HTTP and other application layer protocols overview.HTML basics for creating web pages. Describing the main elements of HTML and its attributes. The main types of HTML lists and building tables using Html. The form input types and its methods, image maps , and most form elements are explained with examples.
The application layer allows users to interface with networks through application layer protocols like HTTP, SMTP, POP3, FTP, Telnet, and DHCP. It provides the interface between applications on different ends of a network. Common application layer protocols include DNS for mapping domain names to IP addresses, HTTP for transferring web page data, and SMTP/POP3 for sending and receiving email messages. The client/server and peer-to-peer models describe how requests are made and fulfilled over the application layer.
Module 5 Application and presentation Layer .pptxAASTHAJAJOO
The document discusses the application and presentation layers of the OSI model. It provides details on:
- The application layer protocols like HTTP, FTP, email and how they use the transport layer protocols TCP and UDP.
- The traditional client-server and new peer-to-peer paradigms used at the application layer.
- How the HTTP protocol works for the world wide web including URL structure, static/dynamic web documents, browser and server functions.
- The key components and functioning of specific application layer protocols - FTP for file transfer and email for electronic mail exchange.
HTTP is the application layer protocol that powers the World Wide Web. It allows for the transfer of various data types like text, images, videos, and sounds between a client and server. HTTP uses TCP and IP to establish connections and transfer packets of data between devices. Requests use methods like GET and POST, and responses include status codes to indicate success or errors. While HTTP is stateless, cookies allow servers to track users across multiple requests.
The purpose of this presentation is to give viewers a basic introduction to web and http concepts. The images in the ppt are sourced from google images and are not my own.
HTTP and other application layer protocols overview.HTML basics for creating web pages. Describing the main elements of HTML and its attributes. The main types of HTML lists and building tables using Html. The form input types and its methods, image maps , and most form elements are explained with examples.
The application layer allows users to interface with networks through application layer protocols like HTTP, SMTP, POP3, FTP, Telnet, and DHCP. It provides the interface between applications on different ends of a network. Common application layer protocols include DNS for mapping domain names to IP addresses, HTTP for transferring web page data, and SMTP/POP3 for sending and receiving email messages. The client/server and peer-to-peer models describe how requests are made and fulfilled over the application layer.
Module 5 Application and presentation Layer .pptxAASTHAJAJOO
The document discusses the application and presentation layers of the OSI model. It provides details on:
- The application layer protocols like HTTP, FTP, email and how they use the transport layer protocols TCP and UDP.
- The traditional client-server and new peer-to-peer paradigms used at the application layer.
- How the HTTP protocol works for the world wide web including URL structure, static/dynamic web documents, browser and server functions.
- The key components and functioning of specific application layer protocols - FTP for file transfer and email for electronic mail exchange.
HTTP is the application layer protocol that powers the World Wide Web. It allows for the transfer of various data types like text, images, videos, and sounds between a client and server. HTTP uses TCP and IP to establish connections and transfer packets of data between devices. Requests use methods like GET and POST, and responses include status codes to indicate success or errors. While HTTP is stateless, cookies allow servers to track users across multiple requests.
The purpose of this presentation is to give viewers a basic introduction to web and http concepts. The images in the ppt are sourced from google images and are not my own.
This document discusses application layer protocols. It begins by introducing the application layer and describing its functions of providing services to users and logical connections between application layers. It then discusses standard protocols like HTTP and SMTP and nonstandard protocols. It describes the traditional client-server paradigm and the emerging peer-to-peer paradigm. Specific application layer protocols covered include WWW/HTTP, FTP, and email. It provides details on how these protocols function, including URL structure for WWW, connections and data transfers for FTP, and message exchanges for email.
The document discusses several key application layer protocols:
1. HTTP is used to transfer web pages over the internet using requests and responses between clients and servers. It operates over TCP port 80.
2. DNS is used to translate between hostnames and IP addresses in a hierarchical system of top-level and subdomain names. It allows humans to use easy-to-remember names.
3. FTP establishes two TCP connections to transfer files between a client and server, using different ports for control commands and the file data. It allows downloading and uploading of files.
The document discusses several key application layer protocols:
1. HTTP is used to transfer web pages over the internet using requests and responses between clients and servers. It operates over TCP port 80.
2. DNS is used to translate between hostnames and IP addresses in a hierarchical system of top-level and subdomain names. DNS servers handle requests to map names to addresses.
3. FTP uses two TCP connections to transfer files between clients and servers - one for commands and one for the actual data transfer. Clients can download or upload files from/to servers.
The document discusses several application layer protocols used in TCP/IP including HTTP, HTTPS, FTP, and Telnet. HTTP is used to access resources on the world wide web over port 80 and is stateless. HTTPS is a secure version of HTTP that encrypts communications over port 443. FTP is used to transfer files between hosts but sends data and passwords in clear text. Telnet allows users to access programs on remote computers.
Roman gave a presentation covering DNS and HTTP. DNS is a globally distributed database that translates website names to IP addresses. It is comprised of name servers, name space, and resolvers. HTTP is the main communication protocol for the internet that allows clients and servers to exchange data. It involves request and response messages with headers and an optional body. Key points are methods like GET and POST, status codes, and headers for cookies, caching, and content type.
application layer protocol for iot.pptxaravind Guru
The document discusses various application layer protocols in the OSI model. It begins with an overview of the OSI model and encapsulation process. It then discusses considerations for application protocol design. The main part of the document describes six important application layer protocols: HTTP for web browsing, DNS for domain name resolution, FTP for file transfer, Telnet for remote terminal access, DHCP for dynamic IP address allocation, and SMTP for email. It concludes with a summary of these protocols and references for further information.
Web services allow disparate applications to exchange messages using protocols like HTTP, XML, SOAP, and WSDL. They enable the building of scalable and loosely coupled applications. XML web service descriptions specify the message formats understood by the service. The SOAP protocol consists of an envelope containing the message and optional parts for data encoding, request-response patterns, and binding with HTTP. To locate a web service, a client searches directories, requests a discovery document containing the service description, and then requests the service.
HTTP is the application-layer protocol for transmitting hypertext documents across the internet. It works by establishing a TCP connection between an HTTP client, like a web browser, and an HTTP server. The client sends a request to the server using methods like GET or POST. The server responds with a status code and the requested resource. HTTP is stateless, meaning each request is independent and servers do not remember past client interactions. Cookies and caching are techniques used to maintain some state and improve performance.
The Hypertext Transfer Protocol (HTTP) is an application layer protocol for distributed, collaborative, hypermedia information systems and is the foundation for data communication on the World Wide Web. HTTP defines methods like GET and POST to indicate the desired action on a resource and uses status codes in responses. It also uses headers in requests and responses to define parameters of the transaction. HTTP typically uses TCP port 80 to allow a client to open a connection and send requests to a server, which responds with messages that may contain requested resources or error information.
This document discusses various client-server protocols:
1. It explains DNS and how it maps domain names to IP addresses.
2. It describes how web clients use HTTP on port 80 to request pages from web servers, and how HTTPS on port 443 provides security.
3. It explains how FTP uses port 21 for control and port 20 for transferring files between FTP clients and servers.
4. It discusses email protocols like SMTP on port 25 for sending mail, POP3 on port 110 for downloading mail, and IMAP4 on port 143 for reading mail.
The document discusses several internet protocols including IP, SMTP, HTTP, FTP, and URLs. IP delivers packets between hosts based on addresses. SMTP is the standard for email transmission using ports 25 or 587. HTTP is the foundation of the World Wide Web. FTP transfers files between clients and servers using separate control and data connections. URLs identify resources on the internet and have the format of protocol://address/path/resource.
This document provides an overview of web servers and introduces Microsoft Internet Information Services (IIS) and the Apache web server. It discusses how HTTP transactions work when a client requests a document from a web server using a URL. The document also describes multitier application architecture with different tiers for the client, business logic/presentation logic, and data. It compares client-side scripting, which runs in the browser, versus server-side scripting, which runs on the web server. Finally, it discusses how to access local and remote web servers.
HTTP is the foundation of data communication for the World Wide Web. It is a protocol for transferring various forms of data between a client and server. HTTP works by establishing a TCP connection between a client and server, through which HTTP request and response messages are exchanged. These messages include request methods like GET and POST, as well as response status codes like 200 for success and 404 for not found. HTTP is a stateless protocol, but cookies and caching allow servers to identify users and reduce response times.
The document discusses application layer protocols in computer networks. It describes how protocols like HTTP, SMTP, POP and IMAP allow end-user applications to transfer files and messages. It explains that HTTP is used for browsing the web, SMTP enables sending email, and POP and IMAP enable receiving email. The document also covers how the Domain Name Service protocol resolves domain names to IP addresses and how protocols like DHCP assign IP addresses to devices on a network.
Proxy servers act as an intermediary for requests from clients seeking resources from other servers. There are different types of proxy servers including cache proxies that speed up access and web proxies that allow users to connect to servers and access the internet. Proxy servers aim to provide privacy by hiding clients' IP addresses and allow access around content blocks. FTP and HTTP are protocols for transferring files and web pages respectively using the client-server model, with FTP using separate control and data connections and HTTP using request and response messages. Proxy servers can also be used with FTP and HTTP to add capabilities like caching, authentication, and traffic monitoring.
The application layer is the topmost layer and closest to the end user. It establishes communication between applications and uses lower layers to transfer data. Some key protocols include HTTP, FTP, SMTP, and DNS. The application layer can use client-server or peer-to-peer architectures. Client-server centralizes resources on a server while peer-to-peer allows direct communication. Key protocols like HTTP and DNS were also summarized.
The document discusses application layer protocols and services. It describes how the application, session, and presentation layers work together to provide network services to end user applications. It provides examples of common application layer protocols like HTTP, SMTP, POP, and IMAP and how they enable services like web browsing and email. It also discusses protocols that provide IP addressing services like DNS and DHCP. The document outlines objectives for explaining application layer protocols, how they interact with applications, well-known examples, and how data moves across the network.
Advanced Web Design And Development BIT 3207Lori Head
This document provides an overview of the key concepts for the Advanced Web Design and Development course (BIT 3207). It lists recommended books and motivation for learning web design. It then covers network fundamentals including IP, IP addressing, transport layer protocols, TCP connections, HTTP protocol, URLs, status codes and methods. It also discusses client-side components like browsers, HTML, HTML5, XML and JavaScript. On the server-side it covers servers, web servers, CGI, JSP, ASP/PHP and databases. It concludes with an explanation of 3-tier architecture and the layers of presentation, application and data.
HTTP is an application layer protocol for transmitting hypermedia documents across the internet. It uses a request-response model where clients make requests which are serviced by HTTP servers. Common HTTP request methods include GET, POST, PUT and DELETE. A GET request retrieves a resource from the server, while POST submits data to be processed. The HTTP protocol defines the format of requests and responses, including request headers, response status codes and more. Other application layer protocols discussed include SMTP for email transmission and POP3 for retrieving emails from a server.
This document discusses application layer protocols. It begins by introducing the application layer and describing its functions of providing services to users and logical connections between application layers. It then discusses standard protocols like HTTP and SMTP and nonstandard protocols. It describes the traditional client-server paradigm and the emerging peer-to-peer paradigm. Specific application layer protocols covered include WWW/HTTP, FTP, and email. It provides details on how these protocols function, including URL structure for WWW, connections and data transfers for FTP, and message exchanges for email.
The document discusses several key application layer protocols:
1. HTTP is used to transfer web pages over the internet using requests and responses between clients and servers. It operates over TCP port 80.
2. DNS is used to translate between hostnames and IP addresses in a hierarchical system of top-level and subdomain names. It allows humans to use easy-to-remember names.
3. FTP establishes two TCP connections to transfer files between a client and server, using different ports for control commands and the file data. It allows downloading and uploading of files.
The document discusses several key application layer protocols:
1. HTTP is used to transfer web pages over the internet using requests and responses between clients and servers. It operates over TCP port 80.
2. DNS is used to translate between hostnames and IP addresses in a hierarchical system of top-level and subdomain names. DNS servers handle requests to map names to addresses.
3. FTP uses two TCP connections to transfer files between clients and servers - one for commands and one for the actual data transfer. Clients can download or upload files from/to servers.
The document discusses several application layer protocols used in TCP/IP including HTTP, HTTPS, FTP, and Telnet. HTTP is used to access resources on the world wide web over port 80 and is stateless. HTTPS is a secure version of HTTP that encrypts communications over port 443. FTP is used to transfer files between hosts but sends data and passwords in clear text. Telnet allows users to access programs on remote computers.
Roman gave a presentation covering DNS and HTTP. DNS is a globally distributed database that translates website names to IP addresses. It is comprised of name servers, name space, and resolvers. HTTP is the main communication protocol for the internet that allows clients and servers to exchange data. It involves request and response messages with headers and an optional body. Key points are methods like GET and POST, status codes, and headers for cookies, caching, and content type.
application layer protocol for iot.pptxaravind Guru
The document discusses various application layer protocols in the OSI model. It begins with an overview of the OSI model and encapsulation process. It then discusses considerations for application protocol design. The main part of the document describes six important application layer protocols: HTTP for web browsing, DNS for domain name resolution, FTP for file transfer, Telnet for remote terminal access, DHCP for dynamic IP address allocation, and SMTP for email. It concludes with a summary of these protocols and references for further information.
Web services allow disparate applications to exchange messages using protocols like HTTP, XML, SOAP, and WSDL. They enable the building of scalable and loosely coupled applications. XML web service descriptions specify the message formats understood by the service. The SOAP protocol consists of an envelope containing the message and optional parts for data encoding, request-response patterns, and binding with HTTP. To locate a web service, a client searches directories, requests a discovery document containing the service description, and then requests the service.
HTTP is the application-layer protocol for transmitting hypertext documents across the internet. It works by establishing a TCP connection between an HTTP client, like a web browser, and an HTTP server. The client sends a request to the server using methods like GET or POST. The server responds with a status code and the requested resource. HTTP is stateless, meaning each request is independent and servers do not remember past client interactions. Cookies and caching are techniques used to maintain some state and improve performance.
The Hypertext Transfer Protocol (HTTP) is an application layer protocol for distributed, collaborative, hypermedia information systems and is the foundation for data communication on the World Wide Web. HTTP defines methods like GET and POST to indicate the desired action on a resource and uses status codes in responses. It also uses headers in requests and responses to define parameters of the transaction. HTTP typically uses TCP port 80 to allow a client to open a connection and send requests to a server, which responds with messages that may contain requested resources or error information.
This document discusses various client-server protocols:
1. It explains DNS and how it maps domain names to IP addresses.
2. It describes how web clients use HTTP on port 80 to request pages from web servers, and how HTTPS on port 443 provides security.
3. It explains how FTP uses port 21 for control and port 20 for transferring files between FTP clients and servers.
4. It discusses email protocols like SMTP on port 25 for sending mail, POP3 on port 110 for downloading mail, and IMAP4 on port 143 for reading mail.
The document discusses several internet protocols including IP, SMTP, HTTP, FTP, and URLs. IP delivers packets between hosts based on addresses. SMTP is the standard for email transmission using ports 25 or 587. HTTP is the foundation of the World Wide Web. FTP transfers files between clients and servers using separate control and data connections. URLs identify resources on the internet and have the format of protocol://address/path/resource.
This document provides an overview of web servers and introduces Microsoft Internet Information Services (IIS) and the Apache web server. It discusses how HTTP transactions work when a client requests a document from a web server using a URL. The document also describes multitier application architecture with different tiers for the client, business logic/presentation logic, and data. It compares client-side scripting, which runs in the browser, versus server-side scripting, which runs on the web server. Finally, it discusses how to access local and remote web servers.
HTTP is the foundation of data communication for the World Wide Web. It is a protocol for transferring various forms of data between a client and server. HTTP works by establishing a TCP connection between a client and server, through which HTTP request and response messages are exchanged. These messages include request methods like GET and POST, as well as response status codes like 200 for success and 404 for not found. HTTP is a stateless protocol, but cookies and caching allow servers to identify users and reduce response times.
The document discusses application layer protocols in computer networks. It describes how protocols like HTTP, SMTP, POP and IMAP allow end-user applications to transfer files and messages. It explains that HTTP is used for browsing the web, SMTP enables sending email, and POP and IMAP enable receiving email. The document also covers how the Domain Name Service protocol resolves domain names to IP addresses and how protocols like DHCP assign IP addresses to devices on a network.
Proxy servers act as an intermediary for requests from clients seeking resources from other servers. There are different types of proxy servers including cache proxies that speed up access and web proxies that allow users to connect to servers and access the internet. Proxy servers aim to provide privacy by hiding clients' IP addresses and allow access around content blocks. FTP and HTTP are protocols for transferring files and web pages respectively using the client-server model, with FTP using separate control and data connections and HTTP using request and response messages. Proxy servers can also be used with FTP and HTTP to add capabilities like caching, authentication, and traffic monitoring.
The application layer is the topmost layer and closest to the end user. It establishes communication between applications and uses lower layers to transfer data. Some key protocols include HTTP, FTP, SMTP, and DNS. The application layer can use client-server or peer-to-peer architectures. Client-server centralizes resources on a server while peer-to-peer allows direct communication. Key protocols like HTTP and DNS were also summarized.
The document discusses application layer protocols and services. It describes how the application, session, and presentation layers work together to provide network services to end user applications. It provides examples of common application layer protocols like HTTP, SMTP, POP, and IMAP and how they enable services like web browsing and email. It also discusses protocols that provide IP addressing services like DNS and DHCP. The document outlines objectives for explaining application layer protocols, how they interact with applications, well-known examples, and how data moves across the network.
Advanced Web Design And Development BIT 3207Lori Head
This document provides an overview of the key concepts for the Advanced Web Design and Development course (BIT 3207). It lists recommended books and motivation for learning web design. It then covers network fundamentals including IP, IP addressing, transport layer protocols, TCP connections, HTTP protocol, URLs, status codes and methods. It also discusses client-side components like browsers, HTML, HTML5, XML and JavaScript. On the server-side it covers servers, web servers, CGI, JSP, ASP/PHP and databases. It concludes with an explanation of 3-tier architecture and the layers of presentation, application and data.
HTTP is an application layer protocol for transmitting hypermedia documents across the internet. It uses a request-response model where clients make requests which are serviced by HTTP servers. Common HTTP request methods include GET, POST, PUT and DELETE. A GET request retrieves a resource from the server, while POST submits data to be processed. The HTTP protocol defines the format of requests and responses, including request headers, response status codes and more. Other application layer protocols discussed include SMTP for email transmission and POP3 for retrieving emails from a server.
HijackLoader Evolution: Interactive Process HollowingDonato Onofri
CrowdStrike researchers have identified a HijackLoader (aka IDAT Loader) sample that employs sophisticated evasion techniques to enhance the complexity of the threat. HijackLoader, an increasingly popular tool among adversaries for deploying additional payloads and tooling, continues to evolve as its developers experiment and enhance its capabilities.
In their analysis of a recent HijackLoader sample, CrowdStrike researchers discovered new techniques designed to increase the defense evasion capabilities of the loader. The malware developer used a standard process hollowing technique coupled with an additional trigger that was activated by the parent process writing to a pipe. This new approach, called "Interactive Process Hollowing", has the potential to make defense evasion stealthier.
Ready to Unlock the Power of Blockchain!Toptal Tech
Imagine a world where data flows freely, yet remains secure. A world where trust is built into the fabric of every transaction. This is the promise of blockchain, a revolutionary technology poised to reshape our digital landscape.
Toptal Tech is at the forefront of this innovation, connecting you with the brightest minds in blockchain development. Together, we can unlock the potential of this transformative technology, building a future of transparency, security, and endless possibilities.
Gen Z and the marketplaces - let's translate their needsLaura Szabó
The product workshop focused on exploring the requirements of Generation Z in relation to marketplace dynamics. We delved into their specific needs, examined the specifics in their shopping preferences, and analyzed their preferred methods for accessing information and making purchases within a marketplace. Through the study of real-life cases , we tried to gain valuable insights into enhancing the marketplace experience for Generation Z.
The workshop was held on the DMA Conference in Vienna June 2024.
Discover the benefits of outsourcing SEO to Indiadavidjhones387
"Discover the benefits of outsourcing SEO to India! From cost-effective services and expert professionals to round-the-clock work advantages, learn how your business can achieve digital success with Indian SEO solutions.
2. z
Objektif dari Sesi 15
Topic Title Topic Objective
Application, Presentation, and Session
Explain how the functions of the application layer, presentation layer, and
session layer work together to provide network services to end user
applications.
Peer-to-Peer Explain how end user applications operate in a peer-to-peer network.
Web and Email Protocols Explain how web and email protocols operate.
IP Addressing Services Explain how DNS and DHCP operate.
File Sharing Services Explain how file transfer protocols operate.
3. z
Application, Presentation, and Session
Application Layer
• The upper three layers of the OSI model
(application, presentation, and session)
define functions of the TCP/IP application
layer.
• The application layer provides the interface
between the applications used to
communicate, and the underlying network
over which messages are transmitted.
• Some of the most widely known application
layer protocols include HTTP, FTP, TFTP,
IMAP and DNS.
4. z Application, Presentation, and Session
Presentation and Session Layer
The presentation layer has three primary functions:
• Formatting, or presenting, data at the source
device into a compatible format for receipt by
the destination device
• Compressing data in a way that can be
decompressed by the destination device
• Encrypting data for transmission and decrypting
data upon receipt
The session layer functions:
• It creates and maintains dialogs between
source and destination applications.
• It handles the exchange of information to
initiate dialogs, keep them active, and to
restart sessions that are disrupted or idle
for a long period of time.
5. z Application, Presentation, and Session
TCP/IP Application Layer Protocols
The TCP/IP application protocols specify the format and control information necessary for many
common internet communication functions.
Application layer protocols are used by both the source and destination devices during a
communication session.
For the communications to be successful, the application layer protocols that are implemented
on the source and destination host must be compatible.
Name System
DNS - Domain Name System
(or Service)
• TCP, UDP client 53
• Translates domain names,
such as cisco.com, into IP
addresses.
Host Config
DHCP - Dynamic Host
Configuration Protocol
• UDP client 68, server 67
• Dynamically assigns IP
addresses to be re-used
when no longer needed
Web
HTTP - Hypertext Transfer
Protocol
• TCP 80, 8080
• A set of rules for exchanging
text, graphic images, sound,
video, and other multimedia
files on the World Wide Web
6. z
Peer-to-Peer
Client-Server Model
• Client and server processes are considered to be in the application layer.
• In the client/server model, the device requesting the information is called a client and the
device responding to the request is called a server.
• Application layer protocols describe the format of the requests and responses between clients
and servers.
7. z
Peer-to-Peer
Peer-to-Peer Networks
In a peer-to-peer (P2P) network, two or more computers are connected via a network and can
share resources (such as printers and files) without having a dedicated server.
Every connected end device (known as a peer) can function as both a server and a client.
One computer might assume the role of server for one transaction while simultaneously
serving as a client for another. The roles of client and server are set on a per request basis.
8. z Peer-to-Peer App
• A P2P application allows a device to act as both a client and a server within the same communication.
• Some P2P applications use a hybrid system where each peer accesses an index server to get the
location of a resource stored on another peer.
9. z
Peer-to-Peer
Common P2P Applications
With P2P applications, each computer in
the network that is running the application
can act as a client or a server for the other
computers in the network that are also
running the application.
Common P2P networks include the
following:
BitTorrent
Direct Connect
eDonkey
Freenet
10. z
Web and Email Protocols
Hypertext Transfer Protocol and Hypertext Markup
Language
When a web address or Uniform Resource Locator (URL) is typed into a web browser, the web
browser establishes a connection to the web service. The web service is running on the server
that is using the HTTP protocol.
To better understand how the web browser and web server interact, examine how a web page is
opened in a browser.
Step 1
The browser interprets the three parts
of the URL:
• http (the protocol or scheme)
• www.cisco.com (the server name)
• index.html (the specific filename
requested)
11. z
Web and Email Protocols
Hypertext Transfer Protocol and Hypertext Markup
Language (Cont.)
Step 2
The browser then checks with a name
server to convert www.cisco.com into
a numeric IP address, which it uses to
connect to the server.
The client initiates an HTTP request to
a server by sending a GET request to
the server and asks for the index.html
file.
Step 3
In response to the request, the server sends the
HTML code for this web page to the browser.
12. z
Web and Email Protocols
Hypertext Transfer Protocol and Hypertext Markup
Language (Cont.)
Step 4
The browser deciphers the HTML code and formats the page for the browser window.
13. z
Web and Email Protocols
HTTP and HTTPS
HTTP is a request/response protocol that
specifies the message types used for that
communication.
The three common message types are GET,
POST, and PUT:
• GET - This is a client request for
data. A client (web browser) sends
the GET message to the web server
to request HTML pages.
• POST - This uploads data files to the
web server, such as form data.
• PUT - This uploads resources or
content to the web server, such as an
image.
Note: HTTP is not a secure protocol. For
secure communications sent across the
internet, HTTPS should be used.
14. z
Web and Email Protocols
Email Protocols
Email is a store-and-forward method of
sending, storing, and retrieving electronic
messages across a network. Email messages
are stored in databases on mail servers. Email
clients communicate with mail servers to send
and receive email.
The email protocols used for operation are:
• Simple Mail Transfer Protocol
(SMTP) – used to send mail.
• Post Office Protocol (POP) & IMAP
– used for clients to receive mail.
15. z
Web and Em
SMTP, POP an
When a client sends email, the client SMTP
process connects with a server SMTP
process on well-known port 25.
After the connection is made, the client
attempts to send the email to the server
across the connection.
When the server receives the message, it
either places the message in a local account,
if the recipient is local, or forwards the
message to another mail server for delivery.
The destination email server may not be
online or may be busy. If so, SMTP spools
messages to be sent at a later time.
Note: SMTP message formats require a message
header (recipient email address & sender email address)
and a message body.
16. z
Web and Ema
SMTP, POP and IMAP
POP is used by an application to retrieve mail from a mail server. When mail is downloaded from
the server to the client using POP the messages are then deleted on the server.
• The server starts the POP service by
passively listening on TCP port 110 for
client connection requests.
• When a client wants to make use of the
service, it sends a request to establish a
TCP connection with the server.
• When the connection is established, the
POP server sends a greeting.
• The client and POP server then
exchange commands and responses
until the connection is closed or
aborted.
Note: Since POP does not store messages, it is not
recommended for small businesses that need a centralized
backup solution.
17. z
Web and Em
SMTP, POP and IMAP
IMAP is another protocol that describes
a method to retrieve email messages.
Unlike POP, when a user connects to
an IMAP server, copies of the
messages are downloaded to the
client application. The original
messages are kept on the server until
manually deleted.
When a user decides to delete a
message, the server synchronizes that
action and deletes the message from
the server.
19. z IP Addressing Services
Domain Name Service
• Domain names were created to
convert the numeric IP addresses
into a simple, recognizable name.
• Fully-qualified domain names
(FQDNs), such
as http://www.cisco.com, are much
easier for people to remember than
198.133.219.25.
• The DNS protocol defines an
automated service that matches
resource names with the required
numeric network address. It includes
the format for queries, responses,
and data.
20. z
IP Addressing Services
DNS Message Format
The DNS server stores different types of resource records that are used to resolve names. These
records contain the name, address, and type of record.
Some of these record types are as follows:
• A - An end device IPv4 address
• NS - An authoritative name server
• AAAA - An end device IPv6 address (pronounced quad-A)
• MX - A mail exchange record
When a client makes a query, the server DNS process first looks at its own records to resolve the
name. If it is unable to resolve the name by using its stored records, it contacts other servers to
resolve the name.
After a match is found and returned to the original requesting server, the server temporarily stores
the numbered address in the event that the same name is requested again.
21. z
IP Addressing Services
DNS Message Format (Cont.)
DNS uses the same message format between servers, consisting of a question, answer, authority,
and additional information for all types of client queries and server responses, error messages,
and transfer of resource record information.
DNS message section Description
Question The question for the name server
Answer Resource Records answering the question
Authority Resource Records pointing toward an authority
Additional Resource Records holding additional information
22. z
IP Addressing Services
DNS Hierarchy
• DNS uses a hierarchical system to create a
database to provide name resolution.
• Each DNS server maintains a specific database
file and is only responsible for managing name-
to-IP mappings for that small portion of the entire
DNS structure.
• When a DNS server receives a request for a
name translation that is not within its DNS zone,
the DNS server forwards the request to another
DNS server within the proper zone for translation.
• Examples of top-level domains:
.com - a business or industry
.org - a non-profit organization
.au - Australia
23. z
IP Addressing Services
The nslookup Command
• Nslookup is a computer operating system utility
that allows a user to manually query the DNS
servers configured on the device to resolve a
given host name.
• This utility can also be used to troubleshoot
name resolution issues and to verify the current
status of the name servers.
• When the nslookup command is issued, the
default DNS server configured for your host is
displayed.
• The name of a host or domain can be entered
at the nslookup prompt.
24. z
IP Addressing Services
Dynamic Host Configuration Protocol
• The Dynamic Host Configuration Protocol
(DHCP) for IPv4 service automates the
assignment of IPv4 addresses, subnet masks,
gateways, and other IPv4 networking
parameters.
• DHCP is considered dynamic addressing
compared to static addressing. Static addressing
is manually entering IP address information.
• When a host connects to the network, the DHCP
server is contacted, and an address is requested.
The DHCP server chooses an address from a
configured range of addresses called a pool and
assigns (leases) it to the host.
• Many networks use both DHCP and static
addressing. DHCP is used for general purpose
hosts, such as end user devices. Static
addressing is used for network devices, such as
gateway routers, switches, servers, and printers.
Note: DHCP for IPv6 (DHCPv6) provides similar
services for IPv6 clients. However, DHCPv6 does
not provide a default gateway address. This can
only be obtained dynamically from the Router
Advertisement message of the router.
25. z
IP Addressing Servic
DHCP Operatio
The DHCP Process:
• When an IPv4, DHCP-configured device boots up
or connects to the network, the client broadcasts a
DHCP discover (DHCPDISCOVER) message to
identify any available DHCP servers on the
network.
• A DHCP server replies with a DHCP offer
(DHCPOFFER) message, which offers a lease to
the client. (If a client receives more than one offer
due to multiple DHCP servers on the network, it
must choose one.)
• The client sends a DHCP request
(DHCPREQUEST) message that identifies the
explicit server and lease offer that the client is
accepting.
• The server then returns a DHCP acknowledgment
(DHCPACK) message that acknowledges to the
client that the lease has been finalized.
• If the offer is no longer valid, then the selected
server responds with a DHCP negative
acknowledgment (DHCPNAK) message and the
process must begin with a new DHCPDISCOVER
message.
Note: DHCPv6 has a set of messages that is similar to those for
DHCPv4. The DHCPv6 messages are SOLICIT, ADVERTISE,
INFORMATION REQUEST, and REPLY.
26. z
File Sharing Services
File Transfer Protocol
FTP was developed to allow for data transfers between a client and a server. An FTP client is an
application which runs on a computer that is being used to push and pull data from an FTP server.
Step 1 - The client establishes the first connection
to the server for control traffic using TCP port 21.
The traffic consists of client commands and server
replies.
Step 2 - The client establishes the second
connection to the server for the actual data transfer
using TCP port 20. This connection is created
every time there is data to be transferred.
Step 3 - The data transfer can happen in either
direction. The client can download (pull) data from
the server, or the client can upload (push) data to
the server.
27. z
File Sharing Services
Server Message Block
The Server Message Block (SMB) is a client/server,
request-response file sharing protocol. Servers can
make their own resources available to clients on the
network.
Three functions of SMB messages:
• Start, authenticate, and terminate sessions
• Control file and printer access
• Allow an application to send or receive messages to
or from another device
Unlike the file sharing supported by FTP, clients
establish a long-term connection to servers. After the
connection is established, the user of the client can
access the resources on the server as though the
resource is local to the client host.
28. z
What did we learn in session 15?
• Application layer protocols are used to exchange data between programs running on the source and destination
hosts. The presentation layer has three primary functions: formatting, or presenting data, compressing data, and
encrypting data for transmission and decrypting data upon receipt. The session layer creates and maintains dialogs
between source and destination applications.
• In the client/server model, the device requesting the information is called a client and the device responding to the
request is called a server.
• In a P2P network, two or more computers are connected via a network and can share resources without having a
dedicated server.
• The three common HTTP message types are GET, POST, and PUT.
• Email supports three separate protocols for operation: SMTP, POP, and IMAP.
• DNS protocol matches resource names with the required numeric network address.
• DHCP for IPv4 service automates the assignment of IPv4 addresses, subnet masks, gateways, and other IPv4
networking parameters. The DHCPv6 messages are SOLICIT, ADVERTISE, INFORMATION REQUEST, and REPLY.
• An FTP client is an application which runs on a computer that is being used to push and pull data from an FTP server.
• Three functions of SMB messages: start, authenticate, and terminate sessions, control file and printer access, and
allow an application to send or receive messages to or from another device.