1. Network Management Chapter 10 Revised January 2007
Panko’s Business Data Networks and Telecommunications, 6th edition Copyright 2007 Prentice-Hall May only be used by adopters of the book

2. Network Simulation Software

3. Figure 10-1: Network 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. Figure 10-1: Network Simulation
What Is: the existing situation R7
Net 1
Net 4
Utilization in
Peak Hour
95%
Net 2
Too high!
Net 5
What Is analysis:
Describe the current situation.
Problem: Utilization in the peak hour
Is too high (95%); this will
create many momentary overloads
Net 3
Net 6

5. Figure 10-1: Network Simulation
What-If: See the Impact of a Change R7
Net 1
Net 4
Est.
Utilization in
Peak Hour
70%
Added
Router
Added
Link R3
Net 2
Net 5
What If analysis:
What will happen if something is done?
Adding a new link between R3 and Net5
will give good peak hour utilization.
Net 3
Net 6

6. Figure 10-1: Network Simulation
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
Work Area
Dragged Icon
The Process: 2.
Add node icons to the
simulation Work Area
(clients, servers,
switches, routers, etc.)
Drag from the
Object Palette
Object Palette

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 transmission line 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. Figure 10-1: Network Simulation
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.

13. 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 ? ? 10 ? ? 12
4,096
4,094 16
65,536
65,534

16. Figure 10-6: IP Subnetting
Step
Description 1
Total size of IP address
(bits) 32
By Definition 2
Size of network part
assigned to firm (bits) 16
Assigned to
the firm 3
Remaining bits for firm to
assign 16
Bits for the
firm to assign 4
Selected subnet/host part
sizes (bits)
8 / 8
The firm’s
decision
Number of possible
Subnets (2N-2)
254
(28-2)
Number of possible hosts
per subnets (2N-2)
254

17. Figure 10-6: IP Subnetting
Step
Description 1
Total size of IP address
(bits) 32
By Definition 2
Size of network part
assigned to firm (bits) 16
Assigned to
the firm 3
Remaining bits for firm to
assign 16
Bits for the
firm to assign 4
Selected subnet/host part
sizes (bits)
6/10
The firm’s
decision
Number of possible
Subnets (2N-2) 62
(26-2)
Number of possible hosts
per subnets (2N-2)
1,022

18. Figure 10-6: IP Subnetting
Step
Description 1
Total size of IP address
(bits) 32
By Definition 2
Size of network part
assigned to firm (bits) 8
Assigned to
the firm 3
Remaining bits for firm to
assign 24
Bits for the
firm to assign 4
Selected subnet/host part
sizes (bits)
12/12
The firm’s
decision
Number of possible
Subnets (2N-2)
4,094
Number of possible hosts
per subnets (2N-2)
4,094

19. Figure 10-6: IP Subnetting
Step
Description 1
Total size of IP address
(bits) 32
By Definition 2
Size of network part
assigned to firm (bits) 8
Assigned to
the firm 3
Remaining bits for firm to
assign 24
Bits for the
firm to assign 4
Selected subnet/host part
sizes (bits)
8/16
The firm’s
decision
Number of possible
Subnets (2N-2)
254
Number of possible hosts
per subnets (2N-2)
65,534

20. Figure 10-6: IP Subnetting
Step
Description 2
Size of network part
assigned to firm (bits) 20 3
Remaining bits for firm to
assign 12
Added
Selected subnet part
sizes (bits) 4 4
Selected host part
sizes (bits) ?
Number of possible
Subnets (2N-2) ?
Number of possible hosts
per subnets (2N-2) ?

21. Figure 10-6: IP Subnetting
Step
Description 2
Size of network part
assigned to firm (bits) 20 3
Remaining bits for firm to
assign 12
Added
Selected subnet part
sizes (bits) 6 4
Selected host part
sizes (bits) ?
Number of possible
Subnets (2N-2) ?
Number of possible hosts
per subnets (2N-2) ?

22. Directory Servers Store corporate information
Hierarchical organization of content
LDAP standard to access directory servers

23. Figure 10-7: Hierarchical Directory Server Name Space
Directory Server with
Hierarchical Object Structure
O=organization
OU=organizational unit
CN=common name
University of Waikiki (O) CN=Waikiki
Astronomy
(OU)
Business (OU)
CprSci
(OU)
Faculty
Staff
Routers
Centralized management requires
Centralized information storage.
Directory servers provide this.
Directory servers are organized
as hierarchies
Chun
Ochoa
Brown CN
Brown
Ext
x6782

24. Figure 10-7: Hierarchical Directory Server Name Space
LDAP Request:
GET .Brown.faculty.business.waikiki
University of Waikiki (O) CN=Waikiki
Astronomy
(OU)
Business (OU)
CprSci
(OU)
LDAP Response:
Faculty
Staff
Routers
Most directories use LDAP
for data queries:
(Lightweight Directory Access Protocol.)
Chun
Ochoa
Brown CN
Brown
Ext
x6782

25. Figure 10-7: Hierarchical Directory Server Name Space
University of Waikiki (O) CN=Waikiki
Astronomy
(OU)
Business (OU)
CprSci
(OU)
Based on the example
in the previous slide,
give the LDAP request
message for Ochoa’s
telephone extension:
Faculty
Staff
Routers
Chun
Ochoa
Brown CN
Brown
Ext
x6782

26. Configuring Routers Needed to set up new routers
Needed to change operation of existing routers
Time consuming and an important skill

27. Cisco dominates the router market Routers are computers
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. Figure 10-8: Cisco Internetwork Operating System (IOS) Command Line Interface (CLI)
Comment
Router>enable[Enter]
Router> is the prompt. The “>” shows
that the user is in non-privileged mode.
This command enables privileged mode
so 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. Figure 10-8: Cisco Internetwork Operating System (IOS) Command Line Interface (CLI)
Comment
Router#hostname julia
Prompt changes to “#” to indicate that
user is in privileged mode.
User gives the router a name, julia.
julia#config t
Enter configuration mode. The t is an
abbreviation for terminal.

30. Figure 10-8: Cisco Internetwork Operating System (IOS) Command Line Interface (CLI)
Comment
julia(config)#int e0
The prompt changes to julia(config) to
indicate that the user is in configuration
mode.
User wishes to configure the first
Ethernet interface, e0. (Router has two
Ethernet interfaces, 0 and 1.)
julia(config-if)#ip address
User gives interface e0 an IP address
( ) and a subnet mask
( ). (Every router
interface must have a separate IP
address.) The IP subnet is 5.

31. Figure 10-8: Cisco Internetwork Operating System (IOS) Command Line Interface (CLI)
Comment
julia(config-if)#no shutdown
This is an odd one. The command to
shut down an interface is “shutdown”.
Correspondingly, “no shutdown” turns
the interface on.
julia(config-if)# Ctrl-Z
User types Ctrl-Z (the key combination,
not the letters) to end the configuration
of e0.

32. Figure 10-8: Cisco Internetwork Operating System (IOS) Command Line Interface (CLI)
Comment
julia(config)#int s1
Next, the user wishes to configure the
Second serial interface, s1. (Router has two serial interfaces, 0 and 1.)
julia(config-if)#ip address
User gives the interface an IP address
and subnet mask. The subnet is 6.
julia(config-if)#no shutdown
Turns on s1.
julia(config-if)# Ctrl-Z
Ends the configuration of s1.

33. Figure 10-8: Cisco Internetwork Operating System (IOS) Command Line Interface (CLI)
Comment
julia# router rip
Enables the Router Information Protocol
(RIP) routing protocol.
julia#disable
Takes user back to non-privileged
mode. This prevents anyone getting
access to the terminal from making
administrative changes to the router.
julia>
The user is now in non-privileged mode

34. Figure 10-8: Cisco Internetwork Operating System (IOS) Command Line Interface (CLI)
Give the commands to configure Ethernet interface 2 with the IP address Do not show Enters. Do show the prompts.
Julia>

35. 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. Figure 10-9: Network Management Utilities
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. Figure 10-9: Network Management Utilities
Windows PC Diagnostic Tools
If there is no connection, do loopback testing and ipconfig/winipconfig
At the command line, Ping 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. Figure 10-9: Network Management Utilities
Windows PC Diagnostic Tools
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. Figure 10-9: Network Management Utilities
Windows PC Diagnostic Tools
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. Figure 10-9: Network Management Utilities
Command prompt>tcpdump www2.pukanui.com 
7: > www2.pukanui.com.http: S : (0) win 4086 <mss1460>
7: is the time
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. Figure 10-9: Network Management Utilities
7: > www2.pukanui.com.http: S : (0) win 4086 <mss1460>
S indicates that the SYN flag is set
: (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 octets
WinDUMP from Ch. 8a

43. Figure 10-9: Network Management Utilities
7: www2.pukanui.com.http > : S : (0) ack win <mss1460>
SYN/ACK from the webserver
7: > www2.pukanui.com.http: . ack 1 win 4086
ACK to finish 3-way open
Change in sequence number to simple numbering (1)
WinDUMP from Ch. 8a

44. Figure 10-11: EtherPeek Packet Capture and Summarization Program
Summarization in a
packet capture
and analysis program

45. Figure 10-9: Network Management Utilities
Windows PC Diagnostic Tools
Connection analysis
At the command line, netstat shows active connections
This can identify problem connections
Figure 10-12
Spyware running on Port 3290

46. Figure 10-9: Network Management Utilities
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 R1 R2 R3
(2)
Tracert
250 ms
25 ms
75 ms
225 ms
150 ms (Problem?)

47. Figure 10-9: Network Management Utilities
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

48. Simple Network Management Protocol (SNMP)

49. Figure 10-13: 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. Figure 10-13: Simple Network Management Protocol (SNMP)
Software (Manager)
Managed
Device
Manager manages multiple managed devices from a central location
RMON Probe

51. Figure 10-13: Simple Network Management Protocol (SNMP)
Agent (Agent),
Objects
Network Management
Software (Manager)
Network
Management
Agent (Agent),
Objects
Manager talks to a network management agent on each managed device—not to the managed device directly.
<Read the text box.>
<Analogy: When you want to hire an actor, you usually must talk to his or her agent rather than directly to the actor.>
RMON Probe

52. Figure 10-13: Simple Network Management Protocol (SNMP)
Agent (Agent),
Objects
Network Management
Software (Manager)
Network
Management
Agent (Agent),
Objects
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.
<Read the text box.>
RMON Probe

53. Figure 10-13: Simple Network Management Protocol (SNMP)
Information
Base (MIB)
Network Management
Software (Manager)
Management
Information
Base (MIB)
Management
Information
Base (MIB)
<Read the text box.>
MIB stores data about devices.
MIB on manager stores all.
MIB on device stores local information
RMON Probe

54. Figure 10-13: Simple Network Management Protocol (SNMP)
Software (Manager)
1. Command (Get, Set, etc.)
2. Response
3. Trap (Alarm) Initiated by
a Managed Device
<This slide shows the three types of messages that can be sent using the Simple Network Management Protocol (SNMP).>
<Go through the command-response cycle (1) and (2).
The Get command asks for data.
The Set command changes the configuration of the remote device.>
<Then note that if agents on managed devices sense a problem, they do not wait for the manager to initiate action. They send an alarm message called a trap in SNMP.>
Simple Network
Management Protocol (SNMP)
Messages
RMON Probe

55. Figure 10-14: SNMP Object Model
Management
Information
Base (MIB)
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) …
<Read the slide.>
System uptime is a good diagnostic tool. If the time since the last reboot is very short, this could indicate an intermittent failure that is causing the device to reboot frequently.

56. Figure 10-14: SNMP Object Model
Management
Information
Base (MIB)
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 …
<Read the slide.>
The number of discards due to resource limitations is important because it indicates that a router is running out of capacity and cannot handle the traffic load.

57. Figure 10-14: SNMP Object Model
Management
Information
Base (MIB)
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 …
<Read the slide.>
The number of rows discarded due to lack of memory space is important because the existence of many discards indicates that the router is running out of memory.
Note that you can retrieve data on individual rows.

58. Figure 10-14: SNMP Object Model
Management
Information
Base (MIB)
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) …
Now we will look at TCP objects in the MIB.
Only host computers have TCP objects. Routers only have IP objects.
<Read the slide.>
<If the minimum retransmission time is too small, many segments will be resent needlessly. Segments retransmitted will be high.>

59. Figure 10-14: SNMP Object Model
Management
Information
Base (MIB)
SNMP UDP Objects
Error: no application on requested port
Traffic statistics
SNMP ICMP Objects
Number of error messages of various types
<Read the slide.>
< “Error: no application on requested port” can indicate attacks. If this number is large, an attacker may be trying a port scan.>
<Certain ICMP error messages also are good indicators that an attack is underway—for instance, if there are many pings.>

60. Figure 10-14: SNMP Object Model
Management
Information
Base (MIB)
SNMP Interface Objects (One per Port)
Type (e.g., 69 is 100Base-FX; 71 is )
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.
SNMP interface (port) objects describe what is happening on a single interface.
Many devices, such as routers, have multiple ports.
There is one set of SNMP interface object for each port.
So if a router has a dozen ports, it will have a dozen different interface object sets.
<Read the slide.>
<You can use the Get command to change the interface to testing mode, turn it on (up mode), or stop traffic from flowing through it (down mode).>

61. Traffic Management Capacity is expensive; it must be used wisely
<Read the text box.>
Capacity is expensive; it must be used wisely
Especially 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
<Read the slide.>

63. Figure 10-15: Traffic Management Methods
Traditional Approaches
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
<Read the slide.>

64. Figure 10-15: Traffic Management Methods
Traditional Approaches
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
<Read the slide.>

65. Figure 10-15: Traffic Management Methods
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
<Read the slide.>
The other methods we have seen—overprovisioning, priority, and QoS—merely cope with congestion. They cannot avoid it.

66. Topics Covered

67. Topics Covered Network Simulation IP Subnetting
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 Configuring Routers
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