Posts by Carl Williams

Virgin Media dishes out free bandwidth boost

OK, now count me stymied

OK, now I'm mystified. Re: Virgin analysing torrent traffic and blocking ports... I've done some more tests, so I shall bore you with tedious details:

I figured it might be down to particular trackers or a particular use of trackers, so I tried starting with a bare un-sullied azureus, shifted to an unblocked port and started a torrent tracked on an obscure german open source tracker. Ran like a dream, no blocking. Then I tried starting a TV episode download tracked at a bunch of places. Sure enough, the port was blocked instantly.

Next, I picked the "dodgiest" looking tracker among the torrents I'd been trying to run when I first encountered this stuff - turned out to be a cartoon TV episode (OK, so I use bit-torrent as a remote video recorder...) tracked at what looks, on closer inspection, to be primarily an "adult" torrent tracker - I blocked access to that IP and also turned off scraping in azureus, switched to an as-yet un-blocked TCP port and fired up another torrent on another mildly suspect tracker.

To my surprise, no port black-hole this time. OK, to see what was responsible, I turned scraping back on and provoked re-scraping. Still no block... Feeling that I'd finally pinned it down, I unblocked access to the dodgier tracker IP, and poked the cartoon torrent back to life. Er, still no block. Forced a tracker update. Still no block.

So for now I'm stumped. Did they try out some torrent-nobbling service on my line, then turn it off? Or maybe it was in fact some DOS type attack being triggered by my torrent activity? Will it happen again? Did I just stumble on a port number they don't block regardless? Or do they, after all, turn this blocking behaviour off at around 2am?

It's more /interesting/ than BT's service, I'll give it that...

Virgin block torrent ports?

Final installment, I hope - more trials and it transpires that what provokes the black hole effect is having the torrent client accept UDP and TCP connections on the same port. Leading me to the Homeric (as in "Doh!") realization that it's possible, just possible, that this may be down to my router being a bit pants and fouling up its NAT routing in a way that my old ADSL Netgear job didn't. Or it might be that UDP/TCP traffic to the same port is part of the torrent traffic signature which triggers packet dropping at the ISP. However, my suspicions are swinging towards the "bad router" explanation, so I'm preparing to accept that maybe in fact I don't know what the **** I'm on about after all...

Well, I did say I'd be pleased to be proven wrong...

Ahem.

Virgin block torrent ports?

Sadly, I think Si Clement's assertion that Virgin don't do deep packet analysis may no longer be true. There seems to be a lot of conflicting experience - people reckoning torrents are limited to 10K, port 80 blocked etc.

Maybe it's subscriber- or area- specific, possibly in part contingent upon which company previously owned the infrastructure (mine used to be Telewest, I think).

For me, (and I am qualified to figure this out: I'm not scrabbling around in the dark with NAT settings and port forwarding; I Know What I'm Doing) I can say that, on the XL service I'm on, I've not found any blocked low-numbered ports, indeed no ports up to the ephemeral range seem to blocked by default. Incoming web and ssh traffic works fine with proper setup. Nor are torrent speeds restricted per-se.

BUT (and it's a big But) incoming torrent connections ARE blocked dynamically, regardless of port chosen. Kill all the torrent clients and wait for a while and the blocks are lifted. Port forwarding checks out properly and definitively using plain TCP listeners on the relevant port(s). Start a torrent client though and the port is blocked. No throttling, no disconnects, just blocked.

US customers of Comcast have similar issues - they're connected via Sandvine devices which analyse traffic and purposely disrupt bit torrents by issuing bogus TCP resets. VirginMedia don't seem to issue resets, they just black-hole incoming connections - the connections just time out.

This isn't throttling or any sort of volume-based limitation, nor does it depend on time of day. Half a meg at 4 AM, makes no difference, as soon as torrent activity is detected, the port is blocked. Switching ports and/or encrypting torrent traffic makes no difference, so the block must be triggered by tracker activity rather than the main torrent traffic.

I thought at first maybe it was denial-of-service protection triggered by lots of incoming connections, but without a torrent client running, lots of connections (to the same port) work just fine.

(I confess I've not pushed this non-torrent testing to the point of triggering any actual D.O.S. defenses, if any exist. I might still be wrong about the whole thing - I'd be delighted to be proven wrong, in fact :-) )

Could it be Virgin smell a competitor in the "content provision" marketplace, who they're not about to allow to deliver via their cable infrastructure? Azureus these days styles itself a content delivery platform for digital media, particularly low budget film, trailers, pop videos and pay-per-view film and so on.

Are we going to see the BBC's iPlayer "traffic shaped" into submission, too?

What other content or connectivity are they going to quietly alter, block, throttle, or otherwise adjust?

As others have said, though BT's service is neither the cheapest nor the fastest, at least with BT's ADSL you don't get this kind of meddling with your traffic - sure they (theoretically) cap bandwidth but I'm not a heavy enough user to have EVER fallen foul of that. For occasional bit torrent use (Linux distros and VMWare/QEMU disc images, say) the 5M BT ADSL connection I used to have was quicker than my outward-connections-only 20MBit virgin cable broadband presently is (though my web browsing & downloads have speeded up, subject to following Virgin's timetable and avoiding peak hours where presumably I should be dutifully watching Virgin TV and/or paying for Virgin pay-as-you-w...er..whatever... porn).

From what I gather here, plenty of Virgin customers with a much "better sounding" so-called 10Mbit cable connection would be rather better off with 5Mbit BT ADSL.

Ho hum. In the immortal words of Jagger and Richards, you cain't always get what you want...

FWIW, if I actually watched the telly I would still reckon the virgin cable and broadband package considerably better value than Sky, and I can't see the Murdoch empire being inherently any cuddlier or less consumer-hostile than Branson's, but still, it's less attractive if you need a proper un-interfered-with internet connection and have to buy a BT one on the side. Hopefully their marketing types will eventually realise this.

This rant brought to you via an alleged 768/20000Kbit, during the Forbidden Hours best suited for short bits of text.