Enter TCP/IP networking, which was simple at firstwith IP address classes and World Wide Web surfing. This soon became more complex as the IP address space was depleted and the Internet grew. Routing required some serious sophistication to support the performance demanded by Internet users. Cisco rose to the challenge, and developed products that met the new challenges posed by an expanding Internet and World Wide Web.
New proprietary and Request For Comments (RFCs) specified that routing protocols were implemented in Cisco products. The old Routing Information Protocol (RIP) was replaced by Cisco-developed Interior Gateway Routing Protocol (IGRP) and EnhancedInterior Gateway Routing Protocol (E-IGRP); and by the RFC-specified Open Shortest Path First (OSPF) routing protocol for routing within a large IP networks. These protocols implemented CIDR. Border Gateway Protocol (BGP or BGFPv4 today) was RFC-specified and implemented in Cisco routers to route packets between IP networks forming the Internet.
Classless Inter-Domain Routing (CIDR) replaced the obsolete and wasteful system of Internet Protocol IP address classes. CIDR allocates Internet IP addresses used for interdomain routing more flexibly than original IPv4 32-bit address A, B, C, and D class allocations. This postponed depletion of IP addresses until the new IPv6 128-bit addressing is fully implemented in the Internet. CIDR effectively solved the IP address-depletion problem by implementing a more flexible way to specify network addresses in routers that permitted them to route more packets more quickly.
This development made installing and configuring Cisco routers a more complex and demanding task. Cisco developed a certification program. The router configuration was performed using a command language such as the DOS command language. Proper configuration prevented split horizon broadcasts, in which routing information was blocked from being rebroadcast from interfaces that originally broadcast the routing information. The result is that Cisco-powered networks required high-paid network engineers to install, configure, and operate them. Comcast's reconfiguration is an example of what happens when the network is upgraded with new Cisco routers. It took several weeks for routing problems to be ironed out, and several more weeks for the network to operate effectively.
Now, IP networks and the Internet are becoming more complex and sophisticated because new Voice over IP (VoIP) and video applications require guaranteed, timely deliveries of packets containing voice or video data. Such a delivery guarantee is generally referred to as Quality of Service (QoS). Robust routers and routing protocols are increasingly important in such converged voice, video, and data IP networks. Cisco routers support these new networking and routing demands with more sophisticated routing software.
However, we are approaching something similar to IBM's SNA networking, in which configuring and operating the software is an increasingly complex and daunting task. High-paid network engineers are needed to operate and maintain IP networks. However, this only works for awhile. All Internet and IP network routers must automatically, with no human intervention, configure themselves and optimize network performance for any network configuration.