 espaethDigital PlumberPremium,MVM
join:2001-04-21
Minneapolis, MN
kudos:2
 ·Clear Wireless
| reply to ztmike
Re: Youtube+HD videos SLOW streaming back.. said by ztmike:What is the deal with Youtube? I haven't had this problem for awhile but since yesterday it seems most of their videos take FOREVER to load. Which DNS servers are you using?
Content distribution networks (Google, Youtube, Akamai) use global load balancing through DNS, so using resolvers outside of your ISP's network can result in suboptimal balancing across the content caches.
Using popular DNS services (ie, OpenDNS, the Level(3) open resolvers) can actually result in overloading of a particular content cluster.
I detailed a bit about how this works here:
»Re: Options for Denver |
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 JohkalCool CatPremium,MVM
join:2002-11-13
Happy Valley
kudos:5
1 edit | I'm using Comcast's DNS just for reference.
Also, the servers are the ones for the "Opt Out for redirection" |
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komat
join:2007-11-07
Morgantown, WV | i have this problem too
only happens with HQ or HD videos. it will burst for 1mb for like 2 sec then go back to 100k. at 100k it cant keep up with without stopping and buffing |
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 ztmikeMark for moderationPremium
join:2001-08-02
Michigan City, IN | reply to espaeth
said by espaeth:said by ztmike:What is the deal with Youtube? I haven't had this problem for awhile but since yesterday it seems most of their videos take FOREVER to load. Which DNS servers are you using? Content distribution networks (Google, Youtube, Akamai) use global load balancing through DNS, so using resolvers outside of your ISP's network can result in suboptimal balancing across the content caches. Using popular DNS services (ie, OpenDNS, the Level(3) open resolvers) can actually result in overloading of a particular content cluster. I detailed a bit about how this works here: » Re: Options for Denver I have my router set to use OpenDNS..I can't say I've heard of that before..I thought I was running off of OpenDNS servers in Chicago and then routed to the nearest Youtube server from there. |
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AVonGaussPremium
join:2007-11-01
Boynton Beach, FL | As a quick test it might be worth doing...
1) Trace route to the YouTube server using OpenDNS
2) Switch your router DNS back to the Comcast DNS servers
3) Verify the test computer is now using the Comcast DNS servers
4) Trace route to the YouTube server (using Comcast now)
5) See if the problem persists when viewing videos
If the problem doesn't persist, posting both trace routes may yield a bit more information. |
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espaethDigital PlumberPremium,MVM
join:2001-04-21
Minneapolis, MN
kudos:2 Reviews:
·Clear Wireless
| reply to ztmike
said by ztmike:I have my router set to use OpenDNS..I can't say I've heard of that before..I thought I was running off of OpenDNS servers in Chicago and then routed to the nearest Youtube server from there. Not necessarily.
OpenDNS, Comcast's DNS servers, Level(3)'s 4.2.2.x servers are all what are known as recursive resolvers. What that means is that you ask it to resolve a DNS name, and it does the full number of queries it takes to get a final resolution and only returns the final result to you.
When you look up "www.youtube.com" that upstream DNS server needs to query the root to find out who to ask about ".com". It will find out it needs to query the g-tld servers, so it sends a query there asking about "youtube.com" -- that server points them to YouTube's DNS servers. YouTube's DNS servers aren't standard DNS servers though -- the next query they are going to get is a request of the IP of "www.youtube.com" -- but they don't respond with the same IP to every query. The global load balancing servers use the IP of the server who initiates the request and respond with the cluster IP that is likely to have the best network performance back to the network the DNS resolver is on.
That last part is the problem. OpenDNS is doing the query on your behalf to YouTube's servers -- and YouTube is going to respond with the server that has the best performance back to OpenDNS, which may be a completely different cluster from what one that would have the best performance back to Comcast. If you use Comcast DNS servers, then YouTube will identify the destination network as Comcast and return the IP of the cluster that has the best possible performance back to Comcast.
OpenDNS and the like work great for fixed IP addresses. www.dslreports.com will always return the same IP because it's only hosted in one location: nac.net. It really screws with global load balancing, however, because those services make the assumption that end-users are using their ISP's DNS resolvers. |
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