FreeBSD Router RAM, BUFFERS,CACHE, BOTTLENECKS ? Please explain?

[xazax]

I had just configured my FreeBSD router to connect to my DSL provider using PPPOE successfully.

My dsl is capped of course, I have about 10 pcs behind it, I can access the internet with no problem from any computer on my LAN.

I understand that DSL bandwith is not that fast in todays standards and I accept that part of it.

My question relates to the router.

I used to do tech support for Linksys and bought a Linksys Router at the time.

Unfortunately Linksys would not release detailed specifications on the Linksys router other than what you will find on the Linksys website.

They would not even release those specs to tech support so I was not fortunate to know advanced details about the product I supported.

I like the Linksys router and feel that they make a product worth the price, so Im not critizing Linksys in any way.

Every now and then I would recieve calls from either CABLE or DSL customers of various providers complaining about the performance drops in their bandwidth since they plugged the router into their modems.

Unfortunately I left the company without ever hearing a logical answer to this question or finding a solution for these customers. This was very dissappointing becasue it didnt happen to many of them, but enough to indicate that there may be a bottle neck in the Linksys router that may be generated.

I never had that problem with my Linksys.

Prior to linksys I worked for Epson. Epson at the time did release specifications on the printers.

What I remember from Epson printers is that they possess a 256 kilobyte buffer in the printer itself.
This 256 kilobyte buffer limited the printer to accept chunks of spooled data from the computer and printed on a 256 by 256 basis.

So if you were printing a small document from Windows NotePad there was no problem at all, but when you printed a Photoshop document that was 55 megabytes in size, you might as well come back the next day to see your hardcopy of that chick in a thong.

There are printers however that have upgradable memory. Given a printer that has the capability of holding 128 megabytes of memory would definitely print out that image in no time.

Heres where I am going with this. The topic of printers was posted to fill you in on the direction that I am going with this in relationship to the routers.

I would like some answers to my questions because I now only have theories, and theories are not actual facts.

To deviate away from the printing subject and return to the routing subject.

I assume that the Linksys router has a small buffer of some sort. I suspect that this buffer given the size of the router measures in either mid to high kilobytes or low megabytes.

Question: 1
In upgrading to my freeBSD router which is a 486 200MHZ computer with 64 megabytes of RAM, is there a chance of performance gain for my client machines accessing the internet and downloading?

Question 2
Is it wise to compare the scenarios between the Epson Printers 256k against an HP with upgradeable RAM to 128mb and the scenarios of the "suspected" buffer in the Linksys router possibly running in kilobytes versus my FreeBSD Router operating on 64 megabytes of RAM?

Question 3
Can it be true that by having more system RAM, I have more buffers available to establish more connections without performance degrade?

Question 4
Does anyone know why some routers like the Linksys slow performance dramatically and if having a pc like mine acting as a router would solve this problem?

I know these questions are novice but, I dont know enough about the internal details of buffers, cache, and I/O in relationship to IP networking.

 

[booze]

Hello xazax,

I don't want to go too deep here, but a place where you could start reading is "man tuning" in FreeBSD.
It should at least give you some hints what you are looking for.

 

[GGORTT]

Sorry but you wore me out about half the way through your memoirs. I had to bail!
Sorry!

 

[rycamor]

The basic answer is: I doubt you will get any better performance by upgradeing or tuning FreeBSD. Assuming you are using ipfw (running the natd daemon) or ipfilter to handle the NAT stuff, then FreeBSD is probably handling all of your network traffic without even the slightest difficulty. My FreeBSD router never even breaks 1% processor usage on natd.

Try this: just log into your router and run 'top'. Then tell all 10 users to blast away at their internet connections, and see how much processor and RAM usage it requires. THink about it: FreeBSD is able to easily handle data from 10-base and 100-base network cards with no trouble at all. Broadband internet usually only passes a fraction of that bandwidth (1 mbps if you are lucky).

And, basic Network Address Translation (NAT) really doesn't use many resources. It doesn't have to hold a large buffer of network data. All it does is pass data back and forth, without having to do any interpretation, except for the minimal manipulation of TCP/IP headers for the internal IP addresses.

Now, If your system were doing some more sophisticated tasks, such as content filtering, spam blocking, virus scanning, etc... then you might want to consider upgrading your machine.

But for NAT stuff, I would suspect that when users experience performance lag, it is probably due to faulty network configuration (PPPoE is really a horrible way to do things anyway). Of course, I don't know the Linksys specs either, so I can't comment there, except to say that I have never noticed a performance drop using Linksys routers for DSL. In fact, sometimes I have noticed a significant performance gain, especially when moving from internal DSL or cable modem cards, needing Windows drivers, etc... -------------------------------------------

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