Syngress - Eleventh Hour Network+ Exam N10-004 Study Guide (11 ...

86 CHAPTER 5 The OSI Model and Networking Protocols
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Information is stored in a management information base (MIB) and
contains a set of objects, each of which represents a particular type of
network information such as an event, an error, or an active session.
SNMP employs UDP datagrams to send messages between the management
console and the agents.
Summary of Exam Objectives
In this chapter, we covered the OSI model, the Microsoft model, and the DoD
model, all of which are similar, share common core elements, but have differences
as well.
From the DARPA experiment came the understanding that networking would
become increasingly common and increasingly complex. The OSI model was
developed, based on the original DARPA model, and approved by the OSI
subcommittee of the ISO. The OSI model defined seven layers for standard, reliable
network communications: physical, data link, network, transport, session,
presentation, and application.
The physical layer is responsible for signaling, transmission medium, and ones
and zeros traversing the wire. The next layer, the data link layer, is where your
MAC address is located. On Ethernet NICs, the physical or MAC address (also
called the hardware address) is expressed as 12 hexadecimal digits, arranged in
pairs with colons between each pair, for example, 12:3A:4D:66:3A:1C. In binary
notation, this translates to a 48-bit (or 6-byte) number, with the initial three bytes
representing the manufacturer and the last three bits representing a unique NIC
made by that manufacturer. The data link layer is subdivided into two sub layers
known as the LLC and MAC layer. The LLC sub layer is responsible for providing
the logic for the data link, and thus, it controls the synchronization, flow control,
and error checking functions of the data link layer.
The TCP/IP suite provides the functionality specified in the OSI model using the
four-related layers of the DoD model: network interface, Internet, host-to-host,
and application. The network interface layer maps to the physical and data link
layers of the OSI model and the Internet layer maps to the OSI network layer. The
host-to-host layer maps to the OSI transport layer and DoD’s application layer
maps to the session, presentation, and application layers of the OSI model. Some
of the more commonly known application layer protocols are FTP, HTTP, POP3,
WINS, DNS, and DHCP.
Understanding the details of the TCP/IP suite is fundamental to managing
computers in today’s networked environment. Being able to subnet, assign IP
addresses, create subnet masks, and set up routing are essential skills you’ll need
on the job and to successfully master the material on the Network+ exam.
Top Five Toughest Questions
1. You are the system administrator for a small company that runs two Windows
servers (Windows Server 2003) and two Linux servers (SUSE Linux).