Computer Communication Network
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1-Define what meant by a protocol? Protocol is a formal description of a set of rules and conventions that govern how devices on a network communicate. Used for communications between entities in a system. 2-What are the reasons for using layered protocols? -
Is a form of hierarchical modularity. Decomposing overall network functions into less complex layers. Each layer provides a given function in support of the functions of the network. The services provided by higher layers are implemented via the services of lower layers.
3-What are the key elements of a protocol? -
Syntax (Data formats – Signal levels). Semantics (Control information – Error handling). Timing (Speed matching – Sequencing).
4-Define the following terms: SAP
(SAP, PDU, and TCP/IP)
Service access point. is an identifying label for network endpoints used in OSI networking
PDU
Protocol Data Units. A unit of data that is passed down from one layer to another in the OSI model. The PDU contains the message and the protocol/control information from the layer above.
TCP/IP The Transmission Control Protocol/Internet Protocol. - Developed by US to work in packet-switched networks. - Used by the global Internet. - No official model but a working one.
5-List the Layers of the OSI model? 6-What are the responsibility of each layer in the OSI model? AL PL
Application Layer User interface to available services (FTP – HTTP - ….). Presentation Layer - Interpreting bits meaning. - Compression & encoding. SL Session Layer - Initiation & release sessions. - Billing TL Transport Layer - Segmentation the traffic. - End–to–End Check (dealing with errors). NL Network Layer - Overall route. - Protocol handling (encapsulation – conversion – extraction) DLL Data Link Layer - Breaking the transmitted bit streams into Frames. - MAC addressing. - LLC(logical link control): error correction and detect crashes. PHL Physical Layer - Transfer Media - Preample (synchronization)
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Computer Communication Network
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7-How do the layers of the TCP/IP protocol suite correlate to the layers of the OSI model? OSI model TCP/IP model Application Layer Presentation Layer Application Layer Session Layer Transport Layer Transport Layer Network Layer Internetwork Layer Data Link Layer Network Interface Layer Physical Layer 8-Why are protocols needed?
Another Form to (TCP/IP) FTP HTTP
Application Layer Transport Layer Internetwork Layer Network Access Layer Physical Layer
TCP, UDP IP Ethernet
To description a set of rules and conventions that govern how difference devices on a network communicate so it is used for communications between entities in a system. 9-Why are standards needed? -To allow for interoperability between equipment 10-List two advantages and two disadvantage of having international standards for network? Adv. Disadv.
1-Ensure a large market for equipment and software. 2-Allows products from different vendors to communicate. 1-Freeze technology. 2-May be multiple standards for the same thing.
11-What is the defference between a De Facto standard and De Jure standard? Is an expression that means "based on law". De Jure Is an expression that means "in fact", by convention. De Facto De Jure Standard Is standard creating not by an organization or company but by officially recognized (on law).
De Facto Standard Is Standard in reality, actual and existing regardless of legal or moral considerations or laws. It is created by an organization or company and it is divided into two categories 1- Proprietary (Close Standard) by one company. 2- Non proprietary (Open Standard) by groups of company.
12-What are the standard organizations? Internet Society ISO ITU-T(CCITT)
: Created by people interested in internet. : International Standards Organization. : ITU = International Telecommunication Union. CCITT = Committee Consultative International Telegraph & Telephone
ATM forum 13-Which of the OSI layer handles each of the following? a. Error correction and retransmission b. Establishes, Manages, and terminate session c. Breaking the transmitted bit streams into Frames. d. Determines which route through the subnet to use. e. Provides log-in and log-out procedures f. Supports end-to-end transimission.
Data Link Layer Session Layer Data Link Layer Network Layer Application Layer Transport Layer
14-What are the main applications for the Internet? Telnet FTP HTTP SMTP
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