Transmission blocks HTTP traffic?

[Magnus]

Hello I'm new at this forum.

I have a problem with Transmission. My machine is a spanking new install of Ubuntu 8.10. I also added the unofficial repositories and upgraded to transmission 1.40 (7096).

Whenever I download torrents my firefox becomes unresponsive. The GUI works, but I get time outs whenever I try to access a web page. I am able to start surfing instantaneously when I press the "pause" button in Transmission. Everything up to the transport layer in the OSI-model seems to work fine: Pinging works (IMCP), I can listen to music using Spotify (UDP) and I am able to open an SSH-tunnel (TCP).

When I use another computer on the same network (like I am doing right now) surfing works just fine, that should rule out both the router(hopefully) and a oversaturated connection as sources of the problem. I do not think there is any traffic shaping going on because then the torrent downloads should probably stop working, not HTTP. When I just tried to use Transmission on this second computer (Kubuntu 8.10, Transmission v1.34) I get the exact same problem.

I have searched around and did find some people describing the same problem, but they only got suggestions to limit their upload speed etc. I already tried that to no avail.

My router is a combined router/access point/cable modem (Scientific Atlanta) so unfortunately I cannot remove it when troubleshooting. However, I have successfully used bit-torrent in the past and surfed at the same time.

I have port forwarding enabled and UPnP disabled in Transmission. Please note that downloading torrents still works just fine.

Any ideas? I'm usually able to resolve any problems I run into but this just makes no sense to me right now.

[iggy78]

I have exactly same problem on my Mac OS 10.5

When it's appends a Netstat -a give me many used sockets. When problem reproduce i will post the netstat -a command result

[Rolcol]

This is almost always tied in with the number of connected peers. Too many connections slow down Routers/Modems regardless of speed.

[Magnus]

I get this problem instantaneously after pressing play in transmission, so I think that the number of connections should not be a problem. When I use another computer on the same network, using the same integrated router/modem HTTP-connections work just fine. I guess the router NAT/firewall could freak out and block only one IP-address in the network. But why block only the HTTP-protocol and not a bittorrent-protocol? Does transmission even use the HTTP-protocol? Sending/receiving TCP-traffic and UDP-traffic works fine on the very same computer when transmission is running.

However I have already tried lowering the number of active connections to 100. No difference.

I will do some more extensive and structured testing this weekend. I will try to eliminate any potential sources of disturbance and see if I can connect using a 3G-modem instead and reproduce the problem. Do you Transmission gurus have any specific advice as to what I should try? What information would you be interested in if I have uncovered some kind of bug?

I will try doing the following:

• Diagnose TCP & UDP connection over the internal network (no routing or NAT involved) then over the external network.

• Try a windows computer with a different client like uTorrent on the same network. Try with Transmission on a windows client

• Using Transmission but instead use a 3G modem.

[pea]

hi Magnus,

my answer is not so related to your problem
but I just trying to clarify what are you talking about..

But why block only the HTTP-protocol and not a bittorrent-protocol?
...
Sending/receiving TCP-traffic and UDP-traffic works fine on the very same computer when transmission is running.

that's not making too much sense
(HTTP runs on TCP)

Does transmission even use the HTTP-protocol?

yes it does (T talks to trackers over HTTP)

Diagnose TCP & UDP connection over the ...

UDP is connectionless protocol, JFYI..


you probably get just better audience if you are using correct terms..

[Magnus]

I appreciate your help pea, however I am already familiar the OSI-model. I do have a CS degree as well as CCNA (Cisco Certified Networks Associate) so I'm well versed with the basics and some. I have configured and preformed troubleshooting on Cisco-router configurations more times than I care to count.

HTTP is a protocol that runs on top of TCP yes, that is exactly why I tested another protocol that runs on top of TCP in the Application layer, namely SSH. To rule out that TCP-traffic was not blocked in its entirely.

At the same time as I diagnosed TCP connections I used UDP connections. Just to make sure that the problem was not in a lower layer. I'm not actually sure what the bit-torrent protocol runs on top of, if it's TCP or UDP, so I verified both. ICMP uses IP so I have basically verified that both statefull TCP/IP and stateless UDP connections works fine.

My testing was done in a slightly ad-hoc manner. So I will try to diagnose the problem in a more structured way tomorrow, as described in the other post above.

I would like to add that I never said that my results made any sense . I'm also quite surprised that my diagnosis seems to single out the HTTP-protocol for one single machine . This is what led me to suspect that this is an application error/bug of some sort. I'm still open to the possibility that my equipment may be faulty in some way. But it seems that I'm not the only one with this problem, as Iggy78 described.

[iggy78]

I have made some tests:

When problem produce (no new HTTP connection possible)
- DNS nslookup (UDP) using distant DNS server: OK
- HTTP connection on a local station: OK
- ICMP on wan (google.com): OK

-> Possible cause timeout on NAT TCP sessions (120s on my router) causing by many HTTP connection no well closed by transmission
-> NAT router used: NeufBox (French Provider BOX)

Shutdown Transmission, all work fine again
Note: if i wait a random time, it can be work fine again during a short moment

Note: to prevent any remark about my comments, i work too in networks

[pea]

I'm not actually sure what the bit-torrent protocol runs on top of, if it's TCP or UDP, ..

BT protocol can run on both of thems, T uses currently only TCP


PS. sorry Magnus,
my previous post wasn't intended to insult you..

[Magnus]

Hello again. Sorry for not posting earlier but I didn't have time to do the testing during Sunday and I have been busy this week.

The thing is that, for some reason, the problem seems to have disappeared for me. I'm not sure if this is temporary or not, but right now I can surf and download torrents at the same time.

As for what the solution was, I'm not quite sure. I'm not sure if it's ISP-related or otherwise. I updated my system (ubuntu), perhaps that could have made a change? Perhaps it had to do with the torrents I was downloading or the tracker used? Not sure.

I'll post back here if it resurfaces.

Pea: No sweat, no offense taken. I have worked as a support technician during my studies to get some extra cash. I know it's necessary to make sure that the basic troubleshooting is done first, to avoid annoying surprises later on. My intention was only to fast track any tedious "did you try turning it off and on again"-discussion, sorry if I came off as if I was offended .

Edit: As for UDP being connectionless, well yes that is true. And UDP can be considered stateful depending on the protocol running on top of it, I know. Sloppy typing on my part.

[Magnus]

I reread iggy78's post. I would like to add my vote to NAT being a part of this. Not sure if the "villain" is Transmisson or a tracker. Makes at least some sense for the shown behavior. I'm unable to access the logs of my router/NAT-firewall because it's locked down, so I was unable to diagnose this part. Quite annoying

[althearim]

Hi im so glad we all are having trouble with this one. Tried all the suggestions above but still can't quite fix this one. Hopefully some would post some further suggestions..

Regards,
althearim
Pret travaux

[jch]

What if you disable the DHT (globally, not in the torrent properties)?

--Juliusz

[Robby]

Juliusz, the post above yours is so generic it looks like spam to me...

[OpasanNekiLik]

Hi guys,

the original post is almost 2 years old and the last reply almost 1 year old but I have the same problem as described here. Torrent traffic somehow blocks my HTTP transfer. I still don't know is it up to my ISP, Transmission BitTorrent client, my router or sth else. Some explanations that I was given on some forums and usenet said that it was up to number of parallel connections but I'm not quite sure. I decreased the number of connections and the problem persisted as somebody noted before me. From these replies here I don't see what was the conclusion and problem resolution. Could somebody recall what was the real cause of this problem and how to solve it?

[kaustic]

Disabling uTP resolved this issue for me.