IP – Internet Protocol
To solve the scaling problem with Ethernet, and to allow support for other types of LANs and point-to-point links as well, the Internet Protocol was developed. Perhaps the central issue…
Password Sniffing
In the fall of 1994 at Loyola University I remotely changed the root password on several CS-department unix machines at the other end of campus, using telnet. I told no…
LANs and Ethernet
A local-area network, or LAN, is a system consisting of • physical links that are, ultimately, serial lines • common interfacing hardware connecting the hosts to the links • protocols to make everything…
Packets Again
Perhaps the core justification for packets, Baran’s concerns about node failure notwithstanding, is that the same link can carry, at different times, different packets representing traffic to different destinations and…
Congestion
Switches introduce the possibility of congestion: packets arriving faster than they can be sent out. This can happen with just two interfaces, if the inbound interface has a higher bandwidth…
Routing Loops
A potential drawback to datagram forwarding is the possibility of a routing loop: a set of entries in the forwarding tables that cause some packets to circulate endlessly. For example,…
Traffic Engineering
In some cases the decision above between routes A S1 S2 S4 B and A S1 S3 S4 B might be of material significance – perhaps the S2–S4 link is…
Topology
In the network diagrammed in the previous section, there are no loops; graph theorists might describe this by saying the network graph is acyclic, or is a tree. In a…
Datagram Forwarding
In the datagram-forwarding model of packet delivery, packet headers contain a destination address. It is up to the intervening switches or routers to look at this address and get the…
Data Rate, Throughput and Bandwidth
Any one network connection – eg at the LAN layer – has a data rate: the rate at which bits are transmitted. In some LANs (eg Wi-Fi) the data rate…
