Network Models Question And Answer | letsbug

 Network Models Question And Answer

1.  Answer the following questions in short.

1. what is network model?

    Answer: 

        A Network Model reflects a design or architecture to accomplish communication between different systems. Network models are also referred to as network stacks or protocol suites. Examples of network models includes  TCP/IP, Sequenced Packet Exchange/Internet Packet Exchange(SPX/IPX) used by Novell Netware, the Network Basic Input Output System (Net-BIOS), which comprises the building blocks for most Microsoft networking and network applications; and AppleTalk, the network model for Apple Macintosh computers.

    A network model usually consists of layers. Each layers of a model represents specific functionality. Within the layers of model, there are usually protocols specified to implement specific tasks.

2. Write name of addresses used in TCP/IP protocol.

    Answer: 

    In TCP/IP, different levels of addresses are used,

1. Physical Address(Hardware Address or Link Address).
2. Logical Address(IP Address)
3. Port Address
4. Specific Address    

3. Differentiate between physical address and logical address.

    Answer: 

• Physical Addresses
• The physical addresses also known as the link address. This is the address of the node that defined by its LAN and WAN.
• Data link layer includes this address into data frame.
• Physical address is used when source and destination are from same network. It is lowest level address.
• The physical address have authority over the network i.e. LAN or WAN. The address size and format depend on the network.
• For example, Ethernet uses 6 byte (48 bit) physical address which is imprinted on the the network interface card(LAN card).
• Example of Physical Address: Most local area network use a 48-bit (6-byte) physical address written as 12 hexadecimal digits; every byte(2 hexadecimal digits) is separated by a colon, as " 07:01:02:01:2C:4B "
• Logical Addresses
• The logical addresses also known as the IP address.
• When source and destination are from different networks or in on internetworking environment, physical addresses are not adequate where different network can have different address format.
• A unique universal addressing system is needed in which every computer can by identified uniquely, regardless of the underlying physical network. The logical address are designed for this purpose.
• Logical addresses in a network in a network model are necessary for universal communications that are independent of underlying physical networks.
• A logical address can uniquely define a host connected to the Internet. No two publicly addressed and visible hosts on the Internet can have same IO addresses. Logical addresses are necessary for universal communications.
• An IP addresses is 32 bit address usually written in dotted decimal format A,B,C,D where each number is in the range 0 to 255. For example, 192.9.100.2.

4. Which device operates at the network layer of the OSI model?

    Answer: 

1. The 3rd layer of the OSI model is the Network layer.
2. The network layer is responsible for the source-to-destination delivery of a packet possibly across multiple networks(links). Whereas, the data link layer oversees the delivery of the packet between two systems on the same network(links). If two systems are connected to the same link, there is usually no need for a network layer.

        Responsibilities or Functions of Network Layer:

• Logical addressing: The physical addressing implemented by the data link layer handles the addressing problem locally. If a packet passes the network boundary, then need of another addressing system to help to distinguish the source and destination systems.
• Routing: When independent networks or links are connected together to create an internetwork ( a network of networks), the connecting devices ( called router or gateway) route the packet to their final destination.
• congestion Control: This layer is also responsible for handling the congestion problem at the node, when there are too many packets stored at the node to be forwarded to the next node.
• Internetworking: One of the main responsibilities of network layer is to provide internetworking between different networks. It provides logical connection between different types of network.    

5. What is subnetting?

    Answer:

    IP networks can be divided into smaller networks called subnetworks(or subnet).

    Subnetting is the process of breaking down a main class A, B, or C network into subnets for routing purposes.

    Subnetting provides the following advantages:

• Network traffic isolation: There is less network on each subnet.
• Simplified Administration: Networks may be managed independently.
• Improved security: Subnets can isolate internal so they are not visible from external networks.    

2.  Define the following terms:

1. Physical address.

    Answer: 

• The physical addresses also known as the link address. This is the address of the node that defined by its LAN and WAN.
• Data link layer includes this address into data frame.
• Physical address is used when source and destination are from same network. It is lowest level address.
• The physical addresses have authority over the network i.e. LAN or WAN. The address size and format depend on the network.
• For example, Ethernet uses 6 byte (48 bit) physical address which is imprinted on the network interface card (LAN card).    

2. Broadcast address.

    Answer: 

        A broadcast address is an IP address that is used to target all systems on a specific subnet network instead of single hosts. In other words broadcast address allows information to be sent to all machines on a given subnet rather than to a specific machine.

3. Port address.

    Answer: 

• The IP address and the physical address in a network model are necessary for a quantity of data to travel from a source host to the destination host.
• However, arrival at the destination host is not the final objective of data communications on the Internet.
• A system that sends nothing but data from one computer to another is not complete.
• Computers are devices that can run multiple processes at the same time. The end objective of Internet communication is a process communicating with another process.
• A port address in TCP/IP network model is 16 bits in length. For example, A port address is a 16-bit address represented by one decimal number as 753. 

4. HTTP

    Answer: 

        A standard Internet protocol that specifies the client/server interaction processes between Web browsers such as Microsoft Internet Explorer and Web servers such as Microsoft Internet Information Services (IIS).

5. Framing

    Answer: 

        The data link layer divides the stream of bits received from the network layer into manageable data units called frames. Data link layer performs various farming functions like Frame Traffic Control, Frame Sequencing, Frame Delimiting and so on.

3.  Answer the following questions:

1. Explain functions of each layer ISO-OSI reference model.

    Answer: 

1. Physical Layer:
1. The Physical Layer is the lowest layer(1st) of the OSI model.
2. Physical layer deals with the mechanical and electrical specifications of the interface and transmission medium.
3. Transmits the unstructured raw bit stream over a physical medium. 
4. Relates the electrical, optical mechanical and functional interfaces to the cables.
5. Responsibilities or functions of the Physical Layer:
1. Physical characteristics of Interfaces and Medium.
2. Representation of Bits(Data Encoding):
3. Data rate:
4. Synchronization of bits:
5. Physical Topology:
6. Transmission mode:
2. Data Link Layer:
1. The 2nd layer of the OSI model is the Data link layer.
2. It makes the physical layer appear error free to the upper layer.
3. Sends data frames from the Network layer to the Physical layer.
4. Packages raw bits into frames for the Network layer at the receiving end.
5. Responsible for providing error free transmission of frames through the Physical layer.
6. This layer if often divided into two parts;
1. Media Access Control(MAC): The Mac sub layer controls the means by which multiple devices share the same media channel. This includes contention methods and other media access details.
2. Logical Link Control(LLC): The LLC sub layer establishes and maintains links between communicating devices.
7. Responsibilities or functions of Data link layer:
1. Framing:
2. Physical Addressing:
3. Flow Control:
4. Error Control:
5. Access Control:
3. Network Layer:
1. The 3rd layer of the OSI model is the Network Layer.
2. The network layer is responsible for the source-to-destination delivery of a packet possibly across multiple networks(links), Whereas, the data link layer oversees the delivery of the packet between two systems on the same network(links). If two systems are connected to the same link, there is usually no need for a network layer.
3. Responsibilities or functions of network layer:
1. Logical Addressing:
2. Routing:
3. Congestion Control:
4. Internetworking:
4. Transport Layer:
1. The 4th layer of the OSI model is the Transport Layers.
2. The transport layer is responsible for source-to-destination, (end-to-end) delivery of the entire message.
3. Network layer treats each packet independently, as though each packet belonged to a separate message, whether or not it does.
4. Responsibilities or functions of the transport layer:
1. Service-point Addressing (Port Addressing):
2. Segmentation and Reassembly:
3. Connection control:
4. Flow control:
5. Error control:
5. Session Layer:
1. The 5th layer of the OSI model is the Session Layer.
2. Session Layer has the primary responsibilities of beginning, maintaining and ending the communication between two devices, which is called Session.
3. It also provides for orderly communication between devices by regulating the flow of data.
4. The session layer is the network dialog controller. It establishes, maintains, and synchronizes the interactions between communicating systems.
5. Responsibilities of the session layer:
1. Dialog Control:
2. Token management:
3. Synchronization:
6. Presentation Layer:
1. The 6th layer of the OSI model is the presentation layer is also called Translation layer.
2. The presentation layer is concerned with the syntax and semantics of the information exchanged between two systems. The presentation layer is concerned with the representation of user or system data. 
3. Responsibilities or functions of the Presentation layer:
1. Translations:
2. Encryption:
3. Compression:
7. Application Layer:
1. The 7th layer of the OSI model is the application layer:
2. The application layer enables the user, whether human or software, to access the network. It provides  user interfaces and support for services such as e-mail, remote file access and transfer, shared database management and other types of distributed information services. Application layer is responsible for providing services to the user.
3. Services provided by the application layer:
1. Network Virtual Terminal (NVT):
2. File Transfer, Access and Management(FTAM):
3. Mail services:
4. HTTP(HyperText Transfer Protocol):     

2. What is addressing? Explain logical addressing in network.

    Answer: 

         A network address serves as a unique identifier for a computer on a network. When set up correctly, computers can determine the addresses of other computers on the network and use these addresses to send messages to each other.

    Logical Addressing:

• The logical addresses also known as the IP address.
• When source and destinations are from different networks or in on internetworking environment, physical addresses are not adequate where different networks can have different address format.
• A unique universal addressing system is needed  in which every computer can be identified uniquely, regardless of the underlying physical  network. The logical addresses are designed for this purpose.
• Logical addresses in a network model are necessary for universal communications that are independent of underlying physical networks.
• A logical address can uniquely define a host connected to the Internet. No two publicly addressed and visible hosts on the Internet can have same IP addresses. Logical addresses are necessary for universal communications.
• An IP addresses is 32-bit address usually written in dotted decimal format A, B, C, D, where each number is in the range 0 to 255. For example, 192.9.100.2.     

3. Explain the functions of Transport Layer in OSI-Reference Model.

    Answer: 

        Functions of Transport Layer in OSI-Reference Model

1. Service-point Addressing(Port Addressing): Computer often run multiple programs at the same time.
1. Source-to-destination delivery means delivery not only from one computer to the next but also from a specific process(running program) on the other. The transport layer header therefore must include a type of address called a Service-point address(or port address).    
2. Segmentation and Reassembly: A message is divided into transmittable segments; each segments containing a sequence number. These number enable the transport layer to reassemble the message correctly upon arriving at the destination and to identify and replace packets that were lost in the transmission.
3. Connection control: It creates a connection between the two end ports. A connection is a single logical path between the source and destination that is associated with all packets in a message. The transport layer can provide connection oriented or connectionless services for connection control.
1. A connectionless transport layer treats each segments as an independent packet and delivers it to the transport layer at the destination.
2. A connection oriented transport layer makes a connection with destination transport layer first and then delivers data. After all data transfer is done, the connection is terminated.
4. Flow control: The transport layer makes sure that the sender and receiver communicate at the rate they both can handle. Flow control at this level is performed end to end rather than across a single link.
5. Error control: Error control at this level is performed end to end. The transport layer without error(damage, loss or duplication).