4.0 Networking

4.1 Summarize the basics of networking fundamentals, including technologies, devices and protocols

  • Basics of configuring IP addressing and TCP/IP properties (DHCP, DNS)

    The Dynamic Host Configuration Protocol (DHCP) is a network configuration protocol that enables a server on an IP network to automatically assign an IP address to a computer from a predetermined range of numbers. The most essential information needed is an IP address, and a default route and routing prefix. DHCP controls the assignment of unique dynamic IP addresses and routing information, eliminating the manual task by a network administrator.

    The Domain Name System (DNS) is a hierarchical naming system for computers, services, or any resource connected to the Internet or a private network. Internet and TCP utilities such as telnet, FTP, and SMTP use DNS to translate computer host and domain names to their corresponding IP addresses. DNS allows you to type recognizable names into your Web browser and your computer will automatically find that address on the Internet. Address information is stored in several locations in a hierarchical structure.

  • Bandwidth and latency

    Bandwidth is described as the difference between the highest and the lowest frequencies in a specific range of frequencies. The range of frequencies is usually specified in hertz (cycles-per-second). The Federal Communications Commision (FCC) is in charge of allocating the bandwidth of various communication systems.

    Latency is a measure of time delay experienced in a system. In a packet-switched network, network latency is measured either one-way or round-trip. Round-trip latency is more often quoted, because it can be measured from a single point. Note that round trip latency excludes the amount of time that a destination system spends processing the packet. Many software platforms provide a service called ping that can be used to measure round-trip latency.

  • Status indicators

  • Protocols (TCP/IP, NETBIOS)

    The TCP/IP suite is a collection of internet protocols developed by the Department of Defense. Designed to permit communication among a variety of independent, multivendor systems, support is provided for a wide variety of protocols and services, including TCP, IP, UDP, ARP, and others, on many different types of media. TCP/IP is routable across more than one local area network (LAN). Named for it's two primary protocols, Transmission Control Protocol (TCP) and Internet Protocol (IP), TCP/IP provides end-to-end connectivity specifying how data should be formatted, addressed, transmitted, routed and received at the destination.

    TCP/IP has four abstraction layers, each with its own protocols. From lowest to highest, the layers are:

    1. The Link Layer (commonly Ethernet) contains communication technologies for a local network.
    2. The Internet Layer (IP) connects local networks, thus establishing internetworking.
    3. The Transport Layer (TCP) handles host-to-host communication.
    4. The Application Layer (for example HTTP) contains all protocols for specific data communications services on a process-to-process level (for example how a web browser communicates with a web server).

    The Network Input Output System (NetBIOS) protocol was originally developed for IBM and Microsoft to support broadband network communication in the small to medium sized local area network environment. It is a Session layer protocol in the OSI model that establishes and manages communication between computers. Data transport services for NetBIOS are provided by NetBEUI.

  • Full-duplex, half-duplex

    Full-duplex transmission is a two-way simultaneous transmission mode. On digital networks, two pairs of wires are necessary to complete the circuit. Analog circuits connected by modems require only one pair. The circuit bandwidth is divided into two frequencies, which allows simultaneous data flow in both directions.

    Half-duplex transmission is a two-way transmission, but only in one direction at a time. Half-duplex circuits use a signaling system yo indicate when one device is finished sending or receiving so the other device can access the line. Half-duplex transmissions are possible with a single, dual-wire cable such as twisted pair.

  • Basics of workgroups and domains

    A workgroup is a collection of users connected to the same network to share documents, applications, email and other system resources.

    A domain contains a group of individual computers or workgroups that can be accessed and administered with a common set of rules. Each domain exercises it's own control, but may be included in larger domains. Domains may also block outside traffic from accessing computers within the network, which adds an extra level of security.

  • Common ports: HTTP, FTP, POP, SMTP, TELNET, HTTPS

    • HTTP - TCP/80

      Hypertext Transfer Protocol (HTTP) is an application-level protocol used to request and deliver web pages between a server and browser. HTTP is the foundation of data communication for the World Wide Web.

      HTTP is typically implemented using TCP port 80.

    • FTP - TCP/21

      File Transfer Protocol (FTP) is a standard network protocol used to transfer files from one host to another host over a TCP-based network, such as the Internet. FTP is built on a client-server architecture and uses separate control and data connections between the client and server. Authentication is accomplished through the use of a clear-text sign-in protocol and is not considered to be secure.

      File Transfer Protocol first establishes, then maintains a control connection throughout the session over TCP port 21. Then a second connection is opened over TCP port 20 for data transfer.

    • POP - TCP/110

      File Transfer Protocol (FTP) is a standard network protocol used to transfer files from one host to another host over a TCP-based network, such as the Internet. FTP is built on a client-server architecture and uses separate control and data connections between the client and server. Authentication is accomplished through the use of a clear-text sign-in protocol and is not considered to be secure.

      POP3 mail retrieval typically uses TCP port 110 by default but may vary depending on provider.

    • SMTP - TCP/25

      Simple Mail Transfer Protocol (SMTP) is a reliable and efficient mail transport and delivery protocol that is capable of transporting outgoing email across multiple networks. SMTP requires a reliable data stream channel for transmission.

      SMTP typically uses TCP port 25

    • TELNET - TCP/23

      Short for Telecommunications network, TELNET is a text based interface protocol that provides an insecure remote access to other computers. Telnet uses a command line interface and can be accessed in Windows from the Start menu by clicking <Start>, <Run>, then by typing: telnet (somesite) 23. Port number 23 is the default port used by telnet, but is usually optional and often not required.

      TELNET typically uses TCP port 23.

    • HTTPS - TCP/443

      Hypertext Transfer Protocol Secure (HTTPS) is a combination of Hypertext Transfer Protocol (HTTP) with SSL/TLS protocol. It provides encrypted communication and secure identification of a network web server. HTTPS connections are often used for payment transactions on the World Wide Web and for sensitive transactions in corporate information systems. HTTPS uses port 443 by default.

      HTTPS is a lower level Application Layer protocol that typically uses TCP port 443 by default.

  • LAN / WAN

    A Local Area Network (LAN) is a network that connects computers in a workgroup, department, or building. A lan is usually controlled and maintained by a single organization. A LAN may include separate networks or subnets, many switches and routers but the entire LAN is under one administration. Simply speaking if you have a bunch of computers and you network them together by connecting them to a switch and give them a common addressing or network protocol scheme then you have a lan. This could also be called an intranet or interior network in that it is interior to that organization only.

    A WAN or wide are network is a communication system that interconnects LANs across wide geographical distances. It links the computers outside of an organization's properties (buildings or campus area) and crosses public areas that are regulated by local, national, or international authorities. It is also the network that is formed between you and your ISP or internet service provider.

  • Hub, switch and router

    A hub is a central concentration point for the attachment of wires from workstations in a network. A passive hub is no more than a connection point, possibly a wiring panel or punchdown block that offers no amplification of the signal, while an active hub is powered and will regenerate signals from one device to another. Commonly referred to as a "dumb repeater", communications received by a hub through one port are sent out, or repeated, to every other available port on the hub. Typically used in a star network topology, hubs operate at the Physical Layer (Layer 1) of the OSI model.

    A network switch or switching hub is a computer networking device that connects network segments or network devices. The term commonly refers to a multi-port network bridge that processes and routes data at the Data Link Layer (Layer 2) of the OSI model.

    Routers are OSI model Network Layer 3 switches that interconnect networks over local or wide areas and provide traffic control and filtering functions when more than one pathway exists between two end-points on the network. Some routers have the capability to connect networks with different physical media and translate between different network architectures.

  • Identify Virtual Private Networks (VPN)

    A Virtual Private Network (VPN) is a network technology that creates a secure network connection over a public network such as the Internet or a private network owned by a service provider. Large corporations, educational institutions, and government agencies use VPN technology to enable remote users to securely connect to a private network.

  • Basic class identification

    • A, B, C and D

    • Class A - 0-127
      Class B - 128 - 255
      Class C - 256 - 191
      Class D - 192 - 223

    • Public vs. Private

    • Public IP Addresses are visible to the public. When the public addresses are assigned, routes are programmed into the routers of the Internet so that traffic to the assigned public addresses can reach their locations.

      Private IP addresses can be used on a private network, but are not routable through the public Internet. The Internet Assigned Numbers Authority (IANA) has reserved three blocks of the IP address space for private internets.

      Private address ranges include:
      Class A - –
      Class B - -
      Class C - -

      More on Address Allocation for Private Networks