Ccna Study Notes

Chapter 1: Internetworking

Ccna Chinese Reading Notes

Cisco Certified Network Associate 640-801 icnd Course Notes

Chapter 1 Internetworking

Internetworking basic

 

Dividing a large network into several smaller networks is called network segments, which are completed by routers, switches, and bridges.

 

The possible causes of LAN congestion are:

1. Too many hosts exist in one broadcast domain)

2. broadcast storm

3. Multicast

4. low bandwidth

 

Routers usage in the Network

1. They do not forward broadcasts by default.

2. They can filter Networks Based on layer-3 (Network Layer) information.

 

Switches's main objective:

Improve LAN performance and provide more bandwidth to users

 

Collision domain: In Internet terminology, a device in a conflicting domain sends packets in a certain network segment, forcing all other devices in the network segment to pay attention to this packet. When different devices try to send packets at the same time, the network segment will cause conflicts and reduce network performance.

 

In a sense, bridges is equivalent to switches. The difference is that bridges only has two to four ports, while switches can have up to hundreds of ports, but in the same place, they can all split up a large number of conflicting domains, but they are still in a large broadcast domain. The task of dividing broadcast domains can be completed by routers.

 

Internetworking Models

In the early days, each network vendor had a private network, which was not easy to communicate with other manufacturers' networks. As a result, at the end of 1970s, the ISO organization created the OSI (Open System Interconnection) Reference Model.

 

The OSI reference model is used to help different manufacturers create network devices and software that can work with each other. The biggest feature of the model is layering. However, it is still a reference model rather than a physical model.

 

Advanced of refernce modles

The OSI reference model is a bit layered:

1. Allow multiple manufacturers to develop network standardization

2. allow communication between different types of network hardware and software

3. Prevent any previous changes from affecting other layers, and avoid interfering with the entire model.

 

The OSI reference model

OSI

 

 

Ccna Study Notes