NO. 2







NO. 1

BUS TOPOLOGY:

STAR TOPOLOGY:

RING TOPOLOGY:

1. Explain the cirumstances under which a token-ring netwrok is more effective than an Ethernet network.




A token ring network is more effective than Ethernet Network in a way that The Token Ring protocol is the second most widely-used protocol on local area networks after Ehthernet. It is known as a Deterministic method of access since a station can only transmit data when a token is available to it, once the station releases the token the next station grabs it, no collisions can occur, and each station has a chance to grab the token whether they have data to transmit or not. Token Ring and FDDI, on the other hand, store the MAC address in the NICs with the Most Significant Bit (MSB) first, or Big-Endian. This is known as Non-Canonical format.



In the Ethernet Network the hardware address, or MAC address is transmitted and stored in Ethernet network devices in Canonical format i.e. Least significant Bit (LSB) first. You may hear the expression Little-Endian to describe the LSB format in which Ethernet is stored and transmitted.
Ethernet is the most widely-installed local area network ( LAN) technology. Specified in a standard, IEEE 802.3,

2. Although security issues were not mentioned in this chapter, every network owner must consider them. Knowing that open networks all data to pass to every node, describe the posssible security concerns of open network achitectures. include the implicatiions of passing logon procedures, user IDs, and passwords openly on the network .

Security Architecture can be defined as the design artifacts that describe how the security controls (security countermeasures) are positioned, and how they relate to the overall information technology architecture. These controls serve the purpose to maintain the system's quality attributes, among them confidentiality, integrity, availability, accountability and assurance."[1]. In simpler words, a security architecture is the plan that shows where security measures need to be placed. If the plan describes a specific solution then, prior to building such a plan, one would make a risk analysis. If the plan describes a generic high level design (reference architecture) then the plan should be based on a threat analysis.


3. Remembering the discussion of deadlocks, if you were designing a networked system, how would you manage the treat of deadlocks in your network? Consider all of the following: prevention, detection, avoidance, and recovery.

Recovery:

Once a deadlock has been detected it must be untangled and system returned to normal as quickly as possible.
There are several recovery algorithms, all requiring at least one victim, an expendable job, which, when removed from deadlock, frees system.
1. Terminate every job that’s active in system and restart them from beginning.
2. Terminate only the jobs involved in deadlock and ask their users to resubmit them.
3. Terminate jobs involved in deadlock one at a time, checking to see if deadlock is eliminated after each removal, until it has been resolved.
4. Have job keep record (snapshot) of its progress so it can be interrupted and then continued without starting again from the beginning of its execution.
5. Select a non-deadlocked job, preempt resources it’s holding, and allocate them to a deadlocked process so it can resume execution, thus breaking the deadlock
6. Stop new jobs from entering system, which allows non-deadlocked jobs to run to completion so they’ll release their resources (no victim).

Avoiding Deadlocks:

•Even if OS can’t remove 1 conditions for deadlock, it can avoid one if system knows ahead of time sequence of requests associated with each of the active processes.
•Dijkstra’s Bankers Algorithm (1965) used to regulate resources allocation to avoid deadlock.
•Safe state -- if there exists a safe sequence of all processes where they can all get the resources needed.
•Unsafe state -- doesn’t necessarily lead to deadlock, but it does indicate that system is an excellent candidate for one.

Prevention of Deadlock:

•To prevent a deadlock OS must eliminate 1 out of 4 necessary conditions.
–Same condition can’t be eliminated from every resource.
•Mutual exclusion is necessary in any computer system because some resources (memory, CPU, dedicated devices) must be exclusively allocated to 1 user at a time.
–Might be able to use spooling for some devices.
–May trade 1 type of deadlock (Case 3) for another (Case 5).

Detection:

•Use directed graphs to show circular wait which indicates a deadlock.
•Algorithm used to detect circularity can be executed whenever it is appropriate

4. Assuming you had sufficient funds to upgrade only one component for a system with which you are familiar, explain which component you would choose to upgrade to improve overall performance, and why?

Every components has its own functions in improving the performance of the computer. Upgarding CPU is one way of improving the over-all performance of the omputer because the computer CPU is responsible for handling all instructions and calculation it receives from other hardware components in the computer and software programs running on the computer.