TCP/IP and Open Systems Interconnection (OSI) Models

• OSI model


  Developed by ISO (International Standard Organization) and provides greater detail of networking assignments within the model
• TCP/IP model


  Covers the same things found in the OSI model, but in fewer layers
• TCP/IP model


  Developed by the Department of Defense (DoD)
• OSI model


  • 7 Layers: Application, Presentation, Session, Transport, Network, Data Link, Physical
• TCP/IP model


  • 4 Layers: Application, Transport, Network, Network Interface
• How data flows in layers 7, 6, and 5 of the OSI model

  1. Application Layer: Supports applications like web browsing, email, and file transfer

  2. Presentation Layer: Data translation, encryption, protocol conversion

  3. Session Layer: Establishes, manages, and terminates connections
• How data flows in layers 4 and 3 of the OSI model

  1. Transport Layer: Ensures error-free packets. End-to-end communication. Breaks up data into segments

  2. Network Layer: Routes the data packets between network. (IP Addressing>NAT & PAT provides translation for IP Addresses)
• How data flows in layers 2 and 1 of the OSI model

  1. Data Link Layer: Packages data into frames and transmits these frames on the network, performing error detection/correction

  2. Physical Layer: Transmission of bits across the network
• Data types in the OSI model

  • Data
  • Segments
  • Packets
  • Frames
  • Bits
• TCP


  Reliable, Connection-Oriented, Segment retransmission/flow control through windowing, Segment sequencing, Acknowledge segments
• UDP


  Does the opposite of TCP
• Hubs


  • Layer 1 device, Multiple RJ45 connectors, Connection point for wired network, Dumb device, Multiport repeater
• Switches


  • Layer 2 device, Smarter version of hub, Learns which MAC address lives on each port, Keeps a table of MAC addresses to port assignments, Data is sent to ONLY the correct recipient
• Wireless Access Point (WAP)


  • Layer 2 OSI model device, Acts as a bridge, Bridges clients such as telephones, tablets, laptops, and other wireless device onto the wired network, Uses MAC addresses to make forwarding decisions
• Routers


  • Layer 3 device, Moves data between one IP network and another, Use IP addressing to make forwarding decisions to ensure the data is being sent to the RIGHT network and RIGHT host
• Firewalls


  • Come in either physical appliances or software-based, Filter traffic based on the set of rules and determines based on the rules if the traffic should be allowed to pass or dropped
• All-in-one device (Small Office/Home Office) & Modem


  • SOHO: one physical device does the functionality of multiple devices, Modem: allows your ISP to give service to your house or business
• Twisted Pair: UTP cable vs. STP cable

  • Twisted Pair: Most common network cable, Insulation of the STP makes it more resistant/protected against EMI, Category 3/4/5 are outdated, Cat5e/6/6a are current standards
• Coaxial


  • Primarily used today, Goes from a cable jack on the wall to a cable modem, Has a center conductor, insulating layer, conducting shield, and an outside sheath/jacket
• Fiber Optic Cabling


  • Does NOT use copper cabling or electricity, Has a glass or plastic core, Uses a light source and light pulse to transmit data, Faster than twisted pair, Can go for very long distances, Immune to EMI/electromagnetic interference
• Single Mode Fiber (SMF)/Multimode Fiber (MMF)

  • SMF: Uses a high quality light source (laser), Can go for miles, Faster, More expensive, MMF: Uses a weaker light source (LED), Sends multiple wavelengths, Less expensive, Ideal for shorter cable runs
• Patch Cables/Crossover Cables

  • Patch Cable: Short version of Ethernet with RJ45 connectors, Used to connect end devices to the wall jack, Crossover Cable: Used to connect same or like devices together with no switch or hub in between
• In the Application Layer of the TCP/IP model, the protocols are: HTTP, FTTP, Telnet, NTP, DHCP, PING, IMAP, AND POP
• In the transport layer of the TCP/IP model, the protocols are TCP, UDP
• In the Network Layer of the TCP/IP model, the protocols are IP, IPX, ARP, ICMP, IGMP
• The TCP/IP model is a shorter version of the OSI model.
• In the Network Interface layer of the TCP/IP model, the primary protocol is Ethernet.
• The application layer defines the applications used to process requests and which ports and sockets are used.
• The transport layer of the TCP/IP model defines the types of connection established between hosts and how acknowledgments are sent.
• The network interface layer of the TCP/IP model defines how the host connects to the network. Ex: physical connections and data transmissions over the networks.
• The application layer of the OSI model provides support for applications and has protocols: HTTP, FTP, and email protocols, such as: POP, IMAP, and SMTP.
• The presentation layer of the OSI layer model's protocols are SSL, ASCII, JPEG, MIDI, MPEG, GIF, MP3, MP4
• The session layer of the OSI model's protocols are NFS, SQL, PPTP, NetBIOS, PAP, SCP (tunneling)
• The data link layer of the OSI model's protocols are MAC addresses, ARP, PPP, HDLC, LLC
• The physical layer of the OSI model's protocols are DSL, ISDN, NICs, twisted pair cables, fiber, bits, hubs, modem, repeaters
• Switches operate at layer 2 network by forwarding data packets from one network segment to another.
• In the transport layer data is broken up into segments.