The term port can refer to either physical or virtual connection points. There are two kinds of port,

Physical port:

Physical network ports allow connecting cables to computers, routers, modems and other peripheral devices. Several different types of physical ports available on computer network hardware. A physical port, as opposed to a virtual or logical port is an interface on a computer into which you can insert a connector for a device.

Examples of Physical Port: RJ45 port (Ethernet/LAN/NIC Port), Serial Port (RS-232), USB Port.

Virtual port:

                Virtual ports are part of TCP/IP networking. These ports allow software applications to share hardware resources without interfering with each other. Computers and routers automatically manage network traffic traveling via their virtual ports.

Port numbers range from 0 to 65536, but only ports numbers 0 to 1024 are reserved for privileged services and designated as well-known ports. This list of well-known port numbers specifies the port used by the server process as its contact port.

This layer 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 transfers-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.

Eg: WWW Browser, FTP, HTTP, Telnet, Nfs, Snmp

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.

Eg:  encryption, ASCII, EBCDIC, TIFF, GIF, PICT, JPEG, MPEG, MIDI.

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.

Eg: NFS, NetBios names, RPC, SQL.

This layer 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.

Eg:  SPX, TCP, UDP.

This layer 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.

Eg: AppleTalk DDP, IP, IPX.

At this layer, 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.

Eg:  PPP, FDDI, ATM, IEEE 802.5/ 802.2, IEEE 802.3/802.2, HDLC, Frame Relay. 

This layer 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.

Eg: Ethernet, FDDI, B8ZS, V.35, V.24, RJ45

Introduction to Networking and Network Basics :

It is important to understand what a network is and the importance of networks themselves. Every host has a Network Interface Card (NIC) that is used to connect it to a network.

A hub is a network device that repeats information received from a host to all other connects hosts. The hub will relay any information received from Host A to Host B and Host C. This means that all the three hosts can communicate with each other. Communication between hosts can be classified into three types:

Unicast – Communication from one host to another host only.

Broadcast – Communication from one host to all the hosts in the network.

Multicast – Communication from one host to few hosts only.

When a hub is used to network hosts, there are two problems that arise:

A hub repeats information received from one host to all the other hosts. To understand this, consider Host A sending a unicast message to Host B. When the hub receives this message; it will relay the message to both Host B and Host C. Even though the message was a unicast intended only for Host B, Host C also receives it. It is up to Host C to read the message and discard it after seeing that the message was not intended for it.

A hub creates a shared network medium where only a single host can send packets at a time. If another host attempts to send packets at the same time, a collision will occur. Then each device will need to resend their packets and hope not to have a collision again. This shared network medium is called a single collision domain. Imagine the impact of having a single collision domain where 50 or 100 hosts are connected to hubs that are interconnected and they are all trying to send data. That is just a recipe for many collisions and an inefficient network.

The problems associated with hubs can cause severe degradation of a network. To overcome these, switches are used instead of hubs. Like hubs, switches are used to connect hosts in a network but switches break up collision domain by providing a single collision domain for every port. This means that every host (one host connects to one port on the switch) gets its own collision domain thereby eliminating the collisions in the network. With switches, each host can transmit data anytime. Switches simply “switch” the data from one port to another in the switched network. Also, unlike hubs, switches do not flood every packet out all ports. They switch a unicast packet to the port where the destination host resides.

Now that you know how a switch works and improves a network, consider the one problem associated with a switched network. Earlier, you learned that hubs flood out all packets, even the unicast ones. A switch does not flood out unicast packets but it does flood out a broadcast packet. All hosts connected to a switched network are said to be in the same broadcast domain. All hosts connected to it will receive any broadcast sent out in this domain. While broadcasts are useful and essential for network operations, in a large switched network too many broadcasts will slow down the network. To remedy this situation, networks are broken into smaller sizes and these separate networks are interconnected using routers. Routers do not allow broadcasts to be transmitted across different networks it interconnects and hence effectively breaks up a broadcast domain.

Mac Address - 12 digit unique value.

IP Address use to find the particular host in the network, it can be considered as 2 values, bit Network bit and Host bit.

IP Address rule for same network: