© 2009 pearson education, inc. publishing as prentice hall chapter 10 panko’s business data...

© 2009 Pearson Education, Inc. Publishing as Prentice Hall

Chapter 10

Panko’sBusiness Data Networks and Telecommunications, 7th edition © 2009 Pearson Education, Inc. Publishing as Prentice Hall

May only be used by adopters of the book

Network Management

© 2009 Pearson Education, Inc. Publishing as Prentice Hall 10-2

10-1: Planning the Technological Infrastructure

• What-Is Analysis

– Understand the current network in detail

– Requires a comprehensive inventory


10-1: Planning the Technological Infrastructure

• Driving Forces for Change

– Normal growth in application demand

– Disruptive applications

• Video requires higher network capacity

• Voice requires high quality of service

– Organizational changes

– Changes in other aspects of IT (data center consolidation, etc.)


10-2: Scalability


Traffic Management

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


10-3: Traditional Traffic Management Methods

As we saw in Chapter 4, even in a network withadequate capacity, there will be occasional

momentary traffic peaks when traffic exceeds capacity


10-3: Traffic Management Methods

• Traditional Approaches to Managing Momentary Traffic Peaks

– Overprovisioning

• 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



• 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


• 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



Figure 10-5: Compression

A fifth way to manage traffic is to use compression.Here, 3 Gbps and 5 Gbps traffic streams go into the network.Without compression, 8 Gbps of capacity would be needed.

With 10:1 compression, only 800 Mbps of capacity is needed.A 1 Gbps line will be adequate.


Network SimulationSoftware


• 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

10-6: Network Simulation



• 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



• 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


• 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



10-7: 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


Specify the Topology

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.


10-8: Configuring Elements in IT Guru

4.Configure EACH node and

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


10-9: Add Applications

5.Add applications, which generate traffic data

Applications



• 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)


10-10: What-If Analysis

7.Do what-if analyses,

trying different alternatives.



• 8. Examine application performance, which goes beyond network performance

– Involves host performance

– Involves application configuration

– OPNET’s Application Characterization Environment (ACE) can do this.


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

IP Subnetting


IP Subnetting

Part Size(bits) 2N 2N-2

4 24 = 16 16-2 = 14

8 ? ?

12 4,096 4,094

65,536 65,53416

10 ? ?

• 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


10-11: 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

(28-2)

By Definition

Assigned tothe firm

Bits for thefirm to assign

The firm’sdecision



DescriptionStep


1


2 16


3 16


4 6/10


62

(26-2)


1,022

(210-2)

By Definition

Assigned tothe firm





DescriptionStep


1


2 8


3 24


4 12/12


4,094

(212-2)


4,094

(212-2)

By Definition

Assigned tothe firm





DescriptionStep


1


2 8


3 24


4 8/16


254

(28-2)


65,534

(216-2)

By Definition

Assigned tothe firm





DescriptionStep


2 20


3 12

Selected host partsizes (bits)

4 ?


?


?

Selected subnet partsizes (bits)

Added 4



DescriptionStep


2 20


3 12

Selected host partsizes (bits)

4 ?


?


?

Selected subnet partsizes (bits)

Added 6


Network Address Translation (NAT)

32


10-12: Network Address Translation (NAT)

• NAT

– Sends packets with false external IP addresses that are different from true internal IP addresses

– NAT Operation (Figure 10-13)



When an internal host sendsa packet, the NAT firewallchanges the source IPaddress and the sourceport number.

The NAT firewall recordsthe original and changedinformation in a translationtable for later use.

1



If an eavesdropper with a sniffer program captures andreads the source IP address and port number, it will notlearn the true source IP address and port number of thesending host. This means that it cannot send attack packetsto the sending host.



• NAT is Transparent to Internal and External Hosts

• Expanding the Number of Available IP Addresses

– Companies may receive a limited number of IP addresses from their ISPs

– There are roughly 4,000 possible ephemeral port numbers for each IP address

– So for each IP address, there can be 4,000 external connections



• Expanding the Number of Available IP Addresses

– If a firm is given 248 IP addresses, there can be roughly one million external connections

– Even if each internal device averages several simultaneously external connections, there should not be a problem providing as many external IP connections as a firm desires



• Private IP addresses

– Can be used only inside firms

– 10.x.x.x

– 192.168.x.x (most popular)

– 172.16.x.x through 172.31.x.s



• Protocol Problems with NAT

– IPsec, VoIP, etc. do not work properly with NAT

• The protocol must know the true IP address of a host

– Work-arounds must be considered very carefully in product selection


Multiprotocol Label Switching

40


10-14: Multiprotocol Label Switching (MPLS)

In normal routing, each router along theroute must do a great deal of work todecide to do with each arriving packet,even if many packets are sent to thesame destination host.



In Multiprotocol Label Switching (MPLS),the routers select the best route betweentwo hosts before transmission begins.This routes is called the label-switchedpath. In other words, routing decisionsare made only once, before any packetsare sent.



The first label-switched router adds aLabel to each packet. This label containsThe number of the label-switched route.

The final label-Switched routerRemoves the label.

Other label-switched routerssend the packet back out onthe basis of the label number.

2


10-14: MPLS

• MPLS is invisible to the hosts

– Label-switching routers add and delete the label

• MPLS Benefits

– Reduced cost per packet because routing decisions are pre-made before any packets are sent

– MPLS allows traffic engineering such as quality of service and load balancing to route packets around congestion


Domain Name System (DNS)

45


10-15: Domain Name System (DNS) Lookup

• In Chapter 1, We Saw DNS Lookup

– A host wishes to know the IP address of a another host

– The host only knows the other host’s host name

– The host sends a DNS request message to a DNS server

• This message contains the other host’s host name

– The DNS server sends a DNS response message

• The message contains the IP address of the other host



Often the local DNS server (in this case theHawaii.edu DNS server) will not know the IP address.

The local DNS server contacts the authoritative DNS server for the domain of the other host.

The remote DNS server sends back the IP address.



The local DNS server sends this IP addressBack to the host that sent the DNS request.


Figure 10-16: Domain Name System (DNS) Hierarchy

More generally,DNS is a hierarchical

naming system fordomains, which are

collections of resourcesunder the control of

an organization.

A host is only one typeof named resource.

The DNS naming system is hierarchical.



At the top level is theRoot, which contains

All domains. There are13 root DNS servers

Below the root areTop-level domains byType (.com, .edu) or

by country (.uk, .ch, etc.)



They can then internallyname subnets and hosts.

What companies really want are good second-level domain names, such as Microsoft.com.

Every second-level domain must maintain an authoritative DNS server.

2


Dynamic Host Configuration Protocol (DHCP)

52


10-17: Dynamic Host Configuration Protocol (DHCP)

When a client PC boots up, it realizes that it does nothave an IP address for itself.

It sends a DHCP Request Message to a DHCP server.this DNS Request Message asks for an IP address for itself.



The DHCP server has a pool of IP addresses to manage.It selects one for the client.



The DHCP server sends this IP address to the client PCIn a DHCP Response Message.

This message also contains other configurationinformation, including a subnet mask, the IP address

of the client’s default router, and theIP addresses of the firm’s DNS servers.


10-17: DHCP

• Servers Get Static (Permanent) IP Addresses

– So that clients can find them

• Clients Could Also Be Configured Manually with Static IP Addresses

– But this would be very time-consuming

– In addition, every time a firm changed the IP addresses of its DNS servers or some other configuration parameter, all clients would have to be changed manually

– With DHCP, clients always get “fresh” configuration data


Simple Network Management Protocol (SNMP)

57


10-18: Simple Network Management Protocol (SNMP)

• Core Elements (from Chapter 1)

– Manager program

– Managed devices

– Agents (communicate with the manager on behalf of the managed device)

– Management information base (MIB)

• Stores the retrieved information

• “MIB” can refer to either the database on the manager or on the database schema



• Messages

– Commands

• Get: Please give me the following data about yourself

• Set: Please change the following parameters in your configuration to the values contained in this message

– Responses

– Traps (alarms sent by agents)

– SNMP uses UDP at the transport layer to minimize the burden on the network



• RMON Probes– Remote monitoring probes– A special type of agent– Collects data for a part of the network– Supplies this information to the manager

NetworkManagement

Agent (Agent),Objects

RMON Probe

NetworkManagement

Software(Manager)



• Objects (see Figure 10-19)

– NOT managed devices

– Information about which information is stored

– E.g., Number of rows in the routing table

– E.g., Number of discards caused by lack of resources (indicates a need for an upgrade)



• Set Commands

– Dangerous if used by attackers

– Many firms disable set to thwart such attacks

– However, they give up the ability to manage remote resources without travel

– SNMPv1: community string shared by the manager and all devices

– SNMPv3: each manager-agent pair has a different password



• User Functionality

– Reports, diagnostics tools, etc. are very important

– They are not built into the standard

– They are added by SNMP manager vendors

– Critical in selection


Directory Servers

Store corporate information

Hierarchical organization of content

LDAP standard to access directory servers


10-20: Directory Server Organization and LDAP

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 managementrequires centralizedinformation storage.

Directory servers do this.

Directory server information is organized in a hierarchy


10-20: Directory Server Organization and LDAP

University of Waikiki (O) CN=Waikiki

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.)


10-21: Active Directory Domains and Domain Controllers

© 2009 pearson education, inc. publishing as prentice hall chapter 10 panko’s business data...

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