2: Application Layer 1
Chapter 2
Application Layer
Sachin Shetty
ECE 355
Prepare for your exams
Study with the several resources on Docsity
Earn points to download
Earn points by helping other students or get them with a premium plan
Guidelines and tips
Prepare for your exams
Study with the several resources on Docsity
Earn points to download
Earn points by helping other students or get them with a premium plan
Understanding Network Communication: Application Layer and Email Protocols - Prof. Sachin , Study notes of Electrical and Electronics Engineering
An in-depth look into the application layer of network communication, focusing on http, electronic mail, and smtp. It covers the principles of network applications, web and http, electronic mail components, and smtp protocol. Learn about the structure of http requests and responses, conditional get, and the differences between http and smtp.
Typology: Study notes
Pre 2010
1 / 74
This page cannot be seen from the preview
Don't miss anything!
Related documents
Partial preview of the text
Download Understanding Network Communication: Application Layer and Email Protocols - Prof. Sachin and more Study notes Electrical and Electronics Engineering in PDF only on Docsity!
2: Application Layer
Chapter 2Application Layer
Sachin Shetty
ECE 355
2: Application Layer
Chapter 2: Application Layer Our goals: r
conceptual,implementationaspects of networkapplication protocols
transport-layerservice models
client-serverparadigm
peer-to-peerparadigm
r
learn about protocolsby examining popularapplication-levelprotocols
HTTP
SMTP / POP3 / IMAP
DNS
2: Application Layer
Creating a network app
write programs that
run on (different)
end
systems
communicate over network
e.g., web server softwarecommunicates with browsersoftware
little software written for
devices in network core
network core devices donot run user applications
applications on end systemsallows for rapid appdevelopment, propagation
application
transport
networkdata linkphysical
application
transport
networkdata linkphysical
application
transport
networkdata linkphysical
2: Application Layer
Chapter 2: Application layer r
2.1 Principles ofnetwork applications
r
2.2 Web and HTTP
r
2.4 Electronic Mail
SMTP, POP3, IMAP
r
2.5 DNS
2: Application Layer
Client-server architecture
server:
always-on host
permanent IP address
server farms forscaling
clients:
communicate with server
may be intermittentlyconnected
may have dynamic IPaddresses
do not communicatedirectly with each other
client/server
2: Application Layer
Processes communicating Process:
program running
within a host.
r
within same host, twoprocesses communicateusing
inter-process
communication
(defined
by OS).
r
processes in differenthosts communicate byexchanging
messages
Client process:
process
that initiatescommunication
Server process:
process
that waits to becontacted
2: Application Layer
Sockets
ApplicationTransportNetworkLink Physical
Socket
2: Application Layer
Addressing processes
r
to receive messages,process must have identifier
r
host device has unique32-bit IP address
r
Q:
does IP address of
host on which processruns suffice foridentifying the process?
2: Application Layer
Port Number
TCP
Web Server
Mail Server
IP = 138.110.1.
Port = 25
Port = 80
2: Application Layer
App-layer protocol defines r
Types of messagesexchanged,
e.g., request, response
r
Message syntax:
what fields in messages &how fields are delineated
r
Message semantics
meaning of information infields
r
Rules for when and howprocesses send &respond to messages
Public-domain protocols: r
defined in RFCs
r
allows forinteroperability
r
e.g., HTTP, SMTP
Proprietary protocols: r
e.g., Skype
2: Application Layer
Transport service requirements of common apps
Application
file transfer
Web documents
real-time audio/video
stored audio/video
interactive games
instant messaging
Data loss no lossno lossno lossloss-tolerantloss-tolerantloss-tolerantno loss
Bandwidth elasticelasticelasticaudio: 5kbps-1Mbpsvideo:10kbps-5Mbpssame as abovefew kbps upelastic
Time Sensitive nononoyes, 100’s msecyes, few secsyes, 100’s msecyes and no
2: Application Layer
Internet transport protocols services TCP service: r
connection-oriented:
setup
required between client andserver processes
r
reliable transport
between
sending and receiving process
r
flow control:
sender won’t
overwhelm receiver
r
congestion control:
throttle
sender when networkoverloaded
r
does not provide:
timing,
minimum bandwidthguarantees
UDP service: r
unreliable data transferbetween sending andreceiving process
r
does not provide:connection setup,reliability, flow control,congestion control, timing,or bandwidth guarantee
Q:
why bother? Why is there a UDP?
2: Application Layer
Applications and App-Layer Protocols
Web Browser
Web Server
HTTP
UI
HTTP
…
File
Access
2: Application Layer
Protocol Stack
Web Browser
HTTP
UI
ApplicationTransportNetworkLink Physical