chapter3 semster one -discovery
TRANSCRIPT
-
8/3/2019 Chapter3 Semster One -Discovery
1/89
2007 Cisco Systems, Inc. All rights reserved. Cisco Public
ITE PC v4.0
Chapter 1 1
Connecting to the
Network
Networking for Home and Small Businesses
Chapter 3
-
8/3/2019 Chapter3 Semster One -Discovery
2/89
ITE PC v4.0
Chapter 1 2 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Objectives Explain the concept of networking and the benefits of
networks.
Explain the concept of communication protocols.
Explain how communication occurs across a localEthernet network.
Describe Access layer devices and communicationmethods on a local Ethernet network.
Describe Distribution layer devices andcommunication methods across networks.
Plan, implement, and verify a local network.
-
8/3/2019 Chapter3 Semster One -Discovery
3/89
ITE PC v4.0
Chapter 1 3 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Networking and Its Benefits Define the term network and identify various types of
networks
-
8/3/2019 Chapter3 Semster One -Discovery
4/89
ITE PC v4.0
Chapter 1 4 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Networks
Communication technology in the 1990s, and before,required separate, dedicated networks for voice, video andcomputer data communications.
Each of these networks required a different type of devicein order to access the network. Telephones, televisions,and computers used specific technologies and differentdedicated network structures, to communicate.
People can now watch live video broadcasts on their
computers, make a telephone call over the Internet, orsearch the Internet using a television. Converged networksmake this possible.
-
8/3/2019 Chapter3 Semster One -Discovery
5/89
ITE PC v4.0
Chapter 1 5 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Network Benefits
Networks range from simple networks consisting of twocomputers, to networks connecting millions of devices.Networks installed in small offices, or homes and homeoffices, are referred to as SOHO networks.
These enable sharing of resources, such as printers,
documents, pictures and music between a few localcomputers.
In business, large networks can be used to advertise andsell products, order supplies, and communicate with
customers. Networks allow for rapid communication such as email
and instant messaging, and provide consolidation,storage, and access to information on network servers.
-
8/3/2019 Chapter3 Semster One -Discovery
6/89
ITE PC v4.0
Chapter 1 6 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Networking and Its Benefits Describe the benefits of computer networking and list
examples of small, medium and large networks
-
8/3/2019 Chapter3 Semster One -Discovery
7/89ITE PC v4.0
Chapter 1 7 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Networking and Its Benefits
Business and SOHO networks usually provide a sharedconnection to the Internet.
The Internet is considered a "network of networks"because it is literally made up of thousands of networks
that are connected to each other.
Here are other uses of a network and the Internet:
Sharing music and video files
Research and on-line learning
Chatting with friends
Planning vacations
Purchasing gifts and supplies
-
8/3/2019 Chapter3 Semster One -Discovery
8/89ITE PC v4.0
Chapter 1 8 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Networking and Its Benefits Define the components of an Information network
-
8/3/2019 Chapter3 Semster One -Discovery
9/89ITE PC v4.0
Chapter 1 9 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Network components
There are many components that can be part of anetwork, for example personal computers, servers,networking devices, and cabling.
These components can be grouped into four main
categories:
Hosts
Shared peripherals
Networking devicesNetworking media
-
8/3/2019 Chapter3 Semster One -Discovery
10/89ITE PC v4.0
Chapter 1 10 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Network components
Hosts are devices that send and receivemessages directly across the network.
Shared peripherals are not directly connected to
the network, but instead are connected to hosts. The network devices, as well as networking
media, are used to interconnect hosts.
-
8/3/2019 Chapter3 Semster One -Discovery
11/89ITE PC v4.0
Chapter 1 11 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Networking and Its Benefits Describe the Roles of computers on a network
Clients and servers
-
8/3/2019 Chapter3 Semster One -Discovery
12/89ITE PC v4.0
Chapter 1 12 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Roles of computers on a network
All computers connected to a network that participate directlyin network communication are classified as hosts.
Hosts can send and receive messages on the network. Inmodern networks, computer hosts can act as a client, aserver, or both. Its the software installed on the computerthat determines which role the computer plays.
Servers are hosts that have software installed that enablethem to provide information, like email or web pages, to otherhosts on the network. (A single computer can run multiple
types of server software. ) Clients are computer hosts that have software installed that
enable them to request and display the information obtainedfrom the server. (A single computer can also run multipletypes of client software.)
-
8/3/2019 Chapter3 Semster One -Discovery
13/89
ITE PC v4.0
Chapter 1 13 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Peer-to-Peer network
Client and server software usually runs on separatecomputers, but it is also possible for one computer tocarry out both roles at the same time.
In small businesses and homes, many computers
function as the servers and clients on the network. Thistype of network is called a peer-to-peer network.
The simplest peer-to-peer network consists of twodirectly connected computers using a wired or
wireless connection.Multiple PCs can also be connected to create alarger peer-to-peer network but this requires a networkdevice, such as a hub, to interconnect the computers.
-
8/3/2019 Chapter3 Semster One -Discovery
14/89
ITE PC v4.0
Chapter 1 14 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Networking and Its Benefits Build computer peer-to-peer network and verify
-
8/3/2019 Chapter3 Semster One -Discovery
15/89
ITE PC v4.0
Chapter 1 15 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Network Topologies Differentiate between logical and physical topologies,
and explain how networks are represented graphically
-
8/3/2019 Chapter3 Semster One -Discovery
16/89
ITE PC v4.0
Chapter 1 16 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Network Topologies
Wired networks require lots of cabling and networkdevices to provide connectivity for all network hosts.
When networks are installed, a physical topology map iscreated to record where each host is located and how it is
connected to the network. The physical topology map also shows where the wiring is
installed and the locations of the networking devices thatconnect the hosts.
In addition to the physical topology map, it is sometimesnecessary to also have a logical view of the networktopology. A logical topology map groups hosts by howthey use the network, no matter where they are physically
located.
-
8/3/2019 Chapter3 Semster One -Discovery
17/89
ITE PC v4.0
Chapter 1 17 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Communication Protocols Explain the concept of communication in terms of
source, destination and channel
-
8/3/2019 Chapter3 Semster One -Discovery
18/89
ITE PC v4.0
Chapter 1 18 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Communication Concept
The primary purpose of any network is to provide amethod to communicate information.
All communication begins with a message, orinformation, that must be sent from one individual or
device to another.
All communication methods have three elements incommon.
The first of these elements is the messagesource, or sender. Message sources are people, orelectronic devices, that need to communicate amessage to other individuals or devices.
-
8/3/2019 Chapter3 Semster One -Discovery
19/89
ITE PC v4.0
Chapter 1 19 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Communication Concept
The second element of communication is thedestination, or receiver, of the message. Thedestination receives the message and interprets it.
A third element, called a channel, provides the
pathway over which the message can travel fromsource to destination.
In any conversation between two people, there aremany rules, or protocols, that the two must follow inorder for the message to be successfully deliveredand understood.
-
8/3/2019 Chapter3 Semster One -Discovery
20/89
ITE PC v4.0
Chapter 1 20 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Communication Concept
Among the protocols for successful humancommunication are:
Identification of sender and receiver
Agreed-upon medium or channel (face-to-face,
telephone, letter, photograph)
Appropriate communication mode (spoken,written, illustrated, interactive or one-way)
Common languageGrammar and sentence structure
Speed and timing of delivery
-
8/3/2019 Chapter3 Semster One -Discovery
21/89
ITE PC v4.0
Chapter 1 21 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Communication Protocols Explain the need for rules and protocols in order for
communication to occur
-
8/3/2019 Chapter3 Semster One -Discovery
22/89
ITE PC v4.0
Chapter 1 22 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Communication Protocols
Protocols are specific to the characteristics of the source,channel and destination of the message.
Protocols define the details of how the message istransmitted, and delivered. This includes issues of:
Message format
Message size
Timing
Encapsulation
Encoding
Standard message pattern
-
8/3/2019 Chapter3 Semster One -Discovery
23/89
ITE PC v4.0
Chapter 1 23 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Communication Protocols
Explain the concept of encoding in relation to humancommunication
-
8/3/2019 Chapter3 Semster One -Discovery
24/89
ITE PC v4.0
Chapter 1 24 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Message Encoding
One of the first steps to sending a message isencoding it. Written words, pictures, and spokenlanguages each use a unique set of codes,sounds, gestures, and/or symbols to represent the
thoughts being shared. Encoding is the process of converting thoughts into
the language, symbols, or sounds, fortransmission.
Decoding reverses this process in order to interpretthe thought.
-
8/3/2019 Chapter3 Semster One -Discovery
25/89
ITE PC v4.0
Chapter 1 25 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Message Encoding
Encoding also occurs in computer communication.Encoding between hosts must be in an appropriateform for the medium.
Messages sent across the network are first
converted into bits by the sending host. Each bit isencoded into a pattern of sounds, light waves, orelectrical impulses depending on the networkmedia over which the bits are transmitted.
The destination host receives and decodes thesignals in order to interpret the message.
-
8/3/2019 Chapter3 Semster One -Discovery
26/89
ITE PC v4.0
Chapter 1 26 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Message Formatting When a message is sent from source to destination,
it must use a specific format or structure.
Message formats depend on the type of messageand the channel that is used to deliver the message.
The process of placing one message format (theletter) inside another message format (theenvelope) is called encapsulation.
De-encapsulation occurs when the process isreversed by the recipient and the letter is removedfrom the envelope.
-
8/3/2019 Chapter3 Semster One -Discovery
27/89
ITE PC v4.0
Chapter 1 27 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Message Formatting
Each computer message is encapsulated in aspecific format, called a frame, before it is sent overthe network.
A frame acts like an envelope; it provides theaddress of the intended destination and the addressof the source host.
-
8/3/2019 Chapter3 Semster One -Discovery
28/89
ITE PC v4.0
Chapter 1 28 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Communication Protocols
Explain the concept of message formatting andencapsulation
-
8/3/2019 Chapter3 Semster One -Discovery
29/89
ITE PC v4.0
Chapter 1 29 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Communication Protocols
Explain that messages have size restrictions dependingon the channel used
-
8/3/2019 Chapter3 Semster One -Discovery
30/89
ITE PC v4.0
Chapter 1 30 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Message size
An individual conversation may be made up of manysmaller sentences to ensure that each part of themessage is received and understood.
Likewise, when a long message is sent from onehost to another over a network, it is necessary tobreak the message into smaller pieces.
The rules that govern the size of the pieces, or
frames, communicated across the network are verystrict. They can also be different, depending on thechannel used. Frames that are too long or too shortare not delivered.
-
8/3/2019 Chapter3 Semster One -Discovery
31/89
ITE PC v4.0
Chapter 1 31 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Timing and Access methods
Explain the concept of timing and access methods inrelation to human communication
Access Method
Access Method determines when someone isable to send a message. These timing rules arebased on the environment.
Therefore , it is necessary for computers todefine an access method. Hosts on a networkneed an access method to know when to beginsending messages and how to respond whenerrors occur.
-
8/3/2019 Chapter3 Semster One -Discovery
32/89
ITE PC v4.0
Chapter 1 32 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Timing and Access methods
Flow Control
Timing also effects how much information can besent and the speed that it can be delivered.
In network communication, a sending host can
transmit messages at a faster rate than thedestination host can receive and process. Sourceand destination hosts use flow control to negotiatecorrect timing for successful communication.
Response Timeout
Hosts on the network have rules that specify howlong to wait for responses and what action to takeif a response timeout occurs.
-
8/3/2019 Chapter3 Semster One -Discovery
33/89
ITE PC v4.0
Chapter 1 33 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Communication Protocols
Explain standard message patterns in relation tohuman communication
Unicast
Multicast
Broadcast
-
8/3/2019 Chapter3 Semster One -Discovery
34/89
ITE PC v4.0
Chapter 1 34 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Message Patterns
A one-to-one message pattern is referred to as aunicast, meaning that there is only a single destinationfor the message.
When a host needs to send messages using a one-to-
many pattern, it is referred to as a multicast. Multicastingis the delivery of the same message to a group of hostdestinations simultaneously.
If all hosts on the network need to receive the messageat the same time, a broadcast is used. Broadcastingrepresents a one-to-all message pattern.
Additionally, hosts have requirements for acknowledgedversus unacknowledged messages.
-
8/3/2019 Chapter3 Semster One -Discovery
35/89
ITE PC v4.0
Chapter 1 35 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Communication Protocols
Relate human communications concepts of messages,unit sizes, timing, encapsulation, encoding andstandard message patterns to the term protocol .
-
8/3/2019 Chapter3 Semster One -Discovery
36/89
ITE PC v4.0
Chapter 1 36 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Protocols and Importance
All communication, both human and computer, isgoverned by pre-established rules, or protocols.These protocols are determined by the characteristicsof the source, channel and destination.
Protocols are especially important on a local network.In a wired environment, a local network is defined asan area where all hosts must "speak the samelanguage" or in computer terms "share a common
protocol".
-
8/3/2019 Chapter3 Semster One -Discovery
37/89
ITE PC v4.0
Chapter 1 37 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Protocols and Importance
The most common set of protocols used on localwired networks is Ethernet.
The Ethernet protocol defines many aspects ofcommunication over the local network, including:
message format, message size, timing, encoding,and message patterns.
-
8/3/2019 Chapter3 Semster One -Discovery
38/89
ITE PC v4.0
Chapter 1 38 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Importance of standardization
In the early days of networking, each vendor used their
own, proprietary methods of interconnecting networkdevices and networking protocols. Equipment from onevendor could not communicate with equipment fromanother.
Standards are beneficial to networking in many ways:
Facilitate design
Simplify product development
Promote competitionProvide consistent interconnections
Facilitate training
Provide more vendor choices for customers
-
8/3/2019 Chapter3 Semster One -Discovery
39/89
ITE PC v4.0
Chapter 1 39 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Protocols
There is no official local networking standard protocol,but over time, one technology, Ethernet, has becomemore common than the others. It has become a defacto standard.
The committee responsible for the Ethernet standardsis 802.3.
Since the creation of Ethernet in 1973, standards have
evolved for specifying faster and more flexible versionsof the technology. This ability for Ethernet to improveover time is one of the main reasons that it hasbecome so popular.
-
8/3/2019 Chapter3 Semster One -Discovery
40/89
ITE PC v4.0
Chapter 1 40 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Communication Across a Local EthernetNetwork
Physical addressing identifies Source, Destination andChannel on an Ethernet Network
-
8/3/2019 Chapter3 Semster One -Discovery
41/89
ITE PC v4.0
Chapter 1 41 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Physical Addressing
All communication requires a way to identify thesource and destination.
On Ethernet networks, a method exists for identifyingsource and destination hosts. Each host connected
to an Ethernet network is assigned a physicaladdress which serves to identify the host on thenetwork.
Every Ethernet network interface has a physicaladdress assigned to it when it is manufactured. Thisaddress is known as the Media Access Control(MAC) Address. The MAC address identifies eachsource and destination host on the network.
-
8/3/2019 Chapter3 Semster One -Discovery
42/89
ITE PC v4.0
Chapter 1 42 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Communication Across a Local EthernetNetwork
Describe some of the basic characteristics of Ethernetfor communicating across the channel
-
8/3/2019 Chapter3 Semster One -Discovery
43/89
ITE PC v4.0
Chapter 1 43 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Ethernet Communication
The Ethernet protocol standards define many aspectsof network communication including frame format,frame size, timing and encoding.
When messages are sent between hosts on an
Ethernet network, the hosts format the messages intothe frame layout that is specified by the standards.
Frames are also referred to as Protocol Data Units(PDUs).
-
8/3/2019 Chapter3 Semster One -Discovery
44/89
ITE PC v4.0
Chapter 1 44 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Ethernet Communication
The format for Ethernet frames specifies the location ofthe destination and source MAC addresses, andadditional information including:
Preamble for sequencing and timing
Start of frame delimiter
Length and type of frame
Frame check sequence to detect transmission
errors.
-
8/3/2019 Chapter3 Semster One -Discovery
45/89
ITE PC v4.0
Chapter 1 45 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Communication Across a Local EthernetNetwork
Describe the need for a hierarchical design in anEthernet Network
-
8/3/2019 Chapter3 Semster One -Discovery
46/89
ITE PC v4.0
Chapter 1 46 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Ethernet Network hierarchical design
On an Ethernet network, the host MAC address issimilar to a person's name.
A MAC address indicates the individual identityof a specific host, but it does not indicate where
on the network the host is located. If all hosts on the Internet (over 400 million of them)
were each identified by only their unique MACaddress, imagine how difficult it would be to locate
a single one.
-
8/3/2019 Chapter3 Semster One -Discovery
47/89
ITE PC v4.0
Chapter 1 47 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Ethernet Network hierarchical design
Ethernet technology generates a large amount ofbroadcast traffic in order for hosts to communicate.
Broadcasts are sent to all hosts within a singlenetwork
Broadcasts consume bandwidth and slow networkperformance. Imagine what would happen if themillions of hosts attached to the Internet were all inone Ethernet network and were using broadcasts!
It is better to divide larger networks into smaller,more manageable pieces and one way to dividelarger networks is to use a hierarchical designmodel.
-
8/3/2019 Chapter3 Semster One -Discovery
48/89
ITE PC v4.0
Chapter 1 48 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Hierarchical design
Hierarchical design is used to group devices intomultiple networks organized in a layered approach, thisallows local traffic to remain local. Only traffic that isdestined for other networks is moved to a higher layer.
It provides increased efficiency, optimization offunction, and increased speed.
The hierarchical design has three basic layers:
Access Layer - to provide connections to hosts in a localEthernet network.
Distribution Layer - to interconnect the smaller local networks.
Core Layer - a high-speed connection between distributionlayer devices.
-
8/3/2019 Chapter3 Semster One -Discovery
49/89
ITE PC v4.0
Chapter 1 49 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Communication Across a Local EthernetNetwork
Explain the purpose of a logical network address as thelocation of a host on a Network (source anddestination)
-
8/3/2019 Chapter3 Semster One -Discovery
50/89
ITE PC v4.0
Chapter 1 50 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Logical addressing With the hierarchical design, there is a need for a logical
addressing scheme that can identify the location of a host.
This is the Internet Protocol (IP) addressing scheme.
On a host, the MAC address does not change; it is
physically assigned to the host NIC and is known as thephysical address. The physical address remains the sameregardless of where the host is placed on the network.
The IP address is similar to the address of a person. It isknown as a logical address because it is assignedlogically based on where the host is located. The IPaddress, or network address, is assigned to each host bya network administrator based on the local network.
-
8/3/2019 Chapter3 Semster One -Discovery
51/89
ITE PC v4.0
Chapter 1 51 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
IP addresses
IP addresses contain two parts.
One part identifies the local network. Thenetwork portion of the IP address will be thesame for all hosts connected to the same localnetwork.
The second part of the IP address identifies theindividual host. Within the same local network, thehost portion of the IP address is unique to eachhost.
-
8/3/2019 Chapter3 Semster One -Discovery
52/89
ITE PC v4.0
Chapter 1 52 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Access Layer Devices and CommunicationMethods
Describe the Purpose of the Access Layer and how itis used within an Ethernet Network
-
8/3/2019 Chapter3 Semster One -Discovery
53/89
ITE PC v4.0
Chapter 1 53 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Access Layer
IP traffic is managed based on the characteristics anddevices associated with each of the three layers:Access, Distribution and Core. The IP address is usedto determine if traffic should remain local or be movedup through the layers of the hierarchical network.
Access Layer
The Access Layer provides a connection point for enduser devices to the network and allows multiple hosts to
connect to other hosts through a network device, usuallya hub or switch.
The Access Layer is the most basic level of the network.It is the part of the network in which people gain access toother hosts and to shared files and printers
-
8/3/2019 Chapter3 Semster One -Discovery
54/89
ITE PC v4.0
Chapter 1 54 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Access Layer Devices and CommunicationMethods
Describe the function of a Hub and how it operateswithin an Ethernet Network
-
8/3/2019 Chapter3 Semster One -Discovery
55/89
ITE PC v4.0
Chapter 1 55 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Function of Hubs
A hub is one type of networking device that is installedat the Access Layer of an Ethernet network.
Hubs are simple multiple port devices that are used toconnect hosts to the network. They do not have the
necessary electronics to decode the messages sentbetween hosts on the network, therefore they cannotdetermine which host should get any particularmessage.
A hub simply accepts electronic signals from one portand regenerates (or repeats) the same message out allof the other ports.
-
8/3/2019 Chapter3 Semster One -Discovery
56/89
ITE PC v4.0
Chapter 1 56 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Function of Hubs
A NIC on a host accepts messages only addressed to thecorrect MAC address. Hosts ignore messages that are notaddressed to them.
Only one message can be sent through an Ethernet hub at
a time. It is possible for two or more hosts to attempt tosend a message at the same time, if this happens, theelectronic signals that make up the messages collide witheach other at the hub.
A collision causes the messages to become garbled andunreadable by the hosts. The area of the network where ahost can receive a garbled message resulting from acollision is known as a collision domain.
It is necessary to limit the size of a collision domain.
-
8/3/2019 Chapter3 Semster One -Discovery
57/89
ITE PC v4.0
Chapter 1 57 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Access Layer Devices and CommunicationMethods
Describe the function of switches and how they areused in an Ethernet network
-
8/3/2019 Chapter3 Semster One -Discovery
58/89
ITE PC v4.0
Chapter 1 58 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Function of switches
An Ethernet switch is a device that is used at theAccess Layer. A switch connects multiple hosts to thenetwork, but unlike a hub, a switch can forward amessage to a specific host.
When a host sends a message to another host on theswitch, the switch accepts and decodes the frames toread the physical (MAC) address portion of themessage.
A table in the switch, called a MAC address table,contains a list of all of the active ports and the hostMAC addresses that are attached to them. When amessage is sent between hosts, the switch checks to
see if the destination MAC address is in the table.
-
8/3/2019 Chapter3 Semster One -Discovery
59/89
ITE PC v4.0
Chapter 1 59 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Function of switches
The MAC address table is dynamically updatedeach time a new source MAC address is read bythe switch. In this way, a switch quickly learns theMAC addresses of all attached hosts.
How does it learn the addresses? A switch buildsthe MAC address table by examining the sourceMAC address of each frame that is sent betweenhosts. When a new host sends a message or
responds to a flooded message, the switchimmediately learns its MAC address and the port towhich it is connected.
-
8/3/2019 Chapter3 Semster One -Discovery
60/89
ITE PC v4.0
Chapter 1 60 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Access Layer Devices and CommunicationMethods
Broadcast Domains and broadcasts using hubs andswitches
-
8/3/2019 Chapter3 Semster One -Discovery
61/89
ITE PC v4.0
Chapter 1 61 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Broadcast Messaging
When hosts are connected using either a hub or aswitch, a single local network is created. Within thelocal network it is often necessary for one host to beable to send messages to all the other hosts at thesame time.
This can be done using a message known as abroadcast.
Remember a message can only contain onedestination MAC address. So, how is it possible for a
host to contact every other host on the local networkwithout sending out a separate message to eachindividual MAC?
-
8/3/2019 Chapter3 Semster One -Discovery
62/89
ITE PC v4.0
Chapter 1 62 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Broadcast Messaging
To solve this problem, broadcast messages are sent toa unique MAC address that is recognized by all hosts.This broadcast MAC address is actually a 48-bitaddress made up of all ones.
The broadcast MAC address in hexadecimal notation isFFFF.FFFF.FFFF. Each F in the hexadecimal notationrepresents four ones in the binary address.
When a host sends a broadcast message, hubs andswitches forward the message to every connected host
within the same local network. For this reason, a localnetwork is also referred to as a broadcast domain.
-
8/3/2019 Chapter3 Semster One -Discovery
63/89
ITE PC v4.0
Chapter 1 63 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
MAC and IP addresses
On a local Ethernet network, a NIC only accepts aframe if the destination address is either the broadcastMAC address, or corresponds to the MAC address ofthe NIC, yet most network applications, however, relyon the logical destination IP address to identify the
location of the servers and clients.
If a sending host only has the logical IP address of thedestination host? How does the sending host determinewhat destination MAC address to place within theframe?
The sending host can use an IP protocol called addressresolution protocol (ARP) to discover the MAC address
of any host on the same local network
-
8/3/2019 Chapter3 Semster One -Discovery
64/89
ITE PC v4.0
Chapter 1 64 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Address Resolution Protocol (ARP)
ARP uses a three step process to discover andstore the MAC address of a host on the localnetwork
1. The sending host creates and sends a frame
addressed to a broadcast MAC address.Contained in the frame is a message with the IPaddress of the intended destination host.
2. Each host on the network receives the broadcast
frame and compares the IP address inside themessage with its configured IP address. Thehost with the matching IP address sends itsMAC address back to the original sending host.
-
8/3/2019 Chapter3 Semster One -Discovery
65/89
ITE PC v4.0
Chapter 1 65 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Address Resolution Protocol (ARP)
3. The sending host receives the message andstores the MAC address and IP addressinformation in a table called an ARP table.
Once the sending host has the MAC address of the
destination host in its ARP table, it can send framesdirectly to the destination without doing an ARPrequest.
-
8/3/2019 Chapter3 Semster One -Discovery
66/89
ITE PC v4.0
Chapter 1 66 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Distribution Layer Devices andCommunication Methods
Describe the reasons for expanding your network with adistribution layer
-
8/3/2019 Chapter3 Semster One -Discovery
67/89
ITE PC v4.0
Chapter 1 67 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Distribution Layer
It is often necessary to divide one local network intomultiple Access Layer networks as the network grows.There are many ways to divide networks based ondifferent criteria, including:
Physical location
Logical function
Security requirements
Application requirements
The Distribution Layer connects these independentlocal networks and controls the traffic flowing betweenthem, therefore, It is responsible for ensuring thattraffic between hosts on the local network stays local.
-
8/3/2019 Chapter3 Semster One -Discovery
68/89
ITE PC v4.0
Chapter 1 68 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Distribution Layer Devices andCommunication Methods
Describe the function of routers and how they are usedin the network
-
8/3/2019 Chapter3 Semster One -Discovery
69/89
ITE PC v4.0
Chapter 1 69 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Routers
A router is a networking device that connects a local
network to other local networks.
Routers, like switches, are able to decode and read themessages that are sent to them. Unlike switches, whichonly decode (unencapsulate) the frame containing theMAC address information, routers decode the packetthat is encapsulated within the frame.
The packet format contains the IP addresses of the
destination and source hosts, as well as the messagedata being sent between them. The router reads thenetwork portion of the destination IP address and usesit to find which one of the attached networks is the bestway to forward the message to the destination.
-
8/3/2019 Chapter3 Semster One -Discovery
70/89
ITE PC v4.0
Chapter 1 70 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Routers How does the router determine what path to send the
message to get to the destination network?Each port, or interface, on a router connects to adifferent local network. Every router contains a table ofall locally-connected networks and the interfaces thatconnect to them called a Routing table. It containsinformation about the routes, or paths, that the routeruses to reach other remote networks that are not locallyattached.
When a router receives a frame, it decodes the frame
to get to the packet containing the destination IPaddress. It matches the address of the destination to allof the networks that are contained in the routing table.
The process of forwarding the packets toward theirdestination network is called routing.
-
8/3/2019 Chapter3 Semster One -Discovery
71/89
ITE PC v4.0
Chapter 1 71 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Distribution Layer Devices andCommunication Methods
Explain the concept of the default gateway
-
8/3/2019 Chapter3 Semster One -Discovery
72/89
ITE PC v4.0
Chapter 1 72 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Default Gateway The method that a host uses to send messages to a
destination on a remote network differs from the way ahost sends messages on the same local network. Whena host needs to send a message to another host locatedon the same network, it will forward the message
directly. When a host needs to send a message to a remote
network, it must use the router. The host includes the IPaddress of the destination host within the packet just likebefore. However, when it encapsulates the packet into aframe, it uses the MAC address of the router as thedestination for the frame. In this way, the router willreceive and accept the frame based on the MACaddress.
-
8/3/2019 Chapter3 Semster One -Discovery
73/89
ITE PC v4.0
Chapter 1 73 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Default Gateway How does the source host determine the MAC address of the
router?
A host is given the IP address of the router throughthe default gateway address configured in its TCP/IPsettings.
The default gateway address is the address of therouter interface connected to the same local networkas the source host. All hosts on the local network usethe default gateway address to send messages to therouter. Once the host knows the default gateway IPaddress, it can use ARP to determine the MACaddress. The MAC address of the router is thenplaced in the frame, destined for another network.
-
8/3/2019 Chapter3 Semster One -Discovery
74/89
ITE PC v4.0
Chapter 1 74 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Distribution Layer Devices andCommunication Methods
Describe how the router keeps tract of multiplenetworks using routing and ARP tables
-
8/3/2019 Chapter3 Semster One -Discovery
75/89
ITE PC v4.0
Chapter 1 75 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Routing and ARP tables
Routers move information between local and remotenetworks, therefore, routers must use both ARP androuting tables to store information.
Routing tables are not concerned with the addressesof individual hosts therefore they contain theaddresses of networks and the best path to reachthose networks.
Entries can be made to the routing table in two ways:dynamically updated by information received fromother routers in the network, or manually entered by anetwork administrator.
-
8/3/2019 Chapter3 Semster One -Discovery
76/89
ITE PC v4.0
Chapter 1 76 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Routing and ARP tables
A router forwards a frame to one of two places: adirectly connected network containing the actualdestination host, or to another router on the path toreach the destination host. When a router
encapsulates the frame to forward it out of an Ethernetinterface, it must include a destination MAC address.
Routers obtain MAC addresses from ARP tables.
Each router interface is part of the local network towhich it is attached and maintains its own ARP tablefor that network. The ARP tables contain the MACaddresses and IP addresses of all of the individualhosts on that network.
-
8/3/2019 Chapter3 Semster One -Discovery
77/89
ITE PC v4.0
Chapter 1 77 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Distribution Layer Devices andCommunication Methods
Define the term local area network (LAN)
-
8/3/2019 Chapter3 Semster One -Discovery
78/89
ITE PC v4.0
Chapter 1 78 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Local Area Network (LAN)
The term Local Area Network (LAN) refers to a localnetwork, or a group of interconnected local networksthat are under the same administrative control.
LANs typically use Ethernet or wireless protocols, and
they support high data rates. The term Intranet is often used to refer to a private
LAN that belongs to an organization, and is designedto be accessible only by the organization's members,
employees, or others with authorization.
-
8/3/2019 Chapter3 Semster One -Discovery
79/89
ITE PC v4.0
Chapter 1 79 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Distribution Layer Devices andCommunication Methods
Differentiate between implications of adding hosts toMy local network vs. adding to a remote network
-
8/3/2019 Chapter3 Semster One -Discovery
80/89
ITE PC v4.0
Chapter 1 80 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Hosts on a local or Remote network
Placing all hosts on a single local network allows them
to be seen by all other hosts. This is because there isone broadcast domain and hosts use ARP to find eachother.
In a simple network design it may be beneficial to keepall hosts within a single local network. However, asnetworks grow in size, increased traffic will decreasenetwork performance and speed. In this case, it may bebeneficial to move some hosts onto a remote network.
Placing additional hosts on a remote network willdecrease the impact of traffic demands. However, hostson one network will not be able to communicate withhosts on the other without the use of routing.
-
8/3/2019 Chapter3 Semster One -Discovery
81/89
ITE PC v4.0
Chapter 1 81 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Distribution Layer Devices andCommunication Methods
Learn to Use Packet Tracer
-
8/3/2019 Chapter3 Semster One -Discovery
82/89
ITE PC v4.0
Chapter 1 82 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Plan, Implement and Verify a Local Network
Plan and document the building of a small home orsmall business Ethernet network
-
8/3/2019 Chapter3 Semster One -Discovery
83/89
ITE PC v4.0
Chapter 1 83 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Plan, Implement and Verify a Local Network
Build a virtual model of their small home or smallbusiness network
-
8/3/2019 Chapter3 Semster One -Discovery
84/89
ITE PC v4.0
Chapter 1 84 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Plan, Implement and Verify a Local Network
Describe the features of multifunction devices and howthey are used in the network
-
8/3/2019 Chapter3 Semster One -Discovery
85/89
ITE PC v4.0
Chapter 1 85 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Plan, Implement and Verify a Local Network
Connect and properly document the network installation
-
8/3/2019 Chapter3 Semster One -Discovery
86/89
ITE PC v4.0
Chapter 1 86 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Plan, Implement and Verify a Local Network
Perform simple workgroup tasks in order to shareresources
-
8/3/2019 Chapter3 Semster One -Discovery
87/89
ITE PC v4.0
Chapter 1 87 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Sharing Resources One of the most common purposes of networking is to share
resources such as files and printers.
By default, Windows XP uses a process known as Simple FileSharing. With Simple File Sharing, specific users and groups cannotbe prevented from accessing shared files.
Simple File Sharing can be disabled so that more specific securityaccess levels can be assigned. When this is done, the followingpermissions are available to assign to resources:
Full Control
Modify
Read & ExecuteList Folder Contents
Read
Write
-
8/3/2019 Chapter3 Semster One -Discovery
88/89
ITE PC v4.0
Chapter 1 88 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Summary Information networks carry data using hosts as clients,
servers, or both.
All computer communication involves a source,destination, and channel.
Rules called protocols govern computercommunications.
Larger networks are divided into smaller, moremanageable ones using a layered hierarchical design.
Each network host needs both a physical MAC addressand a logical IP address.
Good network design requires a network plan.
-
8/3/2019 Chapter3 Semster One -Discovery
89/89