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710 Appendix A: Answers to the "Do I Know This Already?" Quizzes and Q&A Sections
13
How many bits are present in an IPX address?
IPX addresses comprise 80 bits--32 bits in the network portion and 48 bits in the node
portion.
14
Name the two main parts of an IP address. Which part identifies the "group" of which this
address is a member?
Network and host are the two main parts of an IP address. As described in Chapter 5,
"Network Protocols," technically there are three portions of the IP address: network,
subnet, and host. However, because most people think of the network and subnet portions
as one portion, another correct answer to this question, using popular terminology, would
be subnet and host.
15
Describe the differences between a routed protocol and a routing protocol.
The routed protocol defines the addressing and Layer 3 header in the packet that is actually
forwarded by a router. The routing protocol defines the process of routers exchanging
topology data such that the routers know how to forward the data. A router uses the routing
table created by the routing protocol to choose how to forward a routed protocol packet.
16
Name at least three routed protocols.
TCP/IP (IP), Novell (IPX), OSI (CLNP), DECNET (CLNP), AppleTalk (DDP), and
VINES are some examples of routed protocols.
Answers to the Chapter 3 Q&A Section
1
Name the seven layers of the OSI model.
Application (Layer 7), presentation (Layer 6), session (Layer 5), transport (Layer 4),
network (Layer 3), data link (Layer 2), and physical (Layer 1). Some mnemonics to help
you recall the names of the layers are: All People Seem To Need Data Processing (Layer
7 to 1), Please Do Not Take Sausage Pizzas Away (Layer 1 to 7), and the ever-popular
Pew! Dead Ninja Turtles Smell Particularly Awful (Layer 1 to 7).
2
What is the main purpose(s) of Layer 7?
Layer 7 (application layer) provides standardized services to applications. The definition
for this layer is typically ambiguous because it varies. The key is that it does not define a
user interface, but instead is a sort of toolbox used by application developers. For example,
a Web browser is an application that uses HTML format text, as defined by the TCP/IP
application layer, to describe the graphics to be displayed onscreen.
3
What is the main purpose(s) of Layer 6?
Layer 6 (presentation layer) defines data formats, compression, and possibly encryption.
apA.fm Page 710 Monday, March 20, 2000 5:24 PM