读书笔记： 《Content Networking Fundamentals》
在生活的各个方面，需求导致新的创造和发明，网络计算也是一样，它的发展伴随着不断增长的用户需求：更加丰富的内容，更多的带宽，更多的可靠性。要完成这些要求，首先你必须解决以下四个方面：
Scalability and Availability
Bandwidth and Response Times
Customization and Prioritization
Security, Auditing, and Monitoring
content networking 可以为应用提供未来增长的可扩展空间，而不需要改变应用工作的方式，只需要微小的改变网络架构。包括以下的服务：
Content edge delivery Positioning application content away from the origin server, and in closer proximity to clients, scales the application by offloading requests to the content network. 将内容放在更加接近用户的地方。
Enhanced content delivery with IP multicast, stream-splitting, and resource reservation IP multicast and stream-splitting scales the network by avoiding replication of identical flows over the same network link, thus minimizing end-to-end bandwidth consumption of content delivered to a large number of users. Resource reservation scales the application by manipulating network parameters to expedite application traffic delivery.通过组播和流分割技术，避免通过同样的网络连接（？)复制同样的内容，这样最小化了大量用户的端到端的带宽消耗。资源预留可以加快应用的通信传输。
Content transformation and prioritization Transformation provides conversion of content within the network without further burdening of origin servers. Prioritization enables custom network delivery of application traffic.
Flash crowd protection Protection against sudden, but valid, traffic spikes directed toward an application is important to maintaining service levels to customers. 需要在突发的大流量下维持服务水平。
包括以下部分：
Content switching Increases availability by replicating origin server content across numerous identical systems, either within the same data center or across globally distributed data centers. 在多个相同系统复制原始服务器的内容，他们可以在同一个数据中心或者是跨全球的数据中心
Session redundancy Session redundancy provides failover from one network device, such as a firewall or load balancer, to an identical device without dropping existing TCP connections. 在网络设备(firewall or LB)失效切换的时候不丢失已有的tcp连接。
Router redundancy Protocols, such as Hot Standby Router Protocol (HSRP) and Virtual Router Redundancy Protocol (VRRP), provide router gateway redundancy by having two routers or load balancers share a virtual IP (VIP) and MAC address for clients to use as their default gateway. If either fails, the other will take over within seconds.
IP routing redundancy Dynamic IP routing protocols, such as OSPF, EIGRP, and IS-IS, provide availability within a routing domain by maintaining multiple paths to each network in the routing table.
Layer 2 switching redundancy Spanning tree and Cisco Etherchannel provides Layer 2 redundancy in a switched environment.