CCNA - Chapter 1 notes and questions

[M.GRAYSON]

Chapter One - Internetworking

By the end of this chapter I should be able to:

-          Recognise the purpose and functions of various network devices such as Routers, Switches, Bridges and Hubs

-          Select the components required to meet a given network specification

-          Identify common applications and their impact on the network

-          Describe the purpose and basic operation of the protocols in the OSI and TCP/IP models

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Internetwork: You create an internetwork when you connect two or more networks via a router and configure a logical network addressing scheme with a protocol such as IP or IPv6

LAN: Local Area Network

Hub: Device that connects wires together

 

Some things that commonly cause LAN traffic congestion:

-          Too many hosts in a collision or broadcast domain

-          Broadcast storms

-          Too much multicast traffic

-          Low bandwidth

-          Adding hubs for connectivity to the network

-          A bunch of ARP broadcasts

Switches create separate collision domains within a single broadcast domain. Routers provide a separate broadcast domain for each interface.

You would use a bride in a network to reduce collision domains in your network. Doing this provides more bandwidth for users. And never forget that using hubs in your Ethernet network can contribute to congestion.

VLAN= Virtual LAN (Local Area Network)

OSI = Open Systems Interconnection

ISO = International Organisation for Standardisation

IOS = Internetworking Operating System

 

----------------------------------------------------------   OSI Model    ---------------------------------------

 

Application --Layer 7--	·         Provides a user interface
Presentation --Layer 6--	·         Presents data ·         Handles processing such as encryption
Session --Layer 5--	·         Keeps different applications’ data separate
Transport --Layer 4--	·         Provides reliable or unreliable delivery ·         Performs error correction before retransmit
Network --Layer 3--	·         Provides logical addressing, which routers use for path determination ·         Uses IP addresses
Data Link --Layer 2--	·         Combines packets into bytes and bytes into frames ·         Provides access to media using MAC address ·         Performs error detection not correction
Physical --Layer 1--	·         Moves bits between devices ·         Specifies voltage, wire speed, and pinout of cables

 

Network devices that operate on all seven layers of the OSI Model

-          Network Management Stations (NMSs)

-          Web and Application servers

-          Gateways

-          Servers

-          Network hosts

The Application layer works as the interface between actual application programs. This means end-user programs like Microsoft Word don’t reside at the applications layer, they interface with the Application layer protocols.

The term reliable networking can be used at the Transport layer. Reliable networking requires that acknowledgments, sequencing and flow control will all be used.

The purpose of flow control is to provide a way for the receiving device to control the amount of data sent by the sender.

The types of flow control are buffering, windowing, and congestion avoidance.

Windows are used to control the amount of outstanding, unacknowledged data segments.

 

------------------------------------------------- ---   Exam Essentials   --------------------------------------
 

Identify the Possible causes of LAN traffic congestion:



 

Describe the difference between a collision domain and a broadcast domain:



 

Differentiate a MAC address and an IP address and describe how and when each address type is used in a network:

 

 

 

Understand the difference between a hub, a bridge, a switch and a router:



 

Identify the functions and advantages of routers:


 

Differentiate connection-oriented and connectionless network services and describe how each is handled during network communications:


 

Define the OSI layers, explain the function of each, and describe how devices and networking protocols can be mapped to each layer: