Networks have grown and developed over the past few decades with the aim of meeting increasingly complex human needs. Through technological sophistication the need for network resources can be interconnected to serve users.

The picture above is an illustration of the basic network. That a LAN is connected using a hub with the same cable is called a single broadcast domain network. So it needs configuration. Here are the causes of LAN traffic jams, such as:

1. Too much multicast traffic

2. Low bandwidth size

3. Too many hosts in a collision domain

4. Add a hub for connectivity to the network

The picture above shows the network segmented with a switch, the goal is to make each network segment connected to the switch have their own broadcast domain.

So the longer the router on the network will continue to grow as shown above. Where describe about the internet and each has a function in doing broadcast domains. Although routers can break up broadcast domains by default, routers can also break up crash / broadcast domains.

There are two advantages to using routers in your network:  They don’t forward broadcasts by default. They can filter the network based on layer 3, Network layer, information such as an  IP address.

Here are four ways a router functions in your network: Packet switching, Packet filtering , Internetwork communication, Path selection

Routers (layer3switch) use logical addressing and provide important capacity called packetswitching. It also provides packet filtering through access lists, when routers connect two / more shared networks and use logical addressing (IP or IPv6). Then will get internetwork to determine the best path choice. Furthermore the main purpose of the switch is to make the LAN function better, optimize performance, provide additional bandwidth to the user. The process is to switch frames from one port to another in an activated network.

Keep in mind that a switch creates a collision domain separately in one broadcast domain, where the router provides a separate broadcast domain for each interface. Then the user will use a networked bridge to reduce collisions in a broadcast domain, so an increase in bandwidth is required for the user.

The picture above shows the network process on all internetwork devices using bridges / switches for network segmentation.

VLANs are used as broadcast domain breakers at layer 2.

2. Internet Models

History explains when the network was first formed, computers can only communicate with the same manufacturer. Then came the Open Systems Interconnection (OSI) reference model created by the International Organization for Standardization (ISO) in order to break through this barrier.

Layered approach

The OSI model is hierarchical. In this case a model for the development of devices is needed as a reference for the communication process in order to determine the functions that must be completed at a particular layer.

The advantage of the reference model

1. Divide the network communication process into simple components, component development facilities, design, and problem solving

2. Allows the development of multivendors through standardization of network components

3. Encourage industry standardization at each layer of the model.

4. Allows network hardware and software to communicate.

5. Prevent changes between layers to accelerate development

The OSI reference model OSI has seven different layers and is divided into two groups. The top three layers are determinants of the application and the bottom two are the communication between users.

1. Physical Layer

The physical layer is responsible for the transmission and reception of unstructured raw data between the device and the physical transmission media. Serves to convert digital bits into electrical, radio, or optical signals.

2. Data Link Layer

This layer provides node-to-node data transfer on the link between two directly connected nodes. Detect and correct errors that may occur in the physical layer. The goal is to define protocol

3. Network Layer

The network layer provides rules for sending packets from one node to another that is connected in a “different network”.

4. Transport Layer

This layer provides service facilities, functions, in sending sequence data from source to destination by maintaining service quality. This layer controls data flow and errors. Also serves to ensure the success of data transmission. Segmentation is the process of dividing long messages into smaller messages.

5. Session Layer

The session layer controls the connections between computers.

6. Pressentation Layer

This layer serves to determine the usability of the layer and application, using different syntax. This layer translates between application and network format. This layer transforms data into data that an application will receive. This layer is also called the syntax layer.

7. Application Layer

The application layer consists of various protocols. Is the layer closest to the user, so as a layer that interacts directly with the software. The aim is to implement the communication tool component. Other functions are identifying communication partners, determining the availability of resources, and synchronizing communications.

Connection-Oriented Communication

In order for transportation to occur, the device makes communication between remote devices called a three-way handshake arrangement. The process starts from the “Connection agreement” segment asking for synchronization (SYN). The next segment recognizes (ACK) requests, creates connection parameters, and synchronizes in two directions. After that the last segment will indicate synchronization of the connection has been received and the connection has been established.

Flow Control

Served to ensure data integrity at the transport layer. The protocol involved ensures that this can be achieved if:

1 segment submitted is recognized by the sender after receipt,

2 unrecognized segments will be retransmitted

3 segments are arranged in the correct order when arriving to their destination

4. Data flow that can be managed is maintained.

Services are considered to be connection-oriented if they have the following characteristics:

1. Virtual circuit / three way handshake is set

2 use sequencing

3. Using acknowledgments

4. Use flow control


Windows is used to control the number of data segments, by controlling how much information is transferred between ends, while other protocols measure information based on the number of packets, TCP / IP in the number of bytes. For example workstations.


Data transmission ensures the integrity of the data flow that is sent to ensure that data is not duplicated or lost. Transport layers work together and separate data from different applications called multiplexing. Occurs when the client is connected to the server.

Network layer

This layer manages device addressing, tracks device location, and determines the best way to move data.

The picture above shows how the router works in an internetwork.

The following are some router characteristics that should not be forgotten:

1Router, by default it will not forward any broadcast / multicast packets

2router uses the network layer logical address header to determine the next-hop router to forward to other packets

3router can use the access list created by the admin to control the security of packet communications

4router provides functions that bridge between layers

5 Layer 3 devices (routers) can provide connections between LAN / VLAN

6Router can provide quality of service (QoS) for certain types of network traffic.

Data Link Layer

This layer provides physical data transmission and handles network topology error notifications and flow control. Ensuring communication by formatting customized messages. At the IEEE Ethernet Data Link layer has two layers:

1.MAC (Media Access Control)

Determine how packages are placed on the media.

2. LLC (Logical Link Control)

To identify network layer protocols and encapsulate them.

Switches and Bridges at the Data Link Layer

Layer 2 switching is considered a hardware-based bridge using application-specific integrated circuit (ASIC) devices. With gigabit speeds, at low latency. Latency is the time measured when a frame exits a port to another port.

Physical Layer

The physical layer determines the electrical, mechanical, procedural and functional requirements for activating, maintaining, and deactivating the physical connections between end systems. This layer also identifies the interface between the data terminal equipment (DTE) and data communication equipment (DCE). DCE as a service provider, DTE as an attached device. DTE services are accessed via modem // data service unit (CSU / DSU).

Hub in the Physical Layer

Hub as a multi-port repeater. Hubs do not control traffic during data transmission. There is an Ethernet network to run topologies so that signals can be sent between ends


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