1 Everything You Always Wanted to Know About Network Access Chapter 5 –Layered Communication & Internet Access

1

Everything You Always Wanted to Know About

Network Access

Chapter 5 –Layered Communication & Internet

Access

2

Knowledge Checkpoints

PSTN Infrastructure How the OSI model works Message exchange sequence How routers work Cookies HTTP protocol DOS commands for the network

3

Student Notes

Chapter 4 & 5 give background information to understand the network that represents the Internet

The content in these chapters will be more useful when we study WANs

Most of the material in this slide set is not in the book but is necessary for you to understand using networks

Check out the web sites on the course web page for additional information

4

Vocabulary that is Important

HTTP OSI & layers TCP/IP Cookie Router CSU DLC Compression T and E carrier SDH/SONET Frame Packet OC SS7 Architecture Header Encapsulation Router forwarding IP address DNS DHCP

Domain Host Auto-configuration Adaptor Bindings HTML Tags Next hop PSTN PDH

5

PSTN

Infrastructure and design to support voice, only Call length is a component of the

differences between data vs voice carried on network

Channel capacity is narrow band (64 Kbps)

Backbone based on PDH (T-carrier)

6

Array of Service Providers

LEC-local exchange carrier ILEC-incumbent local carrier (monopoly rights) CLEC-competitive local exchange carrier DLEC-data competitive local exchange carrier

(supports data services) IXC-inter-exchange carrier (long distance)

Who are the LEC,ILEC,CLEC,DLEC & IXC for Utah?

7

Access Services

Categories for access services include: Trunks (2-way, DID, DOD) Analog (POTS) or digital services (3 types)

T-1 (1.5 Mbps), J-1 (2.048 Mbps), E-1 (1.544 Mpbs)

ISDN (BRI & PRI)DSL

8

Transport Services

Switched services Local, long distance, toll free, international,

directory assistance, operator, emergency services

Nonswitched services Leased lines, foreign exchange

VPNs Network where customer traffic is isolated

over shared service provider facilities

9

PTSN Architecture

CPE nodes located at customer site Switching nodes interconnect transmission facilities to route

traffic Local Exchange (CO) point of termination for customer line and

location of switching equipment Tandem Office in large metro areas connects switching offices to

route local traffic Toll office is a switching center where long distance connections

are made International gateway is where international services begin Transmission nodes carry user traffic and control information Service nodes handle signaling to control connections and billing

10

PDH Infrastructure

PDH is asynchronous (clocking rates of all components vary slightly)

Digital network Offers different transmission rates Defines the availability of channels

11

Elements of PDH Infrastructure

Transmission media Operates on 4 wire (full-duplex) but higher

bandwidths require coax or fiber CSU-terminates each end and equalizes signal Multiplexers consolidates voice and data

channels to travel over high speed line DLCs concentrates lines DCS allows dynamic rerouting of network traffic

12

SDH/SONET Infrastructure

Family of transmission standards using different fiber optic products

Uses a frame format (how bits are packaged) to travel over fiber

Rapid restoration of interrupted service possible with dual ring configuration

Uses optical carrier levels of OC Synchronous infrastructure (clocking rate

from 1 source)

13

SS7 Architecture

Signaling information carried o a different path from voice and data traffic

Allows passage of information about caller (enhanced services)

SSPs are switches that begin and end calls SS7 networks act as a backbone for AIN

(service independent allows interconnects)

14

Looking Deeper into Data

How Does Data Know Where to Go on a Network?

15

Layered Communication

16

The OSI Layers

OSI ModelLayer User Application Data Format Enabling

Technology

7 Application Common application services (email)

6 Presentation Encryption, code translation,compression

5 Session Establishes, maintains, terminates node-to-node interactive sessions

Session Distributed applications, middleware, NOS

4 Transport Ensures reliability of end-to-end connections

Assembles packets into messages

NOS

3 Network Establishes, maintains, and terminates end-to-end network connections

Packets NOS

2 Data Link Logical link control sub-layer and media access control (802.x) that ensures reliability of point-to-point data links

Frames NICs

1 Physical Establishes, maintains, and terminates point-to-point data links

Bits Media

18

Nested Protocol Headers

Each layer adds information as it passes through

19

Under the Covers

20

Indirect Communication

Application programs on different machines cannot communicate directly--They are on different machines!

BrowserBrowser

TransTrans

IntInt

DLDL

PhyPhy

User PC

Web AppWeb App

TransTrans

IntInt

DLDL

PhyPhy

Webserver

HTTP RequestHTTP Request

21

Indirect Communication

Two processes on different machines cannot communicate directly with one another because they are physically separated

So they communicate indirectly, using cooperation with lower layers

Requests are layered on the sending machine and stripped on the host machine

22

Layer Cooperation on the Source Host

Transport layer process passes the TCP segment down to the internet layer process

ApplicationApplication

TransportTransport

InternetInternet

Data LinkData Link

TCP segmentTCP segment

PhysicalUser PC

23

OSI Model

7

6

5

4

3

2

1

0

APPLICATION LAYER

PRESENTATION LAYER

SESSION LAYER

TRANSPORT LAYER

NETWORK LAYER

DATA LINK LAYER

PHYSICAL LAYER

MEDIA

T H

A H

user data

DL H

DATA

P H

S H

N H

DL T

T H

A H

user data

DATA

P H

S H

N H

A H

user data

DATA

P H

S H

T H

A H

user data

DATA

P H

S H

A H

user data

DATA

P H

user data

DATA

A H

1001001011100011110010Bit Stream

7

6

5

4

3

2

1

APPLICATION LAYER

PRESENTATION LAYER

SESSION LAYER

TRANSPORT LAYER

NETWORK LAYER

DATA LINK LAYER

PHYSICAL LAYER

T H

A H

user data

DL H

DATA

P H

S H

N H

DL T

T H

A H

user data

DATA

P H

S H

N H

A H

user data

DATA

P H

S H

T H

A H

user data

DATA

P H

S H

A H

user data

DATA

P H

user data

DATA

A H

1001001011100011110010Bit Stream

Client to Server Communication

KEY: H header T trailer

Client running front-end application.

Server running back-end engine application.

COMMUNICATIONS PATH

user data

GOLDMAN & RAWLES: ADC3e FIG. 05-02

user data

24

Data Structure

Data --The information to be delivered to another system

Data FieldData Field

Trailer Fields(if there are any)

HeaderFields

25

The Data Structure

Header Fields Initial fields in a message before the data field Source and destination address, error handling

information, etc., Like address and greeting in a written letter

Data FieldData Field

Header Fields

Header Field

26

How Does Data Find It’s Way?

IP Addresses!

27

Assigning Network PartsAssigning Network Parts

An organization applies to an Internet IP address registrar Registrar gives organization a network

part Organization assigns the local part to its

hosts internally Only large organizations and ISPs get

network parts

Registrar Firm128.171

128.171.17.13

128.171.123.130

28

IP Addresses

Each Organization is Given a Network Part Number

For Weber, this is 137.190 All IP Addresses in that organization’s

network begin with that Network Part

Network Part

IP Address

128.171

29

IP Addresses

Local Part The part of the IP address after the

network part is called the local part Total address is 32 bits, so if the

network part is 8, the local part is 24

Network Part Local Part

IP Address (32 bits total)

30

Assigning Parts

IP address registrar gives Weber State University the network part 137.190

Weber State could give the College of Business Administration the subnet part 62

College of Business Administration can give the host part 157 and a host name plogan.cba.hawaii.edu

So the computer’s IP address became 137.190.62.157

31

IP Addresses

Most Organizations Have Multiple Subnets within the Organizational Network

Usually represent each as a Subnet Part within the Local Part

Remaining Bits are the Host Part, designating a particular host on that subnet

Network Part Subnet Part


Host Part

Local Part

32

The First Router

The first router receives an IP message packet in one port (interface)

The router must make a router forwarding decision: which port to use to send it back out

B?

D?

C?

Router A

B

C

DPacket

33

IP Addresses

Between different organization networks, routers look first at the Network Part of an arriving IP packet’s destination address

If the network part is not that of the organization, the router cannot deliver the IP packet locally

Passes the IP packet on to another router, called a next-hop router, to move the IP packet closer to the destination host

Network Part

34

IP Addresses

For IP, Routers Take the Place of Post Offices There are hundreds of millions of IP

addresses on the Internet Routers cannot store decision rules for

reaching each address individually Router simply asks if a destination IP

address is that of a host on one one of the networks or subnets connected to the router or must be passed on to another router

This is the router forwarding decision

35

IP Addresses

To Simplify Router Decisions, IP Addresses are Hierarchical

The Internet is Made of Many Individual Networks Owned by Different Organizations

First route packets to a single network; only need one “sorting bin” for each network!

In the next step, route packet to host on the network

36

Layer Cooperation on the First Router

Routers only have physical, data link, and internet layer processes

So internet layer process is the highest-layer process on a router for router forwarding

Internet layer process decides where to send the packet next: another router or the destination host

Data LinkData Link Data LinkData Link

InternetInternet

First Router

37

Layer Cooperation on the First Router

The data link and physical layer process on the selected port sends the frame encapsulating the IP packet onto the next router (or destination host)

InternetInternet

Data LinkData Link

InternetInternet

Data LinkData LinkFrame

Selected Output PortOn First Router

Input PortOn Next Router

(Or Destination Host)

PhysicalLayer

38

Domain Names

Internet uses hierarchical naming A domain is a collection of resources managed

by an organization Generic top level domains by type of

organization .com for commercial organizations .edu for educational institutions

National top level domains by country .UK United Kingdom .AU Australia

39

Domain Names

Organizations register second-level domain names Microsoft.com weber.edu uahc.org Whitehouse.gov

40

Domain Names

Organizations can create lower-level domain names cba.weber.edu (for the College of

Business Administration) The lowest level domain name is the host

name for an individual host or router www.cba.weber.edu www.microsoft.com

41

Domain Name System (DNS)

Only IP addresses are official--e.g., 137.190.62.157 These are 32-bit binary numbers Only they fit into the 32-bit destination and source

address fields of the IP headers

IP Packet

32-bit Source and Destination Addresses (110011...)

42


Users typically only know host names Plogan.cba.weber.edu or weber.edu

IP Packet

Weber.eduNO

43


User’s computer sends a DNS host the target host’s host name in a DNS Request message

Sending an IP address (URL) is a request that is data

DNS host returns the target host’s IP address in DNS Response message

User PCInternetLayer

Process

DNSHost

Weber.edu

157.190.3.212

44


Organizations or ISPs have local DNS hosts These hosts must know only local host

names and IP addresses For other host names, local DNS host

passes request to another DNS host


Process

LocalDNSHost

RemoteDNSHost

45


Remote DNS host passes information back to the local DNS host Local DNS host passes information back to

user PC Browser only talks to local DNS host


Process

LocalDNSHost

RemoteDNSHost

46

A Closer Look at HTTP

HyperText Transfer Protocol

47

Protocols

A protocol is a standard for communication between peer processes, that is, processes at the same layer, but on different machines

HTTP: Browser and webserver application programs are at the same layer but on different machines

AppApp AppAppHTTPMessage

48

Protocols

A protocol is a standard for communication between peer processes, that is, processes at the same layer, but on different machines

TCP (Transmission Control Protocol) is the protocol governing communication between transport layer processes on two hosts

TransTrans TransTransTCPMessage

49

HTTP: A Closer Look

World Wide Web Standards HTTP (HyperText Transfer Protocol) governs

requests and responses between the browser and the webserver application program

HTML (HyperText Markup Language) governs the structure of the HTML webpage

BrowserWebserverProgram

HTML

HTTP

50

HTTP: A Closer Look

HTML Pages Contain Text to be displayed HTML Pages Contain Tags

Some tags say “place a graphic here”, “place a JAVA applet in a box here”, etc.,

For instance, the tag <img src=“big.jpg> says “Get file big.jpg and place it here in the HTML document”

Graphics, Java programs, are separate files

51

Web Page Code

52

HTTP: A Closer Look

Downloading a “page” may require several downloads One for the HTML document One each for the other files it calls for

HTML

Big.jpg

App.java

WebserverUserPC

File Downloads

2

3

1

53

HTTP: A Closer Look

Each download requires a separate HTTP request-response cycle! So downloading complex webpages may

require many HTTP request-response cycles

HTML

Big.jpg

App.java

WebserverUserPC

HTTPRequest-Response

Cycle 1

2

3

54

HTTP: A Closer Look

HTTP is Unreliable No error detection and correction for

transmission errors HTTP is simple, allowing browsers and

webserver application programs to be simple and inexpensive

TCP at the transport layer is reliable, offering error detection and correction

TCP gives HTTP clean data, so there is no need for HTTP to do error checking

55

HTTP: A Closer Look

HTTP is Connectionless No connection (agreement to communicate) is made

between the browser and webserver application before an HTTP message is sent

Like sending a letter or an E-mail message (connectionless) as compared to taking on the telephone, where a conversation (connection) must be opened, managed, and closed

BrowserWebserverApplication

HTTPRequest

56

A Special HTTP Message --Cookies

Server HTTP responses can include an object to be stored on the client

Cookies (name/value pairs are used to identify user File name of cookie is site Request for URL generates response to look

for cookie Unique ID & other info (Expiration date, PW)

57

Cookies

58

Cookie ContentsRMID

ac83d90b3d70eca0

sportingnews.com/

0

3567004032

30124358

3072481984

29511946

*

SaneID

172.131.217.11-1030810793354

sportingnews.com/

0

2020141696

29879224

3097781984

29511946

*

GUID

000989680F730D8E748BE01CAC10000D

advanstar.com/

0

589457792

29622048

2000816672

29516393

*

59

Cookie Contents

RMID

ac8942ee3d8750c0

www.usatoday.com/

0

3567004032

30124358

1703131552

29515363

*

pluto

110689700|0|

fastclick.net/

0

3444658176

29658594

114276224

29513756

*

m1

5694:1:13601:1:1031587872|||||||||||||||||||||||||

fastclick.net/

0

3635990528

29514157

114276224

29513756

*

60

TCP: A Closer Look

Transmission Control Protocol

61

TCP: A Closer Look

Browser does not send HTTP Requests directly to the webserver application

The application layer programs are not physically connected

Browser sends HTTP Request to the user PC’s transport layer process for delivery

Browser

TransportProcess

HTTP Request

62

TCP: A Closer Look

Transport layer process stores the HTTP Request Temporarily

Browser

TransportProcess

TransportProcess

63

TCP: A Closer Look

User PC transport process opens a connection to the webserver transport layer process

This connection can be used to send several TCP segments to handle a each HTTP request-response cycle

Browser

TransportProcess

TransportProcess

64

Delivering the HTTP Response

Transport layer process on the webserver receives the TCP segment delivering the HTTP Request

The transport process on the webserver passes the HTTP Request in the TCP segment data field to the webserver application program

WebserverApplication

TransportProcess

HTTP Request

65


Webserver application creates the HTTP Response message

Webserver application passes the HTTP Response message to the webserver transport layer process for delivery to the user PC transport layer process

WebserverApplication

TransportProcess

HTTP Response

66


Webserver Transport Process Delivers the Response User PC transport process sends an

acknowledgement

User PCTransportProcess

WebserverTransportProcess

TCP segment containingHTTP Response

ACK

67

TCP: Error Handling

TCP is reliable--it Places TCP Segments in Order

TCP segments are encapsulated in IP packets

IP does not guarantee that packets will arrive in order

TCP can place TCP segments in order based on their sequence numbers

68

TCP: Error Handling

TCP Reliability in Perspective

Provides clean application data to application program

If data link layer frame or IP packet is lost at lower layers, receiving transport process will not acknowledge a segment

The sending transport process will resend automatically

So TCP protects against errors at lower layers as well as transport layer errors

69

More on the IP

Internet Protocol

70

Internet Layer Process

Transport layer process passes EACH TCP segment to the internet layer process for delivery

Transport LayerProcess

Internet LayerProcess

TCP segment

71

IP: Connectionless Service

The Internet Protocol (IP) Internet layer protocol IP messages are called IP packets

No connections are established No open, close, error correction, flow control Low overhead

InternetProcess

InternetProcess

IP Packet

72

IP: Connectionless Service

IP is unreliable No error handling (Let TCP catch errors!) No sequence numbers, so no way to put arriving IP

packets in order (Let TCP put the TCP segments these IP packets contain in order!)

InternetProcess

InternetProcess

IP Packet

73

TCP/IP Partnership

TCP checks for errors once, at the destination host

IP is used in many hops between routers Not checking for errors at each step greatly

reduces overall processing work Reduces router costs

Transport Transport

Internet Internet Internet

Check Only Once

Host Router Host

74

Connectionless IP

IP is unreliable (does not catch errors) But this is not bad

First, errors are caught--at the next-higher layer (transport) if TCP is used

Second, avoiding error checking at each hop between routers lowers router costs

Less expensive to check for errors on one destination host than on many routers along the way

75

IP is a Best-Effort Service

IP Only Offers Best-Effort Service

Does its best to get packets through

No guarantees of delivery

No way to give priority to time-sensitive traffic, such as voice

Overall, low overhead but limited Quality of Service (QoS)

QoS should change in the future

76

IP Addresses and Router Forwarding

Routers use the destination IP address of an incoming packet in the router forwarding decision, that is, to decide what output port to use to send the packet back out to the destination host or to another router

B?

D?

C?

Router A

B

C

DPacket

77

Assigning Subnet Parts

Organization Assigns Subnet Parts Assigns subnet parts to suborganizations Suborganization assigns host bits to hosts

Registrar Firm

128.171 128.171.17.13

128.171.17.13

Suborganization

Host

78

IP Addresses Within an organizational Network

Router looks at Network Plus Subnet Part Combined If destination host is on a subnet attached to the

router, delivers the IP packet to the host Otherwise, passes the packet on to a next-hop

router

Network Part Subnet Part


Host Part

Local Part

79

IP Addresses

In IP Addresses, “Network” and “Subnet” are Organizational Concepts, not Technical Concepts

Network is the collection of individual networks and routers owned by an organization

Subnet is a collection of individual networks and routers owned by a suborganization Often a single physical network (subnet)

80

Importance of Part Sizes

Determine Number of Possible Networks, Subnets, or Hosts

If There are N Bits in the Part, there can be 2N possible Networks, Subnets, or Hosts

Actually, 2N-2 All zeros cannot be used for a part All ones cannot be used for a part

Example: if part has 8 bits, 28-2 possibilities (254)

81

Masks

IP Addresses are Always Paired with a Second 32-bit Number Called a Mask

Two Types: Network Masks and Subnet Masks Network Mask Tells the Length of the

Network Part Subnet Mask Tells the length of the

Network Plus Subnet Parts (not just subnet part)

IP Address will be paired with one or the other, but not both simultaneously

82

Router Delivery

If Destination Host is On the Source Host’s Subnet, Source Host Delivers the Packet Directly No router is involved

Subnet

Subnet

SourceHost

Destination Host

83

Router Delivery

If Destination Host is NOT On the Source Host’s Subnet, Source Host Sends the Packet to a Router for Delivery

Subnet

Subnet

84

Router Delivery

If Destination Host is On One of the Router’s Subnets, the Router Sends the Packet to the Destination Host for Delivery

Subnet

Subnet

85

Router Delivery

If Destination Host is NOT On One of the Router’s Subnets, the Router Sends the Packet to a Next-Hop Router for Delivery

May have to choose among several possible next-hop routers for delivery

Subnet

Subnet

86

Router Delivery

Border Routers Connect Networks, Not Subnets Select between next-hop router on own network

or on another network

Own Network

Other Network

87

Router Forwarding Tables

Allow Routers to Decide Whether Local Delivery is Possible to Destination Host

Allow Routers to Select Next-Hop Router if Local Delivery is Not Possible

88


Router Compares Destination IP Address to Each Row in Router Forwarding Table

If matches IP address, delivers according to Delivery rule So if destination address of IP packet is 128.171.17.13,

router delivers packet locally

IP Address Delivery

128.171.17.13 Local

142.99.171.3 Next-Hop Router A

89


Metric If same length of match, turn to metric column Metric describes the desirability of a choice If metric is cost, choose lowest cost For other metrics (speed, etc.), may chose largest

value

IP Address Part

Mask Metric (Cost)

Delivery

128.171 16 23 Local

128.171 16 45 Next-Hop Router A

90


There May be No Matches One IP Address Part is Always 0.0.0.0 If there is no match, choose its next-hop router

(called the Default Router)

IP Address Delivery

128.171.17.13 Local

0.0.0.0 Next-Hop Router C

91


Recap of Selection Rules

Compare destination IP address of an arriving packet against ALL rows within the router forwarding table because there may be multiple matches

Select the single row that matches

If multiple rows match, select the longest match

If multiple rows tie on the longest match, select the row with the largest or smallest metric, depending on the specific metric

If there is no match, select the default router row

92


Delivery Table not only designates local delivery or a next

hop router Also designates the router interface (port) that

will be used for delivery

Interface Delivery

2 Local

3 Next-Hop Router C

3 Next-Hop Router D

93

Dynamic Routing Protocols

How Do Routers Get Information for their Router Forwarding Tables?

Share router forwarding table information Standards for these exchanges are called dynamic

routing protocols

Router ForwardingTable Information

94

Dynamic Routing Protocols

How Do Routers Get Information for their Router Forwarding Tables?

Thanks to dynamic routing protocols, the Internet needs no central point of control

Routers create their router forwarding tables strictly by information from peers and their own knowledge

Router ForwardingTable Information

95

IP Version 6

Current Version of IP is IP Version 4 This is the version we have been discussing Has 32-bit IP address fields Not long enough; running out of IP addresses

Next Version will be IP Version 6 Will have 128-bit IP address fields Will allow vast numbers of IP addresses (2128) Being adopted slowly

96

Autoconfiguration

Every computer attached to the Internet is a host Including desktop PCs

Every host must have an IP address Some hosts, such as routers and

webservers, get permanent IP addresses

97

Autoconfiguration

User PCs do not need permanent IP addresses They only need to be found within a use

session They usually are given temporary IP

addresses each time they use the Internet

They may get a different IP address each time they use the Internet

98

Autoconfiguration Request-Response Cycle

User software requests IP address for the user PC in Autoconfiguration Request message

Autoconfiguration Response message contains temporary IP address to use in current session

User PCAutoconfiguration

Host

AutoconfigurationRequest

TemporaryIP Address in

Autoconfiguration Response

99

Autoconfiguration

Most popular autoconfiguration protocol is DHCP Dynamic Host Configuration Protocol Built into Windows after Win 3.1 Supplies host with temporary IP address

DHCP can give more information too Usually gives IP address of a default

gateway (Microsoft terminology for router)

Can give IP address of a local DNS host

100

DOS Commands

Ping Tracert IPCONFIG

101

102

103

Windows 98 IP Configuration

0 Ethernet adapter :

IP Address. . . . . . . . . : 172.193.231.170Subnet Mask . . . . . . . . : 255.255.0.0Default Gateway . . . . . . : 172.193.231.170

1 Ethernet adapter :

IP Address. . . . . . . . . : 0.0.0.0Subnet Mask . . . . . . . . : 0.0.0.0Default Gateway . . . . . . :

IPCONFIG

104

Internet Setup in Microsoft Windows

105

Windows Layering vs.

TCP/IP-OSI Protocols

TCP/IP is only one possibility

IPX/SPX for older Novell NetWare servers; Microsoft sometimes calls this NW Link

NetBEUI for some Microsoft servers on small PC networks

106

Windows Layering vs.

TCP/IP-OSI Adapters

Combination of data link layer and physical layer protocols

The subnet layers

Dial-Up adapter sets up a modem and PPP

Other “adapters,” including Ethernet for a network interface card (NIC)

107

Bindings Bindings

Bindings create communication paths between adjacent layer processes

Client for MS Windows Other Added Client

IPX/SPX Protocol TCP/IP Protocol

Ethernet Adapter Dial-Up Adapter

Binding

Binding

108

Configuring Networking in

Windows In Windows 95 and Windows 98

Go to the Start Button Choose Settings Choose Control Panel Double click the Network icon This opens the Network Dialog Box

109

The Network Dialog Box

Be sure the Configuration tab is selected You will see adapters, protocols, clients, and

services that have already been added

Operations Add: To add an adapter, protocol, client, or

service Remove: To remove one Properties: To see or change the properties

of the selected adapter, protocol, client, or service

110

The Network Dialog Box

The Add Button

Clicking the “Add” button takes you to the Select Network Component Type dialog box

Choose client, protocol, adapter, or service, then hit Add

Assume you chose “protocol” You then go to the Select Network Protocol dialog box

Other choices will take you to the relevant Select Network … dialog box

111

112

Broader Perspective

113

You Will Not Always Use TCP/IP-OSI Standards

You almost always will use OSI standards for the data link and the physical layers

At higher layers, you may use Non-TCP protocols IPX/SPX in some Novell NetWare file

servers SNA for mainframes AppleTalk for Macintoshes NetBEUI for servers on some small LANs

114

Implications of Non-TCP/IP

Why does it cause problems?When would it happen?What could be done about it?

115

Important Information

Review Figure 5.1 p. 117 Figure 5.6 p 127 Table 5.1 p. 130 Figure 5.8 p. 134 Table 5.3 p. 135 Figure 5.17

116

Try the Following

All DOS commands must be executed from a DOS shell

Use the DOS command ping to check on a live connection Do this from home as ping is blocked on campus Try weber.edu and another such as Yahoo or

microsoft Use the DOS command tracert to check the route to a

web site Can you tell the last hop router IP address?

Use the DOS command Ipconfig to identify the IP address assigned to your computer

Documents

1 Everything You Always Wanted to Know About Network Access Chapter 5 –Layered Communication & Internet Access