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Unformatted text preview: n the type of networking hardware being used: Ethernet, token ring, FDDI
(Fiber Distributed Data Interface), RS-232 serial lines, and the like.
In this chapter we'll look at some of the details involved in the Ethernet link layer, two specialized
link layers for serial interfaces (SLIP and PPP), and the loopback driver that's part of most
implementations. Ethernet and SLIP are the link layers used for most of the examples in the book.
We also talk about the MTU (Maximum Transmission Unit), a characteristic of the link layer that
we encounter numerous times in the remaining chapters. We also show some calculations of how
to choose the MTU for a serial line. 2.2 Ethernet and IEEE 802 Encapsulation
The term Ethernet generally refers to a standard published in 1982 by Digital Equipment Corp.,
Intel Corp., and Xerox Corp. It is the predominant form of local area network technology used
with TCP/IP today. It uses an access method called CSMA/CD, which stands for Carrier Sense,
Multiple Access with Collision Detection. It operates at 10 Mbits/sec and uses 48-bit addresses.
A few years later the IEEE (Institute of Electrical and Electronics Engineers) 802 Committee
published a sightly different set of standards. 802.3 covers an entire set of
CSMA/CD networks, 802.4 covers token bus networks, and 802.5 covers token ring networks.
Common to all three of these is the 802.2 standard that defines the logical link control (LLC)
common to many of the 802 networks. Unfortunately the combination of 802.2 and 802.3 defines
a different frame format from true Ethernet. ([Stallings 1987] covers all the details of these IEEE
In the TCP/IP world, the encapsulation of IP datagrams is defined in RFC 894 [Hornig 1984] for
Ethernets and in RFC 1042 [Postel and Reynolds 1988] for IEEE 802 networks. The Host
Requirements RFC requires that every Internet host connected to a 10 Mbits/sec Ethernet cable:
1. Must be able to send and receive packets using RFC 894 (Ethernet) encapsulation.
2. Should be able to receive RFC 1042 (IEEE 802) packets...
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This test prep was uploaded on 04/04/2014 for the course ECE EL5373 taught by Professor Guoyang during the Spring '12 term at NYU Poly.
- Spring '12