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Black Hole Routers

Discussion in 'Game News' started by ogreman, Aug 7, 2008.

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    ogreman

    ogreman Ogre In Charge Staff Member GameOgre Admin

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    Has this happened to you lately? You try to log onto your favorite game but it takes multiple tries, and then once you do get in you get kicked right in the middle of a crucial fight, and all support can tell you is that it’s something with the network even though you know there’s nothing wrong with your connection? Well allow me to alert you to a problem which has been discussed on forums as large as “World of Warcraft†and as fresh as “Beyond Protocolâ€: Black Hole Routers.

    Black holes are often the subject of A) science fiction movies and TV shows, ripping star systems apart and wreaking havoc for the protagonist, or B) the focus of a telescope and team of scientists, working to prove that it actually exists while estimating gravity and the distance from earth. However, lately they have become an issue for gamers, networks and IT departments in general. Black Hole Routers have caused data loss, disconnects and inconsistencies in connections to encrypted channels. We at Dark Sky Entertainment, those of us still using Windows XP, have also been plagued by packet loss, over certain ISP networks, with regard to our game, Beyond Protocol. The recent release of Windows XP Service Pack 3 (SP3) seems to have been a silver bullet to this problem. Microsoft obviously took notice of the router issue and took action in this update. In typical Microsoft fashion, only a small blurb was devoted to this topic within the overview:

    “Black Hole†Router Detection - Windows XP SP3 includes improvements to black hole router detection (detecting routers that are silently discarding packets), turning it on by default.
    -Microsoft.com, Overview of Windows XP Service Pack 3.pdf, page 7​

    Quite the simplistic statement to what has been a complex and tedious problem for many an Online Developer, MMOGamer, and IT Technician. Conversely, Maaruthi of Wordpress.com had this to say about SP3:

    “Microsoft is also hardening the Windows IP stack. With this addition comes Microsoft’s new “black hole router†detection. Black hole router detection is a way for routers to detect in advance the shortest path to send a large number of datagrams, without having to fragment them too seriously along the way. As it turned out, some receiving routers that were pegged by sending ones as PMTU members were responding to datagrams with “do not fragment†messages by simply throwing them out. These were referred to as “black hole routers,†and have been a perennial plague to streaming operations. The new router detection scheme enables IP routers along the way to flag misbehaving PMTU candidates in advance and steer around them.â€
    -Maaruthi of Wordpress.com, Microsoft Windows XP Service Pack 3 (SP3) RC1 Build 3264​

    To summarize things somewhat more clearly for those not versed in PMTU protocol or those who lifted an eyebrow at the word datagram, when a sustained connection is made between your computer and a server of some sort, packets of data are regularly sent back and forth. The path between your computer and the server can be comprised of many different routers delivering the information from one part of the digital world to another. If along the way, one of those routers finds a packet that it decides is too large to pass on, the router should either fragment the packet or at least inform the sender that the packet was not forwarded. Occasionally a router will simply erase or drop that packet leaving the sender and recipient clueless, which causes problems in large data file transmission, encrypted data sending, and login attempts. This is a black hole router instance. They can be the result of a malfunction, malicious intervention, or improper setup. SP3’s black hole router detection automatically uses, what used to be a complicated process of pinging and adjusting, to identify these problems before sending data and if necessary and possible, redirecting traffic around such routers.

    If you’d like the full blown, un-translated, pre SP3 description and solution to this problem, feel free to head over to Microsoft.com and look up this article:
    http://support.microsoft.com/kb/314825

    In terms of Beyond Protocol’s networking issues, the installation of SP3 immediately solved these problems. If you play Beyond Protocol, or any other MMO which is having login troubles, connection interruptions, or other unexplained network irregularities, and you are still running Windows XP, then SP3 is recommended, but not guaranteed, solution.

    If you have not already updated, hopefully this article will save you a lot of grief.

    -The Diplomat of Dark Sky Entertainment
     
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