Chapter 10 Revised January 2007 Panko’s Business Data Networks and Telecommunications, 6th edition Copyright 2007 Prentice-Hall May only be used by adopters

Chapter 10

Revised January 2007

Panko’sBusiness Data Networks and Telecommunications, 6th edition

Copyright 2007 Prentice-HallMay only be used by adopters of the book

Network Management

Network SimulationSoftware

3

Figure 10-1: Network Simulation

• Simulation

– Build a model, study its implications

– More economical to simulate network alternatives than to build several networks and see which one is best

• Purposes– Compare alternatives to select the best one

– Sensitivity analysis to see what will happen if the values of variables were varied over a range

– Anticipating bottlenecks because procurement cycles are long in business, so problems must be anticipated well ahead of time

4


• What Is: the existing situation

Net 1

Net 2

Net 3

Net 4

Net 5

Net 6

Utilization inPeak Hour

95%

Too high!

R7

What Is analysis:Describe the current situation.

Problem: Utilization in the peak hourIs too high (95%); this will

create many momentary overloads

5


• What-If: See the Impact of a Change

Net 1

Net 2

Net 3

Net 4

Net 5

Net 6

Est.Utilization inPeak Hour

70%

AddedRouter

AddedLink

What If analysis:What will happen if something is done?

Adding a new link between R3 and Net5will give good peak hour utilization.

R3

R7

6


• The Simulation Process:Step 1: Before the Simulation, Collect Data

– Data must be good

– Otherwise, GIGO (garbage in, garbage out)

– Collect data on the current network

– Forecast growth

7

Figure 10-2: OPNET IT Guru Node Template

Dragged IconThe Process:

2.Add node icons to thesimulation Work Area

(clients, servers,switches, routers, etc.)

Drag from theObject Palette

Object Palette

Work Area

8

Figure 10-4: Configured Simulation Model

3.Specify the topology by adding transmission lines

between nodes (and specifying line speeds).

Click on two nodes, click on a transmissionline icon in the object palette.

9

Figure 10-3: Configuring a Frame Relay CIR

4.Configure EACH node and

transmission lines (IP Time-to-Live value, etc.).In this case, Frame Relay burst speed rate.

10

Figure 10-4: Configured Simulation Model

5.Add applications, which generate traffic data

Applications

11


• 6. Run the simulation for some simulated period of time

– Examine the output to determine implications

– Validate the simulation if possible (compare with actual data to see if it is correct)

12

Figure 10-5: What-If Analysis

7.Do what-if analyses,

trying different alternatives.

IP Subnetting

14

IP Subnetting

• IP Addresses always are 32 bits long

• The firm is assigned a network part– Usually with 8 to 24 bits

• The firm can assign the remaining bits to the subnet part and the host part

– Different choices give different numbers of subnets and hosts per subnet, as in the following examples

– Firms must trade-off the number of subnets and the number of hosts per subnet in a way that makes sense for their organizational situation

15

IP Subnetting

• If a part has N bits, it can represent 2N-2 subnets or hosts per subnet

– 2N because if you have N bits, you can represent 2N possibilities

– Minus 2 is because you cannot have a part that is all zeros or all ones

Part Size(bits) 2N 2N-2

4 24 = 16 16-2 = 14

8 ? ?

12 4,096 4,094

65,536 65,53416

10 ? ?

16

Figure 10-6: IP Subnetting

DescriptionStep

32Total size of IP address(bits)

1

Size of network partassigned to firm (bits)

2 16

Remaining bits for firm toassign

3 16

Selected subnet/host partsizes (bits)

4 8 / 8

Number of possibleSubnets (2N-2)

254

(28-2)

Number of possible hostsper subnets (2N-2)

254

By Definition

Assigned tothe firm

Bits for thefirm to assign

The firm’sdecision

17


DescriptionStep


1


2 16


3 16


4 6/10


62

(26-2)


1,022

By Definition

Assigned tothe firm



18


DescriptionStep


1


2 8


3 24


4 12/12


4,094


4,094

By Definition

Assigned tothe firm



19


DescriptionStep


1


2 8


3 24


4 8/16


254


65,534

By Definition

Assigned tothe firm



20


DescriptionStep


2 20


3 12

Selected host partsizes (bits)

4 ?


?


?

Selected subnet partsizes (bits)

Added 4

21


DescriptionStep


2 20


3 12

Selected host partsizes (bits)

4 ?


?


?

Selected subnet partsizes (bits)

Added 6

Directory Servers

Store corporate information

Hierarchical organization of content

LDAP standard to access directory servers

23

Figure 10-7: Hierarchical Directory Server Name Space

University of Waikiki (O) CN=Waikiki

Astronomy(OU)

Staff

Chun

CNBrown

Extx6782

Directory Server withHierarchical Object Structure

Ochoa

Routers

CprSci(OU)

Brown

Faculty

[email protected]

Business (OU)

O=organizationOU=organizational unitCN=common name

Centralized management requiresCentralized information storage.

Directory servers provide this.

Directory servers are organizedas hierarchies

24



Astronomy(OU)

Staff

Chun

CNBrown

Extx6782

Ochoa

Routers

CprSci(OU)

Brown

Faculty

[email protected]

Business (OU)

LDAP Request:GET e-mail.Brown.faculty.business.waikiki

LDAP Response:[email protected]

Most directories use LDAPfor data queries:

(Lightweight DirectoryAccess Protocol.)

25



Astronomy(OU)

Staff

Chun

CNBrown

Extx6782

Ochoa

Routers

CprSci(OU)

Brown

Faculty

[email protected]

Business (OU)

Based on the example

in the previous slide,

give the LDAP request

message for Ochoa’s

telephone extension:

Needed to set up new routers

Needed to change operation of existing routers

Time consuming and an important skill

Configuring Routers

27

Figure 10-8: Cisco Internetwork Operating System (IOS) Command Line Interface (CLI)

• Cisco dominates the router market

• Routers are computers

– They have operating systems

– The Cisco operating system is called the Internetwork Operating System (IOS)

– IOS is also used in other Cisco products

• IOS uses a command line interface (CLI)

– Type complex commands at a prompt:

• Router#hostname julia

28


Command Comment

Router>enable[Enter]Router> is the prompt. The “>” showsthat the user is in non-privileged mode.

This command enables privileged modeso that user can take supervisory actions. User must enter the enable secret.

Note: All commands end with [Enter]. Enter is not shown in subsequent commands.

29


Command Comment

Router#hostname julia

Prompt changes to “#” to indicate thatuser is in privileged mode.

User gives the router a name, julia.

julia#config t

Enter configuration mode. The t is anabbreviation for terminal.

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Command Comment

julia(config)#int e0

The prompt changes to julia(config) toindicate that the user is in configurationmode.

User wishes to configure the first Ethernet interface, e0. (Router has two Ethernet interfaces, 0 and 1.)

julia(config-if)#ip address

10.5.0.6 255.255.0.0

User gives interface e0 an IP address(10.5.0.6) and a subnet mask(255.255.0.0). (Every routerinterface must have a separate IPaddress.) The IP subnet is 5.

31


Command Comment

julia(config-if)#no shutdown

This is an odd one. The command toshut down an interface is “shutdown”.Correspondingly, “no shutdown” turnsthe interface on.

julia(config-if)# Ctrl-Z

User types Ctrl-Z (the key combination,not the letters) to end the configurationof e0.

32


Command Comment

julia(config-if)#ip address10.6.0.1 255.255.0.0

User gives the interface an IP addressand subnet mask. The subnet is 6.

julia(config-if)#no shutdown Turns on s1.

julia(config-if)# Ctrl-Z Ends the configuration of s1.

julia(config)#int s1

Next, the user wishes to configure the Second serial interface, s1. (Router has two serial interfaces, 0 and 1.)

33


Command Comment

julia#disable

Takes user back to non-privilegedmode. This prevents anyone gettingaccess to the terminal from makingadministrative changes to the router.

julia> The user is now in non-privileged mode

julia# router rip

Enables the Router Information Protocol(RIP) routing protocol.

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Give the commands to configure Ethernet interface 2 with the IP address 192.168.47.3. Do not show Enters. Do show the prompts.

Julia>

Network Management Utilities

36

Figure 10-9: Network Management Utilities

• Network management utilities are programs to help network managers administer the network

• Security Concerns

– Danger: management tools can be used to make attacks

– So policies should limit these tools to certain employees and to certain purposes

– Firewalls block many network management tools to avoid attacks

37


• Windows PC Diagnostic Tools

– Normally, the network connection to the Internet is set up automatically

– If it is not setup, the Network Setup Wizard will set it up

– To test your connection

• Simply open the browser and see if you can connect to a known website

– If the connection works but seems slow

• Ping a host to see if latency is acceptable

38



– If there is no connection, do loopback testing and ipconfig/winipconfig

• At the command line, Ping 127.0.0.1. This is the loopback interface (you ping yourself)

• If it works, the problem is likely to be in the network.

– For detailed information on the connection: ipconfig /all or winipconfig (older versions of Windows)

• This can let you see if your IP address is reasonable, your network mask is correct, etc.

39



– If you suspect your NIC in Windows XP

• Right-click on a connection and select Properties

• Select the NIC and hit the Configuration button

– The dialog box that appears will show you the status of the NIC

– It also offers a Troubleshooting wizard if the NIC is not working

40



– Packet capture and display programs

• Capture data on individual packets

• Allows extremely detailed analysis of the traffic

• You can look at individual packet data or summaries

• WinDUMP is a popular packet capture and display program on Windows

• So is Ethereal

41


Command prompt>tcpdump www2.pukanui.com

7:50.10.500020 10.0.5.3.62030 >www2.pukanui.com.http: S 800000050:800000050(0) win 4086 <mss1460>

7:50.10.500020 is the time

10.0.5.3.62030 is the source host (62030 is the port number)

www2.pukanui.com.http is the destination host. Its port is http (80)

WinDUMP from Ch. 8a

42


7:50.10.500020 10.0.5.3.62030 > www2.pukanui.com.http: S 800000050:800000050(0) win 4086 <mss1460>

S indicates that the SYN flag is set

800000050:800000050(0) Seq. No. and length

Win 4086 is the window size (for flow control)

<mss1460> is an option that sets the maximum segment size (size of the TCP data field) to 1460 octets

WinDUMP from Ch. 8a

43


7:50.10.500030 www2.pukanui.com.http > 10.0.5.3.62030 : S 300000030:300000030(0) ack 800000051 win 8760 <mss1460>

SYN/ACK from the webserver

7:50.10.500040 10.0.5.3.62030 > www2.pukanui.com.http: . ack 1 win 4086

ACK to finish 3-way open

Change in sequence numberto simple numbering (1)

WinDUMP from Ch. 8a

44

Figure 10-11: EtherPeek Packet Capture and Summarization Program

Summarization in apacket capture

and analysis program

45



– Connection analysis

• At the command line, netstat shows active connections

• This can identify problem connections

Spyware running on Port 3290

Figure 10-12

46


• Route Analysis Tools

– To test the route to another host

– (1) Ping gives the latency of a whole route

– (2) Tracert gives latencies to each router

• Note the high latency between R2 and R3.This could indicate a network problem.

(1) Ping 275 ms

(2)Tracert

25 ms 75 ms

250 ms

225 ms

150 ms (Problem?)

R1 R2 R3

47


• Network Mapping Tools

– To understand how the network is organized

– Discovering IP addresses with active devices

– Fingerprinting them to determine their operating system (client, server, or router)

– A popular network mapping program is nmap (shown in Chapter 9)

• Loved by hackers

• Use carefully: Can crash some hosts

Simple Network Management Protocol (SNMP)

49

Figure 10-13: Simple Network Management Protocol (SNMP)

• Simple Network Management Protocol (SNMP)

– A protocol for remotely managing network devices from a centralized device

– For many tasks, avoid the expense of traveling to many devices

– SNMP standardizes remote management communication

– Collects information from remote devices to give the network administrator an overview of the network

– Optionally, allows the network administrator to reconfigure remote devices

– Potential for large labor cost savings

50


Network ManagementSoftware (Manager)

RMON Probe

ManagedDevice

Manager manages multiple managed devices from a central location

51



NetworkManagement

Agent (Agent),Objects

RMON Probe

NetworkManagement


Manager talks to a network management agent on each managed device—not to themanaged device directly.

52



NetworkManagement


RMON Probe

NetworkManagement


RMON (remote monitoring) probe is a special agent that collects data about multiple devices in a region of in the network. It is like a local manager that can be queried by the main manager.

53


ManagementInformationBase (MIB)




RMON Probe

MIB stores data about devices.MIB on manager stores all.MIB on device stores local information

54



Simple NetworkManagement Protocol (SNMP)

Messages RMON Probe

1.Command (Get, Set, etc.)

2.Response

3.Trap (Alarm) Initiated by

a Managed Device

55

Figure 10-14: SNMP Object Model

• SNMP Object Model

– The MIB database schema

– Defines objects (parameters) about which information is stored for each managed device

• SNMP System Objects– System name

– System description

– System contact person

– System uptime (since last reboot)

– …


56


• SNMP IP Objects

– Forwarding (for routers). Yes if forwarding (routing), No if not

– Subnet mask

– Default time to live

– Traffic statistics

– Number of discards due to resource limitations

– …


57


• SNMP IP Objects (Continued)

– Number of discards because could not find route

– Number of rows in routing table

– Rows discarded because of lack of space

– Individual row data in the routing table

– …


58


• SNMP TCP Objects

– Maximum / minimum retransmission time

– Maximum number of TCP connections allowed

– Opens / failed connections / resets

– Segments sent

– Segments retransmitted

– Errors in incoming segments

– No open port errors

– Data on individual connections (sockets, states)

– …


59


• SNMP UDP Objects

– Error: no application on requested port

– Traffic statistics

• SNMP ICMP Objects

– Number of error messages of various types


60


• SNMP Interface Objects (One per Port)

– Type (e.g., 69 is 100Base-FX; 71 is 802.11)

– Status: up / down / testing

– Speed

– MTU (maximum transmission unit—the maximum packet size)

– Traffic statistics: octets, unicast / broadcast / multicast packets

– Errors: discards, unknown protocols, etc.


Traffic Management

Capacity is expensive; it must be used wiselyEspecially in WANs, where capacity is expensive

62

Figure 10-15: Traffic Management Methods

• Traditional Approaches

– Overprovisioning

• In Ethernet, install much more capacity than is needed most of the time

• This is wasteful of capacity

• Unacceptable in WANs, where capacity is expensive

• Does not require much ongoing management labor

63



– Priority

• In Ethernet, assign priority to applications based on sensitivity to latency

• In momentary periods of congestion, switch sends high-priority frames through

• Substantial ongoing management labor

• Used heavily in WANs

64



– QoS Reservations

• In ATM, reserve capacity on each switch and transmission line for an application

• Allows strong QoS guarantees for voice traffic

• Wasteful if the reserved capacity is not sued

• Highly labor-intensive

• Usually, data gets the scraps—capacity that is not reserved for voice

65


• Traffic Shaping

– The Concept

• Control traffic coming into the network at access switches

– Like the doorman in a night club

– Filter out unwanted applications

– Give a maximum percentage of traffic to other applications

• Prevents congestion from starting instead of just coping when congestion occurs—controls the on ramp to the network

Topics Covered

67

Topics Covered

• Network Simulation

– Study before you install equipment

– There is a process to follow

– What Is versus What If

• IP Subnetting

– Must balance number of subnets with number of hosts per subnet

– A part with N bits can support 2N-2 subnets or hosts

68

Topics Covered

• Directory Servers

– Centralized storage of information

– Hierarchical organization

– LDAP is the protocol for data queries

• Configuring Routers

– Cisco IOS command line interface (CLI)

– Worked through a simple example

• Network Management Utilities

– Diagnose a network connection for a client PC

69

Topics Covered

• Simple Network Management Protocol (SNMP)

– Protocol for managing network devices remotely

– Manager, managed device, agent, RMON probe

– Management information base (MIB)

– SNMP messages: commands and responses, traps

• Traffic Management

– Overprovisioning

– Priority

– QoS reservations

– Traffic shaping: prevent congestion from occurring

Documents

Chapter 10 Revised January 2007 Panko’s Business Data Networks and Telecommunications, 6th edition Copyright 2007 Prentice-Hall May only be used by adopters