Question

V

At the completion of the chapter you should have an understanding of the following Chapter Objectives:

1. What is the Purpose of a Network Model?
2. What are the layers of the OSI Model?
3. What are the characteristics of each layer of the OSI Model?
4. How does the TCP/IP stack compare to the OSI Model?
5. What are the Well Known TCP and/or UDP Port Numbers for a given collection of common applications?

1. Define the Following Terms:
   1. Application Layer (OSI Model):
   2. Application Layer (TCP/IP Stack): Current State Modulation:
   3. Cyclic Redundancy Check (CRC): Data Link Layer:
   4. Internet Layer:
   5. Network Interface Layer:
   6. Network Layer:
   7. Open System Interconnection (OSI) Reference Model:
   8. Physical Layer:
   9. Presentation Layer:
   10. Protocol Data Units (PDU):
   11. Session Layer:
   12. State Transition Modulation: TCP/IP Stack:
   13. Time-Division Multiplexing (TDM):
   14. Transmission Control Protocol (TCP):
   15. Transport Layer (OSI Model):
   16. Transport Layer (TCP/IP Stack):
   17. User Datagram Protocol (UDP):
   18. Broadband:
   19. Baseband:
2. Fill-in the Blanks:        
   1. What year did the International Organization for Standardization (ISO) set up a subcommittee to develop the OSI Model? ________

2. At upper layers, however, bits are grouped together, into what is known as a Protocol Data Unit (PDU) or a _____ ______ _____.

3. Two fundamental approaches to bandwidth usage on a network are:
   1. __________
   2. __________

4. What are some examples of devices defined by the Physical Layer of the OSI Model?
   1. _______
   2. ______ _______ _______
   3. ______ _______

5. The Network Device called a Hub belongs to which layer of the OSI Model? __

6. The Data Link Layer has two additional sub-layer what are they? ____ & ____

7. This sub-layer is responsible for 1) Physical Addressing 2) Logical Topology 3) Method of Transmitting on the Media? ______ ________ ________ (__ __ __)

8. This sub-layer is responsible for 1) Connection Services 2) Synchronizing Transmissions? _________ ________ __________ (__ __ __)

1. What layer of the OSI Model is the Network Interface Card (NCI) assigned to? __

10. The Network Layer or Layer 3 of the OSI Model provides what services?
    1. __________ _______________
    2. __________
    3. _________ _________ _________ _________
    4. __________ ___________
    5. _________ _________
    6. __________ __________

11. In Message Switching Devices might briefly store the messages before forwarding them, a Network using Message Switching is sometimes called a _______-_____ -________ Network.

12. The Transport Layer or Layer 4 of the OSI Model provides what services?
    1. _____/_____
    2. _____________
    3. _____________

13. With ___________, a device (for example a router) allocates a chunk of memory to store segments if bandwidth is not currently available to transmit those segments.

14. The Session Layer or Layer 5 of the OSI Model provides what services?
    1. _________ ____ ___ __________
    2. _________ ____ ________
    3. _________ _____ ________

• The Presentation Layer or Layer 6 of the OSI Model provides what services?
  1. ______ ________
  2. ______________

16. What are the Two Data Formatting examples cited in the text?
    1. _____________________________________________(__________)
    2. _____________________________________________(__________)

17. The Application Layer of Layer 7 of the OSI Model provides what services?
    1. _______ __________
    2. ________ __________

18. What is the range of Port Numbers which are called Well-Known? __________

19. What is the Maximum value of Port Numbers? ________

Fill in the Table – Application Layer Protocols/Applications – Fill in the Blanks – You will need to know these Protocols and Port Numbers.

Protocol	Description	TCP Port	UDP Port
FTP
SSH
SFTP
SCP
Telnet
rsh
DNS
SMB
TFTP
DHCP
HTTP
HTTPS
SMTP
POP3
IMAP
NNTP
NTP
SNTP
IMAP4
LDAP
RTSP
RDP
SNMP
SNAP Trap
SIP
MGCP
H.323
RTP

Answer 1

V.

1. The purpose of the network model is that it is a hypothetical chart that is used to represent the flow of data.

2 .The OSI Model has seven layers.The upper layer consisting of layer 7 ,6 and 5 are implemented using software and the lower layer consisting of layer 4,3,2,1 are implemented using both hardware and software. The layers are

layer 7 (Application layer), layer 6 (Presentation layer) , layer 5 (Session layer) , layer 4(Transport layer), layer 3(Network layer) layer 2( Data link layer) layer 1(Physical layer)

3. The Characteristics of the layers are as follows:-

layer 7 (Application layer):- this layer provides services to support end user application such as email, file-transfer,user interface, data base access etc.

layer 6 (Presentation layer):- this layer translates the data into a standard format to be sent on the network.and the another function of this layer is data compression.

layer 5 (Session layer):-This layer enables the application on the sender and the receiver to communicate with each other using a session.This layer established ,coordinates,manages and terminate connection between the two application(sender and receiver).

layer 4(Transport layer):- It provides reliable delivering of messages and it performs data multiplexing.

layer 3(Network layer) layer:- It also control the operation of a submit and decides the optical part for the data based on network condition,priorities and services.

layer 2( Data link layer) :- This layer converts the data packets into a string of zeros and ones .It is also responsible for error control ,flow control and reliable data transfer.

layer 1(Physical layer) :- This layer converts the row string of bits into electrical signals ,optical signal or electromagnetic signal depending on the network usecable circuit.It establish , maintain and terminate physical connection between computers. It also decides the mode of transission.

4. differnce between TCP/IP and OSI Model.

  OSI Is generic protocal independent where as TCP/IP is a standard protocol.

OSI follows vertical approach where as Horizontal approach.

OSI has 7 layers where as TCP/IP has 4 layers

Transport layer is connection orieted where as TCP/IP does not have.

5. Port numbers 0 to 1024 are reserved for privileged services and designated as well-known ports

port no. | Description

1	TCP Port Service Multiplexer (TCPMUX)
5	Remote Job Entry (RJE)
7	ECHO
18	Message Send Protocol (MSP)
20	FTP -- Data
21	FTP -- Control
22	SSH Remote Login Protocol
23	Telnet
25	Simple Mail Transfer Protocol (SMTP)
29	MSG ICP
37	Time
42	Host Name Server (Nameserv)
43	WhoIs
49	Login Host Protocol (Login)
53	Domain Name System (DNS)
69	Trivial File Transfer Protocol (TFTP)
70	Gopher Services
79	Finger
80	HTTP
103	X.400 Standard
108	SNA Gateway Access Server
109	POP2
110	POP3
115	Simple File Transfer Protocol (SFTP)
118	SQL Services
119	Newsgroup (NNTP)
137	NetBIOS Name Service
139	NetBIOS Datagram Service
143	Interim Mail Access Protocol (IMAP)
150	NetBIOS Session Service
156	SQL Server
161	SNMP
179	Border Gateway Protocol (BGP)
190	Gateway Access Control Protocol (GACP)
194	Internet Relay Chat (IRC)
197	Directory Location Service (DLS)
389	Lightweight Directory Access Protocol (LDAP)
396	Novell Netware over IP
443	HTTPS
444	Simple Network Paging Protocol (SNPP)
445	Microsoft-DS
458	Apple QuickTime
546	DHCP Client
547	DHCP Server
563	SNEWS
569	MSN
1080	Socks

Defination of the terms :-

a. Application Layer (OSI Model):- This layer provides services to support end user application such as email, file-transfer,user interface, data base access etcThe commonly used protocols includes HTTP,www, FTP,TELNET and SMTP.The prime responsibility of the layer is to hide the incompatibility and complexity of neywork communications to enable a smooth transfer of data between sender and receiver. .

b. Application Layer (TCP/IP Stack) :-It provides application with standarised data exchanges .It protocol includes HTTP, FTP, and POP, SMTP, & SNMP.

Current State Modulation :- Data on a computer network is represented as a binary expression.

Electrical voltage (on copper wiring) or light (carried via fiber-optic cabling) can represent these 1s and 0s.The presence or the absence of voltage on a wire can represent a binary 1 or a binary 0, respectively. The presence or absence of light on a fiber-optic cable can represent a 1 or 0 in binary.

c. Cyclic Redundancy Check (CRC): - A mathematical algorithm that is executed on a data string by both the sender and receiver of the data string. If the calculated CRC values match, the receiver can conclude that the data string was not corrupted during transmission.This technique is more powerful than parity check and error detection.It works on binary divisor.A sequence redundant bits called CRC.It cannot detect all types of errors.

Data Link Layer: - This layer converts the data packets into a string of zeros and ones .It is also responsible for error control ,flow control and reliable data transfer.The data link layer divides into two sublayers further.they are - Media access control(MAC) and Logiccal link Control(LLC).

d. Internet Layer:-The internet layer is a group of internetworking methods, protocols, and specifications in the Internet protocol suite that are used to transport network packets from the originating host across network boundaries; if necessary, to the destination host specified by an IP address

e network interface layer :- commonly referred to as the data link layer, is the physical interface between the . Network Interface Layer system and the network hardware. It defines how data packets are to be formatted for transmission and routings.

f. Network Layer :- It also control the operation of a submit and decides the optical part for the data based on network condition,priorities and services.

g. OSI given by ISO ( International organisation for standards ) is an abstract model that provides a networking framework of standards to enable diverse equipment and applications,from different venders to communicate with each other.The OSI model divides the complex task of computer to computer communication into a series of seven layers.The upper layer consisting of layer 7 ,6 and 5 are implemented using software and the lower layer consisting of layer 4,3,2,1 are implemented using both hardware and software.In this layer data is transfered from one layer to the next.It starts from the application layer of the sending device to the physical layer.

h .physical layer :- This layer converts the row string of bits into electrical signals ,optical signal or electromagnetic signal depending on the network usecable circuit.It establish , maintain and terminate physical connection between computers. It also decides the mode of transission.It Decides how much volts should be used to represent the 0's and 1's .and it also decides how much bits should be transmitted in a second.

i. Presentation Layer:- This layer is concerned with the syntax and semantics of data to be transmitted.It is also called the syntax layer.This layer translates the data into a standard format to be sent on the network.and the another function of this layer is data compression.

j. Protocol Data Units (PDU):- a protocol data unit (PDU) is a single unit of information transmitted among peer entities of a computer network. A PDU is composed of protocol-specific control information and user data.

k. Session Layer:- This layer enables the application on the sender and the receiver to communicate with each other using a session.Session layer allows data to be transmitted in one direction or both direction simultaneously and hence this layer established ,coordinates,manages and terminate connection between the two application (sender and receiver).

l. State Transition Modulation: - One way to electrically or optically represent a binary 1 or 0 is to use the transition between a voltage level (for example, going from a state of no voltage to a state of voltage, or vice versa, on a copper cable) or the transition of having light or no light on a fiber optic cable to represent a binary 1. Similarly, a binary 0 is represented by having no transition in a voltage level or light level from one time period to the next. This approach of representing binary digits is called state transition modulation.

m. Time-Division Multiplexing (TDM):- Supports different communication sessions (for example, different telephone conversations in a telephony network) on the same physical medium, by allowing sessions to take turns. For a brief period of time, defined as a time slot, data from the first session is sent, followed by data from the second sessions. This continues until all sessions have had a turn, and the process repeats itself. Its a digital multiplexing technology that seperate data streams based on time .In this technique a MUX collects and store the incoming data from the sending device through this slow speed communication channel connected to it.

n. Transmission Control Protocol (TCP):-  A connection-oriented transport protocol. Connection-oriented transport protocols provide reliable transport, in that if a segment is dropped, the sender can detect that drop and retransmit that dropped segment. Specifically, a receiver acknowledges segments that it receives. Based on those acknowledgments, a sender can determine which segments were successfully received.

o. Transport Layer (OSI Model):-This layer is responsible for data transfer between two systems.It also provides error control and flow control mechanism to ensure complete and reliable data transfer .It enable the receiver accurate data in the right sequence without any loss or duplicates. It also provides reliable delivering of messages and it performs data multiplexing.

p. Transport Layer (TCP/IP Stack):- stack Also known as the DoD model , this four-layer model (as opposed to the seven-layer OSI model) targets the suite of TCP/IP protocols.This layer also responsible for maintaining end to end communication accross the network.

q. User Datagram Protocol (UDP):- A connectionless transport protocol. Connectionless transport protocols provide unreliable transport, in that if a segment is dropped, the sender is unaware of the drop, and no retransmission occurs.

r. Broadband:- Broadband technologies divide the bandwidth available on a medium into different channels.Different communication streams are then transmitted over the various channels.

s. Baseband :- Baseband technologies, in contrast, use all the available frequencieson a medium to transmit data. Ethernet is an example of a networking technology that uses baseband.

------------------------------------------------------------------------Thank You----------------------------------------------------------------