Assigment # 1

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

In a Token Ring network, each computer is constantly in direct contact with the next node in the ring but a Token Ring network cannot communicate within itself if any one of the rings is broken.
The token ring network architecture was developed by IBM and later standardized as the IEEE 802.5 standard and is the second most widely-used protocol on local area networks after Ethernet.

Token ring is more effective under high sustained load, and each slot may be used to carry a message, providing highthroughput.

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.

Active networks are an exciting development in networking services in which the infrastructure provides customizable network services to packets. These custom network services can be deployed by the user inside the packets themselves. Furthermore, the custom network services require that the infrastructure performs much more sophisticated operations on packets than the traditional forwarding. Consequently, there are heightened concerns from users and network operators about security. We discuss security requirements and issues in active networks with respect to authentication and authorization in a node. We describe our prototype implementation of a solution to those issues. We go on to describe a security architecture derived from our experience and relate our prototype to the architecture.

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.
Prevention => A common scheme for preventing deadlock in networks is the virtual channel method of Dally and Seitz [DS87]. Due to the nature of this scheme, an otherwise completely uniform network will have non-uniformities introduced into it. The variations introduce several effects, ranging from limitations on overall network performance to differences in observed network characteristics from node to node and from message to message.

Detection and Recovery => Deadlock detection and recovery-based routing protocols in wormhole networks have gained attraction because they do not restrict routing adaptability unlike deadlock avoidance-based protocols. Network performance largely relies on the accuracy of deadlock detection. The lower the number of packets presumed as deadlocked by a protocol, the better the network performs, since the network rarely enters into deadlock state in reality and those packets presumed as deadlocked are usually killed or recovered according to a recovery procedure, causing extra overhead to the network. This paper proposes a deadlock detection protocol based on the turn model. It declares only one packet per simple cycle of blocked packets as deadlocked in most cases, thus considerably reducing the number of false deadlock detections over previous protocols. This results in less number of unnecessary recoveries to resolve deadlock. This achievement is made with lower hardware complexity than a most sophisticated previous protocol. The simulation study shows that our protocol outperforms previous protocols in the number of deadlock detections.

Avoidance => A feasible solution to cope with such unpredictable situations is to introduce an automated manufacturing system characterized by high flexibility, autonomy and cooperation. Much research has been done on negotiation-based scheduling and control under the distributed control architecture due to its operational flexibility and scalability. Despite many advantages, the probability of the system stalling at a deadlock state is high. Specifically, it is difficult to detect impending part flow deadlocks within the system. A system request network model is defined here to analyse various deadlock situations. Request cycles are then identified by a virtual part flow control mechanism. No request cycle in the system request network represents 'no system deadlock'. For any request cycle, a deadlock analysis is performed. If any request cycle exists that represents either a part flow deadlock or an impending part flow deadlock, then the system will be deadlocked. The proposed model can analyse all types of impending part flow deadlocks. Furthermore, it is more efficient through the reduction of search space, is applicable to various configurations and is less restrictive in dynamic shop floor control.

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?

Computer workstations are now an indispensable component of every office. Faculty, staff, and administrators use their workstations in every aspect of their duties. Since computers on campus are connected in a network, it is essential that each workstation represent current technology and be able to run the essential applications that define the University's business environment. It is also essential that each departmental file server be upgraded on a regular basis so that the network can function effectively. This plan describes an orderly approach to upgrading or replacing all computer workstations and large file servers on a regular basis, and it enables budget authorities to project the costs of such upgrades. This proposal does not affect computers used for special instrumentation purposes in University research laboratories.

Form Factors in Motherboard

ATX Motherboard


ATX was developed as an evolution of the Baby-AT form factor and was defined to address ease of use, support for current and future I/O, support for current and future processor technology, and reduced total system cost.


ATX Specification v2.2 Revision 2.2 - [432 KB] Key changes for the ATX Specification Version 2.2 include Main Power Connector changed from 20 pin to 24 pin ( 2 x12) to support PCI-Express* requirements and removed Aux Power Connector Recommendation if using a power supply designed using ATX12V Power Supply Design Guide Rev 2.0 or greater. Also updated the +3.3 V tolerance.


MicroATX Motherboard



The microATX form factor was developed as a natural evolution of the ATX form factor to address new market trends and PC technologies. While offering the same benefits of the ATX form factor specification, the microATX form factor improves upon the previous specification in several key areas. Current trends in the industry indicate that users require a lower-cost solution for their PC needs. Without sacrificing the benefits of ATX, this form factor addresses the cost requirement by reducing the size of the motherboard. The smaller motherboard is made possible by reducing the number of I/O slots supported on the board. The overall effect of these size changes reduces the costs associated with the entire system design. The expected effect of these reductions is to lower the total system cost to the end user.


Through careful designing of a microATX motherboard, an OEM can capitalize on the benefits of a reduction in total system costs. These cost savings come from a reduced-output power supply (see the separate document SFX Power Supply Design Guide), reduced chassis costs, and minimal redesign of existing ATX compliant chassis for backward-compatibility.


microATX benefits also include those found with the current ATX form factor: more I/O space at the rear and reduced emissions from using integrated I/O connectors.


microATX Motherboard Interface Specification v 1.2 Revision 1.2 - [278 KB] Key changes for the microATX Motherboard Interface Specification Version 1.2 include Main Power Connector changed from 20 pin to 24 pin ( 2 x12) to support PCI-Express* requirements

FlexATX Motherboard


FlexATX offers the opportunity for system developers to create many new personal computer designs.

Balanced Technology Extended (BTX) Form Factor


The BTX form factor specification gives developers options to balance thermal management, acoustics, system performance, and size in the system form factors and stylish designs that are desired in today's products. The BTX form factor is a clear break from previous ATX form factor layouts and was developed with emerging technologies such as Serial ATA, USB 2.0, and PCI Express*.

Thermal improvements come primarily from taking advantage of in-line airflow. The BTX defined in-line airflow layout allows many of the main board components (i.e.: processor, chipset, and graphics controller) to utilize the same primary fan airflow, thereby reducing the need for, and noise from, additional system fans. In some cases this also allows fewer and/or less expensive heat sinks to be used when compared to ATX solutions. The system level acoustics are also improved by the reduced air turbulence within the in-line airflow system. The BTX layout supports better component placement for back panel I/O controllers – important as the signal speed of external devices continues to increase. In addition to smaller than microATX system sizes, BTX was designed to scale up to tower size systems using the same core layout by increasing the number of system slots included.




Balanced Technology Extended (BTX) Interface Specification Revision 1.0b - [305 KB]


LPX

White ATX is the most well-known and used form factor, there is also a non-standard proprietary form factor which falls under the name of LPX, and Mini-LPX. The LPX form factor is found in low-profile cases (desktop model as opposed to a tower or mini-tower) with a riser card arrangement for expansion cards where expansion boards run parallel to the motherboard. While this allows for smaller cases it also limits the number of expansion slots available. Most LPX motherboards have sound and video integrated onto the motherboard. While this can make for a low-cost and space saving product they are generally difficult to repair due to a lack of space and overall non-standardization. The LPX form factor is not suited to upgrading and offer poor cooling.


NLX

Boards based on the NLX form factor hit the market in the late 1990's. This "updated LPX" form factor offered support for larger memory modules, tower cases, AGP video support and reduced cable length. In addition, motherboards are easier to remove. The NLX form factor, unlike LPX is an actual standard which means there is more component options for upgrading and repair.
Many systems that were formerly designed to fit the LPX form factor are moving over to NLX. The NLX form factor is well-suited to mass-market retail PCs.