* Posts by Jason King

1 publicly visible post • joined 6 Dec 2008

BitTorrent net meltdown delayed

Jason King

It's not the backbone

Mr Bennett,.. Richard,.. please, do a little more research and have a little less to drink when you're going to write a piece on networking technologies. That way, you might avoid publishing a piece like this.

Firstly, Compound TCP is a native part of the Vista and Windows 2008 Server (beta) TCP stack. Take a minute to think about that - Vista and Win2k8 SERVER beta versions... and it's disabled by default in Vista. Oh, and MS has made a hotfix for 64-bit XP... and Win 2k3 Server. Massive industry leaders in consumer computing, all four of them. Huge retail market share. (Don't forget, disabled by default in Vista. The command to enable it, by the way is: "netsh interface tcp set global congestionprovider=ctcp".[1] Which you have to execute using admin privileges in a command shell. Not really something you can type by mistake.)

Now, I've worked as a Cisco engineer for close to ten years and have never heard of Compound TCP. I'm not scared of learning and I'm happy to do follow-up research on stories of new technologies (you can't know everything, as you have demonstrated so spectacularly) so I followed your link, it was rubbish. I did a google search and, fortunately, Wikipedia saved the day. [2]

Compound TCP is TCP/IP, the clue is in the title. I know it sounds sexy at first but you have to read all the way to the end. Looking at the descriptions I could find, it seems that the client/host/endpoint (whichever name you prefer) is responsible for throttling the data flow based on timestamps or duplicate ACKs; it is, therefore, completely transparent to the network devices along the path.

TCP Congestion avoidance and management will still be the only way to provide traffic management on those devices and, although VPNs and encrypted torrents prevent DPI and the port customisation inherent in many BitTorrent clients prevents accurate port-based filtering / management, ISP consumer ADSL links have very clever ways of determining who is 'hogging' the bandwidth and they are quite prepared to pare down a particular customer's share where the fair usage policy has been breached.

IntServ, RSVP, DiffServ, ECN, and Re-ECN all require accurate per-packet marking which is never going to be reliable on consumer ADSL networks and ISP marking would require DPI, which is unlikely to happen. Add to that the various tunneling technologies (which require pre-encryption classification) and it becomes unmanageable, from a supplier's perspective.

For what it's worth, I agree that massive illegal file sharing needs controlling: there's no reason that some numpty downloading all 500,000 CSI episodes (or whatever) should send my connection to xbox live through the floor when we're both paying for reliable (and usable) internet access. Having said that, making sensationalist claims that the decision of one company to switch its base protocol will cause all delay-sensitive traffic to be held, unrecognised, in ever-increasing interface queues, is just irresponsible. Writing a follow-up piece less than a week later (with all the hallmarks of a party political u-turn) is just embarrassing.

Getting away from the technicalities, I would like to ask you about the assertion that you are "a network inventor who helped design THE modern, manageable local area network". "THE"? and how are you defining "modern"? and when did ISPs have much to do with a local area network or indeed any corporate network that's not run over the internet... using consumer ADSL services. So, unless you actually know Bob Metcalfe or David Boggs (and the lack of any piece in El Reg about Ethernet's 25th birthday this year suggests that you probably don't) maybe you should consider adding a qualifying statement to each article. Can I suggest: "he vaguely remembers reading some stuff about a LAN at Networkers once."

I liked the piece but surely it should have been filed under 'Odds & Sods', or B-Journo-FH perhaps? If you want to write a technical piece, please have a chat with Verity. She, at least, has been through Open University. Such as it's worth.[3]


[1] Source: http://en.wikipedia.org/wiki/Compound_TCP#Supported_platforms

[2] Source: http://en.wikipedia.org/wiki/Compound_TCP

[3] Source: http://www.theregister.co.uk/2008/10/14/verity_stob_further_eduation

PS: @James Butler: I wasn't going to reply to your comments but, well,.. look, please, pretty please, do a business course... or finish high school... or (preferably) both. ISPs are there to make money. Simple. End of story. There are so many and you can change ISPs in a week or two. If a customer doesn't like one, they have the choice to move on to another one. The best ones are usually the little ones whose brand name isn't strong enough to retain customers on its own. Those are the ones have to work at it. However, like their larger competitors, they quickly learn that customers will act like spoilt children when they are asked not to abuse the contention-based network that is ADSL. Contention. Key word. Look it up. That's why fair use policies exist.

I would, however, like to congratulate you on not living outside your means. Well done you. It's very grown up, very 'adult'.