cable topology (I have a wall chart from CED magazine hanging on my office wall with all the cable technologies), you can guess the number of neighbors: 255.255.255.0 254 255.255.254.0 510 255.255.253.0 1022 255.255.252.0 4046 The local Comcast system runs with 1000 users per node. Incidentally, the big CISCO CMTS boxes can handle up to 65,000 customers per box (though up to 64 remote nodes).
The more users on your segment, the slower your cable modem will run. The limitation is not much in the download speed, but in the return channel (between 5-45MHz) which tends to get clogged with outgoing traffic (servers) and polluted by ingres (RF interference). This is why the cable modem providers don't offer symmetrical or business class service suitable for servers.
Start reading here:
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Reply to
Jeff Liebermann
If home cable and DSL connections were suitable for hosting, there would be no need for big server farms, full of web hosting servers, and big fat pipes to the internet. I run a few weather stations on local DSL connections. One or two users every few days is not much of a load. That works fine. However, for the ones that are publicly accessible, I mirror it to a hosting service.
Reply to
Jeff Liebermann

I have had cable service for a few years.
I leave the cable modem powered on all the time.
As I recall when I first got the unit the activity light would flash mostly
when I was using it.
Now it seems to be flashing all the time even when the computer is off.
Is the flashing light reflecting a huge volume of activity on the cable?
William Lee
Reply to
Will-Lee-Cue
I wonder if it is reflecting the increased number of subscribers on the cable system? Ya think it can ever bog down from high traffic?
William Lee
Reply to
Will-Lee-Cue
Thanks Jeff, That is intresting information. I was reading about website hosting and wondering if the cable would suport me being the server to my website. Looks like that is not such a good idea.
William Lee
Reply to
Will-Lee-Cue
Jeff,
Do you recall which issue of CED your chart came from?
I'm on Comcast with a netmask 255.255.252.0. I think that means 4046 max users for a specific upstream freq?
Mike N6DZU
Reply to
M2
Nope. There's a foldout insert in every issue. Usually it's sponsored by some manufactory. Once a year, they include the latest cable network topology diagrams. I save them all and have about 8 years worth. It's amazing to watch how topology changes along with alliances and mergers. Anyway, you'll see some of the wall charts at the bottom of:
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foundit:
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That's from 2003 which is ancient. I won't be in the office for a few daze, but I'll see if I can find it online.
Comcasts hybrid dual fiber pretzel ring star/bus topology will handle up to about 4000 homes per node. Very reliable on the backbone and to the main nodes. Constipated to the max on the mini-nodes and local distribution bus.
Reply to
Jeff Liebermann
and any broadcast packets that your ISP does't filter.
Reply to
Mark McIntyre
Copied from the following URL.
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Host/Subnet Quantities Table Class B Effective Effective # bits Mask Subnets Hosts ------- --------------- --------- --------- 1 255.255.128.0 2 32766 2 255.255.192.0 4 16382 3 255.255.224.0 8 8190 4 255.255.240.0 16 4094 5 255.255.248.0 32 2046 6 255.255.252.0 64 1022 7 255.255.254.0 128 510 8 255.255.255.0 256 254 9 255.255.255.128 512 126 10 255.255.255.192 1024 62 11 255.255.255.224 2048 30 12 255.255.255.240 4096 14 13 255.255.255.248 8192 6 14 255.255.255.252 16384 2
Class C Effective Effective # bits Mask Subnets Hosts ------- --------------- --------- --------- 1 255.255.255.128 2 126 2 255.255.255.192 4 62 3 255.255.255.224 8 30 4 255.255.255.240 16 14 5 255.255.255.248 32 6 6 255.255.255.252 64 2
*Subnet all zeroes and all ones included. These might not be supported on some legacy systems. *Host all zeroes and all ones excluded.
Lars
Reply to
Lars
except that the Internet hasn't been using Class A, B, or C for about 12 years now. See RFC1517, RFC1518, and RFC1519. A nice table to look at is found in RFC1878
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Replace the four zeros with the four digit document number.
Currently, there are 66770 network assignments by the five Regional Internet Registers (AFRINIC, APNIC, ARIN, LACNIC and RIPE). Most of those networks use a binary mask:
[compton ~]$ cut -d' ' -f3 < IP.ADDR/stats/[ALR]* | grep '2[45][08245]\\.[012]' | sort | uniq -c | column 44 255.0.0.0 9568 255.255.0.0 29350 255.255.255.0 2 255.128.0.0 1340 255.255.128.0 51 255.255.255.128 13 255.192.0.0 2346 255.255.192.0 35 255.255.255.192 21 255.224.0.0 6620 255.255.224.0 29 255.255.255.224 66 255.240.0.0 5480 255.255.240.0 11 255.255.255.240 163 255.248.0.0 1761 255.255.248.0 5 255.255.255.248 378 255.252.0.0 2858 255.255.252.0 550 255.254.0.0 3686 255.255.254.0 [compton ~]$
However, that's only 64377 assignments. The remaining 2393 assignments are in 186 non-binary sizes from '36' to '12582912' addresses - the latter being a network that could be divided into 192 255.255.0.0 sized subnets. Note that only 38962 assignments world wide use what had been called Class A, B, or C.
Old guy
Reply to
Moe Trin

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