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RBNetEngr
join:2009-05-07
San Antonio, TX
| [Wired] BEFSR41 V1 and V2 Slowness - Explanation
I have read through many postings, including those which are several years old, which discuss slowness problems with the BEFSR41. Generally they indicate that if the BEFSR41 is bypassed and the PC connected directly to the cable/DSL modem, the slowness goes away. They also discuss slowness when multiple computers are trying to share the internet connection.
Well, I can confirm to you that the reason you will experience this with the BEFSR41 Version 1 (V1) and Version 2 (V2) units is that the WAN connection only operates at 10Mb/s, HALF-DUPLEX. What half-duplex means is that the connection between the BEFSR41 and the cable/DSL modem can only transmit OR receive at one time. It cannot simultaneously transmit AND receive at the same time. To attempt this will result in a collision of the transmit and receive frames, and the frames will need to be retransmitted, resulting in delays.
Conversely, all modern computers are equipped with Network Interface Cards (NICs) which support both full-duplex and half- duplex modes, as well as speeds of 10 and 100 Mb/s, and most new NICs even support 1000 Mb/s. By default, these NICs will automatically negotiate the highest common speed and duplex mode available between the NIC and connecting device (switch, router, modem). Likewise, the DSL/cable modems also support 10/100Mb/s and full/half duplex, and will auto negotiate to the highest common speed and duplex mode.
In the human world, think of a road with a bridge that crosses a small creek. The bridge is only one lane wide, and traffic comes from both directions to cross the bridge. Only one vehicle, going in one direction, may cross the bridge at any one time, with the other vehicles (in both directions) waiting their turn.
THAT IS HALF-DUPLEX, and that is what is happening between your BEFSR41 and your DSL/cable modem!
By contrast, FULL-DUPLEX allows the transmit and receive frames to flow independently of each other, (think of a two-lane bridge analogy). In this case, the limit will be the uplink and downlink speeds provided by your ISP, as well as the network latency between you and your source or destination host.
Getting back to the BEFSR41: as a result of this half- duplex mode, the best throughput that you can expect to achieve with the V1 and V2 units is about 5Mb/s, which is the value that many people have measured. This will vary based on the amount of transmit and receive data that is simultaneously being transferred. THERE IS NO WAY TO IMPROVE THE PERFORMANCE OF THE BEFSR41 V1 OR V2. Even the latest firmware upgrade will not change this characteristic.
With more and more home DSL and cable services offering speeds above 10Mb/s, there is no way to realize a speed improvement by using the BEFSR41 V1 or V2. You will need to replace the unit. And even for those broadband services that operate at speeds below 10Mb/s, you will still deal with the contention issue caused by the half-duplex connection between the BEFSR41 and the DSL/cable modem.
I suspect that the V1 and V2 versions of the BEFSR81 also suffer from the same problem, since it is essentially the same device, but has an additional four switch ports.
I can't speak for the V3, V4, and V5 versions of the BEFSR41, as I do not have them available for testing. I have seen comments posted which state that these later versions do support 10/100Mb/s ethernet on the WAN link, but nobody has confirmed whether they operate in Half-Duplex or Full-Duplex mode.
I hope this helps!
-rb | |
keithrunfola
join:2001-12-03
Atlanta, GA
 ·Comcast
| "I hope this helps!"
It sure does. I get 1MB/s with the Linksys BEFSR41 and 2MB/s
without it. I've tried everything to get the Linksys up to 2MB/s but nothing works. Your post is very convincing that the box just sucks and need to be replaced. That's my next mission.
Thanks. | |
RationalRabb
join:2009-07-04
Coeur D Alene, ID
| reply to RBNetEngr
Probably should be noted that specs on the newer, Cisco/Linksys BEFSR41 say 10/100 mb/s. However, I found it curious that, while places like Amazon and Best Buy advertise this router as full-duplex, Cisco does not even mention whether it is full or half in the spec sheet or ANY of their literature on the router. Are we to assume that 100 mb/s can only be achieved at full duplex?
Note that I am talking about the newer router, which is since Cisco bought Linksys, not versions 1 or 2 mentioned above. The latest version is 4.3.
I am in the process of throwing my v2 in the garbage. It has served me fairly well over the past few years (although I find, after reading RB's post above, less than optimally), but began slowing down about a week ago. It has gotten slower on a daily basis until I am to a point where Web page loads take anywhere from 5 minutes to an hour if they are anything other than plain text.
I've made no drastic changes in my network configuration, Internet connection is fine direct from the modem, and my D-Link wireless router (which I'm using now) is working fine as long as I take the BEFSR out of the picture. I have only to conclude the BEFSR is failing, unless someone else has another idea. I have not upgraded the firmware, but, as I say, the router has been working fine for the last 5-6 years. | |
Ratha
join:2003-01-07
Missoula, MT
2 edits | Heres something i recently noticed with all the testing i have done on a fairly broken and lossy bresnan cable connection in missoula lately.
»img233.imageshack.us/img233/6735···ksys.jpg
In this image im downloading the exact same file: »www.fileshack.com/file_download.x/14564
This is a comparison download between being directly connected to my modem, a Motorola Surfboard SB5100 against a 5-7 year old Linksys BEFSR41 version 2, 1.46.02 firmware router which is then plugged into the modem. The modem has a rock solid steady download, even considering that theres a bit of packetloss out there to be contended with.. in the area of around ~8% at the moment. The router im using is suffering as you can see.. the download took less than half the time when direct plugged into the modem.
Normally i thought of my router as having worked much better than this, but one of three things is happening, either my router is just plain failing, or its not capable of handling the speed (8mbps / 384k) from bresnan or it just cant deal with the packetloss at these speeds. My guess is that its the latter two. I guess im going to need to replace the router if i want to get full speed, and have nicer looking graphs and performance?
EDIT: Did another test, this time when there wasnt any packetloss on the line that i could see. »img504.imageshack.us/img504/9499···0709.jpg. All i can conclude is that it further confirms my suspicions that my router does not handle packetloss very well, notice how much more close to the direct-modem connect download it looks like this time. The first hiccup on the far left was when i actually pressed the save button.. apparently it was downloading in firefox before i actually pressed save and gave it a location. The one in the center was likely some sort of retransmission. | |
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