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Management Architecture and
Standards
IACT 418 IACT 918
Corporate Network Planning
Gene Awyzio
Spring 2001
Objectives
Recognise the protocols used in management
of a telecommunications network with
reference to the OSI stack, in particular
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SNMP
ASN 1
MIB
Identify databases and their use to manage
the telecommunications network
Objectives
Understand what is involved in change
control, configuration management and
configuring a network
Demonstrate appropriate practical and
problem solving skills
The OSI Stack
Proposed by the International
Organisation for Standardisation (ISO)
and other standards bodies
Its a layered approach to network
protocols involving encapsulation of
packets at each level of the stack and
the sub-layers
The OSI Stack
Each layer has its own functionality
All layers are likely present at the end
user’s host machine or Front End
processor (FEP) or customers
equipment, but …
The OSI Stack
Inside the network you may have only the
first two or three layers

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A router mostly has up to the network layer
A bridge uses the data link layer (sublayers LLC
[Logical Link Control] and MAC [Medium Access
Control])
The network management protocols operate
at the APPLICATION layer, like TELNET and
FTP
The OSI Stack
7
Application
6
Presentation
5
Session
4
Transport
3
Network
2
Data Link
1
Physical
The OSI Stack
Layer
Name
Encapsulation Component
7
Application
Data
Software
6
Presentation
Data
Software
5
Session
Data
Software
4
Transport
Segments
Router
3
Network
Packets,
Datagrams
Router
2
Data Link
Frames
NIC. ( LLC & MAC )
1
Physical
Bits
NIC.( Physical ) Hub, Repeater.
DCE & DTE
Network Management
Software Architecture
A network management system consists of
incremental hardware and software additions
(scalable) implemented among existing
network elements
The software used to accomplish the network
management tasks resides in the host
computers and communications processors:

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Front End Processors (FEP)
terminal cluster controllers
Bridges
Routers
Network Management
Software Architecture
A network management system allows
viewing of the entire network as a unified
architecture:

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With addresses and labels assigned to each
network element
With specific attributes of each network element
and its connectivity known to the system
The active elements of the network provide
regular feedback of status information to the
network control centre
Network Management
Software Architecture
A generic network management
structure might be as given in the
following figure:
Network Management
Software Architecture
NMA
NME Appl
Comm
NME Appl
Comm
NMA
NMA
NME
Comm
NME Appl
Comm
NMA
OS
Network Management
Software Architecture
Each node contains a collection of
software devoted to an appropriate
network management task

Referred to as the network
management entity ( NME)
Network Management
Software Architecture
At least one (and probably more )
host in the network is designated
the network control host or
manager
As well as the software for a NME,
these hosts include extra software
called the network management
application (NMA)
Distributed Network
Management
Centralised network management
systems are devolving into distributed
network management systems
Due to the same factors are involved
that have lead to the distributed
networks
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Low cost of hardware / PC’s
High powered PC’s
Proliferation of LAN’s
Distributed Network
Management
A distributed management system
replaces the single network control
centre with interoperable workstations
located on LANs distributed throughout
the organisation
This gives departmental (local) level
managers the tools they need to
maintain responsive networks, systems
and applications for their local end
users
Distributed Network
Management
But… how do we avoid anarchy?
Distributed Network
Management
Management clients
(PCs, workstations)
Network
Management server
Management
Application
Management server
Management
Application
MIB
MIB
Network
Network
Element
Manager
Element
Manager
Network Resources
(servers, routers, hosts)
with management agents
Distributed Network
Management
The distributed system has the
following benefits:
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Network management traffic is minimised
Distributed management offers greater
scalability
 adding capability only involves adding another
workstation in the appropriate location
 The use of multiple networked stations eliminates
the single point of failure represented by having
only one central manager
Proxies
Proxies may be required when:
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Older network elements exist in the network that
do not use the protocols implemented by the
management servers
Small systems that would be unduly burdened
(too many management packets would flow on
the system) to support a full blown NME (agent)
Modems and multiplexers which do not support
additional software / agents
SNMP
The term Simple Network Management
Protocol (SNMP) actually refers to a collection
of specifications that include:

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the protocol itself
the definition of data structures
associated concepts (eg proxies)
We will now look at a brief overview of the
SNMP setup, the most prolific method of
network management today
The History
SNMP’s development follows a similar
pattern to the development of TCP/IP
ARPANET evolved during 1970’s, into a
set of protocols approved by the
internet architecture board (IAB)
{www.iab.Org}
The History
Standards were issued as RFC’s
(Request for comment) and were
adopted by the military in the United
States in their procurement policies,
forming the core of the TCP/IP protocol
suite, which was adopted by vendors
for non military activities, and grew
dramatically during the 1980’s
The History
Many still predict that OSI standards will
replace TCP/IP, but this has not occurred at
this time. Why? Possible reasons are:
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TCP/IP suite is mature, and adapts to
interoperability issues via the IAB / IETF
TCP/IP provides a high level of functionality - from
the majority of users points of view
The international standards have been slowly
developed (OSI), while providing a richer
functionality they will also require more effort in
implementation and conformance testing
The History
As TCP/IP developed little thought was given
to network management, especially in the
early days where many programmers and
protocol designers would modify the network
as required
Through the late 1970’s there were still no
network management protocols, but the one
tool used for management that was available
was the Internet Control Message Protocol
(ICMP)
Internet Control Message
Protocol:
ICMP
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Provides a means for transferring control
messages from routers and other hosts to a host
to provide feedback about problems in the
networking environment
Most useful message is the echo / echo reply
message pair - provides a mechanism to test if
communication is possible between two network
elements / entities on the TCP/IP network
Also provides a mechanism for measuring delay
across the connection using time stamp and
time stamp reply
Internet Control Message
Protocol:
The ICMP messages can be used with
IP header options such as source
routing and record route ( a trace
route feature) to develop simple but
powerful management tools
The most useful example of this is the
widely used PING (Packet INternet
Groper)
Internet Control Message
Protocol:
PING can perform a variety of functions
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Determine if a particular network element
can be addressed
Verifying that a network can be addressed
Observe variations in round trip times
Observe datagram loss rates, which can
help isolate points of congestion and high
error rates / points of failure
Internet Control Message
Protocol:
This was satisfactory up until the late
1980’s when exponential growth in the
internet required more powerful
network management capability
In November 1987, the Simple Gateway
Monitoring Protocol (SGMP) was issued,
providing a way to monitor gateways
on the internet
Internet Control Message
Protocol:
At this time three approaches were
proposed or emerged:
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High Level Entity Management System
(HEMS)
Simple Network Management Protocol
(SNMP)
CMIP (Common Management Information
Protocol from OSI) over TCP /IP (CMOT
Internet Control Message
Protocol:
In 1988 the IAB reviewed these proposals
and approved SNMP for a short term solution
and CMOT as the long range solution

Both SNMP and CMOT were to use the same
database of managed objects
There would be only a single
 Structure of Management Information (SMI - the basic
format conventions for objects)
 Management Information Base (MIB - the actual
structure or schema of the database)
Internet Control Message
Protocol:
In 1989, after it was found impractical
to have the same set of managed
objects, the IAB relaxed its condition of
common SMI / MIB and allowed the two
protocols to develop independently
Freedom from OSI constraints led to
rapid SNMP development
SNMP Related Standards
Three foundation specifications of SNMP are:
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Structure and Identification of Management
Information for TCP/IP-based networks (RFC
1155)
Management Information Base for Network
Management of TCP/IP-based Internets: MIB-II
(RFC 1213)
Simple Network Management Protocol (RFC
1157)
The SNMP Network
Management Architecture

The model used for network management
of TCP/IP includes the key elements:
 Management station
 Management agent
 Management Information Base
 Network management protocol
Management Station
Typically a stand-alone network
element, but may be a capability on a
shared system (eg mainframe)
Serves as the network interface for the
human network manager into the
network management system
Management Station
As a minimum the network management
station will have:
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A set of management applications
An interface
The capability of translating the network
manager's requirements into the actual monitoring
and control of remote elements in the network
A database of information extracted from the MIBs
of all the managed entities in the network
SNMP standards only cover points 3 and 4
Management agent
The management agent
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Responds to requests for information and
actions from the management station
May asynchronously provide the
management station with important but
unsolicited information
Managed objects
Resources in the network may be managed
by representing these resources as objects

Each object is a data variable that represents one
aspect of the managed agent
The collection of objects is referred to as a
Management Information Base (MIB)

The MIB functions as a collection of access points
at the agent for the management station
Management Information
Base
The objects are standardized across
systems of a particular class

For example, a common set of objects is
used for the management of various
bridges
A management station performs the
monitoring function by retrieving the
value of MIB objects
Management Information
Base
A management station can
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Cause an action to take place at an agent
change the configuration settings at an
agent by modifying the value of specific
variables
The management station and agents
are linked by a network management
protocol
SNMP - the Management
Protocol Used for TCP/IP
SNMP includes the following key capabilities:
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Get
Set
Trap
The standards do not specify
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The number of management stations
The ratio of management stations to agents
SNMP - the Management
Protocol Used for TCP/IP
In general, it is prudent to have at least two
systems capable of performing the
management station functions
As SNMP is simple it can handle many agents
SNMP is designed to be an application-level
protocol that is part of the TCP/IP protocol
suite which operates over the user datagram
protocol (UDP)
SNMP - the Management
Protocol Used for TCP/IP
SNMP - the Management
Protocol Used for TCP/IP
SNMP - the Management
Protocol Used for TCP/IP
From a management station, three
types of SNMP messages are issued on
behalf of a management application:
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GetRequest
GetNextRequest
SetRequest
SNMP - the Management
Protocol Used for TCP/IP
The first two are two variations of the
get function
All three messages are acknowledged
by the agent in the form of a
GetResponse message, which is
passed up to the management
application
SNMP - the Management
Protocol Used for TCP/IP
An agent may issue a trap message in
response to an event that affects the MIB and
the underlying managed resources - this is
received by the manager
SNMP relies on UDP, which is
connectionless so SNMP is itself
connectionless ie each exchange is a
separate transaction between a
management station and an agent
Trap - Directed Polling
Preferred strategy is:
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A management station can poll all of the
agents it knows for some key information
Once the baseline is established, the
management station refrains from polling
Each agent is responsible for notifying the
management station of any unusual event
Trap - Directed Polling
These events are communicated in
SNMP messages known as traps
Once a management station is alerted
to an exception condition, it chooses to
take the appropriate action
Trap - Directed Polling
Trap-directed polling can result in
substantial savings of
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Network capacity
Agent processing time
Reduces unnecessary polling of agents
by managers thus reducing
management induced network traffic
Limitations of SNMP
SNMP may not be suitable for the
management of very large networks
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Each agent needs to be polled and generates trap
traffic
SNMP is not suited to retrieving large volumes of
data such as a entire routing table
SNMP traps are unacknowledged meaning the
agent generating the trap does not know if
the manager received it
Limitations of SNMP
Basic SNMP standard only provides
trivial authentication
SNMP does not directly support
imperative commands with parameters,
conditions, status and results
Limitations of SNMP
SNMP MIB model is limited not
supporting sophisticated management
queries based on object values or types
SNMP does not support manager to
manager communications ie no
mechanism for one manager to find out
about another network managers,
managed network elements