Networking Quiz OSI TCP IP

The OSI model

was designed to promote interoperability by creating a guideline for network data transmission between computers that have different hardware vendors, software, operating systems, and protocols.

Open Systems Interconnection

OSI meaning

by ISO (International Organization for Standardization)

OSI or open systems interconnection was developed by

Greek word “isos”

. ISO is not an abbreviation for the International Organization for Standardization, but is instead derived from the WORD, which means “equal,” and was adopted by the organization.

The Physical layer

is the lowest, or first, layer of the OSI model. Protocols at the BLANK accept frames from the Data Link layer and generate signals as changes in voltage at the NIC.

The Data Link layer

takes raw data from the Physical layer and gives it a logical structure. This logic includes information about where the data is meant to go, which computer sent the data, and the overall validity of the bytes sent.

Framing -

Breaks the input data into data frames (typically a few hundred of bytes) and reassemble the received frames.

Frame –

a unit of data transmitted on a network contains control and address information.

Flow control –

is the control over the rate of traffic.

Network Layer

The primary function of protocols at the BLANK, the third layer in the OSI model, is to translate network addresses into their physical counterparts and decide how to route data from the sender to the receiver.

ROUTING –

is defined as the ability of the network to select a path.

PACKET –

is a discrete unit of data that is formatted as a signal for transmission over a network.

Transport Layer

Protocols in the BLANK accept data from the Session layer and manage end-to-end delivery of data. Purpose of this layer is to provide a reliable mechanism for the exchange of data between two processes in different computers.

segmentation

is the process of transport layer where user data is divided into smaller units called segments. For example, when we upload or download a file on the internet or to another device, it is divided into segments.

flow control

is the process of limiting the transport layer to the size, quantity or rate of data that the receiver can handle. For example, when the size of a segment is large or too large for the receiver to handle, it will send a signal / message that the sender will reduce it so that it can handle the data flow properly.

Multi-plexing Session

- the process by which different applications communicate and connect at the same time on one device. It uses different ports or socket numbers.

Session layer

defines how two computers establish, synchronize, maintain, and end a session. Sessions offer various services, including dialog control (keeping track of whose turn it is to transmit), token management (preventing two parties from attempting the same critical operation simultaneously), and synchronization (checkpointing long transmissions to allow them to pick up from where they left off in the event of a crash and subsequent recovery).

Presentation layer

is concern with the presentation of data. This layer ensures that the data format from the sending device is presented correctly when it is received by the receiving device.

ENCRYPTION –

is a process that scrambles the data so that it cannot be read if intercepted by unauthorized users.

The application layer

is the last layer in the OSI model but it is the closest to end user. The software or applications we use or are used by network devices use "protocols" that belong to the application layer.

FTAM(file transfer,access,mgmt) -

Allows user to access files in a remote host.

Mail services -

Provides email forwarding and storage.

Directory services -

Provides database sources to access information about various sources and objects.

Encapsulation

is the process by which each layer of the OSI model adds the corresponding information so that the corresponding OSI layers of the receiving device can be understood. OR When the sending device communicates or sends information to another device, it also goes from top to bottom or layer 7 to layer 1

decapsulation.

When data or information enters in the OSI layers of the receiving device, it goes from bottom to top starting in layer 1 to layer 7. The corresponding layer in the receiving device gradually removes the corresponding information entered or added by the OSI layers from the sending device. This process is called

Transmission Control Protocol/ Internet Protocol.

TCP/IP stands for

ARPANET

developed TCP/IP

Advanced Research Project Agency Network

ARPANET Means?

HTTP or Hypertext transfer protocol

it allows the user to interact with World Wide Web through the browser application. It is used to transfer Webpages and such resources from the Web Server or Blank server to the Web Client or the Blank client. When you use a web browser such as Internet Explorer or Firefox, you are using a web client. It uses Blank to transfer web pages that you request from the remote servers.

Hypertext transfer protocol

HTTP stands for

FTP or File Transfer Protocol.

This protocol is used for transmitting files from one system to another system. Just like telnet and HTTP, one host runs the FTP server application (or daemon) and is called the FTP server while the FTP client runs the FTP client application. A client connecting to the FTP server may be required to authenticate before being given access to the file structure. Once authenticated, the client can view directory listings, get and send files, and perform some other file related functions. Just like telnet, the FTP client application available in most operating systems is called ftp.

File Transfer Protocol.

FTP stands for

TELNET

is a client-server protocol. It is a reliable connection oriented protocol. This protocol is used on internet or on LAN to provide a bidirectional (both ways) text based communication through a virtual terminal connection. A host, called the Telnet server, runs a telnet server application (or daemon in Unix terms) that receives a connection from a remote host called the Telnet client. This connection is presented to the operating system of the telnet server as though it is a terminal connection connected directly

DNS

Each computer on a network has different IP address, a computer is known by its IP address. It provides a mapping to a name to the IP Address so a name can be used to identify a system on network rather than IP address itself.

Domain Name System

DNS stands for

SNMP or Simple Network Management Protocol.

It managers the devices connected to the internet using TCP/IP protocol.

Simple Network Management Protocol.

SNMP stands for

SMTP or Simple mail transfer protocol.

It is used for email services, using this protocol a email containing data can be sent to another email address.

Simple mail transfer protocol.

SMTP stands for

DHCP –

As you know, every host requires a logical address such as an IP address to communicate in a network. The host gets this logical address either by manual configuration or by a protocol such as Dynamic Host Configuration Protocol (DHCP). Using DHCP, a host can be provided with an IP address automatically. To understand the importance of DHCP, imagine having to manage 5000 hosts in a network and assigning them IP address manually! Apart from the IP address, a host needs other information such as the address of the DNS server it needs to contact to resolve names, gateways, subnet masks, etc. DHCP can be used to provide all these information along with the IP address.

Dynamic Host Configuration Protocol

DHCP stands for

transport layer

is responsible for the reliability, flow control, and correction of data which is being sent over the network.

User Datagram protocol (UDP)

is a process to process protocol used for data transmission.

Transmission control protocol (TCP)

1. Unlike UDP which is a connectionless protocol, the Blank is a connection oriented protocol. 2. A connection must be made between sender and receiver before the transmission of data. 3. Blank protocol divides the data in small units called segments. Each segment contains the sequence number which makes it possible to rearrange the segments in correct order at the receiver side to make the complete data. 4. It also adds acknowledgement number to the segments to verify that the data is actually reached its destination or not. 5. Unlike UDP which is unable to specify the exact error in transmission, this protocol does error control and specifies the exact error which makes Blank a reliable protocol.

Stream Control Transmission Protocol (SCTP)

1. This protocol combines the best features of TCP and UDP protocols. 2. It was discovered later to support newer applications such as voice data transmission over the internet.

Internet layer

TCP/IP model corresponds to the Network layer of the OSI reference model in function. It provides logical addressing, path determination and forwarding.

Interruption

is a security threat in which availability of resources is attacked. For example, a user is unable to access its web-server or the web server is hijacked.

Privacy-Breach

In this threat, the privacy of a user is compromised. Someone, who is not the authorized person is accessing or intercepting data sent or received by the original authenticated user.

Integrity

This type of threat includes any alteration or modification in the original context of communication. The attacker intercepts and receives the data sent by the sender and the attacker then either modifies or generates false data and sends to the receiver. The receiver receives the data assuming that it is being sent by the original Sender.

Authenticity

This threat occurs when an attacker or a security violator poses as a genuine person and accesses the resources or communicates with other genuine users.

Cryptography

is a technique to encrypt the plain-text data which makes it difficult to understand and interpret. There are several cryptographic algorithms available present day as described below:  Secret Key  Public Key  Message Digest

Secret Key Encryption

Both sender and receiver have one secret key. This secret key is used to encrypt the data at sender’s end. After the data is encrypted, it is sent on the public domain to the receiver. Because the receiver knows and has the Secret Key, the encrypted data packets can easily be decrypted. Example of secret key encryption is Data Encryption Standard (DES). In Secret Key encryption, it is required to have a separate key for each host on the network making it difficult to manage.

Public Key Encryption

In this encryption system, every user has its own Secret Key and it is not in the shared domain. The secret key is never revealed on public domain. Along with secret key, every user has its own but public key. Public key is always made public and is used by Senders to encrypt the data. When the user receives the encrypted data, he can easily decrypt it by using its own Secret Key. Example of public key encryption is Rivest-Shamir-Adleman (RSA)..

Message Digest

In this method, actual data is not sent; instead a hash value is calculated and sent. The other end user, computes its own hash value and compares with the one just received. If both hash values are matched, then it is accepted; otherwise rejected. Example of Message Digest is MD5 hashing. It is mostly used in authentication where user password is cross checked with the one saved on the server.