Ethernet Packet Format
Here is the format of a typical Ethernet packet (DIX specification); it is still used for newer, faster Ethernets: The destination and source addresses are 48-bit quantities; the type is…
10-Mbps Classic Ethernet
Originally, Ethernet consisted of a long piece of cable (possibly spliced by repeaters). When a station transmitted, the data went everywhere along that cable. Such an arrangement is known as…
Ethernet
We now turn to a deeper analysis of the ubiquitous Ethernet LAN protocol. Current user-level Ethernet today (2013) is usually 100 Mbps, with Gigabit and 10 Gigabit Ethernet standard in…
IETF and OSI
The Internet protocols discussed above are defined by the Internet Engineering Task Force, or IETF (under the aegis of the Internet Architecture Board, or IAB, in turn under the aegis…
Some Useful Utilities
There exists a great variety of useful programs for probing and diagnosing networks. Here we list a few of the simpler, more common and available ones; some of these are…
Firewalls
One problem with having a program on your machine listening on an open TCP port is that someone may connect and then, using some flaw in the software on your…
Content-Distribution Networks
Sites with an extremely large volume of content to distribute often turn to a specialized communication pattern called a content-distribution network or CDN. To reduce the amount of long-distance traffic,…
Transport Communications Patterns
The two “classic” traffic patterns for Internet communication are these: • Interactive or bursty communications such as via ssh or telnet, with long idle times between short bursts • Bulk…
Transport
The IP layer gets packets from one node to another, but it is not well-suited to transport. First, IP routing is a “best-effort” mechanism, which means packets can and do…
The Future of IPv4
As mentioned earlier, allocation of blocks of IP addresses is the responsibility of the Internet Assigned Numbers Authority. IANA long ago delegated the job of allocating network prefixes to individual…
