Linksys → Re: Looking for the Common Thread in router problems

said by someoneyoudonotknow:

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...Cable is not switched at this time it is simply repeated like a hub. ...[and you can therefore sniff your neighbors traffic]...I use Comcast cable...

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My understanding is that switches are about the same price as hubs (at least for home users, I assume it carries through on the business end), and it would seem to be insane for a major ISP to use hubs on their network from a network-congestion point of view. Especially with hundreds of people potentially connected to a single node.

said by ToasterMan78:

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said by someoneyoudonotknow:

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...Cable is not switched at this time it is simply repeated like a hub. ...[and you can therefore sniff your neighbors traffic]...I use Comcast cable...

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My understanding is that switches are about the same price as hubs (at least for home users, I assume it carries through on the business end), and it would seem to be insane for a major ISP to use hubs on their network from a network-congestion point of view. Especially with hundreds of people potentially connected to a single node.

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If you think about it - a head end device may be responsible for 250 end user nodes. Of those - how many are actually allocated and in use in your neighborhood?? 20% or less - Total broadband users are only at 20% of households - that includes cable and DSL.

There is alot of traffic on the local segment of the ISP's LAN. You are using a shared resource. In some home installations,there may only be a few active drops - in some MANY active drops....

Bottom line - the more traffic present, the more traffic your router will have to handle on it's WAN side. From what I read on the boards, ALL the cheap routers have some type of lock-out problems - most likely under load.

AT the lab where I work, part of our certification of routers for OUR network is to load test them - crash them!! We make sure our configurations work - and tune config parameters if needed. Just remember the router does not have much of a CPU and memory (no P4 and gigs of mem). Think how easily you could crash a 386 box

The wireless Linksys I bought froze once a day (4 times in 4 days), any time of day with no discernable pattern (my setup details are in an earlier post.)

On Sunday, I ran a couple cable runs and put in a refurbished (wired) DLink DI-604. No freezes in 3 days (logging is enabled.)

For comparison's sake, I wish I could snag a new wired Linksys and see if that freezes on me.

dellswieg,

Fact:
In a lab envirnonment you can crash any router no matter how well you tune its config. Very simple, use pageant, smartbits, or agilent route injectors and apply and withdraw thousands of BGP or OSPF or even RIP routes per second and in a few minutes you expensive powerful router is toast! You don't even need a traffic load.(Usually not even that long. But boy is it kinda fun!)
Do not forget that even though these routers are small they have fairly respectable specs for the processor speeds, and memory and flash sizes. Do not forget that a Cisco 2600 router has a 50Mhz 486/Pentium class CPU with between 8-16 MB of RAM, and 4 - 32MB of Flash. And that router costs much more. I have pounded on all sorts of routers. And with its processor memory specs the Linksys should eat up the 2600 but it doesnt. For comparison the BEFSX41 has a 162Mhz ARM 9 processor, 16MB of RAM and 4MB of Flash! Linksys has a problem with its firmware developement,optimzation, source code versioning, and physical quality control. All symptoms of the sub $50 prices for a lot of their gear.

That was it for you.

Regarding cable internet architecture.
Cable Internet services piggyback off of traditional cable by being Frequency Division Multiplexed into a higher carrier that is filtered out of traditional devices. Only devices that listen for that carrier can pick it up. The data signal is encoded with 16-64 QAM and can be upwards of 30Mhz of spectral width. Because of the nature of legacy cable for each neighborhood or collection of neighborhoods there is a cable "node". A cable node is a router with a tie in into the neighborhood cable run. That same cable run phsically and electricaly connects to EVERY home that recieves cable, even if they do not subscribe to cable internet service. Thus cable is a hubbed architecture. If the cable were switched every home would not be electircally connected to the other. (This is what ethernet switches do, they segment the physical ethernet collision domain into a collision domain per port instead of per switch.) But the cable companies would have to replicate the analog and/or digital baseband video signal to many different physical segments. Not only would signal quality suffer due to increased load impedance, but costs would skyrocket due to the vastly increased cost of balancing out the impedance load, and building so many different physically seperate cable segments would simply not be pratical. Remember, why does cable get slower as more users use it? Because it is a shared architecture. Switches do not have this penalty.

Do not confuse the cost of little home switches and hubs with the costs of gear that ISP's have to pay. Their gear has to be reliable and the firmware needs to be bulletproof, not to mention that the basic technology of cable service just described, at this time mitigates against using cable "switches".
Cable modems are indeed the bridges between the cable wire and the ethernet wire. But only newer cable modems have the built in MAC-Filtering (L2 Bridging) capabilities. The data is still there on the wire for all to see.

Regarding heat, this certainly could not hurt any devices. Go buy some small aluminum heatsinks and glue them to the switch chip and the CPU chip in the linksys routers. It will help pull the heat out of the silicon mutch better.

James