The word protocol is derived from the Greek word “protocollon” which means a leaf of paper glued to manuscript volume. In computer protocols means a set of rules, a communication language or set of standards between two or more computing devices. Protocols exist at the several levels of the OSI (open system interconnectivity) layers model. In the telecommunication system, there are one more protocols at each layer of the telephone exchange. On the internet, there is a suite of the protocols known as TCP/IP protocols that are consisting of transmission control protocol, internet protocol, file transfer protocol, dynamic host configuration protocol, Border gateway protocol and a number of other protocols.
In the telecommunication, a protocol is set of rules for data representation, authentication, and error detection. The communication protocols in the computer networking are intended for the secure, fast and error free data delivery between two communication devices. Communication protocols follow certain rules for the transmission of the data.
Protocols Properties
Different protocols perform different functions so it is difficult to generalize the properties of the protocols. There are some basic properties of most of the protocols.
• Detection of the physical (wired or wireless connection)
• Handshaking
• How to format a message.
• How to send and receive a message.
• Negotiation of the various connections
• Correction of the corrupted or improperly formatted messages.
• Termination of the session.
The widespread use of the communication protocols is a prerequisite to the internet. The term TCP/IP refers to the protocols suite and a pair of the TCP and IP protocols are the most important internet communication protocols. Most protocols in communication are layered together where the various tasks listed above are divided. Protocols stacks refer to the combination of the different protocols. The OSI reference model is the conceptual model that is used to represent the protocols stacks. There are different network protocols that perform different functions. Following is the description of the some of the most commonly used protocols.
HTTP (Hyper Text Transfer Protocol)
Hypertext transfer protocol is a method of transmitting the information on the web. HTTP basically publishes and retrieves the HTTP pages on the World Wide Web. HTTP is a language that is used to communicate between the browser and web server. The information that is transferred using HTTP can be plain text, audio, video, images, and hypertext. HTTP is a request/response protocol between the client and server. Many proxies, tunnels, and gateways can be existing between the web browser (client) and server (web server). An HTTP client initializes a request by establishing a TCP connection to a particular port on the remote host (typically 80 or 8080). An HTTP server listens to that port and receives a request message from the client. Upon receiving the request, server sends back 200 OK messages, its own message, an error message or other message.
POP3 (Post Office Protocol)
In computing, e-mail clients such as (MS outlook, outlook express and thunderbird) use Post office Protocol to retreive emails from the remote server over the TCP/IP connection. Nearly all the users of the Internet service providers use POP 3 in the email clients to retrieve the emails from the email servers. Most email applications use POP protocol.
SMTP (Simple Mail Transfer Protocol)
Simple Mail Transfer Protocol is a protocol that is used to send the email messages between the servers. Most email systems and email clients use the SMTP protocol to send messages to one server to another. In configuring an email application, you need to configure POP, SMTP and IMAP protocols in your email software. SMTP is a simple, text based protocol and one or more recipient of the message is specified and then the message is transferred. SMTP connection is easily tested by the Telnet utility. SMTP uses the by default TCP port number 25
FTP (File Transfer Protocol)
FTP or file transfer protocol is used to transfer (upload/download) data from one computer to another over the internet or through or computer network. FTP is a most commonly communication protocol for transferring the files over the internet. Typically, there are two computers are involved in the transferring the files a server and a client. The client computer that is running FTP client software such as Cuteftp and AceFTP etc initiates a connection with the remote computer (server). After successfully connected with the server, the client computer can perform a number of the operations like downloading the files, uploading, renaming and deleting the files, creating the new folders etc. Virtually operating system supports FTP protocols.
IP (Internet Protocol)
An Internet protocol (IP) is a unique address or identifier of each computer or communication devices on the network and internet. Any participating computer networking device such as routers, computers, printers, internet fax machines and switches may have their own unique IP address. Personal information about someone can be found by the IP address. Every domain on the internet must have a unique or shared IP address.
DHCP (Dynamic Host Configuration Protocol)
The DHCP or Dynamic Host Configuration Protocol is a set of rules used by a communication device such as router, computer or network adapter to allow the device to request and obtain and IP address from a server which has a list of the larger number of addresses. DHCP is a protocol that is used by the network computers to obtain the IP addresses and other settings such as gateway, DNS, subnet mask from the DHCP server. DHCP ensures that all the IP addresses are unique and the IP address management is done by the server and not by the human. The assignment of the IP addresses is expires after the predetermined period of time. DHCP works in four phases known as DORA such as Discover, Observe, Request and Authorize
IMAP (Internet Message Access Protocol)
The Internet Message Access Protocol known as IMAP is an application layer protocol that is used to access to access the emails on the remote servers. POP3 and IMAP are the two most commonly used email retrieval protocols. Most of the email clients such as outlook express, thunderbird and MS outlooks support POP3 and IMAP. The email messages are generally stored on the email server and the users generally retreive these messages whether by the web browser or email clients. IMAP is generally used in the large networks. IMAP allows users to access their messages instantly on their systems.
ARCNET
ARCNET is a local area network technology that uses token bus scheme for managing line sharing among the workstations. When a device on a network wants to send a message, it inserts a token that is set to 1 and when a destination device reads the message it resets the token to 0 so that the frame can be used by another device.
FDDI
Fiber distributed data interface (FDDI) provides a standard for data transmission in a local area network that can extend a range of 200 kilometers. The FDDI uses token ring protocol as its basis. FDDI local area network can support a large number of users and can cover a large geographical area. FDDI uses fiber optic as a standard communication medium. FDDI uses dual attached token ring topology. A FDDI network contains two token rings and the primary ring offers the capacity of 100 Mbits/s. FDDI is an ANSI standard network and it can support 500 stations in 2 kilometers.
UDP
The user datagram protocol is a most important protocol of the TCP/IP suite and is used to send the short messages known as datagram. Common network applications that uses UDP are DNS, online games, IPTV, TFTP and VOIP. UDP is very fast and light weight. UDP is an unreliable connectionless protocol that operates on the transport layer and it is sometimes called Universal Datagram Protocol.
X.25
X.25 is a standard protocol suite for wide area networks using a phone line or ISDN system. The X.25 standard was approved by CCITT now ITU in 1976.
TFTP
Trivial File Transfer Protocol (TFTP) is a very simple file transfer protocol with the very basic features of the FTP. TFTP can be implemented in a very small amount of memory. TFTP is useful for booting computers such as routers. TFTP is also used to transfer the files over the network. TFPT uses UDP and provides no security features.
SNMP
The simple network management protocol (SNMP) forms the TCP/IP suite. SNMP is used to manage the network attached devices of the complex network.
PPTP
The point to point tunneling protocol is used in the virtual private networks. PPP works by sending regular PPP session. PPTP is a method of implementing VPN networks.
OTHER PROTOCOLS
VTP, ARP, IPX, OSPF, RARP, NFS, BOOTP, NNTP, IRC, RADIUS, Soap, Telnet, RIP, SSH.
Saturday, October 11, 2008
Introduction to TCP/IP
Here you will learn about Tcp ip network overview, data communication, ip addressing introduction, basic protocols, routing in the internet. TCP/IP short for Transmission Control Protocol is a suite of the communication protocols used to connect the hosts on the internet. TCP and IP were developed by a department of defense (DOD) in a research project to connect the number of networks by different vendors to form a big network of networks (the Internet).
It was originally successfully because of the services it gave, which everyone wanted to use such as file transfer, electronic mail, remote logon across a very large number of clients and server system. Several computers in a small network can use TCP/IP to communicate with each other. The IP component of the TCP/IP suites provides the routing between the two locally or remote computers.
IP forwards each packet based on a four byte, 32 bits address. TCP is responsible for verifying the correct delivery of data from the client to server. TCP also supports to detect the errors in the transmission and also triggers the data to retransmit correctly.
TCP/IP is a de facto standard of transferring the data on the network and on the internet. Each network operating systems that have their own protocols must support TCP/IP too. All the computers in a network must follow the rules to communication with each other.
TCP/IP stands for Transmission Control Protocol and Internet Protocol and it is a communication standard that defines how data travels on the internet and how network/communication devices communication with each other.
Inside the TCP/IP
TCP/IP is a not a single protocol but it is a suite of the protocols. There are the numerous protocols in the TCP/IP suite such as TCP, UDP, ICMP, DHCP, IMAP, HTTP, HTTPS, SSL, SMTP and many others.
Internet Protocol is a connectionless protocol that is used to communicate between the two computers. IP does not occupy the communication line between the two computers. With the IP communication, data is broken into the smaller pieces called packets, and these packets communicate between the two locally or remotely connected devices in a computer network or via internet. IP is also responsible for routing the packets to its destination. Routers are responsible for routing the packets towards its destination when a computer sends packets to an IP router. Data is routed towards its destination is all by a router. Router works as a post office.
TCP/IP
The TCP/IP (transmission control protocol/Internet protocol) work together in which TCP takes care communication between the application software i.e browsers whereas IP takes care of the communication between the computers. TCP breaks the data into smaller packets before they can be sent and IP sends the packets to the receivers.
IP Addresses
Each computer in a network or on internet must have a unique IP address before it can communicate with the other computer. The packets must have the address of the destination computers or devices. Each IP address is composed of 32 bits and 4 octets each packet must have an address before it can be sent to another computer.
This is an IP address 100.100.100.10 and this website http://www.example.com might have mapped with the same IP address. Without a unique IP address the communication on the internet is impossible. The numbers in the address must range between 0 and 255 in four period separated portions. Each IP address consists of 32 bits and 32 bits are consisting of 4 bytes. A computer byte can contain 256 different values e.g 00000000, 00100010, 00000111, 11111000, 01010101, 001100110 and up to 11111111.
Domain Names
Domain names are the unique identifier of a website because 12 digits numbers are difficult to remember. The name used for the web address is called a domain name e.g www.google.com, www.msn.com, www.yahoo.com all are domain names and comparatively are easy to remember instead of 12 digits numbers like, 123.220.44.240, 100.100.100.101 and 202.202.56.110. When you type a domain name in your web browser the domain name is translated into IP address by the DNS server, which is managed by your local ISPs or your corporate DNS servers.
All over the world a larger number of the DNS servers are connected with each other some are primary DNS servers, secondary DNS servers, Master DNS servers and Root DNS servers. When a new domain is registered by a domain registrar with associated TCP/IP address then DNS servers from all over the world are updated.
TCP/IP is a large collection of the different communication protocols.
TCP/IP is a large collection of different communication protocols.
A Family of Protocols
TCP/IP is a large collection of different communication protocols based upon the two original protocols TCP and IP. Each protocol in the TCP/IP suite is responsible for the different communication tasks. HTTP is responsible for the communication between the web server and the web browser. It sends requests from the client (browser) to web server and returning the web pages to the client.
HTTPS is responsible for the secure communication between the web browser and the web server. HTTPS usually handles the credit card transactions and other sensitive and secure data. SSL is responsible for the encryption of the data for the secure communication. SMTP (Simple mail transfer protocol) is responsible for sending the emails. MIME (Multi purpose Internet mail extension) is responsible for communicating the multimedia data such as, voice, video, graphics etc. IMAP (Internet Message Access Protocol) is responsible for storing and retrieving the emails.
POP (post office protocol) is used for downloading the emails from the email server to the personal computer. FTP (File transfer protocol) it takes cares of transferring the files between the computers. NTP (Network time protocol) is used to synchronize the time between the networks. DHCP (Dynamic host configuration protocol) is responsible for assigning the IP address dynamically to the network computers. SNMP (Simple Network Management Protocol) is used for administration of a computer network.
LDAP (Light weight directory access protocol) is used for storing the names and email addresses on the internet and also communicating with the Active directory in computer network. ARP (Address resolution protocol) is used to find the hardware address of a computer based on the IP address. Boot P protocol is used for starting computers in a network. PPTP (Point to point tunneling protocol) is used to make a secure tunnel in the private networks such as VPN.
TCP/IP is the Internet Communication Protocol.
A protocol is a set of rules, agreed upon methods or a communication language, which both computers understand and agree upon. TCP/IP defines the rules to communicate over the internet. Internet browsers and Internet servers uses TCP/IP to communicate on the internet
Web browsers, Web servers, Email programs and internet address all follow TCP/IP. An IP address is a part of the TCP/IP protocols.
It was originally successfully because of the services it gave, which everyone wanted to use such as file transfer, electronic mail, remote logon across a very large number of clients and server system. Several computers in a small network can use TCP/IP to communicate with each other. The IP component of the TCP/IP suites provides the routing between the two locally or remote computers.
IP forwards each packet based on a four byte, 32 bits address. TCP is responsible for verifying the correct delivery of data from the client to server. TCP also supports to detect the errors in the transmission and also triggers the data to retransmit correctly.
TCP/IP is a de facto standard of transferring the data on the network and on the internet. Each network operating systems that have their own protocols must support TCP/IP too. All the computers in a network must follow the rules to communication with each other.
TCP/IP stands for Transmission Control Protocol and Internet Protocol and it is a communication standard that defines how data travels on the internet and how network/communication devices communication with each other.
Inside the TCP/IP
TCP/IP is a not a single protocol but it is a suite of the protocols. There are the numerous protocols in the TCP/IP suite such as TCP, UDP, ICMP, DHCP, IMAP, HTTP, HTTPS, SSL, SMTP and many others.
Internet Protocol is a connectionless protocol that is used to communicate between the two computers. IP does not occupy the communication line between the two computers. With the IP communication, data is broken into the smaller pieces called packets, and these packets communicate between the two locally or remotely connected devices in a computer network or via internet. IP is also responsible for routing the packets to its destination. Routers are responsible for routing the packets towards its destination when a computer sends packets to an IP router. Data is routed towards its destination is all by a router. Router works as a post office.
TCP/IP
The TCP/IP (transmission control protocol/Internet protocol) work together in which TCP takes care communication between the application software i.e browsers whereas IP takes care of the communication between the computers. TCP breaks the data into smaller packets before they can be sent and IP sends the packets to the receivers.
IP Addresses
Each computer in a network or on internet must have a unique IP address before it can communicate with the other computer. The packets must have the address of the destination computers or devices. Each IP address is composed of 32 bits and 4 octets each packet must have an address before it can be sent to another computer.
This is an IP address 100.100.100.10 and this website http://www.example.com might have mapped with the same IP address. Without a unique IP address the communication on the internet is impossible. The numbers in the address must range between 0 and 255 in four period separated portions. Each IP address consists of 32 bits and 32 bits are consisting of 4 bytes. A computer byte can contain 256 different values e.g 00000000, 00100010, 00000111, 11111000, 01010101, 001100110 and up to 11111111.
Domain Names
Domain names are the unique identifier of a website because 12 digits numbers are difficult to remember. The name used for the web address is called a domain name e.g www.google.com, www.msn.com, www.yahoo.com all are domain names and comparatively are easy to remember instead of 12 digits numbers like, 123.220.44.240, 100.100.100.101 and 202.202.56.110. When you type a domain name in your web browser the domain name is translated into IP address by the DNS server, which is managed by your local ISPs or your corporate DNS servers.
All over the world a larger number of the DNS servers are connected with each other some are primary DNS servers, secondary DNS servers, Master DNS servers and Root DNS servers. When a new domain is registered by a domain registrar with associated TCP/IP address then DNS servers from all over the world are updated.
TCP/IP is a large collection of the different communication protocols.
TCP/IP is a large collection of different communication protocols.
A Family of Protocols
TCP/IP is a large collection of different communication protocols based upon the two original protocols TCP and IP. Each protocol in the TCP/IP suite is responsible for the different communication tasks. HTTP is responsible for the communication between the web server and the web browser. It sends requests from the client (browser) to web server and returning the web pages to the client.
HTTPS is responsible for the secure communication between the web browser and the web server. HTTPS usually handles the credit card transactions and other sensitive and secure data. SSL is responsible for the encryption of the data for the secure communication. SMTP (Simple mail transfer protocol) is responsible for sending the emails. MIME (Multi purpose Internet mail extension) is responsible for communicating the multimedia data such as, voice, video, graphics etc. IMAP (Internet Message Access Protocol) is responsible for storing and retrieving the emails.
POP (post office protocol) is used for downloading the emails from the email server to the personal computer. FTP (File transfer protocol) it takes cares of transferring the files between the computers. NTP (Network time protocol) is used to synchronize the time between the networks. DHCP (Dynamic host configuration protocol) is responsible for assigning the IP address dynamically to the network computers. SNMP (Simple Network Management Protocol) is used for administration of a computer network.
LDAP (Light weight directory access protocol) is used for storing the names and email addresses on the internet and also communicating with the Active directory in computer network. ARP (Address resolution protocol) is used to find the hardware address of a computer based on the IP address. Boot P protocol is used for starting computers in a network. PPTP (Point to point tunneling protocol) is used to make a secure tunnel in the private networks such as VPN.
TCP/IP is the Internet Communication Protocol.
A protocol is a set of rules, agreed upon methods or a communication language, which both computers understand and agree upon. TCP/IP defines the rules to communicate over the internet. Internet browsers and Internet servers uses TCP/IP to communicate on the internet
Web browsers, Web servers, Email programs and internet address all follow TCP/IP. An IP address is a part of the TCP/IP protocols.
OSI 7 Layers Reference Model
Here you will learn OSI Model Layer Introduction, overview of the 7 OSI reference model, applicaion, session, transport, network and physical layers. If you want to remember the sequence of the OSI layers model name then the following two sentences can help you a lot for this purpose.“All People Seems To Need Data Processing”. Open Systems Interconnection (OSI) model is developed by ISO (International organization for standardization) in 1984. OSI reference model is a logical framework for standards for the network communication.
OSI reference model is now considered as a primary standard for internetworking and inter computing. Today many network communication protocols are based on the standards of OSI model. In the OSI model the network/data communication is defined into seven layers.
These 7 layers further divide the tasks of moving the data across the network into subtask and hence complete one communication cycle between two computers or two network devices. Each layer is assigned a task and the task is completed independently. The OSI layers have the clear and independent characteristics and tasks.
The 7 layers of the OSI models can be divided into upper and lower layers. I have defined the characteristics, tasks and features of each layer separately.
Layer 7: Application Layer
The application layer defines the interfaces for communication and data transfer.
This layer also provides and support services such as job transfer, handles network access, e-mail, supports user applications and error recovery.
Protocols: FTP, DNS, SNMP, SMTP, FINGER, TELNET, TFTP, BOOTP and SMB protocol are operated on the application layer.
Network Devices: Gateway network device is operated on the application layer.
Layer 6:Presentation Layer
The presentation layer presents the data into a uniform format and masks the difference of data format between two dissimilar systems. It also translates the data from application to the network format. Presentation layer is also responsible for the protocol conversion, encryption, decryption and data compression. Presentation layer is a best layer for cryptography.
Network Devices: Gateway Redirector is operates on the presentation layer.
Layer 5: Session Layer
Session layer establish and manages the session between the two users at different ends in a network. Session layer also manages who can transfer the data in a certain amount of time and for how long. The examples of session layers and the interactive logins and file transfer sessions. Session layer reconnect the session if it disconnects. It also reports and logs and upper layer errors.
Protocols: The protocols that work on the session layer are NetBIOS, Mail Slots, Names Pipes, RPC
Network Devices: Gateway
Layer 4: Transport Layer
Transport layer manages end to end message delivery in a network and also provides the error checking and hence guarantees that no duplication or errors are occurring in the data transfers across the network. Transport layer also provides the acknowledgement of the successful data transmission and retransmits the data if no error free data was transferred.
It also provides and error handling and connectionless oriented data deliver in the network.
Protocols: These protocols work on the transport layer TCP, SPX, NETBIOS, ATP and NWLINK.
Network Devices: The Brouter, Gateway and Cable tester work on the transport layer.
Layer 3: Network Layer
The network layer determines that how data transmits between the network devices. It also translates the logical address into the physical address e.g computer name into MAC address. It is also responsible for defining the route, managing the network problems and addressing. Router works on the network layer and if a sending device does not break the data into the similar packets as the receiving device then network layer split the data into the smaller units and at the receiving end the network layer reassemble the data.
Network layer routes the packets according to the unique network addresses. Router works as the post office and network layer stamps the letters (data) for the specific destinations.
Protocols: These protocols work on the network layer IP, ICMP, ARP, RIP, OSI, IPX and OSPF.
Network Devices: Network devices including Router, Brouter, Frame Relay device and ATM switch devices work on the network layer.
Layer 2:Data Link Layer
Defines procedures for operating the communication links
Frames packets
Detects and corrects packets transmit errors
Protocols: Logical Link Control
• error correction and flow control
• manages link control and defines SAPs
802.1 OSI Model
802.2 Logical Link Control
Media Access Control
• communicates with the adapter card
• controls the type of media being used:
802.3 CSMA/CD (Ethernet)
802.4 Token Bus (ARCnet)
802.5 Token Ring
802.12 Demand Priority
Network Devices: Bridge
Switch
ISDN Router
Intelligent Hub
NIC
Advanced Cable Tester
Layer 1: Physical Layer
Physical layer defines and cables, network cards and physical aspects. It defines raw bit stream on the physical media. It also provides the interface between network and network communication devices. It is also responsible for how many volts for 0 and how many for 1. Physical layer also checks the number of bits transmitted per second and two ways or one way transmission. Physical layer also dealing with the optical, mechanical and electrical features.
Protocols: Protocols that work on the physical layer are ISDN, IEEE 802 and IEEE 802.2
Network Devices: Hubs, Repeaters, Oscilloscope and Amplifier works on the network devices.
OSI reference model is now considered as a primary standard for internetworking and inter computing. Today many network communication protocols are based on the standards of OSI model. In the OSI model the network/data communication is defined into seven layers.
These 7 layers further divide the tasks of moving the data across the network into subtask and hence complete one communication cycle between two computers or two network devices. Each layer is assigned a task and the task is completed independently. The OSI layers have the clear and independent characteristics and tasks.
The 7 layers of the OSI models can be divided into upper and lower layers. I have defined the characteristics, tasks and features of each layer separately.
Layer 7: Application Layer
The application layer defines the interfaces for communication and data transfer.
This layer also provides and support services such as job transfer, handles network access, e-mail, supports user applications and error recovery.
Protocols: FTP, DNS, SNMP, SMTP, FINGER, TELNET, TFTP, BOOTP and SMB protocol are operated on the application layer.
Network Devices: Gateway network device is operated on the application layer.
Layer 6:Presentation Layer
The presentation layer presents the data into a uniform format and masks the difference of data format between two dissimilar systems. It also translates the data from application to the network format. Presentation layer is also responsible for the protocol conversion, encryption, decryption and data compression. Presentation layer is a best layer for cryptography.
Network Devices: Gateway Redirector is operates on the presentation layer.
Layer 5: Session Layer
Session layer establish and manages the session between the two users at different ends in a network. Session layer also manages who can transfer the data in a certain amount of time and for how long. The examples of session layers and the interactive logins and file transfer sessions. Session layer reconnect the session if it disconnects. It also reports and logs and upper layer errors.
Protocols: The protocols that work on the session layer are NetBIOS, Mail Slots, Names Pipes, RPC
Network Devices: Gateway
Layer 4: Transport Layer
Transport layer manages end to end message delivery in a network and also provides the error checking and hence guarantees that no duplication or errors are occurring in the data transfers across the network. Transport layer also provides the acknowledgement of the successful data transmission and retransmits the data if no error free data was transferred.
It also provides and error handling and connectionless oriented data deliver in the network.
Protocols: These protocols work on the transport layer TCP, SPX, NETBIOS, ATP and NWLINK.
Network Devices: The Brouter, Gateway and Cable tester work on the transport layer.
Layer 3: Network Layer
The network layer determines that how data transmits between the network devices. It also translates the logical address into the physical address e.g computer name into MAC address. It is also responsible for defining the route, managing the network problems and addressing. Router works on the network layer and if a sending device does not break the data into the similar packets as the receiving device then network layer split the data into the smaller units and at the receiving end the network layer reassemble the data.
Network layer routes the packets according to the unique network addresses. Router works as the post office and network layer stamps the letters (data) for the specific destinations.
Protocols: These protocols work on the network layer IP, ICMP, ARP, RIP, OSI, IPX and OSPF.
Network Devices: Network devices including Router, Brouter, Frame Relay device and ATM switch devices work on the network layer.
Layer 2:Data Link Layer
Defines procedures for operating the communication links
Frames packets
Detects and corrects packets transmit errors
Protocols: Logical Link Control
• error correction and flow control
• manages link control and defines SAPs
802.1 OSI Model
802.2 Logical Link Control
Media Access Control
• communicates with the adapter card
• controls the type of media being used:
802.3 CSMA/CD (Ethernet)
802.4 Token Bus (ARCnet)
802.5 Token Ring
802.12 Demand Priority
Network Devices: Bridge
Switch
ISDN Router
Intelligent Hub
NIC
Advanced Cable Tester
Layer 1: Physical Layer
Physical layer defines and cables, network cards and physical aspects. It defines raw bit stream on the physical media. It also provides the interface between network and network communication devices. It is also responsible for how many volts for 0 and how many for 1. Physical layer also checks the number of bits transmitted per second and two ways or one way transmission. Physical layer also dealing with the optical, mechanical and electrical features.
Protocols: Protocols that work on the physical layer are ISDN, IEEE 802 and IEEE 802.2
Network Devices: Hubs, Repeaters, Oscilloscope and Amplifier works on the network devices.
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