2.1 Introduction to IP - CompTIA A+ 220-1101

Moving Data Across Networks

• Moving Truck Analogy:

  • The concept of transferring data across networks can be likened to moving boxes with a moving truck.

  • Truck represents Internet Protocol (IP), serving as the vehicle for data transport.

  • Types of networks include wireless, DSL, cable modem, and Ethernet.

Data Packaging

• Each truck carries a box which encapsulates your data.

• The truck itself is unaware of the box's contents; it simply transports it.

• The encapsulation process allows data to move efficiently across the network.

Network Operation Visual

• Client-Server Interaction:

  • A client (such as a laptop) communicates with a server (like a web or mail server) over a network.

• Data sent is encapsulated in packets which include headers and trailers.

  • Ethernet Frames:

    • Contains an Ethernet header, payload (where IP is found), and trailer.

• IP Payload:

  • Carries the transport layer protocols: TCP or UDP.

IP Packet Structure

• Layers of Encapsulation:

  • Ethernet Frame contains:

    • IP header and payload.

  • Inside IP, there’s TCP/UDP data; TCP includes TCP header and payload.

  • Inside TCP, HTTP data might be present.

Transport Layer Protocols

• TCP (Transmission Control Protocol):

  • Connection-oriented protocol ensuring reliable delivery of data.

  • Establishes a connection before data transfer and has a formal teardown process at the end.

  • Key Features:

    • Reliable delivery with acknowledgment of received packets.

    • Reordering of messages when they arrive out of order.

    • Flow control to manage the rate of data transmission.

• UDP (User Datagram Protocol):

  • Connectionless protocol, lacking acknowledgment processes.

  • Suitable for real-time applications where speed is preferred over reliability.

  • Examples include DHCP for assigning IP addresses and TFTP for file transfers.

Use Cases for TCP and UDP

• TCP Protocol Examples:

  • HTTPS (Hypertext Transfer Protocol Secure):

    • Reliable data transfer for web browsers.

  • SSH (Secure Shell):

    • Encrypted terminal communication.

• UDP Protocol Examples:

  • DHCP:

    • Automatically assigns IP addresses without acknowledgment.

  • VoIP Traffic:

    • Maintains active communication without missed packet retransmissions.

Delivery Mechanism

• IP address serves as the delivery point akin to a mailing address.

• Each server has unique IP addresses with specific port numbers assigned to services/applications.

• Port Numbers:

  • Identify the specific service in the device (e.g., web traffic on port 80).

  • Well-known Ports:

    • HTTP: port 80

    • HTTPS: port 443

    • Email (SMTP): port 25

    • Time Protocol: port 123

• Port numbers help direct incoming traffic to the correct server application.

Client-Server Communication

• Client IP and port number must correspond to destination IP and port of the server.

• TCP Sessions:

  • Start with a source port established and directed toward the service port on the server.

• Temporary (Ephemeral) Ports:

  • Clients assign random source ports (e.g., 3000, 7100, etc.) for outgoing connections.

Importance of Port Numbers

• Essential for communication management and preventing confusion with services running on the same server IP address.

• Using the same well-known port numbers simplifies access to services.

• TCP port numbers can differ from UDP port numbers, allowing separate services on the same port number without conflicts.

Simultaneous Connections Example

• Example Configuration:

  • Client IP: 10001 sending traffic to

  • Server IP: 10002

  • Traffic Types:

    • Web traffic (TCP 80), VoIP (UDP 5004), Email (TCP 143).

  • Each traffic type maintains its own port source, ensuring proper routing and data integrity.