Date post: | 10-Apr-2018 |
Category: |
Documents |
Upload: | prakashreddy4007 |
View: | 232 times |
Download: | 0 times |
8/8/2019 Network OSI
http://slidepdf.com/reader/full/network-osi 1/35
Computer Networks
overview
Network Components
Overview of Network Management
8/8/2019 Network OSI
http://slidepdf.com/reader/full/network-osi 2/35
Communication Architecture 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.
8/8/2019 Network OSI
http://slidepdf.com/reader/full/network-osi 3/35
OSI Reference Model
8/8/2019 Network OSI
http://slidepdf.com/reader/full/network-osi 4/35
OSI Reference Model The model does not specify how to
implement the function in each layer.
The functions in each layer are defined byprotocol, which are implemented in software.
The software in each layer provides servicesto the layer above it.
Layering concept simplifies the developmentprocess and allows improvements of software in one layer without affecting other layers.
8/8/2019 Network OSI
http://slidepdf.com/reader/full/network-osi 5/35
Physical Layer
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
8/8/2019 Network OSI
http://slidepdf.com/reader/full/network-osi 6/35
Data Link Layer
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
8/8/2019 Network OSI
http://slidepdf.com/reader/full/network-osi 7/35
Data Link Layer (cont¶d)
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.
8/8/2019 Network OSI
http://slidepdf.com/reader/full/network-osi 8/35
Network Layer 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.
8/8/2019 Network OSI
http://slidepdf.com/reader/full/network-osi 9/35
Transport Layer Transport layer provides reliable and
unreliable transport protocols.
The reliable protocol, which is called theTransport Control Protocol (TCP), provides
the mechanisms that enable end-to-end
reliability.
TCP accomplishes this by the use of
automated acknowledgement and
automated retransmissions.
8/8/2019 Network OSI
http://slidepdf.com/reader/full/network-osi 10/35
Transport Layer (cont¶d) 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.
8/8/2019 Network OSI
http://slidepdf.com/reader/full/network-osi 11/35
Session Layer The Session layer provides the mechanisms
necessary to open and close multiple logical
connections between processes on differentPCs.
These logical connections are called
session.
Many logical connections can use the same
physical connection.
8/8/2019 Network OSI
http://slidepdf.com/reader/full/network-osi 12/35
Presentation Layer
This layer provides a commonrepresentation of data transferred between
peer application layer entities on differentstations.
Abstract syntax notation.one (ASN.1) formatis useful for application layer.
However, the layers below the presentationlayer use a formant call transfer syntax.
The presentation layer translates between ASN.1 and transfer syntax.
8/8/2019 Network OSI
http://slidepdf.com/reader/full/network-osi 13/35
Application Layer 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.
8/8/2019 Network OSI
http://slidepdf.com/reader/full/network-osi 14/35
Frames
Frame construction
Application program makes a request.
The request is passed to the appropriateapplication-layer-entity.
The application-layer-entity constructs an Application layer protocol data unit (PDU).
The Application layer PDU is then passedto the appropriate presentation-layer-entity. This entity constructs aPresentation layer PDU.
8/8/2019 Network OSI
http://slidepdf.com/reader/full/network-osi 15/35
NetworkD
evice Workstations
Servers
Repeaters
Hubs
Bridges
Switches Routers
Probes
8/8/2019 Network OSI
http://slidepdf.com/reader/full/network-osi 16/35
Workstations 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.
8/8/2019 Network OSI
http://slidepdf.com/reader/full/network-osi 17/35
Repeater Repeater amplifies the signal between
segments and extends the length of a LAN.
Repeaters are used on 10BASE2 and10BASE5 LANs.
8/8/2019 Network OSI
http://slidepdf.com/reader/full/network-osi 18/35
Hubs A hub is a repeater with many input and
output ports.
Every transmission received by the hub onone port is amplified and retransmitted outof all other ports.
Hub do not examine information in any field
of the frame. Repeaters and hubs are consider a Physical
layer device.
8/8/2019 Network OSI
http://slidepdf.com/reader/full/network-osi 19/35
Bridges Transparent bridge
divides a LAN into segments that use the
same media access control specificationand it controls what traffic is passedbetween segments.
uses bridge table to learn which devices
are on which segments. Translating bridges connects networks
using different MAC layer specifications.
8/8/2019 Network OSI
http://slidepdf.com/reader/full/network-osi 20/35
Bridges (cont¶d) 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.
8/8/2019 Network OSI
http://slidepdf.com/reader/full/network-osi 21/35
Switches A switch is a multiport bridge.
Switches are typically configured to forward
incoming frames to outgoing ports based ondestination 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.
8/8/2019 Network OSI
http://slidepdf.com/reader/full/network-osi 22/35
Switches (cont¶d) Higher layers of the protocol stack are now
being implemented in switches.
Layer 3 switch also can function like router.
8/8/2019 Network OSI
http://slidepdf.com/reader/full/network-osi 23/35
Routers Router reads the Network layer header in
packet to find the destination network
address and then looks up the address inrouting table.
The routing table is a list of mappings of
network addresses to ports that will get the
packet to the destination networks by thebest means.
8/8/2019 Network OSI
http://slidepdf.com/reader/full/network-osi 24/35
Routers (cont¶d)
Routing table
8/8/2019 Network OSI
http://slidepdf.com/reader/full/network-osi 25/35
Probes
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.
8/8/2019 Network OSI
http://slidepdf.com/reader/full/network-osi 26/35
Outline
Network Components
Overview of Network Management
8/8/2019 Network OSI
http://slidepdf.com/reader/full/network-osi 27/35
Network Management
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
8/8/2019 Network OSI
http://slidepdf.com/reader/full/network-osi 28/35
Network Management (cont¶d)
Access control
The manager might write a script for the
server to control access to information onit.
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.
8/8/2019 Network OSI
http://slidepdf.com/reader/full/network-osi 29/35
Network Management (cont¶d)
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 andsubnet mask.
Finally, installing user applications on
PCs is necessary for interfacing correctly
with OS.
8/8/2019 Network OSI
http://slidepdf.com/reader/full/network-osi 30/35
Maintenance
After configuring primary network
ingredients, here comes the maintenance.
Network performance is not optimized, therewill be software and hardware failures and
network resources will change.
The manager is required to make estimates
of the network ca pacity .
There was a need for minimal security .
8/8/2019 Network OSI
http://slidepdf.com/reader/full/network-osi 31/35
Maintenance (cont¶d)
New work management has divided intospecialties nowadays.
Administration Backing up servers
Maintaining security
Installing OS and applications
Network engineer
Be responsible for the health of thenetwork and its availability to user.
8/8/2019 Network OSI
http://slidepdf.com/reader/full/network-osi 32/35
Network-Based Management
As network has grown larger and morecomplicated, network manager needed to findmore 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)
8/8/2019 Network OSI
http://slidepdf.com/reader/full/network-osi 33/35
Network Management Protocol
Stack
Management Station and Management
Agent.
8/8/2019 Network OSI
http://slidepdf.com/reader/full/network-osi 34/35
Network Management
Example
Step 1
NMS calls for the service of the managementprocess
Step 2
the management process call the program theimplements network management protocol.
Step 3
NMP constructs a request packet to the programon the management agent.
Step 4
NMP on the management agent cause therequest packet to be passed to the agent process.
8/8/2019 Network OSI
http://slidepdf.com/reader/full/network-osi 35/35
Network Management Example
(cont¶d)
Step 5
The agent process accesses the value of therequested 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 responsepacket.
Step 8
The management process passes the requestedvalue to the application program.