Data Center Content Delivery Network

Transcription

1 BM 465E Distributed Systems Lecture 4 Networking (cont.) Mehmet Demirci

2 Today Overlay networks Data centers Content delivery networks

3 Overlay Network A virtual network built on top of another network Overlay Substrate Mapping: Overlay node to substrate node Overlay link to substrate path Multiple overlays on the same substrate

4 Overlay Networks The Internet has many shortcomings. Overlay networks are a popular way of adding new functionality to the Internet. Overlays rely on the underlying Internet to provide connectivity, and they offer a variety of services.

5 Overlay Network Examples Goal: Multicast Unicast: Single sender Single receiver Broadcast: Single sender All possible receivers Multicast: Single (or more) sender(s) A specific subset of all possible receivers Members of the multicast group

6 Overlay Network Examples Internet-layer solution: IP multicast Routers copy and forward packets as necessary. Adds complexity to ISPs, no not very widely deployed.

7 Overlay Network Examples Overlay solution: End-system multicast Does not require support from network devices. Constructs an overlay tree to distribute multicast traffic. Not optimal in terms of resource usage, but simpler.

8 Overlay Network Examples Goal: Reliable routing Resilient Overlay Networks (RON) Improves the robustness and availability of Internet paths. Continuously monitors all paths between its nodes. When there is a problem, it quickly finds a better path.

9 Data Centers A data center is a facility hosting many servers. These servers usually perform tasks in a distributed manner. Google, Bing, Amazon, E-Bay, Facebook, Twitter etc. have their own (multiple) data centers. A large data center can have tens or even hundreds of thousands of servers.

10 Data Centers Data center structure Servers (called blades) are distributed among racks. At the top of each rack, there is a top-of-rack switch (ToR switch). These switches are connected to each other as part of the data center network. The network also has routers for connecting the Internet.

11 Data Centers Data center topology

12 Data Centers Data center characteristics Many users (multi-tenant environment) Elastic resources Flexible service management Workload movement Virtual machine migration

13 Data Centers Data center challenges Balancing the load and the traffic Support for VM migration Reducing costs and saving energy Allocating resources according to dynamically changing demands Security

14 Content Delivery Network (CDN) Also called Content Distribution Network Distributed system of servers in multiple data centers Used to improve performance and availability for end users. Can be viewed as an overlay network.

15 Content Delivery Network (CDN) Goal: Deliver the content to the end user from the optimal point.

16 Content Delivery Network (CDN) Who builds CDNs? Content providers (Google) Internet service providers (AT&T, Level 3) Independent companies (Akamai)

17 Content Delivery Network (CDN) Advantages of CDNs Faster response Load balancing Protection against Denial-of-Service attacks

18 Content Delivery Network (CDN) CDN Questions How to make the replication Where to place the replicas How to make users find the right replica Which replica to choose (Server selection) How to direct the user to it

19 Content Delivery Network (CDN) Server selection Involves deciding where to redirect a content request. Some possible criteria are: Server with the lowest load or largest capacity Server with the lowest latency Server with the shortest geographical distance Any live server

20 Content Delivery Network (CDN) Content routing Involves directing the user to the server. Some possible methods are: Over Internet routing using anycast Application-based method (HTTP redirect) Using the naming system (DNS-based routing)