Alrafidain University College Questions with Solutions Chapter Two The OSI Model and TCP/IP Model 2020/2021 Q1/ List the specific responsibilities of the Physical Layer? Ans. The specific responsibilities of the Physical Layer: a) Convert the logical 1’s and 0’s coming from layer 2 into electrical signals. b) Transmission of the electrical signals over a communication channel. Q2/ List the specific responsibilities of the Data link Layer? Ans. a) Error control to compensate for the imperfections of the physical layer. b) Flow control to keep a fast sender from swamping a slow receiver. Q3/ List the specific responsibilities of the Network Layer? Ans. a) Chose the best path from Source-to-destination Packet delivery. b) Routing packets from source to destination. c) Logical addressing. Q4/ List the specific responsibilities of the Session Layer? Ans. a) Managing dialogue control. b) Graceful close. c) Token management. d) Synchronization. Assistant Lecturer / Hussain Kassim Ahmad 1 Alrafidain University College Q5/ List the specific responsibilities of the Presentation Layer? Ans. a) Data Representation, and Translation. b) Compressing and decompressing data. c) Data compression. d) Data Encryption and decryption. e) Security. Q6/ List the specific responsibilities of the Application Layer? Ans. a) Allows user to interface with the network. b) Provides protocols that are commonly needed. Q7/ Compare between specific responsibilities of the Transport vs. network layer. Ans. Transport layer network layer logical communication between processes logical communication between hosts Sender: breaks application messages into Sender:, encapsulates the PDU that it segments (Segment the PDU), and passes to receives from the Transport layer in the network layer form of packet PDU and passes to data link layer Assistant Lecturer / Hussain Kassim Ahmad 2 Alrafidain University College Q8/ What is the main differences between TCP and UDP Services? Ans. Transmission Control Protocol (TCP) User Datagram Protocol (UDP) Service Service 1. Connection-oriented Connectionless 2. Reliable transfer of data. Unreliable Not guaranteed. 3. Segment retransmission and flow No windowing or retransmission control through windowing 4. Segment sequencing No sequencing 5. Acknowledge sequencing No acknowledgment 6. Lost data retransmission Feasible Practically, not possible. 7. There is a delay in transfer of The transmission is faster. Due to the information. absence of connection establishment phase, Q9/ Give the Definition of the Connection-Oriented and Connectionless. Ans. Connection-Oriented: – before data is sent, the service from the sending computer must establish a connection with the receiving computer. (Email is connection-oriented). Connectionless: – data can be sent at any time by the service from the sending computer. (Downloading a music file from the Internet is connectionless). Q10/ What does PDU abbreviation stands for in computer networking? Then draw table showing the shape for the PDU for each layer? Answer: PDU stands for: Protocol Data Unit The Layer Shape of data (PDU) Top three layers (Application layer). Data Transport layer Segment Network layer Packets Data Link layer Frames Physical layer Bits Assistant Lecturer / Hussain Kassim Ahmad 3 Alrafidain University College Q11/ Explain the delivery of data with shapes of data and type of addressing in Layered model? Or Q11/ Fill the following table of the delivery data in layered model. layer Type of delivery Shape of data Type of addressing Ans. layer Type of delivery Shape of data Type of addressing Transport End to End Segment Port (socket) Network Source To Destination Packet Logical (IP) Data Link Node to Node Frame Physical (MAC) Q12/ Define OSI protocol model Encapsulation and the PDU protocol. OR Q20/ Explain with drawing the Encapsulation process and the PDU protocol. Ans. Encapsulation: As application data is passed down the protocol stack on its way to be transmitted across the network media, various protocols add information to it at each level. This is commonly known as the encapsulation process. The form that a piece of data takes at any layer is called a Protocol Data Unit (PDU). PDU’s are used for peer-to-peer contact between corresponding layers. Assistant Lecturer / Hussain Kassim Ahmad 4 Alrafidain University College Q13/ Describe the OSI model and explain each layers function and assign each protocol in the layer. Layer layers function Protocols 7th Application To allow access to network DNS TELNET 6th Presentation To translate, encrypt, and compress data FTP HTTP SMTP 5th Session To establish, manage, and terminate DHCP sessions 4th Transport To provide reliable process-to-process TCP UDP message and error recovery 3rd Network layer To move packet from source to destination IP ICMP ARP to provide internetworking 2nd Data link To organize bits into frames to provide hop to hop delivery ETHERNET 1st Physical To transmit bits over a medium to provide Bluetooth mechanical and electrical specifications Q14/ Match of the following responsibilities with the corresponding OSI layer? 1- To allow access to network resource. Ans. (Application laver) 2- Data compression. Ans. (Presentation layer) 3- Token management. Ans. (session laver) 4- Connection-oriented and connectionless services. Ans. (Transport layer) 5-Internet Protocol (IP) addressing (Logical addressing). Ans. (Network Layer) 6-Bridges & Switches (multi-port bridges). Ans. (data link laver) 7-Transmission mediums (transmit bits over medium). Ans. (physical laver) Assistant Lecturer / Hussain Kassim Ahmad 5 Alrafidain University College Q15/ Match of the following responsibilities with the corresponding OSI model. 1- Provides protocols that are commonly needed. Ans. (Application laver) 2- Data encryption. Ans. (Presentation laver) 3- Managing dialogue control. Ans. (session laver) 4- Provide reliable process to process message delivery & error recovery. Ans. (Transport Laver) 5- Controls the operation of the subnet. Ans. (Network Laver) 6- Error detection and correction methods. Ans. (data link laver) 7- Provide mechanical and electrical specification. Ans. (physical laver) Q16/ Match of the following responsibilities with the corresponding OSI model? 1- (FTP), (HTTP). (SMTP). (DNS), (DHCP), (Telnet). Ans. (Application laver) 2- Concerned with the syntax and semantics of the information. Ans. (Presentation laver) 3-Allows users on different machines to establish sessions (dialogue) Ans. (Session laver) 4-End-to-end flow control. Ans. (Transport laver) 5-Routing algorithms (Routing packets from source to destination). Ans. (Network Laver) 6-Hop to hop delivery. Ans. (data link laver) 7-Hubs (multi-port repeater). Ans. (physical laver) Assistant Lecturer / Hussain Kassim Ahmad 6 Alrafidain University College Q17/ which of the OSI layers handles each of the following functions: 1. Sequencing and reassembling? Ans.- The transport layer 2. Proving best path to reach destination? Ans.- The network layer 3. Dividing the transmitted bit stream into frames? Ans.- Data link layer 4. Responsible for error detection? Ans.- Data link layer 5. Determining which route through the subnet to use? Ans.- the network layer 6. The layer is closest to the transmission media? Ans.- The physical layer. 7. Reliable process to process data transportation? Ans.- The transport layer. 8.Provides access to the network for end user? Ans.- The application layer. 9.Flow control? Ans.- Data link layer. Q18/ Which OSI layers is the network support layers? Answer: (Physical, Data link, network layers) Q19/ Which OSI layers is the user support layers? Answer: (Session, Presentation, Application) Q20/ Which OSI layer functions as a liaison between user support layers and network support layers? a) Network b) Physical c) Transport d) Application Answer: c) Transport Assistant Lecturer / Hussain Kassim Ahmad 7 Alrafidain University College Q21/ What are the main protocols used in application layer and mention the job of each one. Ans. protocols Job Description DNS (Domain Name System) Matches domain names with IP addresses. HTTP (Hyper Text Transfer to transfer data between clients/servers. Protocol) SMTP (Simple Mail Transfer Used to send email messages from clients to servers over Protocol) & POP3 (Post the internet. Office Protocol version 3) FTP (File Transfer Protocol) Allows the download/upload of files between a client/server Telnet Allows users to login to a host from a remote location and take control as if they were sitting at the machine (virtual connection). DHCP (Dynamic Host Assigns IP addresses, subnet masks, default gateways, Configuration Protocol) DNS servers, etc. to users as they login the network. Q22/ Classify the following protocol with their uses in each layer in the TCP/IP reference model. TCP, IP, HTTP, UDP, ETHERNET, ICMP, FTP, TELNET, SMTP, DHCP Ans. Layer Protocols Application HTTP TELNET FTP SMTP DHCP Transport TCP UDP Internet IP ICMP Network access (Host-to-network) ETHERNET Assistant Lecturer / Hussain Kassim Ahmad 8 Alrafidain University College Q23/ What are the main differences between TCP/IP and OSI 7-layers model? Ans. The main differences between TCP/IP and OSI 7-layers model? OSI Model TCP/IP Model 1. OSI refers to Open Systems TCP refers to Transmission Control Interconnection. Protocol. 2. OSI uses the network layer to define TCP/IP uses only the Internet layer. routing standards and protocols. 3. OSI layers have seven layers. TCP/IP has four layers. 4. In the OSI model, the data link layer and In TCP, physical