Transcript Network Management Concepts and Practice

Network Management
Concepts and Practice
Author: J. Richard Burke
Presentation by Shu-Ping Lin
Outline
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Network Components
Overview of Network Management
Communication Architecture
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A communication architecture integrates
many protocols and the software that
implements them.
These parts can be developed
independently of one another as long as the
developers adhere to the standard
interfaces between them.
OSI Reference Model
OSI Reference Model
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The model does not specify how to
implement the function in each layer.
The functions in each layer are defined by
protocol, which are implemented in software.
The software in each layer provides services
to the layer above it.
Layering concept simplifies the development
process and allows improvements of
software in one layer without affecting other
layers.
Physical Layer
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This layer defines the electrical, mechanical,
functional specifications for hardware that
connects a device to the network.
Physical layer standards would specify
 Connector’s size and shape
 Exact number of pins
 The signals that can be used to those
pins
Data Link Layer
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This layer specifies the procedures in order
to achieve reliable point-to-point transfer of
information between two devices.
Data link layer can be divided into two
sublayers.
 Logical Link Control
 Medium Access Control
Data Link Layer (cont’d)
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CSMA/CD is implemented in Ethernet.
CSMA means that a computer waits until
there is no signal from any other computer
on LAN before transmitting a message.
CD reduces the probability that a collision
will occur by backoff its transmission.
Bridge is a typical device working on data
link layer.
Network Layer
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This layer provides the mechanisms for
transporting a packet from the source
networks to the destination network.
Packets are messages constructed by the
network layer and higher layers.
A router is called a network layer device
because it is controlled by protocols up to
and including the network layer.
Transport Layer
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Transport layer provides reliable and
unreliable transport protocols.
The reliable protocol, which is called the
Transport Control Protocol (TCP), provides
the mechanisms that enable end-to-end
reliability.
TCP accomplishes this by the use of
automated acknowledgement and
automated retransmissions.
Transport Layer (cont’d)
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The unreliable transport protocol, which is
called the User Datagram Protocol (UDP),
places no constrains on the network.
Best-effort delivery from the source device
to the destination device is all that is
required.
UDP is used when speed is of the essence
and the effort spent on ensuring reliability is
not cost-effective.
Session Layer
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The Session layer provides the mechanisms
necessary to open and close multiple logical
connections between processes on different
PCs.
These logical connections are called
session.
Many logical connections can use the same
physical connection.
Presentation Layer
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This layer provides a common
representation of data transferred between
peer application layer entities on different
stations.
Abstract syntax notation.one (ASN.1) format
is useful for application layer.
However, the layers below the presentation
layer use a formant call transfer syntax.
The presentation layer translates between
ASN.1 and transfer syntax.
Application Layer
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Common Application Service Elements
provide service generally useful to a variety
of application programs provided by vendors.
Specific Application Service Elements
service the additional needs of particular
application programs.
Frames
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Frame construction
 Application program makes a request.
 The request is passed to the appropriate
application-layer-entity.
 The application-layer-entity constructs an
Application layer protocol data unit (PDU).
 The Application layer PDU is then passed
to the appropriate presentation-layerentity. This entity constructs a
Presentation layer PDU.
Frames (cont’d)
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PDUs continue to be constructed and
passed to the layers below. This process
continues until the Network layer PDU is
received by the Data Link layer.
The frame is construct in the Data Link
layer. The Network Layer PDU is
encapsulated in a Data Link layer header
and trailer.
Frames (cont’d)
TCP/IP Protocol Stack
Network Device
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Workstations
Servers
Repeaters
Hubs
Bridges
Switches
Routers
Probes
Workstations
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Workstations typical make use of the
services of all layers of a protocol stack
because they process the requests of
application programs for information on
servers.
Server is like workstation making use of all
layers of the protocol stack.
Repeater
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Repeater amplifies the signal between
segments and extends the length of a LAN.
Repeaters are used on 10BASE2 and
10BASE5 LANs.
Hubs
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A hub is a repeater with many input and
output ports.
Every transmission received by the hub on
one port is amplified and retransmitted out
of all other ports.
Hub do not examine information in any field
of the frame.
Repeaters and hubs are consider a Physical
layer device.
Bridges
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Transparent bridge
 divides a LAN into segments that use the
same media access control specification
and it controls what traffic is passed
between segments.
 uses bridge table to learn which devices
are on which segments.
Translating bridges connects networks using
different MAC layer specifications.
Bridges (cont’d)
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Errors and collisions that take place on one
segment are not propagated to devices on
the other segment.
The use of switches rather than bridges is
commonplace today.
Switches
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A switch is a multiport bridge.
Switches are typically configured to forward
incoming frames to outgoing ports based on
destination MAC addresses associated with
those ports in the switch table.
Switches also can be configured to drop
frames based on MAC destination or to
redirect frames to other MAC address.
Switches (cont’d)
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Higher layers of the protocol stack are now
being implemented in switches.
Layer 3 switch also can function like router.
Routers
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Router reads the Network layer header in
packet to find the destination network
address and then looks up the address in
routing table.
The routing table is a list of mappings of
network addresses to ports that will get the
packet to the destination networks by the
best means.
Routers (cont’d)
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Routing table
Probes
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Probes are tools for learning about the
details of the communication between
devices.
Probes can be placed on a network and the
information they gather transferred to the
Management Station fro analysis of the
traffic.
Outline
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Network Components
Overview of Network Management
Network Management
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Jobs of network management in early day
 Attaching PCs and server to a LAN using
Network Interface Cards (NICs)
 Installing protocol stacks
 Configuring NIC I/O addresses and
interrupts so as not to conflict with other
NIC selections.
 Using Ping application to ensure that all
devices on the network could
communicate with one another
Network Management (cont’d)
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Access control
 The manager might write a script for the
server to control access to information on
it.
 The script would provide access to drives,
folders or files that use or group of users
needed.
 Install a print server to manage the print
jobs from each of the PCs.
Network Management (cont’d)
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Network configuration
 If the networks were to be divided into
subnets, then a bridge would be used to
connect them.
 The manager would configure a routing
table to enable connectivity according to
network address, subnet address and
subnet mask.
 Finally, installing user applications on
PCs is necessary for interfacing correctly
with OS.
Maintenance
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After configuring primary network
ingredients, here comes the maintenance.
Network performance is not optimized, there
will be software and hardware failures and
network resources will change.
The manager is required to make estimates
of the network capacity.
There was a need for minimal security.
Maintenance (cont’d)
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New work management has divided into
specialties nowadays.
Administration
 Backing up servers
 Maintaining security
 Installing OS and applications
Network engineer
 Be responsible for the health of the
network and its availability to user.
Network-Based Management
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As network has grown larger and more
complicated, network manager needed to find
more efficient way to determine and control the
state of network.
Some protocols could be used by network
manager to remotely control devices.
 Simple Network Management Protocol
(SNMP)
 Management Information Base (MIBs)
 Network Management Systems (NMS)
Network Management Protocol
Stack
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Management Station and Management
Agent.
Network Management
Example
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Step 1
 NMS calls for the service of the management
process
Step 2
 the management process call the program the
implements network management protocol.
Step 3
 NMP constructs a request packet to the program
on the management agent.
Step 4
 NMP on the management agent cause the
request packet to be passed to the agent process.
Network Management Example
(cont’d)
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Step 5
 The agent process accesses the value of the
requested variable and passes it to NMP.
Step 6
 NMP constructs the response packet which is
sent back to the management station.
Step 7
 At the management station the program that
implements the NMP receives the response
packet.
Step 8
 The management process passes the requested
value to the application program.