Transmission Medium:-
Data is represented by computers and other telecommunication devices using signals. Signals are transmitted in the form of electromagnetic energy from one device to another. Electromagnetic signals travel through vacuum, air or other transmission mediums to move from one point to another(from sender to receiver).
Electromagnetic energy (includes electrical and magnetic fields) consists of power, voice, visible light, radio waves, ultraviolet light, gamma rays etc.
Transmission medium is the means through which we send our data from one place to another. The first layer (physical layer) of Communication Networks OSI Seven layer model is dedicated to the transmission media.
Types of Transmission media:-
1. Guided media (wired media)
2. Unguided media (wireless media)
watch this video for more learning about Transmission Medium:-
The TCP/IP Reference Model
TCP/IP means Transmission Control Protocol and Internet Protocol. It is the network model used in the current Internet architecture as well. Protocols are set of rules which govern every possible communication over a network. These protocols describe the movement of data between the source and destination or the internet.
1. host to network layer
-Lowest layer of the all.
-Protocol is used to connect to the host, so that the packets can
be sent over it.
-Varies from host to host and network to network.
2. Internet layer
-Selection of a packet switching network which is based on a
connectionless internetwork layer is called a internet layer.
-It is the layer which holds the whole architecture together.
-It helps the packet to travel independently to the destination.
-Order in which packets are received is different from the way
they are sent.
-IP (Internet Protocol) is used in this layer.
3. Transport layer
-It decides if data transmission should be on parallel path or
single path.
-Functions such as multiplexing, segmenting or splitting on the
data is done by transport layer.
-The applications can read and write to the transport layer.
-Transport layer adds header information to the data.
-Transport layer breaks the message (data) into small units so
that they are handled more efficiently by the network layer.
-Transport layer also arrange the packets to be sent, in sequence.
4. Application layer
The TCP/IP specifications described a lot of applications that were at the top of the protocol stack. Some of them were TELNET, FTP, SMTP, DNS etc.
-TELNET is a two-way communication protocol which allows
connecting to a remote machine and run applications on it.
-FTP(File Transfer Protocol) is a protocol, that allows File transfer
amongst computer users connected over a network. It is reliable,
simple and efficient.
-SMTP(Simple Mail Transport Protocol) is a protocol, which is
used to transport electronic mail between a source and
destination, directed via a route.
-DNS(Domain Name Server) resolves an IP address into a textual
address for Hosts connected over a network. watch video for more learn about TCP/IP:-
OSI (Open Systems Interconnection) is reference model for how applications can communicate over a network. A reference model is a conceptual framework for understanding relationships.
OSI Layers:-
Layer 7 - Application
Layer 6 - Presentation
Layer 5 - Session
Layer 4 - Transport
Layer 3 - Network
Layer 2 - Data Link
Layer 1 - Physical
OSI Model, Layer 7, supports application and end-user processes. Communication partners are identified, quality of service is identified, user authentication and privacy are considered, and any constraints on data syntax are identified. Everything at this layer is application-specific. This layer provides application services for file transfers, e-mail, and other network software services. Telnet and FTP are applications that exist entirely in the application level. Tiered application architectures are part of this layer.
Layer 7 Application examples include WWW browsers, NFS, SNMP, Telnet, HTTP, FTP.
Presentation (Layer 6)
This layer provides independence from differences in data representation (e.g., encryption) by translating from application to network format, and vice versa. The presentation layer works to transform data into the form that the application layer can accept. This layer formats and encrypts data to be sent across a network, providing freedom from compatibility problems. It is sometimes called the syntax layer.
Layer 6 Presentation examples include encryption, ASCII, EBCDIC, TIFF, GIF, PICT, JPEG, MPEG, MIDI.
Session (Layer 5)
This layer establishes, manages and terminates connections between applications. The session layer sets up, coordinates, and terminates conversations, exchanges, and dialogues between the applications at each end. It deals with session and connection coordination.
Layer 5 Session examples include NFS, NetBios names, RPC, SQL.
Transport (Layer 4)
OSI Model, Layer 4, provides transparent transfer of data between end systems, or hosts, and is responsible for end-to-end error recovery and flow control. It ensures complete data transfer.
Layer 4 Transport examples include SPX, TCP, UDP.
Network (Layer 3)
Layer 3 provides switching and routing technologies, creating logical paths, known as virtual circuits, for transmitting data from node to node. Routing and forwarding are functions of this layer, as well as addressing, internetworking, error handling, congestion control and packet sequencing.
Layer 3 Network examples include AppleTalk DDP, IP, IPX.
Data Link (Layer 2)
At OSI Model, Layer 2, data packets are encoded and decoded into bits. It furnishes transmission protocol knowledge and management and handles errors in the physical layer, flow control and frame synchronization. The data link layer is divided into two sub layers: The Media Access Control (MAC) layer and the Logical Link Control (LLC) layer. The MAC sub layer controls how a computer on the network gains access to the data and permission to transmit it. The LLC layer controls frame synchronization, flow control and error checking.
Layer 2 Data Link examples include PPP, FDDI, ATM, IEEE 802.5/ 802.2, IEEE 802.3/802.2, HDLC, Frame Relay.
Physical (Layer 1)
OSI Model, Layer 1 conveys the bit stream - electrical impulse, light or radio signal — through the network at the electrical and mechanical level. It provides the hardware means of sending and receiving data on a carrier, including defining cables, cards and physical aspects. Fast Ethernet, RS232, and ATM are protocols with physical layer components.
Layer 1 Physical examples include Ethernet, FDDI, B8ZS, V.35, V.24, RJ45. watch this video for more learning about OSI model:-
