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jimankrum

join:2008-03-18
Fort Collins, CO

Modem Settings

I bought a 3com modem »www.3com.com/products/en_US/deta···purchase
and have it hooked up and working but have a question on one of the settings.

In the ATM settings area are settings for PCR/SCR/MBS with default values of 4000/4000/10. What would be the best settings for these with Qwest dsl? If there is no blanket answer to this how would I go about finding the best settings? I've changed the values around and had some interesting results, but haven't really made heads or tails of it.



christcorp
Premium
join:2001-05-21
Cheyenne, WY
kudos:1

PCR/SCR/MBRhave to do with priority packeting when using an ATM in CBR and VBR. Constant Bit Rate and Variable Bit Rate.

Qwest uses UBR which is Unspecified Bit Rate. In other words, your packets go in whichever order they do along with the rest of the packets. So, it doesn't matter what those settings are because you aren't using them. You are using UBR.

Some modems may allow you to change to it, but it's the Qwest side that will dictate. So basically it's not an issue. Later... Mike.....


jimankrum

join:2008-03-18
Fort Collins, CO
reply to jimankrum

I did a little looking before I came here, and picked up that much before I asked. I just don't know how to apply the numbers.

By changing the settings I was able to affect my pings, by a significant amount. Some added ~500ms to the first hop. Obviously the settings make a difference even if ultimately Qwest has the settings at thier end which override any setting I put in. If I were to set these to values to something that would be throttled back by qwest, what would those settings be? I'd rather just match their settings though.



christcorp
Premium
join:2001-05-21
Cheyenne, WY
kudos:1

Using UBR, you won't put any settings in the PCR, SCR, MBS, or CDVT settings.


jimankrum

join:2008-03-18
Fort Collins, CO

OK, just did a test. If I put in 1/1/1 then my line will train, but ppp won't authenticate. I waited 5 minutes after power cycling the modem just to be sure. If I put in 9999/9999/9999, then everything is fine, good pings, feels pretty much normal.

I don't want to leave it like that though. I'm assuming that if I leave those settings then my modem is trying to force a priority on my packets and even though Qwest's server is limiting me it just seems rude on my part to impose that extra load on their server, however trivial that load may be.

I liken it to setting my max http max connections settings to 1000 in Firefox, the server I'm going to may have me limited to 8 and my setting is forcing the server to drop the other 992. That may not be an accurate analogy, but hopefully you get my point.

By the same token, I don't want to limit myself even more than Qwest is already. If Qwest's servers are limiting me to 6000 then I'm self limiting by accepting the defaults of 4000. I'd like to enjoy as much as I'm paying for.


jimankrum

join:2008-03-18
Fort Collins, CO

Actually, upon further inspection my pings are a little lower with everything at 9999. Only by about 3-4ms but it is consistent. Packet loss seems a little lower too, but I can't really measure that as consistently.