AbstractsComputer Science

Request Routing In Content Delivery Networks

by Alzoubi A Hussein

Institution: Case Western Reserve University
Department: EECS - Computer Engineering
Degree: PhD
Year: 2015
Keywords: Computer Engineering; Computer Science; Content Delivery Netowrks, Anycast, CDN, DNS
Record ID: 2058336
Full text PDF: http://rave.ohiolink.edu/etdc/view?acc_num=case1417768000


Internet has become - and continues to grow as - the main distributor of digital media content. The media content in question runs the gamut from operating system patches and gaming software, to more traditional Web objects and streaming events and more recently user generated video content. Content Delivery Networks (CDNs) (e.g. Akamai, Limelight, AT&T ICDS) have emerged over the last decade to help Internet content providers deliver their digital content to end users in a timely and efficient manner.The challenge to the effective operation of any CDN is to redirect clients to the ``best'' service server from which to retrieve the content, a process normally referred to as ``redirection'' or ``request routing''. Most commercial CDNs make use of DNS-based request routing mechanism to perform redirection. In this mechanism, the Domain Name System (DNS) operated by the CDN receives queries - via clients Local DNS (LDNS) servers- for hostnames of the accelerated URLs and resolves these queries into the IP address of a CDN server that the DNS system selects for a given query.DNS-based request routing, however, exhibits several well-known limitations. First, DNS based request routing operates at the granularity of LDNS servers and what might be a good choice for an LDNS is not necessary a good choice for all its clients. Second, redirecting a single LDNS might cause a large number of clients behind that LDNS to be redirect to the same CDN node causing potential load balancing problems. In addition, DNS based CDNs suffers from the limitation that DNS system was not designed for very dynamic changes in the mapping between hostnames and IP addresses.Another problem that is facing not only CDNs but also the entire Internet apparatus, is the scarcity of available IPv4 addresses. IPv4 only supports 4 billion globally routed IP addresses. Even though IPv6 was developed to deal with this long-anticipated IPv4 address exhaustion, the overall Internet transition to IPv6 is still lagging. Further, network paths between clients to Web sites commonly do not support IPv6 even if the two end-hosts are both IPv6-enabled. This dissertation quantifies the effect of the above limitations of DNS-based request routing in CDNs, and offers a practical mechanism for replacing DNS-based with anycast-based request routing. Our proposed CDN architecture effectively addresses the long-known drawbacks of anycast request routing allowing us to reconsider the practicality of this mechanism. Further, this dissertation addresses the issue of transitioning to IPv6, by first showing that there is virtually no performance penalty for a web site to unilaterally enable IPv6 support, and then proposing a light-weight architecture for implementing IPv6 anycast for connection oriented transport. The proposed architecture preserves security and privacy, and facilitates anycast's inherent proximal routing. In addition, this dissertation presents an architecture of an anycast IPv6 CDN that utilizes the proposed IPv6 anycast architecture as the redirection…