The nameserver as CDN vantage point

I was just thinking about the nameserver as a vantage point in the Microsoft CDN study, and I remembered that for the CDNs themselves, the nameserver is normally their point of reference to the customer.

When a content provider uses a CDN, they typically use a DNS CNAME to alias a hostname to a hostname of the CDN provider. For instance, http://www.nbc.com maps to http://www.nbc.com.edgesuite.net; the edgesuite.net domain is owned by Akamai. That means that when a DNS resolver goes to try to figure out what the IP address of that hostname is, it’s going to query the CDN’s DNS servers for that answer. The CDN’s DNS server looks at the IP address of the querying nameserver, and tries to return a server that is good for that location.

Notably, the CDN’s DNS server does not know the user’s actual IP. That information is not present in the DNS query (RFC 1035 specifies the structure of queries).

Therefore, what nameserver you use, and its proximity to where you actually are on the network, will determine how good the CDN’s response actually is.

I did a little bit of testing, which has some interesting results. I’m using a combination of traceroute and IP geolocation to figure out where things are.

At home, I have my servers configured to use the UltraDNS “DNS Advantage” free resolvers. They return their own ad server rather than NXDOMAIN, which is an annoyance, but they are also very fast, and the speed difference makes a noticeable dent in the amount of time that my mail server spends in (SpamAssassin-based) anti-spam processing. But I can also use the nameservers provided to me by MegaPath; these are open-recursive.

UltraDNS appears to use anycast. The DNS server that it picks for me seems to be in New York. And http://www.nbc.com ends up mapping to an Akamai server that’s in New York City, 12 ms away.

MegaPath does not. Using the MegaPath DNS server, which is in the Washington DC area, somewhere near me, http://www.nbc.com ends up mapping to a server that’s directly off the MegaPath network, but which is 18 ms away. (IP geolocation says it’s in DC, but there’s a 13 ms hop between two points in the traceroute, which is either an awfully slow router or more likely, genuine distance.)

Now, let’s take my friend who lives about 20 miles from me and is on Verizon FIOS. Using Verizon’s DC-area nameserver, he gets the IP address of a server that seems to live off Comcast’s local network — and is a mere 6 ms from me.

For Limelight, I’m looking up http://www.dallascowboys.com. From UltraDNS in NYC, I’m getting a Limelight server that’s 14 ms away in NYC. Via MegaPath, I’m getting one in Atlanta, about 21 ms away. And asking my friend what IP address he gets off a Verizon lookup, I get a server here in Washington DC, 7 ms away.

Summing this up in a chart:

My DNS / CDN PingAkamaiLimelight
UltraDNS12 ms14 ms
MegaPath18 ms21 ms
Verizon6 ms7 ms

The fact that Verizon has local nameservers and the others don’t makes a big difference as to the quality of a CDN’s guess as to what server it ought to be using. Here’s a callout to service providers: Given the increasing amount of content, especially video, now served from CDNs, local DNS infrastructure is now really important to you. Not only will it affect your end-user performance, but it will also affect how much traffic you’re backhauling across your network or across your peers.

On the surface, this might make an argument for server selection via AnyCast, which is used by some lower-cost CDNs. Since you can’t rely upon a user’s nameserver actually being close to them, it’s possible that the crude BGP metric could return better results than you’d expect. AnyCast isn’t going to cut it if you’ve got lots of nodes, but for the many CDNs out there with a handful of nodes, it might not be that bad.

I went looking for other comparables. I was originally interested in Level 3, and dissected http://www.ageofconan.com (because there was a press release indicating an exclusive deal), but from that, discovered Funcom actually uses CacheFly for the website. funcom.cachefly.net returns the same IP no matter where you look it up from (I tried it locally, and from servers I have access to in Colorado and California). But traceroute clearly shows it’s going to different places, indicating an anycast implementation. Locally, I’ve got a CacheFly server a mere 6 ms away. From California, there’s also a local server, 13 ms away. Colorado, unfortunately, uses Chicago, a full 32 ms away. Unfortunately, this doesn’t tell us much, beyond the fact that CacheFly has limited footprint; we’d need to look at a CDN with enough footprint that uses AnyCast to see whether it actually return results better than the nameserver method does.

So here’s something for future researchers to explore: How well does resolver location correspond to user location? How much optimization is lost as a result? And how much better or worse would AnyCast be?

Bookmark and Share

Advertisements

Posted on October 15, 2008, in Infrastructure and tagged . Bookmark the permalink. 41 Comments.

  1. Lydia,

    I’d love to hear your results comparing OpenDNS in that mix. OpenDNS has been providing anycated recursive DNS and security service for years to millions of consumers, SMBs and enterprise customers.

    Like

  2. Both of your nameserver addresses seem to map to someplace close to me — my last hop has a label of Equinix Ashburn, in the ‘burbs of DC, and my ping to them is 7 ms.

    They both result in the same Akamai edge servers for me, connected via NTT’s network, also marked Ashburn. My ping to those is 6 ms. Note that these are different servers than the ones that Verizon returns to my friend, yet they are equally close to me.

    Both of your nameservers also return identical Limelight servers. These are the same servers that Verizon returns to my friend, the ones that are 7 ms and regional to Washington DC.

    What this also tells me is that I can immediately get an improvement in my content download performance from Akamai and Limelight, by switching my nameservers to yours, which I am going to do now. (Sadly, OpenDNS also does the NXDOMAIN hijack, but I’ve learned to live with it, even though it drives me batty every time I mistype a hostname when doing app development.)

    I’ve also tried the same experiment on my server in Colorado (off Time Warner Telecom), where the difference is pretty significant. UltraDNS and OpenDNS both have identical Akamai results, 34 ms away; its ISP nameserver results in an Akamai server 49 ms away. UltraDNS and OpenDNS return identical Limelight results 33 ms away, in Chicago. But the ISP nameserver has a much better result, 15 ms away, in Dallas.

    Like

  3. Lydia,

    Create an OpenDNS account and disable “typo correction.” We’ll provide you standard NXDOMAIN responses then. Everything we do is for your benefit, and if you don’t like a feature, you can disable it. We’ve been doing this a long time and have millions of happy customers; no advertising or marketing; just word-of-mouth from IT person to IT person.

    Thanks for the great feedback and tests.

    -David

    Like

  4. Has anybody really got a free iPad? I just saw this on Twitter: Win a FREE Apple iPad before they’re all gone! Enter Your Zip @ http://x.vu/27632

    Like

  5. Hi there, a little off topic but is anybody experiencing a blank page when they view this webpage? thanks

    Like

  6. Thanks in support of sharing such a fastidious opinion, post is good, thats
    why i have read it fully

    Like

  7. I have been explokring for a little bit for any high-quality articles or weblog posts in this
    sort of house . Exploring in Yahoo I at last stumbled upon this site.

    Reading this information So i’m satisfied to express that I have a very just right uncanny feeling I found out just what
    I needed. I so much definitely will make certain to do not overlook
    this web site and give it a glance on a continuing basis.

    Like

  8. I have read so many posts concerning the blogger lovers but this article is genuinely a fastidious post, keep
    it up.
    Bringing many new functions, we are content to present to you the new and updated clash of clans hack!
    You will be able to do many various issues to a certain extent.

    With this hack, you will be ready to obtain as numerous Gems, Resources and Poins that you need for the game!

    Does it sound also hard? Nicely its not! This new and updated Clash Of clans hack will do it immediately, without having
    you getting to do any a lot more perform than a click on of a
    button!

    Very best portion about this hack, is that you dont need a Jailbroken device!
    It is as simple as connecting the unit and clicking a button!
    There is no better support than ours on the web! We have the speediest and most secute
    servers.

    Special Functions:
    -Gather all gems
    -Supports any gadget
    -No jailbroken device necessary
    -Undetected

    Like

  9. Policzmy to razem sprawdziany do pobrania

    Like

  10. Grand Theft Auto V officially releases to the PS3 and Xbox on Sept 17.
    This time she is providing tips for earning farm
    cash. Learning the theme of your collection is also
    important in spotting an antique piece.

    Like

  11. Everything is very open with a precise explanation of the challenges.
    It was really informative. Youur site is extremely helpful.

    Many thanks for sharing!

    Like

  12. Again, your biggest hope for future survival is
    to work together, cooperate tto the mutual benefit
    of all. While it is true that Kant soundly distinguishes
    the AUTONOMOUS AUTHORITYof tthe Categorical Imperative,
    his Firrst Postulate of Pure-Practical Reason, from
    God, in its Thre Formulations, thus likewise, in the process, reflecting a more
    SOBERLY WELL-BALANCED Spirit of the Modern Age,
    this distinction is merely something “provisionally epistemic” in scope, and meant, iin the
    most Rationally A-Priori frame of reference, to lead to a realization of
    the NECESSARY CONNECTION of the First Postulate with the OTHER TWO POSTULATES.
    The costs for safe guarding and operation of how
    the server, as well as new developments are usually passed on to
    customers through monthly fees.

    Like

  13. This post is worth everyone’s attention.
    Where can I find out more?

    Like

  14. This is my first time go to see at here and i am really pleassant
    to read all at alone place.

    Like

  15. Wow that was odd. I just wrote an very long comment but
    after I clicked submit my comment didn’t appear. Grrrr…
    well I’m not writing all that over again.
    Anyhow, just wanted to say superb blog!

    Like

  16. Hello There. I found your blog using msn. This is a very well
    written article. I will be sure to bookmark it and
    return to read more of your useful information. Thanks for the post.

    I’ll certainly comeback.

    Like

  17. hello!,I love your writing very much! proportion we
    communicate more about your article on AOL? I need an expert in this space
    to unravel my problem. May be that is you! Having a look forward to peer you.

    Like

  18. Thank you for the auspicious writeup. It in fact
    used to be a enjoyment account it. Glance complex to more brought agreeable from you!
    By the way, how could we be in contact?

    Like

  19. AK-Player also makes it exceptionally easy and efficient to find media files.
    Once you access the system on your laptop, it will go through a series of steps that will
    configure the local stations and the video quality on your computer.
    Keep your eyes peeled online for discounts bringing this
    very popular player down to under $70, or for the $100 price with some extra goodies thrown in.

    Like

  20. A freeware program for burning CD’s and DVD’s, Deep Burner offers the ability
    to create CD’s with a simple drag and drop interface. You’ll then be
    able to choose the output format for your audio and, for more
    advanced users, specify some additional parameters to further customize
    your results. What we can hope to see are further changes to the very definition of Portable Media Player.

    Like

  21. I’m not that much of a online reader to be honest but your
    sites really nice, keep it up! I’ll go ahead and bookmark your site
    to come back later on. Many thanks

    Like

  22. In a year, thousands and even millions of dollars are
    being spent in products and treatments that help keep the face look young.
    Burt’s Bees has created Naturally Ageless Line Smoothing Eye Crme and Naturally Ageless Intensive Repairing Serum, which use the anti-oxidant power of pomegranate extract.
    All parabens are known to irritate the skin, causing allergic and adverse
    reactions.

    Like

  23. Thanks for any other magnificent article. Where else could anybody get that kind of info in such an ideal means of writing?
    I’ve a presentation subsequent week, and I’m on the look for such info.

    Like

  24. Je souhaiterai vous dire que c’est infiniment un plaisir de visiter ce site web

    Like

  25. I used to be suggested this web site by way of my cousin.
    I’m not certain whether or not this publish is written by him as no one else understand such
    specified about my difficulty. You are amazing! Thank you!

    Like

  26. Hi, Neat post. There is an issue together with your web site in internet explorer, could test this?
    IE still is the marketplace chief and a big part of people will omit your fantastic writing due to
    this problem.

    Like

  27. We’re a flock a group of volunteers and starting a brand
    new scheme in our community. Your web site provided us with valuable information and work on .
    You made ​​an impressive task and our all the neighborhood
    can be thankful to you .
    Unquestionably Account that you stated . Your favorite justification seemed to be at the net simple factor to understand of .
    I tell you , i definitely get annoyed same as any other people people
    think worries just do not realize about . You controlled
    and defined on all managed to hit the nail on the top no need side-effects , other folks
    cAN could take a signal. Will probably be again to get more.
    Thank you

    Like

  28. In a home unlicensed contractors is definitely the biggest decision you seek.
    You may also be good, they will always be people willing and able to understand
    what consulting and legal expenses. Step Five: Continue down the goal.

    Being a general contractor for unlicensed contractors your contractor you see a more pleasing appearance, Gene copied
    photos taken of the way. You need funds to buy or rent tools to accomplish.
    The Best Foam Insulation Contractor Mankato are considered
    a demolition service made available are granite, limestone, marble, sandstone, slate requires a lot of customer complaints.

    Like

  29. I’ve read some excellent stuff here. Definitely value bookmarking for revisiting.
    I surprise how much attempt you set to make this sort of magnificent informative
    website.

    Like

  30. Do you mind if I quote a few of your posts as long as
    I provide credit and sources back to your website?

    My blog is in the exact same niche as yours and my users
    would truly benefit from some of the information you provide here.
    Please let me know if this alright with you.
    Thanks!

    Like

  31. When someone writes an post he/she retains the plan of
    a user in his/her brain that how a user can understand it.
    Therefore that’s why this piece of writing is great. Thanks!

    Like

  32. wonderful put up, very informative. I ponder why the other experts of this
    sector do not understand this. You should continue your writing.
    I’m confident, you’ve a great readers’ base already!

    Like

  33. Our minecraft force op instrument has completely changed the way minecraft web servers function. An admin perceives
    they are really the only kinds which will control their host.
    They are really completely wrong! Together
    with the minecraft force op instrument, you can now take
    total charge of the hosting server and do with it, while you
    please. You may even strike out the other administration!

    Like

  34. Today, the company continues to manufacture hand-constructed box spring and mattresses in three U.
    However, this means that a field worker needs a place to live as they is working–while accommodation is
    sometimes provided, it’s not a given like it is on a rig.
    Combining this with the large display and QWERTY keyboard means you get the best mobile email experience available.

    Like

  35. Each new age brought the criminal element forward with it.
    However Yahoo marketing and other pay per click search engines offer some
    excellent traffic at a more reasonable price. Daily, even hourly, businesses can see how many individuals clicked on their ads
    and the traffic that is being driven to their website.

    Like

  36. What’s up mates, how is everything, and what you wish for to say about this paragraph, in my view
    its in fact amazing in support of me.

    Like

  37. Since the dwelling room is probably the most diarrhea and pregnancy cost-effective, and will make you one!
    Also, they should be aimed at helping you to get a real idea about
    the value of the room where you want to playwith colors,
    creativity and need a place with scintillating theme.

    Make a set for each season on top of that,
    they’re protected by the liner so water and lime develop should really not be a difficult decision.

    Like

  38. Howdy are using WordPress for your site platform? I’m new to the blog world but I’m
    trying to get started and set up my own. Do you need any html coding
    knowledge to make your own blog? Any help would be really appreciated!

    Like

  39. It’s always the same loving, there are a big hug from Mr. What part of the
    Thomas the Train birthday birthday wishes party successful.
    Most opals are the normal birthday-invitations cards available for both vegetarian and non-vegetarian consumers.
    Of course, having a list put together some of the little things that are provided on-site.

    Like

  40. WhattsApp is eigentlich ganz gut doch ein riesiger
    Nachteil ist es ist wirklich leicht zu hacken hab’s selbst
    erlebt!

    Like

  1. Pingback: jaket kulit

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: