TCP/IP and OSI Model Overview

Introduction

• TCP/IP (Transmission Control Protocol/Internet Protocol) is a fundamental protocol suite used for communication on the Internet and intranets.
• TCP/IP is based on the Department of Defense (DOD) model.

IP (Internet Protocol)

• IP is a network layer protocol responsible for addressing and routing data packets across networks.
• IP defines a logical addressing scheme (IP addresses) for devices.
• Examples of network layer protocols: RIP, OSPF, EIGRP, IS-IS
• Examples of routed protocols: IP, Apple Talk, IPX (Internetwork Packet Exchange)
• Examples of message and control protocols: ICMP (Internet Control Message Protocol), Error Message, Ping, Traceroute
• ARP (Address Resolution Protocol) is used to translate logical IP addresses to physical MAC addresses.

TCP (Transmission Control Protocol)

• TCP provides reliable and ordered delivery of data segments.
• TCP uses a three-way handshake to establish a connection between two devices.

OSI (Open Systems Interconnection) Model & TCP/IP Relationship

• The OSI model is a theoretical framework that defines seven layers of network communication.
• TCP/IP maps to the OSI model but does not strictly follow all its layers.

Network Access Layer

• The Network Access Layer is responsible for the physical transmission of data over a network medium.
• Examples of LAN protocols: Ethernet, Token Ring, ARC-NET
• Examples of WAN protocols: HDLC, PPP, ISDN, Frame Relay, ATM
• MAC addresses are physical addresses that uniquely identifies a device on a network.
• The Network Access Layer converts binary data into signals suitable for the network media.

TCP Segment Header Fields

• Source port number: Specifies the port number of the sending device.
• Destination port number: Specifies the port number of the receiving device.
• Total Length: Indicates the total length of the TCP segment (header + data).
• Checksum: Ensures data integrity during transmission by performing an arithmetic operation on the segment.

TCP Segment Header Fields for Connection Management

• Sequence number: Identifies individual data segments and facilitates in order delivery.
• Acknowledgment number: Confirms receipt of segments from the sender.
• DO: Shows the size of the TCP header.
• RSV: Reserved field for future use.
• Flags: Control bits that manage the connection state and data transfer.
• Window: Specifies the allowed number of segments that can be sent without acknowledgment.

Ethernet Frame Structure

• Preamble: Contains a synchronization pattern that allows the receiver to identify the start of a frame.
• Start of Frame Delimiter (SOF)/Synch: Marks the beginning of the frame.
• Destination Address (DA): 48-bit MAC address of the intended recipient.
• Source Address (SA): 48-bit MAC address of the transmitting device.
• Length or Type: Specifies the total length of the frame or indicates the upper layer protocol.
• Data: Data payload from the Network layer.
• Frame Check Sequence (FCS): CRC value used for error detection.

Token Ring Network

• Devices in a token ring network are connected in a closed loop, creating a circular path for data transmission.
• A special token circulates around the ring.
• A device can transfer data only when it possesses the token.

ARC-NET

• A token passing network, using UTP or fiber optic cables.

Ethernet Network

• Ethernet uses a contention-based media access method called Carrier Sense Multiple Access with Collision Detection (CSMA/CD).
• Devices share the same bandwidth.
• Collisions can occur when multiple devices attempt to transmit simultaneously.
• Collision domains are network segments where a collision can occur.
• Broadcast domains are network segments where broadcasts can reach all devices.

Star Topology

• Devices are connected to a central hub, switch, or access point.
• Offers better fault tolerance compared to bus topology.
• Offers easier troubleshooting.