During this lesson you will be introduced to the components that make up a network as well as knowing the components of a network, several different models and topologies will also be discussed.
By the end of this lesson, you will be able to:
- Describe TCP/IP model and the relationship with the OSI model.
- Describe the items that exist on a network.
- Explain the concept of host virtualization.
- Compare the various network models and topologies.
The Transmission Control Protocol and Internet Protocol (TCP/IP) Model consists of four layers. It is important to remember that the TCP/IP is a two way model (up and down data flow).
Figure 1 TCP/IP Model
1. Network Interface: The Network Interface layer is also known as the Link Layer. It describes how a host accesses the network. For example, copper wire (Ethernet), fiber optics, or radio spectrum (wireless).
2. Internet: The Internet layer determines the routing decisions based on the protocol being used and the information in the data packet.
3. Transport: The Transport layer ensures protocols are followed in host to host communications.
4. Application: The Application layer is responsible for the protocol needed for an application to run. It specifies which ports and sockets are needed for the application.
A good way to think about the TCP/IP model is a condensed version of the Open Systems Interconnection (OSI) model, where some layers are combined into one. See Figure 2 to review the TCP/IP layers and how they coincide with the four OSI layers: 1) Data Physical Link, 2) Network, 3) Transport, and 4) Application Presentation Session.
Figure 2 OSI Data Flow: Representations of TCP/IP and OSI Layers
Anatomy of a Computer Network
In the following section you will learn about components that comprise a computer network. A is a device connected to a network is a host. A host serves some kind of purpose on the network no matter how unsophisticated.
A host can be a number of things: computer workstation, phone (VoIP), printer, server, router, switch (multilayer), hub, bridge, and a repeater.
A computer workstation can be a Desktop or Laptop computer commonly used for personal use. Their purpose can be business, recreational or both. An organization may have several computer workstations “attached” or running on their network.
A VoIP telephone uses an Ethernet connection in order to place and receive calls. This functionality is different from traditional phones systems which use Plain Old Telephones Service (POTS) lines.
Network printers allow for multiple users within a organization to print. This is different from local printers where only the person attached via a serial cable could print at a time.
Servers are computational systems with expanded resources needed to provide service to clients (i.e. computer workstations) on a network. They will typically have more memory, hard drive space, processor cores, as well as advanced software and interface cards.
Routers are used to direct data traffic through different network segments and are often located near the network perimeter. Routers are also used to pass data packets through the internet to a given destination. The tall beige router with the green tag is one of the first routers ever developed for ARPANET. Other more modern and Wireless Routers are seen here as well. In data centers or highly connected environments, it is common to see routers in a network rack.
The network switch is used to interconnect multiple hosts on a network. A switch has some intelligence built into it. A switch can map the media access control (MAC) addresses of hosts connected to its ports. When data comes into the switch, it can direct that traffic to a specific port where the destined host is located.
A bridge joins two separate networks into one. This functionality can be accomplished using a network switch.
A network hub is also used to connect host on a network, however they are not used in highly active environments. Hubs have no intelligence built into them and can often drop packets in a highly active networks. Hubs have one collision domain, meaning no matter how many devices you have connected, only one is allowed to use the media at one time. Hosts connected to a hub may try to send and receive at the same time, which will create a collision and data packets can get “lost” or drop.
A wireless repeater is used when a wireless (RF) signal is weak and needs to be amplified. The wireless repeater extends the range of a wireless signal. For example, if a wireless signal has a range of 50 meters and you were 75 meters away, you could use a wireless repeater to connect.
A virtual switch can shape and control network traffic, and employ protective measures against other virtual machines. Virtual switches are often used within virtualization products like Hyper V and VMware.
Offsite hosting is similar to a hosted environment where someone else manages your servers on their network. Whereas, in an onsite environment your organization supplies the network resources, servers and employees needed to manage the equipment.
Organizations may consider using offsite hosting for a lower cost vs. hosting onsite which will have higher costs and overhead expenses. Review the following list of key facts that are important to be aware of.
Network Models and Topologies
There are network models and topologies which describe how computational systems communicate and interconnect with each other. The most popular network model is the Client – Server model.
The Client – Server model describes when a computer system processes request from other computer systems and is used for large networks, centralized administration and security, and provides performance benefits.
Figure 3 Client- Server Model
The other well-known network model is the Peer-to-Peer model. The Peer-to-Peer model describes when each computer system on the network can request or processes request from other computers.
The benefit this model provides for large networks are performance, security, and centralized administration. A Peer-to-Peer model is easy to set up, used for small networks, and decentralizes administration.
Figure 4 Peer-to-Peer Model
Network topologies can be viewed as a “MAP” of the network. It shows how the nodes interconnect. The Institute of Electrical and Electronic Engineers (IEEE) set the standards for computer network technology. There are five topologies identified below: Bus, Token Ring, Star, Mesh and Hybrid.
1. In Bus topology all network components communicate across one media segment. Bus topology can be viewed like an outdoor clothes line. If the line breaks all hosts on that line lose the ability to communicate. (IEEE 802.3)
Figure 5 Bus Topology: Black lines indicate endpoints.
2. In Token Ring topology all network components communicate by passing a token to access the network. The topology is described as a ring. Token Ring topology has the 802.5 IEEE standard. Token Ring topology is a logical ring; it is not implemented as a physical ring. Multi-station Access Units (MAU’s) installed within a Hub provide the effect of the ring topology.
Figure 6 Token Ring Topology
3. In Star topology all network components are interconnected through a hub or switch.
Figure 7 Star Topology
4. In Mesh topology all network components are directly connected through multiple links.
Figure 8 Mesh Topology
5. Hybrid topology is a combination of any two network topologies. It is common for the Star and Mesh topologies to be combined.
Area Networks Types
There are various area networks that describe the scope or boundary of a network. The following images represent examples of several types of area network layouts.
Figure 9 LAN – Local Area Network (i.e. Office Building)
Figure 10 WLAN – Wireless Area Network (i.e. Wireless LAN)
Figure 11 CAN – Campus Area Network (i.e. University Campus)
Figure 12 MAN – Metropolitan Area Network (i.e. City limits)
Figure13 WAN – Wide Area Network (i.e. New York to Chicago)
This lesson introduced the physical and virtual network components. The information covered various objects which will help when discussing models and topologies.
The TCP/IP model along with two common network models were described, the Client – Server and Peer-to-Peer network models. The lesson explained the models and relating them to physical systems helped one see how each host, work station, makes-up a network.
Network topologies and types were also discussed to provide an idea of the various ways a network can be constructed and the scope or range they have.