CMSC506 study guide for final exam
Question format:
 Term explanations: e.g., what is CSMA/CD?
 Short question: e.g., what is the hidden node problem and
what causes this problem.
 Simple math and terminology: e.g., calculating effective data
rate for Ethernet.
 Protocol tracing: Explain binary countdown algorithm and its
motivation.
o What is binary exponential backoff algorithm? Where
is it being used?

Scope:
 Mostly after midterm.
 Network Layer, Chapter 5, Mainly on 5.2 and 5.6
o Routing Related Topics
o The fundamental routing scheme is store-and-forward
o 5.2.2 Should be able to step-by-step construct Shortest
Path Routing path for a given graph. You should be
very familiar with Figure 5-7.
o 5.2.3 The pros and cons of flooding. How to improve
it?
o 5.2.4 Distance Vector Routing: focus on updating
process. The main drawback of DVR: count-to-infinity
problem
o 5.2.5 Link state Routing: each node will calculate
routing table when received enough information. Notice
how link stage packet is defined and passed around.
o 5.2.6 Hierarchical routing: able to determine the size of
routing table when the hierarchical structure is given.
o 5.2.7 Broadcasting routing: spanning tree and reverse
path forwarding
o Internet Related Topics
o 5.5.6-7 Internetwork routing, Fragmentation
o 5.6.1 understand various fields in IPv4 header, such as
TTL and MF. The IP routing options (strict and loose
source) and their functionality. When studying these,
always ask yourself why a particular IP feature is
their.
o 5.6.2 Subnet and netmask.
o 5.6.3 ICMP types. ARP and RARP. Keep in mind that
these are IP level protocols. But the functionalities of
ARP and RARP is to translate IP and MAC address.
o 5.6.8 IPv6. Difference when compared to IPv4.
 Media Access Layer: mainly at 4.1 4.2 4.3 4.4 4.5 and some
subsection in 4.6 and 4.7.
 Understand three types of access methods:
o Fixed channel allocation: FDMA, TDMA. Often
centralized.
o Dynamic allocation with collision: ALOHA,
CSMA/CD, CSMA/CA
o Dynamic allocation and collision-free: bit-map, binary
countdown…
 4.1.1 and 4.1.2 basic concepts and terms.
 4.2.1 the difference between pure aloha and slotted aloha.
The vulnerable period.
 4.2.2 CSMA and several variations. Persistent or not.
Augmented by collision detection (Figure 4.5).
 4.2.3 collision free protocols. pros and cons. Efficiency
calculation.
 4.2.6 wireless properties: range, hidden node and exposed
node. MACA, collision avoidance.
 4.3 Ethernet related topics
 4.3.1 4.3.2 Basic specifications: physical dimension, physical
media, speeds. Signal forms.
 4.3.2 Frame format, collision detection in Ethernet.
Propagation delay, minimum packet size.
 4.3.4 Binary Exponential Backoff algorithm: what is its
purpose?
 4.3.7 and 4.3.8 switched Ethernet and gigabit Ethernet
 4.4 WLAN related topics: basic protocol is also at 4.2.6
 4.4.1-4.4.2 physical layer specification and Different versions
in 802.11 family
 4.4.3 RTS/CTS handshake, and Network Allocation Vector.
Figure 4.27. Fragmentation transmission.
 DCF and PCF operation mode in 802.11.
 Base station (AP), beacon frame and channels in 802.11
 4.4.4 802.11 framing.
 4.5.1 Compare 802.11 and 802.16
 4.6.1 bluetooth