 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: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. |
