TCP/IP

Protocols and Standards

● A protocol is a set of rules defining how data should be communicated between devices over a network.

● A standard is agreed-upon specification that describes how a protocol or technology should work.

IEEE (Institue of Electrical and Electronics Engineers)

● Develops many of the technologies used on local area network

● Ethernet (802.3)

● Wi-Fi (802.11)

IETF (Internet Engineering Task Force)

● Open community that defines protocols use on the internet:

● TCP, IP ,UDP, HTTP, DNS, etc.

Application Layer

● Protocols for communication between application process; create and interpret the data.

● Protocols at this layers define message formats and rules for specific tasks, such as:

■ Browsing web pages (HTTP/HTTPS)

■ Transferring files (FTP, TFTP)

■ Sending/ receiving email (SMTP, POP3, IMAP)

Transport Layer

● Provides end-of-end communication between application process using port numbers. Also called “process-to-process or service-to-service

● Protocol at the layer inculde:

■ UDP (User Datagram Protocol) simple and efficient

■ TCP (Transmission Control Protocol) more robust features beyond basic message addressing

Internet layer

● Provides end-to-end communication between host across networks using IP addresses and routers

Local Network layer

● (Layer 2)Provides hop-to-hop delivery within a local network using MAC addresses and switches. (Local network)

● A hopbisbone stepbalong the path between two devices from one router or host , to the next router or host in the path

● Switches don't count: a Switch just extends the local network allowing multiple devices to connect.

● Use MAC (Media Access Control) addresses to identify interfaces.

● Protocols at this layer:

● Ethernet (802.3)

● Wi-Fi (802.11)

Physical Layer

● (Layer 1) Sends bits as electrical, optical, or radio signals over the physical medium

● Defines things like cables, connectors, signal levels, and link speeds.

● Examples: copper UTP cables, fiber-optic cables, Wi-Fi radios and antennas, network interface cards( NICs)

Encapsulation

● The Application layer prepares the data to be sent over the network.

● As the message moves down the stack, each layer encapsulates the data with a header including the information needed for that layer.

■ Source and the destination addresses (port numbers ,IP addresses, MAC addresses), etc

■ Layer 2 also adds a trailer that the receiving device users to check for transmission errors.

● The physically, transmits the bits as signals over the physical medium.

■ The L2 header is transmitted first and then the L2 trailer is transmitted last.

Decapsulation

● The received a device receives the message as a stream of bits at level 1.

● The device examines the information in the layer 2 header and trailer, and then removes them. (Decapsulation)

■ The decapsulation the process continues up to stack layer 3 removing the L3 header, then layer 4 removes the L4 header, and then the data is delivered to the application layer.

● The application processes the data, and if needed generates a response that goes back down the stack.

Protocol data units

● At each stage in the encapsulation/ decapsulation process, there's a name given to the message:

■ The combination of the data and a L4 header is called a segment(TCP) or datagram (UDP)