Unit 28

Website

ProductionASSIGNMENT 1

Last week

Learning outcomes

History

HTML skeleton

Annotated diagram of a WAN

Servers, routers, client PC, browser, Server OS Switch, packet

Architecture

ISP

Web Hosting Services

Domain structure

Domain name leasing

IP address

Understanding Web

Servers

Need protocols to ensure each computer can

exchange data.

Most important protocols are:

Transmission Control Protocol

Allows for the delivery of data

Internet Protocol

Establishes consistent address format to allow

machines to contact each other

Both of these date back to 1960s

IP Any device connecting to internet must have

unique IP address (currently version 4)

Four octets of numbers (range 0 -255) separated by

dots

Gives ~4 billion unique addresses

Now running out so moving to version 6 this will yield

3.4 * 10 38

For comparison, if IPv4 were represented as a golf ball, then IPv6 would be

approaching the size of the Sun. https://www.nro.net/ipv6-%E2%80%93-what-is-it-why-is-it-

important-and-who-is-in-charge/

IP 4IP 6

The TCP/IP Reference Model

Description Protocols

ApplicationProvides network services to user applications

HTTP, HTML, Telnet, FTP, SMTP, DNS

TransportProvides end-to-end management of data and divides data into segments

TCP, UDP

InternetProvides connectivity between hosts in the network

IP, ICMP, RIP, ARP

Network Access

Describes the standards that hosts use to access the physical media

Frame of reference used to develop the Internet's protocols.

Consists of layers that perform functions necessary to prepare data for transmission over a network.

The OSI Model

The OSI model is an industry standard framework that is used

to divide network communications into seven layers.

Although other models exist, most network vendors today

build their products using this framework.

A protocol stack is a system that implements protocol

behavior using a series of layers.

Protocol stacks can be implemented either in hardware or

software, or in a combination of both.

Typically, only the lower layers are implemented in hardware,

and the higher layers are implemented in software.

The OSI ModelLayer Description

Application 7 Responsible for network services to applications

Presentation 6Transforms data formats to provide a standard interface for the Application layer

Session 5Establishes, manages and terminates the connections between the local and remote application

Transport 4Provides reliable transport and flow control across a network

Network 3Responsible for logical addressing and the domain of routing

Data Link 2Provides physical addressing and media access procedures

Physical 1Defines all the electrical and physical specifications for devices

Remember the OSI layers with this mnemonic:

"Please Do Not Throw Sausage Pizza Away"

Compare OSI and TCP/IP Models

Application Layer

The Application layer, Layer seven, is the top layer of both the OSI and TCP/IP models.

It provides the interface between the applications we use to communicate and the underlying network over which our messages are transmitted.

Application layer protocols are used to exchange data between programs running on the source and destination hosts.

There are many Application layer protocols and new protocols are always being developed

Application Layer

Functions

In order for the communications to be successful, the application layer protocols implemented on the source and destination host must match.

Protocols establish consistent rules for exchanging data between applications and services loaded on the participating devices

Many different types of applications communicate across data networks. Therefore, Application layer services must implement multiple protocols to provide the desired range of communication experiences

Applications and services may also use multiple protocols in the course of a single conversation.

TCP/IP Application layer

Application Layer protocols provide network

services to user applications such as web browsers and e-mail programs

They include:

HTTP,

HTML,

Telnet,

FTP,

SMTP,

DNS

Find definitions for each of

these, explain what they do.

The functionality of the TCP/IP

application layer protocols fit roughly

into the framework of the top three

layers of the OSI model: Application,

Presentation and Session layers

Application Layer Protocol

Functions

In order for the communications to be successful, the application layer protocols implemented on the source and destination host must match.

Protocols establish consistent rules for exchanging data between applications and services loaded on the participating devices

Many different types of applications communicate across data networks. Therefore, Application layer services must implement multiple protocols to provide the desired range of communication experiences

Applications and services may also use multiple protocols in the course of a single conversation.

DNS

The Domain Name System (DNS) was created for

domain name to address resolution for these networks.

DNS is a client/server service but a bit different

from others

The DNS client runs as a service itself.

The DNS client, sometimes called the DNS resolver,

supports name resolution for our other network

applications and other services that need it

Try nslookup

DNS cont’d

A DNS server provides the name resolution using the name daemon, which is often called named, (pronounced name-dee).

When a client makes a query, the server's "named" process first looks at its own records to see if it can resolve the name. If it is unable to resolve the name using its stored records, it contacts other servers in order to resolve the name

Once a match is found and returned to the original requesting server, the server temporarily stores the numbered address that matches the name in cache.

ipconfig /displaydns command displays all of the cached DNS entries on a Windows XP or 2000 computer system.

DNS Heirarchy

HTTP When a web address (or URL) is typed into a web browser, the web browser

establishes a connection to the web service running on the server using the

HTTP protocol.

The browser interprets the 3 parts of the URL:

1. http (the protocol or scheme)

2. www.cisco.com(the server name)

3. web-server.htm (the specific file name requested).

HTTP specifies a request/response protocol. When a client, typically a web

browser, sends a request message to a server, the HTTP protocol defines the

message types the client uses to request the web page and also the

message types the server uses to respond. The three common message types

are GET, POST, and PUT.

GET is a client request for data. A web browser sends the GET message to request pages from a web server.

POST and PUT are used to send messages that upload data to the web server

HTTPS?

E-mail protocols

Post Office Protocol (POP) and Simple Mail

Transfer Protocol (SMTP) are involved in email services.

Users use an application called a Mail User Agent

(MUA), or e-mail client to allow messages to be sent and places received messages into the

client's mailbox.

In order to receive e-mail messages from an e-

mail server, the e-mail client can use POP.

Sending e-mail from either a client or a server uses

message formats and command strings defined

by the SMTP protocol.

E-mail schematic

FTP

FTP was developed to allow for file transfers between a client and a server. An FTP client is an application that runs on a computer that is used to push and pull files from a server running the FTP daemon (FTPd).

The client establishes the first connection to the server on TCP port 21. This connection is used for control traffic, consisting of client commands and server replies.

The client establishes the second connection to the server over TCP port 20. This connection is for the actual file transfer and is created every time there is a file transferred.

The file transfer can happen in either direction. The client can download (pull) a file from the server or, the client can upload (push) a file to the server.

DHCP The Dynamic Host

Confirmation Protocol (DHCP) service enables devices on a network to obtain IP addresses and other information from a DHCP server. This service automates the assignment of IP addresses, subnet masks, gateway and other IP networking parameters.

Telnet Telnet provides a standard method of emulating text-

based terminal devices over the data network.

A connection using Telnet is called a Virtual Terminal (VTY)

session, or connection.

Rather than using a physical device to connect to the

server, Telnet uses software to create a virtual device that

provides the same features of a terminal session with

access to the server command line interface (CLI).

To support Telnet client connections, the server runs a

service called the Telnet daemon. A virtual terminal

connection is established from an end device using a

Telnet client application.

If security is a concern, the Secure Shell (SSH) protocol

offers an alternate and secure method for server access.

Assignment 1

P1 outline the web architecture and components

which enable internet and web functionality

P2 explain the user side and server side factors

that influence the performance of a website

M1 explain the role of web architecture in website

communications

D1 explain the role of the TCP/IP protocol and

how it links to application layer protocols

Initial assessment

P1 outline the web architecture and components

which enable internet and web functionality

D1 explain the role of the TCP/IP protocol and

how it links to application layer protocols

Initial Assessment: Web

architecture - Scenario

You have a new post at a local website

company as a junior web developer. You

will shortly be given a brief to produce a

website for a local company. Before that,

you have been asked to prepare some

introductory information for clients to be included on your company’s website.

Initial Assessment: Web

architecture – Task 1, P1 Compose a brief outline of the web architecture and

components which allow the internet and websites to function.

Describe to customers how their web-site makes its way from the company server to their customers’ homes. The information should outline the various stages and processes that information must pass through to get from server to screen. This description should be based on the traditional/historic scheme of web architecture. It is suggested that this information is presented in the form of an annotated diagram.

Notes: The following terms should be included:

Server Internet Service Providers (ISP);

Packet web hosting services;

Router worldwide web

Switch

Browser

Initial Assessment: Web

architecture – Task 2, D1 Write a technical explanation of application layer

protocols in relation to the TCP/IP protocol stack model.

This short explanation could include diagrams to give a technical explanation of the application layer protocols and how they relate to the TCP/IP protocols. Strengths and weaknesses of the protocols should be included.

Notes: This should include:

TCP/IP

HTTP

FTP

DNS

SMTP