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Chapter 8. Hardware and Network Protection

8.1.1.2. Linear Bus Topology

The linear bus topology consists of nodes which connect to a terminated main linear cable (the back 

bone). The linear bus topology requires the least amount of cabling and networking equipment, mak 

ing it the most cost effective topology. However, the linear bus depends on the backbone being con 

stantly available, making it a single point of failure if it has to be taken off line or is severed. Linear

bus topologies are commonly used in peer to peer LANs using co axial (coax) cabling and 50 93 ohm

terminators at both ends of the bus.

8.1.1.3. Star Topology

The Star topology incorporates a central point where nodes connect and through which communica 

tion is passed. This centerpoint, called a hub can be either broadcasted or switched. This topology

does introduce a single point of failure in the centralized networking hardware that will connect the

nodes. However, because of this centralization, networking issues that affect segments or the entire

LAN itself is easily traceable to this one source.

8.1.2. Transmission Considerations

In a broadcast network, a node will send a packet that traverses through every other node until the

recipient accepts the packet. Every node in the network will conceivably receive this packet of data

until the recipient processes the packet. In a broadcast network, all packets are sent in this manner.

In a switched network, packets are not broadcasted, but are processed in the switched hub which,

in turn, will create a direct connection between the sending and recipient nodes using the unicast

transmission principles. This eliminates the need to broadcast packets to each node, thus lowering

traffic overhead.

The switched network also prevents packets from being intercepted by malicious nodes or users. In

a broadcast network, since each node receives the packet en route to its destination, malicious users

can set their Ethernet device to promiscuous mode and accept all packets regardless of whether or

not the data is intended for them. Once in promiscuous mode, a sniffer application can be used to

filter, analyze, and reconstruct packets for passwords, personal data, and more. Sophisticated sniffer

applications will store such information in a text file and, perhaps, even send the information to an

arbitrary source (for example, the malicious user's email address).

A switched network requires a network switch, a specialized piece of hardware which replaces the role

of the traditional hub in which all nodes on a LAN are connected. Switches store MAC addresses of all

nodes within an internal database, which it uses to perform its direct routing. Several manufacturers,

including Cisco Systems, Linksys, and Netgear offer various types of switches with features such

as 10/100 Base T compatibility, gigabit Ethernet support, and support for Carrier Sensing Multiple

Access and Collision Detection (CSMA/CD) which is ideal for high traffic networks because it will

queue connections and detect when packets collide in transit.

8.1.3. Wireless Networks

An emerging issue for enterprises today is that of mobility. Remote workers, field technicians, and

executives require portable solutions, including laptops, Personal Digital Assistants (PDAs), and wire 

less access to network resources. The IEEE has established a standards body for the 802.11 wireless

specification, which establishes standards for wireless data communication throughout all industries.

The current standard in practice today is the 802.11b specification.

The 802.11b specification is actually a group of standards governing wireless communication and

access control at the 2.4 GHz communication band. This specification has already been adopted at