Unit 28 Website Production ASSIGNMENT 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-itimportant-and-who-is-in-charge/ IP 4 IP 6
The TCP/IP Reference Model 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. Description Protocols Application Transport Internet Network Access Provides network services to user applications Provides end-to-end management of data and divides data into segments Provides connectivity between hosts in the network Describes the standards that hosts use to access the physical media HTTP, HTML, Telnet, FTP, SMTP, DNS TCP, UDP IP, ICMP, RIP, ARP
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 Model Layer Description Application 7 Responsible for network services to applications Presentation 6 Session 5 Transport 4 Network 3 Data Link 2 Physical 1 Transforms data formats to provide a standard interface for the Application layer Establishes, manages and terminates the connections between the local and remote application Provides reliable transport and flow control across a network Responsible for logical addressing and the domain of routing Provides physical addressing and media access procedures Defines 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 textbased 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