Transcript chapter_2

Chapter 2 Overview
Why is network mgmt necessary?
 Network managers job
 Network management vocabulary
 Network management principles
 Example implementation
 New approaches to network mgmt
 Evolution of network mgmt

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What is Network Mgmt?
 In
the past network was small, local
 Managers job included…
o Attach PC’s, etc., to LAN using NIC’s
o Configure NIC’s, protocol stack, user
app’s, shared printers, etc.
o Ping was sufficient to “manage” network
 Job
was manageable
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What is Network Mgmt?
Above only deals with configuration
 Ongoing maintenance issues

o
o
o
o
o

Improve performance
Handle failures, changes to network
More capacity/bandwidth may be needed
May need to account for usage
Security needs to be addressed
Highlighted terms: ISO mgmt categories
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What is Network Mgmt?
 In
past, one network manager might
be able to handle all responsibilities
 Today there are specializations
o
o
o
o
Network architect
Installation, configuration, etc.
Ongoing maintenance, security, etc.
Different certifications for these
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What is Network Mgmt?
Today, networks not local, more complex,
so more demands on network manager
 Mgmt tools are needed
 Network-based mgmt tools: use the
network to manage the network

o
o
o
o
Simple Network Management Protocol (SNMP)
Management Information Base (MIB)
Network Management System (NMS)
Remote Monitor (RMON)
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A Note on RFCs
RFC == Request for Comments
 Officially, an RFC is a proposed standard
 In reality, an RFC is a de facto standard

o Time for “comments” is before RFC is issued

IETF is responsible for RFCs
o All RFCs available on the Web

IEEE and ISO also important sources for
standards-related information
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Network Mgmt Vocabulary
 Network
mgmt: local and remote
o Local management station
o Remote management agent
NMS
Management Agent
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Management Station
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Network Mgmt Vocabulary

Mgmt agent provides information on the
device and/or local environment
o Can be hosted on a workstation, laptop, hub,
switch, router, …
Mgmt station runs the Network
Management System (NMS)
 NMS displays/analyzes info from agents

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Mgmt and Agent Processes
Mgmt
App
Mgmt
Mgmt
Process
Protocol
Presentation
Agent
Agent
Process
Protocol
Presentation
Session
Session
Transport
Transport
Network
Network
Data Link
Data Link
Physical
Physical
Management Station
Management Agent
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
Mgmt process is
software on the
Mgmt Station
o Interface to SNMP

Agent process is
software on the
Mgmt Agent
o Collects info
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NMS Overview
NMS includes all management apps
 Agent processes run on any device

o PC, server, hub, switch, router, etc.
o Agent collects info at request of mgmt station
o The database of information is a Management
Information Base (MIB)

Mgmt application queries agent’s MIB
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Network Mgmt Example

To get value of MIB variable from mgmt agent
1. Mgmt app (part of NMS) on mgmt station passes
2.
3.
4.
5.
6.
7.
8.
request to mgmt process
Mgmt process calls network mgmt protocol (SNMP)
SNMP constructs Get-Request packet
Mgmt agent receives Get-Request
Agent process accesses requested value
SNMP constructs Get-Response packet
Mgmt process on mgmt station receives response
Mgmt process passes data to mgmt application
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Network Mgmt Overhead
 There
is overhead in terms of
o CPU cycles to generate and process
information/packets
 May require dedicated Management Station
o Bandwidth usage for sending request and
receiving responses
A
tradeoff between cost and benefit
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Additional Mgmt Capabilities
For efficiency, can request multiple values
in a single Get-Request
 Can traverse MIB in logical order
 Mgmt agent can send unsolicited msgs

o These are known as traps
o For example, if a device goes down

Can request info from device or probe
o Probe is a remote monitor (RMON)
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Additional Mgmt Capabilities

RMON might monitor a network segment
o Source/destination addresses
o Protocols used
o Usage statistics, etc.

Management station accesses RMON info
o Using steps 1 thru 8, above
o May also routinely poll RMON
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Network Mgmt History

In 1977 International Organization for
Standards (ISO) began work on Open Systems
Interconnection (OSI) reference model
o Purpose was to “provide a common basis for the
coordination of standards developments for the
purpose of system interconnection, while allowing
existing standards to be placed in perspective
within the overall Reference Model”

OSI model published in 1984 (7 years!)
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Network Mgmt History

In March 1987, effort to develop Simple
Gateway Monitoring Protocol (SGMP)
o SGMP out by November 1987
o Could “get” and “set” variable values

About same time Common Mgmt Information
Protocol (CMIP) developed for OSI model
o CMIP is roughly SMNP for the OSI model
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Effort to develop CMIP Over TCP (CMOT)
as alternative to SGMP
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Network Mgmt History

CMIP uses Remote Operations Services
Elements (ROSE)
o ROSE is for communication with distributed apps
in OSI model
OSI mgmt process is richer and more
comprehensive than that provided by SNMP
 But OSI approach is more complex and took
longer to develop

o SNMP: “keep it simple”, and it’s good enough
o So SNMP won out in practice
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Network Mgmt History
 Due
to controversy/delays in OSI
approach, Internet Activities Board
(IAB) held meeting in 1988
o Decided to pursue both CMOT and SGMP
o Eventually abandoned CMOT (complexity)
 Eventually,
three RFCs resulted…
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Network Mgmt History

The three RFCs
o Structure of Management Information (SMI),
uses Abstract Syntax Notation One (ASN.1)
o Management Information Base (MIB), the data
structure on the mgmt agent
o Simple Network Management Protocol (SNMP)

By 1989, SNMP was the de facto standard
for management of TCP/IP networks
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2004
Network
Management
History
Web
Based
Mgmt
2000
SNMPv3
DMI
RMON 2
1996
SNMPv2 MIB
RMON 1
SNMPv2
1992
MIB 2
CMOT
SGMP & CMIP
1988
SMI
MIB1
SNMPv1
SGMP
1984
OSI
Reference
1980
Model
Development
Ethernet
1976
TCP/IP
1972
1968
Packet Switching
(ARPA)
1964
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TCP/IP Development
 TCP/IP
(and SNMP) were viewed as
temporary, since OSI was coming…
 TCP/IP was part of Berkeley Unix
 Corporations started using Unix (and
hence TCP/IP, SNMP, etc.) so that
OSI model was DOA
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Chapter 2 Summary
Overview of network management
 Responsibilities of network manager
 Need for remote monitoring
 Terminology
 Basic principles
 Simple example
 History

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