Objective 1 --> TCP/IP/OSI Model

TCP/IP Model

• Reference model that describes the way data flows through computer networks

• Composed of various protocols to govern packet switched networks

• Adopted by DARPA in 1983 to provide compatibility to end nodes

Protocols

• A set of rules used to standardize data formatting and allow network communication

Application Layer (TCP/IP)

• Defines the protocols that process data intended for the application software running on the computer

  • Provides an interface between the user and transport layer

  • PDU: data

  • Common Equipment: Terminal, equipment, computers, printers

  • Common Protocols: DNS, SNMP (Simple Network Management Protocol), HTTP/S, FTP, SSH

Transport Layer (TCP/IP)

• End-to-end communication between hosts

  • Interface between computer application software and the network hardware

  • Flow control and error recovery

  • PDU: TCP = segments, UDP (User Datagram Protocol) = datagrams

  • Common Protocols: UDP, TCP

Network Layer (TCP/IP)

• How data is routed across networks

  • Uses IP addresses and subnet masks to route the data

  • PDU: packets

  • Common Equipment: routers

  • Common Protocols: IP/ICMP

Data Link Layer (TCP/IP)

• Performs logical ops associated with LAN media

• Encapsulates bits received from LAN media and encodes it for the computer to process it

• Only performs error detection

• Functions:

  • Encapsulation and MAC addresses

  • Frame check sequence (FCS) —> performs error checks through a ‘checksum’

  • ARP —> maps an IP with a MAC address

• PDU: frames

• Common Equipment: switches

• Common Protocols: ARP

Physical Layer (TCP/IP)

• Where the host device connects to the LAN media

• Physical characteristics of cabling

• Fiber optic (light), copper (electric), and wireless transmissions (waves)

• PDU: bits

• Common Equipment: wires, connectors, hubs, media convertors

Protocol Data Unit (PDU)

• Enables same-layer interaction on different computers

• Adjacent-layer interaction adds its distinct PDU

• TCP = segments

• UDP = datagrams

• Data Link = frames

• Physical = bits

• *Visual —> Layered Russian doll* —> data is in the center

OSI Model

• Created by International Organization for Standards (ISO)

• Designed to enable any computer on any network to communicate with any other computer on any other network

• Not as common as TCP/IP

• More troubleshooting-orientated, standardization, vendor interoperability

• All PDUs are data

Application Layer

• Same as TCP/IP

• Serves an interface for the user between the app/transport layer

• DNS, HTTP/S

Presentation Layer

• Negotiates data formats (JPEG, ASCII text, pdf, GIF)

Session Layer

• Establishes, manages, and terminates connections between applications

  • SSH, video conferences, online gaming

Transport Layer

• Similar to TCP/IP, forwards data between networks