Make your own free website on Tripod.com

  

        We Engineers move the world

 

Exam Details

Braindump

Favorites

 

Email: Webmaster

 

 

 

 

 

 

Define common networking terms for LANs and WANs.
Compare a file-and-print server with an application server
File Server Centralised storage for files needed by a user group. Benefits:
Centralised location
Power conditioning / UPS
Consistent data archiving / backups
Speed (over peer-to-peer) - server usually higher spec
Print Server Receive print requests from all networked devices, put in a queue and spool to relevant printer. Some printers can have there own Network Interface Card and therefore directly connect to the LAN. Still controlled by a print server - just not directly tied to its parallel port.
Application Server Actually host application software. To run an application the client establishes a connection across the network to the application which runs on the server.
Note: Servers that allow clients to download application software to run on the client are acting as file servers where the files are application software.
Compare user-level security with access permission assigned to a shared directory on a server
Share Level Security (Password protected shares) Individual resources given access passwords. Useful on small networks (i.e. Peer-To-Peer) but cumbersome on large networks with more resources and more passwords to remember.
User Level Security User has an account to logon to the network. Permissions to access resources are assigned to users on an individual basis. User only needs to know one password. Benefits from higher security, central administration.
Compare a client/server network with a peer-to-peer network
Peer to Peer Unstructured access to network-attached resources. Each device can be a client and server simultaneously. Every machine is a peer of every other.

Benefits:

Inexpensive to operate - lack expensive servers and admin staff
Familiar operating systems: Windows 3.11 / 95 / NT
Can be more fault tolerant - server can be c
Considered single point of failure

Limitations:

Users must maintain multiple passwords - typically one for each resource they need to access
Burden for administration on each user - need good admin policies: backups, filenaming, storage locations etc
Security distributed throughout network
Technical proficiency varies amongst users - security only as valid as weakest peer
Performance - each machine both client and server

Recommend:

Max 10 computers in peer-to-peer network
Client / Server Frequently shared resources consolidated onto a separate tier of servers. Typically do not have a primary user.

Benefits:

Security - server can be made more secure (locked away) and use of user level security (centrally managed, only one logon password)
Performance - each client works for its primary user only; server can be configured for optimised performance (faster processor, disks, more memory etc)
Administration - centrally co-ordinated backups, storage locations etc
Scalability - size of network limited only by hardware

Limitations:

Costs more to implement and operate than peer-to-peer
Loss of a server can impact all users of the network
Compare the implications of using connection-oriented communications with connectionless communications
Connection oriented Establishes a path between the two computers before sending. Assures reliable delivery, i.e. phone conversation 
Connectionless Just sends packets, no checking whether they get there. Fast but no assurance of delivery, i.e. letter mail
Distinguish whether SLIP or PPP is used as the communications protocol for various situations
SLIP (Serial Line Interface Protocol) Developed to provide dial-up IP connections in Unix
TCP/IP only
Does not allow for dynamic IP addressing
No software compression
No encryption or password authentication
PPP (Point to Point Protocol) Default option in Windows NT Dial-Up Networking. Newest packet framing protocol that provides self-configuring, full-duplex, bi-directional, peer-to-peer connections.
Allows for dynamic IP addressing
Can negotiate header compression
Supports error control
Offers encryption and password authentication
Supports NetBEUI, TCP/IP, IPX/SPX
Define the communication devices that communicate at each level of the OSI model
Layer Description
Application
7
This layer is used for those applications that are specifically written to run over the network. Example applications such as file transfer, terminal emulation, electronic mail, and NetBIOS-based applications.

Protocols: DNS, SNMP, TELNET, FTP, SMTP, NFS, SMB

Devices: Gateway (can work at all layers)

Presentation
6
Data formatting, character code conversion and data encryption.

This layer is responsible for data translation (format of the data) and data encryption (scrambling and descrambling the data as it is transmitted and received). It is not always implemented in a network protocol.

Redirector sits here.

Session
5
Negotiation and establishment of a connection with another node.

This layer establishes, maintains and disconnects a communications link between two stations on a network. Determines if mono- or bi-directional and ensures one request is completed before a new one is accepted.

Transport
4
Provides reliable end-to-end delivery of data beyond local LAN segment.

Can detect packets discarded by routers and automatically generate a retransmit request. Re-sequences packets that arrive out of order before passing them to the Session Layer.

Protocols: TCP, UDP, SPX, NetBEUI.

Network
3
Routing of packets of information across multiple networks.

Lacks any native error correction/detection and so relies on Data Link Layer for end-t-end reliable transmission. This layer used to establish comms with computer systems beyond the local LAN segment. Has own routing addressing architecture (different from Data Link Layer machine addressing).

Protocols: IP, IPX, AppleTalk, ARP, RARP, RIP, OSPF

Devices: Router

Data link
2
Responsible for providing end-to-end validity of data being transmitted. Packs data into frames. Has own address architecture, applicable only to other networked devices that reside locally. Successful delivery achieved by originating node receiving an 'ACK' sent by destination node to indicate frame received correctly. Errors detected and corrected via CRC check.

IEEE split this layer into Media Access Control (MAC) and Logical Link Control (LLC) layers.

Protocols: SLIP, PPP, DLC

Devices: Bridge, Switch

Physical
1
Accepts frames of data from Layer 2 and transmits their structure serially, one bit at a time. Does reverse on receive.

Defines the methods used to transmit and receive data on the network. It consists of the wiring, the devices that are used to connect a station's network interface controller to the wiring, the signalling involved to transmit/receive data.

Protocols: IEEE 802.2

Devices: Repeater

Describe the characteristics and purpose of the media used in IEEE 802.3 and IEEE 802.5 standards.
Common features Common basis for hardware level addressing, management and monitoring - permits mixed topology networks.
802.3 (Ethernet) Contention based media access - devices compete for the right to transmit. Dominant form now CSMA/CD (Carrier Sense Multiple Access with Collision Detection). If a device detects a collision, it backs off, waits a pseudo-random period and then tries again. Only one device can transmit at a time, half duplex.

Logical bus network that can transmit data at 10Mbps. Data is transmitted on the wire to every computer. Only those meant to receive the data acknowledge the transmission.

All devices on a segment share a collision domain (share same bandwidth). Can be improved by a switch which gives a collision domain of two - the port and the device connected to it. Device has full bandwidth to itself.
Probabilistic (cannot state when a packet will reach its destination - a collision may occur)
Baseband transmission (digital signalling over a single frequency)
Media: thicknet (10Base5), thinnet (10Base2), UTP (10BaseT)

Fast Ethernet (100Mbps) 802.3u

802.5 (Token Ring) Token based media access - regulates access by passing tokens, only the device holding the token can transmit.

Logical ring (actual ring is in hub) that transmits at either 4Mbps or 16Mbps.

Deterministic (no collisions, so can accurately determine max delay that can be experienced) ideal for applications that require predictable delays.
Baseband transmission
Shielded and unshielded twisted-pair cabling
Uses hubs known as MAU, MSAU, SMAU
A 16Mbps network will not accept a 4Mbps network adapter card
802.12 (VG-AnyLAN) Demand priority media access - central repeater 'polls' ports connected to it. Not really in use - failed in the market place !
Explain the purpose of NDIS and Novell ODI network standards
NDIS (Network Driver Interface Specification) Developed by Microsoft and 3Com - defines interface between the network transport protocol and the Data Link layer network adapter driver.
Permits any NDIS-compliant protocol stack to operate with any NDIS-compliant adapter driver.
Defines a method for binding multiple protocols to a single driver or one protocol to more than one adapter.
ODI (Open Data-Link Interface) Serves the same function as NDIS for Novell NetWare and Apple environments. Provides support for multiple protocols on a single network adapter card.