2. What is an Overlay ? What is the topology of this network? WHICH network?? Figure borrowed from www.isi.edu/xbone
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17. CDN Architecture Surrogate Surrogate Request Routing Infrastructure Distribution and Accounting Infrastructure CDN Origin Server Client Client
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23. DNS based Request-Routing Akamai DNS Q: How does the Akamai DNS know which surrogate is closest ? DNS query: www.cnn.com DNS response: A 145.155.10.15 Session local DNS server (louie.udel.edu) 128.4.4.12 DNS query: www.cnn.com DNS response: A 145.155.10.15 www.cnn.com Surrogate 145.155.10.15 Surrogate 58.15.100.152 Akamai CDN merlot.cis.udel.edu 128.4.30.15 delaware.cnn.akamai.com california.cnn.akamai.com
24. DNS based Request-Routing DNS query DNS response Session Akamai DNS www.cnn.com Surrogate Surrogate Akamai CDN merlot.cis.udel.edu 128.4.30.15 local DNS server ( louie.udel.edu) 128.4.4.12 DNS query DNS response Measure to Client DNS Measure to Client DNS Measurement results Measurement results Measurements Measurements
25. DNS based Request Routing: Caching Requesting DNS - 76.43.32.4 Surrogate - 145.155.10.15 www.cnn.com A 145.155.10.15 TTL = 10s www.cnn.com Client DNS 76.43.32.4 Surrogate 145.155.10.15 Surrogate 58.15.100.152 Akamai DNS Akamai CDN Client 76.43.35.53 Requesting DNS - 76.43.32.4 Available Bandwidth = 10 kbps RTT = 10 ms Requesting DNS - 76.43.32.4 Available Bandwidth = 5 kbps RTT = 100 ms
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30. CDI: Architecture CDN1 CDN2 CDN3 CN4 For instance,cache network of some ISPx - Content Peering Gateway
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34. CDN with Full-Site Delivery Surrogate Server CDN Origin Server Client GET index.html GET image1.gif, image2.gif index.html, image1.gif, image2.gif index.html embedded image1.gif image2.gif
35. CDN with Partial-Site Delivery Origin Server Surrogate Server CDN Client GET index.html GET image1.gif, image2.gif image1.gif, image2.gif index.html embedded image1.gif image2.gif
36. CDN Types (Skeletal) CDNs Hosting CDN Relaying CDN Partial Site Content Delivery Full Site Content Delivery URL Rewriting DNS based Request Routing Techniques
37. DNS Outsourcing Customer DNS (DNS containing NS entry for customer site) Content Provider CDN DNS (DNS server maintained by CDN company) CDN Client DNS (Local DNS server for client) Client ISP Clients 1 6 2 3 5 4 A or CNAME redirection
38. Tunneling v6 v6 v6 v4 v4 v4 v4 v4 IP proto = 6 (TCP) IP proto = 6 (TCP) IP proto = 41 (IPv6) v6 header v4 header IPv6-SDU IPv6-SDU v6 header
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Editor's Notes
Tunneling is a technique which can be used for transporting new — not yet universally supported — protocols or services, such as IPv6 or multicasting, over the Internet. The unsupported packets are "wrapped" in standard IP packets and transported across the Internet between routers that do support the protocol
Hosting CDNs or Relaying CDNs that use URL rewriting do not have the Client DNS masking problem since the domain of the CDN (a1055.g.akamai.com) is within the CDN’s control. The DNS server for the CDN can refuse recursion. Typically, a domain name such as akamai.worldnet.att.com will not be chosen.
Tunneling is a technique which can be used for transporting new — not yet universally supported — protocols or services, such as IPv6 or multicasting, over the Internet. The unsupported packets are "wrapped" in standard IP packets and transported across the Internet between routers that do support the protocol
Tunneling is a technique which can be used for transporting new — not yet universally supported — protocols or services, such as IPv6 or multicasting, over the Internet. The unsupported packets are "wrapped" in standard IP packets and transported across the Internet between routers that do support the protocol
