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Dynamic CDN application for GMPLS networks

Dynamic CDN application for GMPLS networks

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Dynamic CDN application for GMPLS networks

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  1. Dynamic CDN application for GMPLS networks • Outline • Three key points • CDN and GMPLS networks • Overview of today's CDN service • Proposed application: "Dynamic" CDN • What advantage does GMPLS bring to this application? • Plan for implementation/experimentation on CHEETAH network using Globule CDN • Automatic private line rate increase application Malathi Veeraraghavan, Tao Li and Mark McGinley University of Virginia Nov. 1, 2007 1

  2. Key point 1 • Current usage of PDH/SONET circuits and Ethernet virtual connections (E-Line): • router-to-router • switch-to-switch (ATM or Ethernet) • PBX-to-PBX • New market: Server-to-server circuits • Cluster-to-cluster • Or, single server-to-server

  3. Key points • Conventional thinking: • High-speed links needed for • Aggregated traffic • New thought: • High-speed links needed for • Single (large) file transfer • Dynamically increase the rate of the bottleneck link to decrease file-transfer delay in lightly (or heavily) loaded environments

  4. File transfer delay • File transfer delay is determined by • bottleneck link rate, r = min(r1, r2, r3, r4, r5) • packet loss rate on end-to-end path, Ploss • round-trip time (RTT) • On lightly loaded paths, RTT and Ploss do not matter for large files • Only bottleneck link rate, r, matters r3 r2 r4 r1 r5

  5. TCP/IP file-transfer delays • In heavily loaded paths, e.g., if • Ploss = 1% • RTT = 50ms • effective transfer rate  1.8Mbps • if r is more than this value, it does not determine effective rate. Ploss and RTT are main factors. • if increasing r causes Ploss to decrease, effective rate can be improved. • Metro area, e.g. • RTT = 1ms, Ploss = 1% • effective transfer rate  75Mbps

  6. Key point 3: Growth rate for PL • Projections for Private Line (PL) market by Insight reports • Total market (2007): $39,870million • Total market (2012): $48,070million • CAGR 07-12: 3.81% • Private line vs. dynamic circuit services • Private line too expensive for server-to-server • No aggregation driver for high bandwidth • Hence need dynamic circuit services

  7. Outline • Key points • Dynamic CDN and GMPLS networks • Overview of today's CDN service • Proposed application: "Dynamic" CDN • What advantage does GMPLS bring to this application? • Plan for implementation/experimentation on CHEETAH network using Globule CDN • Automatic private line rate increase application

  8. Content Delivery Network (CDN) concept • CDN emerged in 1998 • Aimed at solving the “flash crowd” problem • Problem: Sudden surge of web traffic to a particular web site overwhelms the web server • Causes: • major events, e.g., CNN on 9/11 • “cold” sites can become “hot”, e.g., slashdot effect • slashdot is "News for nerds" • if a company is featured on, that company's web site becomes "hot" • CDN servers maintain replicas and serve client requests from closest CDN server 8

  9. CDN concept – cont’d • Type of traffic delivered through CDNs • Early 1999: static web objects such as documents and images • Now (2007): • Static web objects as well as dynamic content • Live and on-demand video streaming • Not just Youtube type of low-resolution video at around 300kbps • High Definition (HD) streaming at 5Mbps+ started to appear recently, e.g., • Software downloads • Gaming 9

  10. CDN providers Major CDN providers: Akamai, Limelight Others: MirrorImage and Inktomi CDN servers placed in PoPs Akamai: 25,000+ servers; 1200 PoPs; 900+ Networks; 650+ Cities; 69 Counties; Daily traffic: 170+ billion hits, 100+ million streams, 3000+ terabytes delivered LimeLight: 72 PoPs around the world

  11. Video, a big driver! • Volume of traffic delivered by CDNs • Youtube, carried by CDN provider LimeLight, alone accounts for ~10% of Internet traffic or ~20% of all HTTP traffic according to an Ellacoya’s report published in June/07 • Traffic data: HTTP (46%) overtook P2P (37%) • Likely due to service providers limiting P2P • Other traffic: Newsgroups (9%); non-HTTP video streaming: 3%; Gaming: 2%; VoIP: 1% • Within HTTP traffic: traditional web page (text&image) 45%; Video streaming: 36%; audio streaming: 5% • Conclusion: A significant portion of traffic already carried by CDNs 11

  12. CDN pricing • CDN’s pricing structure • Typically based on a monthly commitment • Commitment and corresponding $xx/GB/month ( , Aug. 2007) : • 1Tera Byte (TB): High, $2.00/GB/month, Low $1.50/GB/month • 10TB: High, $1.20/GB/month, Low $0.89/GB/month • 100TB: High, $0.24/GB/month, Low, $0.15/GB/month • Above 100TB: It's all over the map. Could be as low as $0.12 • Implication: CDN expensive for small-to-moderate enterprises 12

  13. CDN pricing – cont’d • But the trend shows dropping CDN costs • Competition fierce • Contract length • Used to be one year or half year; now month-by-month • New player: Level3 • Willing to provide CDN service attransit cost (cost of high speed Internet access) • According to Level3: CDN services have historically been offered at a 20 to 30 percent premium to transit. "We have a unique advantage in this market space, and we intend to take that advantage." • CDNs to be absorbed by large ISPs eventually? 13

  14. CDN’s major components • Origin server: Publish authoritative content • Surrogate/replica servers • Hold replica; offload requests from origin server • Content distribution subsystem • Push content to replica servers a priori • Or, pull content to replica servers on-demand • Request routing subsystem • Direct request to “nearby” surrogate server • Common techniques: DNS redirection and HTTP redirection • Accounting subsystem • Monitoring status of service, server and network • Help request routing; Collect statistics for billing 14

  15. How it works Europe Asia Origin server at US Replica server Replica server CDN Replica server Replica server Client A Client B Client C • Clients fetch content from nearby server • Load on origin server reduced • Download speed and reliability improved 15

  16. Request routing: DNS redirection example • Get • Local DNS sends a query • CNAME • Query • Eventually returns an IP for; TTL: 20s • Return replica’s IP to client • Get content from the selected server • Replica server replies DNS server for Replica server Akamai DNS server hierarchy 2 3 4 5 7 1 Local DNS server 8 6 Client at UVA C:\>Ping Pinging [] with 32 bytes of data: Reply from bytes=32 time=5ms TTL=58 16

  17. HTML page modification + HTTP redirection example Tanenbaum claims Akamai uses this model Step 5: does not have to be "after click," e.g., for images Courtesy: Tanenbaum's Fourth Edition slides from Prentice Hall

  18. Content Delivery Networks (a) Original Web page. (b) Same page after transformation. Courtesy: Tanenbaum's Fourth Edition slides from Prentice Hall

  19. DNS redirection DNS redirection: the DNS server serving the origin server needs to be modified to provide the IP address of an appropriate CDN server based on the client location Replica server should ideally have the first page to minimize delay (should have been "pushed"a priori) For subsequent pages, replica server can "pull" page from origin server For popular pages, "pull" approach works one "pull" helps reduce delay for subsequent users For rarely accessed pages, no load-balancing nor client-experienced delay benefits are gained when pages are pulled from origin server only when client requests arrive

  20. HTTP redirection • HTTP supports a Location header, which can be included in the response with the URL of the CDN server to which the http request is redirected • With HTML page modification: • CDN server typically stores image files that do not change as often. • These files are likely pushed a priori

  21. Cost of using CDN Bandwidth cost Variation of traffic distribution Size of content replicated over surrogate servers Number of surrogate servers Reliability and stability of surrogate servers 21

  22. Outline check • Three key points • Dynamic CDN and GMPLS networks • Overview of today's CDN service • Proposed application: "Dynamic" CDN • What advantage does GMPLS bring to this application? • Plan for implementation/experimentation on CHEETAH network using Globule CDN • Automatic private line rate increase application

  23. "Dynamic CDN" concept With pricing in the $1500-2000/month range, is it likely that there are small-to-moderate sized enterprises unable to afford CDN service? Can the Google business mode of aggregating revenues from small advertisers be used to develop a "dynamic" CDN solution "pay only when people click on your ad" approach similarly, "pay for CDN service only when it is used"

  24. Need for "Dynamic" CDN • When would enterprises need to dynamically "recruit" one or more CDN servers? • Small- & moderate-sized enterprises • Sudden surge: Recruit CDN servers located at a few PoPs when a sudden surge of traffic is seen at their web servers (e.g., slashdot phenomenon) • Large-, moderate- and small-sized enterprises • For large enterprises that may have a CDN service contract: • When a distant (remote) client starts a session from a location where web pages or image files had not been pushed a priori

  25. "Dynamic" CDN: Example 1 • Connecting to from a small village in Western Ireland • Service was slow on a broadband access link (slower than on my broadband link here in VA) • A quick (not thorough) analysis made me think it could be the long-distance server hits to a far-away (perhaps loaded) server that was causing this slow response • Hurts business when user leaves without purchase!

  26. "Dynamic" CDN: Example 2 • Connecting to a major university (IIT) web site in India from UVA • Very slow service • Could have been the access link at IIT • Could have been some intermediate link • But it also could have been server speed • Possible solution • If a CDN mirror was recruited at UVA dynamically and a few "popular" web pages from IIT's web site were downloaded during my think time, I would at least have seen faster service for subsequent hits on the same server

  27. Globalization and "Long Tail" • Globalization: • A web server could potentially be accessed from a web client anywhere • Makes it hard to push data a priori to the "right" set of CDN mirrors. • If pull-based, some prefetching of subsequent pages should occur to improve user's perceived response time

  28. "The Long Tail" by Chris Anderson (2006) • ECAST: Digital jukebox • What % of the 10K albums available on the jukebox sold at least 1 track per quarter? Answer: 98% • Apple's iTunes • Every one of the 1 million tracks (2004-2005) in iTunes sold at least once • Rhapsody: Online music store • Even the 100,000th track downloads/month was in the 1000s • Netflix • 95% of its 25K DVDs (2004-2005) rented at least once a quarter • Amazon • 98% of top 100K books sold at least once a quarter • Conclusion:Why the Future of Business is Selling Less of More

  29. Has this affected the 80-20 rule? • Yes! • Rhapsody • 25,000th - 100,000th ranked tracks downloaded on average 250 times/month for a total of 22 million downloads/month, resulting in 25% of business • 100,000th - 800,000th tracks had total of 16M downloads/month for 15% of the business • Each track is downloaded few times, but there are so many of these non-popular songs that the aggregate is large • PRX, which sells PBX programming: bottom 80% of products provide 50% sales

  30. Implication to CDN • "Dynamic" CDN: Long-tail aggregator of CDN service • Provide low-cost, pay-as-you-use CDN service to small- and moderate-sized enterprises and individuals

  31. Push vs. pull in current CDN • Literature unclear on whether data is pushed to replica servers or pulled only when a client request comes through • Push: • Disadvantage for small enterprises - Long tail ignored • Pull: • Value only for "hits" not niches • If bulk of accesses are "niches" then just an extra server involved - more delay and no load-balancing advantage for web server • Again, Long tail ignored

  32. Dynamic CDN (DCDN) design • Two proposed methods • DNS redirection • requires "DNS contract" • Example: IIT should give its domain name to CDN server for management • HTML page modification + HTTP redirection

  33. Dynamic CDN using DNS redirection = Pull + prefetching 4. Pull first page + prefetch Replica server DNS(IIT) 1. through DNS hierarchy 3. Get page Web Client 2. IP address of replica returned IIT’s WebServer (Origin) VA India DNS lookup should be iterative (not recursive) to avoid intermediate DNS servers caching data mapping to VA replica's IP address

  34. Dynamic CDN using DNS redirection • Drawbacks • Need "DNS contract" • Delay in serving first page while data is being pulled to replica server • Compared to “normal” CDN where data is likely already on the replica (if pushed) • After first page, client is well served • Need high-speed transfer between replica and backup servers to minimize delay • where GMPLS comes in handy

  35. Alternative Dynamic CDN (DCDN) design: no prior contract required • Assumes a backup server to allow for web-page push so that it does not interfere with pulls from origin server (useful for suddenly "hot" servers) 6. Pushes all-or-popular pages BackupServer 5. Triggers push Replica server DNS(IIT) 1. through DNS hierarchy DNS 6. subsequent GET 2. IP address of origin returned 5a. for replica server Web Client 3. Get URL IIT’s WebServer (origin) 4. First page(html modified based on client address with selected replica server URL) VA India

  36. Dynamic version of html page modification + http redirection • HTTP redirection • First page’s text received directly from origin server • Origin server changes links in first page to refer to replica server • Links to images, other pages, refer to closest replica server • Need high-speed transfer between replica servers and backup servers to minimize delay on first page’s embedded objects, and subsequent pages

  37. Which files to push? Look at page ranks An apache web server records all requests in access log files Log entry example: - - [14/Oct/2007:12:05:21 -0400] "GET /test_100M HTTP/1.0" 200 104857600 "-" "Wget/1.10.2 (Red Hat modified)” Tools available to collect statistics from log files e.g., AWstats reports top 10 URLs 37

  38. Example of software needed on a "recruitable" replica server web site states that all these software modules are required to run the web site (Univ. of North Carolina, Chapel Hill) Apache, Squid, ProFTPD MySQL, PostgreSQL Mailman, Icecast, Tomcat PHP, Perl OpenSSL, mod_SSL LVS (Linux Virtual Server) keepalived Nagios, Cricket 38

  39. Outline check • Three key points • Dynamic CDN and GMPLS networks • Overview of today's CDN service • Proposed application: "Dynamic" CDN • What advantage does GMPLS bring to this application? • Plan for implementation/experimentation on CHEETAH network using Globule CDN • Automatic private line rate increase application

  40. Insight report on Private line (2006-2012) • Insight research predicts • By 2012, video traffic will be 16.6Tb/s while data will be only 3Tb/s • In 2007, video is 3.3Tb/s and data 3.0 Tb/s • It notes that ASPs that provide CDN service optimized for distribution of video content will need to lease private lines • It predicts video will have a "dramatic effect" on private line market. • Conclusion: expectation is that private lines will be needed between CDN servers from which video is streamed locally? • if so, prime target for dynamic GMPLS circuits.

  41. Core GMPLS networks • CDN servers are typically located in metro NAPs/PoPs • SONET networks extend between NAPs/PoPs • With Sycamore SN16000's support for GbE and 10GbE, CDN servers with GbE and 10GbE NICs can be directly connected to a core GMPLS network of SN16000s. • Dynamically set up 1-10Gbps circuit from CDN server to CDN server (or backup server) • Use dedicated circuit to transfer web-pages files between CDN servers whenever a new CDN server is recruited • Replicate as much of the web site as possible

  42. Technology trends favor aggressive replication From "Potential Costs and Benefits of Long-term Prefetching for CDNs"byArun Venkataramani, Praveen Yalagandula, Ravi Kokku, Sadia Sharif, Mike Dahlin, Department of Computer Sciences, UT Austin, 21 June 2001: Storage is cheap Today: less than $200/100GB Network prices are falling Improving at > 100% per year New technologies - Lower cost of prefetch traffic [Byers98, Crovella98] User time is valuable March 12, 2014

  43. Use Internet2's core network s an example Yellow nodes: Ciena CD-CI SONET switches Blue nodes: Juniper T640 IP routers Courtesy: Rick Summerhill (2006)

  44. Two parallel networks • IP network: Juniper T640 routers interconnected by OC192s • Dynamic Circuit Services (DCS) network: Ciena CD-CI nodes with GbE, 10GbE, SONET (OC192) cards

  45. Example of how Dynamic CDN can be deployed on Internet2 Deploy CDN servers at some Internet2 PoPs. 1Gbps 10Gbps 45 1Gbps into IP-routed network: server clients in local regions 10Gbps into DCS network: push between replica servers

  46. Why Dynamic circuit service? • Can create a higher-rate circuit for temporary use between replica servers and backup (origin) servers than possible with • private line • IP • Allows for larger prefetch and faster push • Prefetching can be of the first N "hottest" URLs based on recent click history 46 46

  47. Delay is key in dynamic CDN • Remote client example (Long Tail) • Quick copy of many pages from origin or backup server to remote replica server for fast service • Slashdot effect example • Quick copy to multiple replica servers

  48. Combination of requirements • Requirements • Large file transfer • Fast file transfer • Higher the speed of the circuit, the better • Expensive to get HIGH-SPEED private line service between many replica server-origin/backup server pairs • Also IP service is expensive at high speeds

  49. Internet2 fee structure Started by seeing Internet2 fee structure 1GbE link into Internet2's IP-routed network: $250K annual cost Two 1GbEs: one into IP-routed and second into DCS netwok: $340K Corresponding numbers for 10GbE: $480K and $550K Hence cannot afford to keep 10GbE link into IP-routed network turned up at all times Recruiting it when needed with dynamic GMPLS circuit setup allows for delay improvement in downloading "whole" web site fast for improved user-perceived response time 49

  50. Attraction of GMPLS networks at high speeds Because high-speed interface cards cost less in SONET switches than in IP routers For high switching capacity nodes, which are mainly required in the core. Cost comparison Per OC192 port on SN16k: $37,500 Per POS OC192 port on 12416 GSR: $225,000 10GbE card on 12416 GSR: $125K 50