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System support & Management Protocols

Lesson 13

NETS2150/2850School of Information Technologies

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Lecture Outline

Simple Network Management Protocol- SNMP

Domain Name System- DNS Dynamic Host Configuration Protocol-

DHCP

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Network Management - SNMP Simple Network Management Protocol Networks are becoming indispensable More complexity makes failure more likely Require automatic network management tools Standards required to allow multi-vendor networks Covering:

– Services– Protocols

– Management information base (MIB)

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Network Management Systems

Collection of tools for network management Single operator interface Powerful, user friendly command set Performing most or all management tasks Minimal amount of separate equipment

– i.e. use existing equipment View entire network as unified architecture Active elements provide regular feedback

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Key Elements

Management station or manager Agent Management information base Network management protocol

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Management Station Stand alone system or part of shared system Interface for human network manager Set of management applications

– Data analysis– Fault recovery

Interface to monitor and control network Translate manager’s requirements into monitoring

and control of remote elements Data base of network management information

extracted from managed entities

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Management Agent

Hosts, bridges, hubs, routers equipped with agent software

Allow them to be managed from management station

Respond to requests for information Respond to requests for action Asynchronously supply unsolicited

information

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Management Information Base MIB Representation of network resources as

objects Each object a variable representing one aspect

of managed object MIB is collection of access points at agent for

management of station Objects standardized across class of system

– Bridge, router etc.

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Network Management Protocol Link between management station and

agent TCP/IP uses SNMP OSI uses Common Management

Information Protocol (CMIP)

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Protocol Capabilities

Get Set Notify

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Management Layout

May be centralized in simple network May be distributed in large, complex

network– Multiple management servers– Each manages pool of agents– Management may be delegated to

intermediate manager

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Example of Distributed Network Management Configuration

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Network Management Protocol Architecture Application-level protocol Part of TCP/IP protocol suite Runs over UDP From management station, three types of SNMP messages

issued– GetRequest, GetNextRequest, and SetRequest – Port 161

Agent replies with GetResponse Agent may issue trap message in response to event that

affects MIB and underlying managed – Port 162

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SNMP v3: The latest version

Addresses security issues of SNMP v1/2

RFC 2570-2575 Proposed standard January 1998 Defines overall architecture and security

capability To be used with SNMP v2

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SNMP v3 Services Authentication

– Part of User-Based Security (UBS)– Assures that message:

• Came from identified source• Has not been altered• Has not been delayed or replayed

Privacy– Encrypted messages using DES

Access control– Can configure agents to provide a number of levels of access

to MIB– Access to information– Limit operations

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Domain Name System – DNSDomain Name System – DNS

Name Space Flat Hierarchical

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Domain Name Space

Was designed in order to have a hierarchical name space

Label Domain Name

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Domain name space

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Domain names and labels

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Domain Names: FQDN and PQDN

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Domains

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Distribution of Name SpacesDistribution of Name Spaces

Hierarchy of Name Servers Zone Root Server Primary and Secondary Servers

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Hierarchy of name servers

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Zones and domains

A primary server loads all information from the disk file; the secondary server loads all information from the primary server.

Note

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DNS In The InternetDNS In The Internet

Generic Domain

Country Domain

Inverse Domain

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DNS in the Internet

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Generic domains

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New generic domain labels New generic domain labels

Label Description

aero Airlines and aerospace companies

biz Businesses or firms (similar to com)

coop Cooperative business organizations

info Information service providers

museum Museums and other nonprofit organizations

name Personal names (individuals)

pro Professional individual organizations

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Country domains

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Inverse domain

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ResolutionResolution

Resolver Mapping Names to Addresses Mapping Addresses to Names Recursive Resolution Iterative Resolution Caching

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Recursive resolution

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Query and response messages

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DNS can use the services of UDP or TCP,

using the well-known port 53.

NoteNote::

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Dynamic Address Configuration

Each computer attached to the Internet must have:– Its own IP address– Its subnet mask– The IP address of a Router– The IP address of a name server

Usually stored in a config file– Used at bootup

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Dynamic Address Configuration…

How about first-time bootup? Diskless terminal? Or, the movement of a computer from

one subnet to another?– Protocols needed for on-demand config

(dynamically)– Example: DHCP

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DHCP Client-server program DHCP server: two databases

– First one: Statically binds physical addresses to IP addresses (Static db)

– Second one: makes DHCP dynamic (Dynamic db)• Temporary IP addresses are assigned consulting available

(unused) address pool• Valid for a negotiated time period only (leased)

– Must renew or stop using after the lease expires

– Renewal may or may not be granted by the server

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DHCP: Client Transition States

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Recommended Reading:– Stallings 22.3 (SNMP), – Forouzan 25 (DNS) & 19.2 (DHCP)