Internetworking Lecture 10 October 23, 2000

Introduction to Internetworking So far, we’ve discussed about how a single network functions. Internetworking is how multiple networks are connected. All material from here relates to “the big picture.”

Why Internetworking? Each network has its own specific task. – LAN functionality – WAN functionality Internetworking is a culmination of multiple, independent networks being developed. In another light, internetworking is the glue behind the Internet.

Universal Service Universal Service is the concept that any device on any network can communicate with any arbitrary device on another network. The Internet is a heterogeneous environment, with multiple, independent network topologies. In LANs, we have seen that heterogeneous technologies cannot interconnect without the help of a device to translate from one medium to another.

Internetworking The interconnects between different networks are a combination of hardware and software elements. Routers provide the proper hardware/software translation to connect two different networks together. – LAN routers – WAN routers

The Router The router is very similar to a bridge. – Memory – CPU – Separate I/O ports for each network topology

The Router (cont.) The router can perform multiple tasks – LAN / LAN routing – WAN / WAN routing – LAN / WAN routing The clouds in each picture can represent a different network topology (FDDI, Ethernet), address scheme (IP, IPX), or both!

Internet Architecture The book likes to use the cloud diagram:

I Like This Diagram

Why the Later is Realistic Rarely do you have a “linear” network! – Inefficient transport – Bandwidth limitations in the “middle” A Universal Service goal not only dictates if you can talk to another machine, but how fast! Reliability Capacity Cost

Internet as a Virtual Network

Internetworking and TCP/IP ARPANet NSFNet TCP/IP

TCP/IP Layers These are not hard and fast rules. Many different models exist. Layer 1: Physical Layer 2: Network Interface Layer 3: Internet Layer 4: Transport Layer 5: Application

TCP/IP & ISO Model Application (Layers 6 and 7 in ISO model) Transport (Layer 4 in ISO model) Internet (Layer 3 in ISO) Network Interface (Layer 2 in ISO) Physical (Layer 1 in ISO)