Example networks

• internetwork – interconnection of networks – also called an “internet”
• Subnetwork – a constituent of an internet
• Intermediate system – a device used to connect two networks allowing hosts of
the networks to correspond with each other
• Internet is an example of an internetwork.
• internet : collection of networks interconnected by router and/or bridges
• The Internet
• The global collection of thousands of individual machines and networks
• Intranet
• Corporate internet operating within the organization
• Uses Internet (TCP/IP and http) technology to deliver documents and resources
• End System (ES)
• Device attached to one of the networks of an internet
• Supports end-user applications or services
• ES sometimes called DTE
• Intermediate System (IS)
• Device used to connect two networks
• Permits communication between end systems attached to different networks
• Examples: Routers and Bridges
• Bridge
– IS used to connect two LANs using similar LAN protocols
– Address filter passing on packets to the required network only
– OSI layer 2 (Data Link)
• Router
– Connects two (possibly dissimilar) networks
– Uses internet protocol present in each router and end system
– OSI Layer 3 (Network)
– First public data network
– Connection number used for data transfer of packets
– data packets contain 3 byte header and upto 128 bytes of data

– X.25 replaced by Frame Relay