Packet switching refers to protocols where messages are divided into packets before being transmitted. Each packet is transmitted individually and can take different routes to the destination. Once all packets arrive, they are recompiled into the original message. There are two main approaches: virtual circuits establish a pre-planned route before transmission, while datagrams treat each packet independently without connection setup. Virtual circuits provide sequencing but are less reliable if a node fails, while datagrams are more flexible but packets may arrive out of order.
The network layer is responsible for routing packets from the source to destination. The routing algorithm is the piece of software that decides where a packet goes next (e.g., which output line, or which node on a broadcast channel).For connectionless networks, the routing decision is made for each datagram. For connection-oriented networks, the decision is made once, at circuit setup time.
Routing Issues
The routing algorithm must deal with the following issues:
Correctness and simplicity: networks are never taken down; individual parts (e.g., links, routers) may fail, but the whole network should not.
Stability: if a link or router fails, how much time elapses before the remaining routers recognize the topology change? (Some never do..)
Fairness and optimality: an inherently intractable problem. Definition of optimality usually doesn't consider fairness. Do we want to maximize channel usage? Minimize average delay?
When we look at routing in detail, we'll consider both adaptive--those that take current traffic and topology into consideration--and nonadaptive algorithms.
switching techniques in data communication and networkingHarshita Yadav
it is a detailed presentation on switching techniques. it includes the three types of switching technique. it is described in such manner that you can learn switching without any difficulties.
This presentation is about the introduction to network switch layer technology. A network switch is a device tha is used to connect different segments over the network.This ppt includes introduction to switch,types of switches or layer specification,advantages and disadvantages of switch..
I hope it will be very helpful for the engineering students and the others who are interested to search in deep about network switch.
The network layer is responsible for routing packets from the source to destination. The routing algorithm is the piece of software that decides where a packet goes next (e.g., which output line, or which node on a broadcast channel).For connectionless networks, the routing decision is made for each datagram. For connection-oriented networks, the decision is made once, at circuit setup time.
Routing Issues
The routing algorithm must deal with the following issues:
Correctness and simplicity: networks are never taken down; individual parts (e.g., links, routers) may fail, but the whole network should not.
Stability: if a link or router fails, how much time elapses before the remaining routers recognize the topology change? (Some never do..)
Fairness and optimality: an inherently intractable problem. Definition of optimality usually doesn't consider fairness. Do we want to maximize channel usage? Minimize average delay?
When we look at routing in detail, we'll consider both adaptive--those that take current traffic and topology into consideration--and nonadaptive algorithms.
switching techniques in data communication and networkingHarshita Yadav
it is a detailed presentation on switching techniques. it includes the three types of switching technique. it is described in such manner that you can learn switching without any difficulties.
This presentation is about the introduction to network switch layer technology. A network switch is a device tha is used to connect different segments over the network.This ppt includes introduction to switch,types of switches or layer specification,advantages and disadvantages of switch..
I hope it will be very helpful for the engineering students and the others who are interested to search in deep about network switch.
These slides cover a topic on Introduction to switching & circuit switching in Data Communication. All the slides are explained in a very simple manner. It is useful for engineering students & also for the candidates who want to master data communication & computer networking.
Network layer - design Issues ,Store-and-Forward Packet Switching, Services Provided to the Transport Layer, Which service is the best , Implementation of Service , Implementation of Connectionless Service , Implementation of Connection-Oriented Service
INTRODUCTION
WHAT IS OSI?
OSI MODEL
TYPES OF LAYERS
PHYSICAL LAYER
DATA LINK LAYER
NETWORK LAYER
TRANSPORT LAYER
SESSION LAYER
PRESENTATION LAYER
APPLICATION LAYER
Switching Nodes:
Intermediate switching device that moves data
Not concerned with content of data
Stations:
End devices that wish to communicate
Each station is connected to a switching node
Communications Network:
A collection of switching nodes
www.amazontedx.com
These slides cover a topic on Introduction to switching & circuit switching in Data Communication. All the slides are explained in a very simple manner. It is useful for engineering students & also for the candidates who want to master data communication & computer networking.
Network layer - design Issues ,Store-and-Forward Packet Switching, Services Provided to the Transport Layer, Which service is the best , Implementation of Service , Implementation of Connectionless Service , Implementation of Connection-Oriented Service
INTRODUCTION
WHAT IS OSI?
OSI MODEL
TYPES OF LAYERS
PHYSICAL LAYER
DATA LINK LAYER
NETWORK LAYER
TRANSPORT LAYER
SESSION LAYER
PRESENTATION LAYER
APPLICATION LAYER
Switching Nodes:
Intermediate switching device that moves data
Not concerned with content of data
Stations:
End devices that wish to communicate
Each station is connected to a switching node
Communications Network:
A collection of switching nodes
www.amazontedx.com
Illustration 2
Assume that the direct material inventory of Saron Furniture Factory amounts to Br. 248,000 at the beginning of the year i.e., as of July 1, 2014. Purchases of direct materials amounting Br. 440,000 was made and freight cost of Br. 3,200 is incurred during the year, and the amount of direct materials inventory at the end of the year is Br. 234,900.
Compute the direct materials used
Assume further that Saron Furniture Factory has beginning work in process of Br. 220,000 and ending work in process of Br. 263,200. The direct labor cost incurred in the year is Br. 875,000 and the different manufacturing overhead costs incurred during the year are given below:
Indirect labor
Br. 98, 600
Depreciation on factory equipment
44,600
Light and power
43,600
Depreciation of factory building
12,000
Insurance expense on factory properties
9,500
Property tax
19,500
Factory supplies
9,900
Total Manufacturing overhead cost
Br. 237, 700
Compute the cost of goods manufactured.
Assume also that the finished goods inventory at the beginning of the year was Br. 314,000 and the ending inventory of finished goods is Br. 364,000 for Saron Furniture Factory.
Compute the cost of goods sold
Illustration 2
Assume that the direct material inventory of Saron Furniture Factory amounts to Br. 248,000 at the beginning of the year i.e., as of July 1, 2014. Purchases of direct materials amounting Br. 440,000 was made and freight cost of Br. 3,200 is incurred during the year, and the amount of direct materials inventory at the end of the year is Br. 234,900.
Compute the direct materials used
Assume further that Saron Furniture Factory has beginning work in process of Br. 220,000 and ending work in process of Br. 263,200. The direct labor cost incurred in the year is Br. 875,000 and the different manufacturing overhead costs incurred during the year are given below:
Indirect labor
Br. 98, 600
Depreciation on factory equipment
44,600
Light and power
43,600
Depreciation of factory building
12,000
Insurance expense on factory properties
9,500
Property tax
19,500
Factory supplies
9,900
Total Manufacturing overhead cost
Br. 237, 700
Compute the cost of goods manufactured.
Assume also that the finished goods inventory at the beginning of the year was Br. 314,000 and the ending inventory of finished goods is Br. 364,000 for Saron Furniture Factory.
Compute the cost of goods sold
Illustration 2
Assume that the direct material inventory of Saron Furniture Factory amounts to Br. 248,000 at the beginning of the year i.e., as of July 1, 2014. Purchases of direct materials amounting Br. 440,000 was made and freight cost of Br. 3,200 is incurred during the year, and the amount of direct materials inventory at the end of the year is Br. 234,900.
Compute the direct materials used
Assume further that Saron Furniture Factory has beginning work in process of Br. 220,000 and e
Software engineering task bridging the gap between system requirements engineering and software design.
Provides software designer with a model of:
system information
function
behavior
Model can be translated to data, architectural, and component-level designs.
Expect to do a little bit of design during analysis and a little bit of analysis during design.
Object-Oriented Concepts
Attribute: the basic data of the class.
Method (operation): an executable procedure that is encapsulated in a class and is designed to
operate on one or more data attributes that are defined as part of the class.
Object: when specific values are assigned to all the resources defined in a class, the result is an
instance of that class. Any instance of any class is called an object.
1. Packet Switching
Around 1970, research began on a new form
of architecture for long distance
communications: Packet Switching.
1
2. Introduction
Packet Switching refers to protocols in
which messages are divided into packets
before they are sent. Each packet is then
transmitted individually and can even follow
different routes to its destination. Once all
the packets forming a message arrive at
the destination, they are recompiled into
the original message.
2
3. Packet Switching Operation
Data are transmitted in short packets. Typically
an upper bound on packet size is 1000 octets.
If a station has a longer message to send it
breaks it up into a series of small packets. Each
packet now contains part of the user's data and
some control information.
The control information should at least contain:
Destination Address
Source Address
Store and forward - Packets are received, stored
briefly (buffered) and past on to the next node
3
4. Advantages
Line efficiency
Single node to node link can be shared by many
packets over time
Packets queued and transmitted as fast as possible
Data rate conversion
Each station connects to the local node at its own
speed
Nodes buffer data if required to equalize rates
Packets are accepted even when network is busy
Delivery may slow down
Priorities can be used
4
5. Switching Technique - Virtual
Circuits and Datagrams
Station breaks long message into packets
Packets sent one at a time to the network
Packets handled in two ways
Datagram
Virtual circuit
5
6. Datagram Packet Switching
In datagram approach each packet is treated
independently with no reference to packets that
have gone before. No connection is set up.
Packets can take any practical route
Packets may arrive out of order
Packets may go missing
Up to receiver to re-order packets and recover
from missing packets
More processing time per packet per node
Robust in the face of link or node failures.
6
8. Virtual Circuit Packet
Switching
In the Virtual Circuit approach a pre-planned route is
established before any packets are sent.
There is a call set up before the exchange of data
(handshake).
All packets follow the same route and therefore arrive in
sequence.
Each packet contains a virtual circuit identifier instead of
destination address
More set up time
No routing decisions required for each packet - Less routing
or processing time
Susceptible to data loss in the face of link or node failure
Clear request to drop circuit
Not a dedicated path 8
10. Virtual Circuits vs. Datagram
Virtual circuits
Network can provide sequencing and error
control
Packets are forwarded more quickly
No routing decisions to make
Less reliable
Loss of a node looses all circuits through that node
Datagram
No call setup phase
Better if few packets
More flexible
Routing can be used to avoid congested parts of the
network 10
11. Packet switching -
datagrams or virtual circuits
Interface between station and network node
Connection oriented
Station requests logical connection (virtual circuit)
All packets identified as belonging to that connection
& sequentially numbered
Network delivers packets in sequence
External virtual circuit service
e.g. X.25
Different from internal virtual circuit operation
Connectionless
Packets handled independently
External datagram service
Different from internal datagram operation
11
18. Switching vs Routing
Switching Routing
path set up at connection can work as connectionless
time complex routing algorithm
simple table look up table maintainance via
table maintainance via protocol
signaling out of sequence delivery
no out of sequence delivery likely
lost path may lose robust: no connections lost
connection significant processing delay
much faster than pure output link decision based on
routing packet header contents - at
link decision made ahead of every node
time, and resources
allocated then 18