e-business technologies1 chapter 3 internetworking basics

E-Business Technologies 1

Chapter 3

Internetworking Basics


Objectives

In this chapter, you will learn to:

• Identify internetworking hardware, Internet connections, and network addressing issues

• Describe the TCP/IP protocol suite, IP addresses, and logical ports

• Explain domain names, the Domain Name System, and Uniform Resource Locators

• Identify organizations that provide oversight for the Internet and the World Wide Web


Internetworking Hardware

• Special network devices, called switches and routers, control data transmissions within and between network segments

• A network segment is part of a network, usually made up of computers that share a common function

• These network devices ensure that data sent between computers on the same segment are transmitted only on that segment

Valued Gateway Client:

Valued Gateway Client:


Hubs

• Used to connect groups of computers, generally fewer than 64 computers (inexpensive hubs generally stop at 6 computer connections)

• Repeats a signal, passing transmissions to all computers on a segment and the signal can be 'heard' by all computers connected via the hub

• Each computer connects to a hub using a separate cable

• Hubs can interconnect to other hubs, switches, and routers


Switches

• An intelligent device that analyzes data packets to determine how to route a data transmission to its destination

• Reduces congestion by directing data transmissions to specific ports used to connect with each computer or device

• Switches can interconnect with hubs, switches, and routers


Routers

• Analyzes data packets to determine how to route a data

• Specialized computers designed to manage data transmissions over large LANs and WANs

• Relies on databases containing address information to locate computers on network (these 'databases' can be maintained within the memory of the router itself)


Firewalls

• A security tool - stands between the outside networks and the inside networks

• Specialized hardware or software or a combination of both, that filters all incoming

and outgoing transmissions

• Blocks transmissions that do not meet specific security criteria

why is this important for denial of service attacks, spoofed e-mail, etc?


Firewalls

• Placed between the public network and private network– Public network identifies the external

network connection or portion of the Internet on the outside of a firewall

– Private network identifies a network or LAN on the inside of a firewall, such as a corporate LAN


Packet Switching

• The practice of breaking data transmissions into packets that can travel independently across a network

• Packets are assigned sequence numbers so they can be reassembled in the correct order at the destination

• Routers direct packets across the network/Internet to their assigned destination


Internet Connections

• Internet connections can take place using many different types of telecommunications media– Access devices range from a standard phone line

and a modem to wireless satellite connections

– Individual consumers usually obtain Internet access through an Internet service provider (ISP) such as America Online (AOL)

– Businesses usually obtain Internet access using a shared connection consisting of a router on a corporate LAN and a telecommunications connection between the router and the Internet


Internet Connection Methods• Dial-up router - 56Kbps

– Includes a modem that connects to the Internet when it detects an office computer trying to access the Internet

• Leased line/Frame relay

– A connection that is always on and much more reliable than a dial-up connection

• Integrated Services Digital Network (ISDN) - 128Kbps to 1.5Mbps (Table 3.1 in text is wrong)

– A dial-up connection about twice as fast as a dial-up router


Internet Connection Methods

• Digital Subscriber Line (DSL) - generally 32Mbps but up to 52Mbps

– A connection that operates over a standard phone line, but on a different set of frequencies than voice conversations; much faster than ISDN and usually less expensive

• T1 and T3 - 1.5Mbps and 43Mbps

– Communication lines leased from a common carrier such as AT&T suitable for both voice and data


Network and Internetwork Addresses

• Physical addresses are used in communications between computers on the same network

• MAC (physical) addresses are permanently set in a device’s network interface card, such as:

52-54-50-21-D8-9B

• Virtual address, such as an IP address or Domain Name, are used in communications between computers over the Internet


Internet Addressing

• Routers and other internetworking devices use logical (virtual) addresses to identify devices or applications on the Internet

• IP addresses are 32-bit number containing four 8-bit octets that identifies a device connected to the Internet

• Domain Names are text addresses that are translated to IP addresses

• Port addresses identify the logical connection between a server and a client application


Transmission ControlProtocol/Internet Protocol

• The TCP/IP protocols operate within specific layers of the OSI Model

OSI Model Layer

Protocol Description

Transport TCP Connects two computers, transmits data packets, verifies data delivery

UDP Sends data in packets, no data verificationSKIP SLIDE



OSI Model Layer


Network or Internet

IP Transmits data packets, routes over intranet/Internet, assembles at destination

ARP Identifies host computer, converts IP address to MAC address

Reverse ARP Converts MAC address to IP address

ICMP Reports transmission errors to routers and host computers

SKIP SLIDE



OSI Model Layer


Application HTTP Controls delivery of Web pages to Web browser

POP3 Provides storage and forwarding of e-mail

SMTP Sends e-mail between mail servers on an IP network

IMAP4 Provides POP3 services, and remote user access to mail server

FTP Enables file upload/download between computers

SKIP SLIDE


TCP Segments

• Data packets created at the Transport layer by TCP• Requires an established connection between sending

and receiving computer before transmission

SKIP SLIDE


TCP Segment Data

Data Description

Source Port Logical port address of the sending computer

Destination Port Logical port address of the destination computer

Sequence Number Specifies the position of the packet in the flow of data

Acknowledgement Number

Contains receipt of data confirmation number

TCP Header Length

Designates the TCP header length

SKIP SLIDE


TCP Segment Data

Data Description

Codes Specifies any special condition, such as “urgent”

Sliding-window Size

Number of data blocks that the destination computer can receive

Checksum A value used to ensure data is transmitted without error

Urgent Pointer Identifies location of urgent data

Options Specifies any special options

Padding Ensures the TCP header is a multiple of 32 bits

Data Contains the sent data

SKIP SLIDE


IP Datagram

• Created in the Network layer by the IP protocol• Does not require a connection between sending

and destination computer• Does not provide error-checking• Does not guarantee data delivery

SKIP SLIDE


IP Datagram

Data Description

Version Identifies the version of IP used for packet formatting

Internet Header Length

Defines the IP header length

Type of Service (ToS)

Specifies the speed, priority, or reliability of the data

Total Length Total number of bytes in the IP datagram

Identification Specifies the datagram’s sequence

SKIP SLIDE


IP Datagram

Data Description

Flags Specifics whether the datagram is part of a fragmented sequence

Fragment Offset Reports the relative position of the datagram in a fragmented sequence

Time to Live Delay time before a datagram is discarded as undeliverable

Protocol Identifies the protocol which receives the datagram (TCP or UDP)

Header Checksum

A value used to ensure the Header is transmitted without error

SKIP SLIDE


IP Datagram

Data Description

Source IP address

IP address of the sending computer

Destination IP address

IP address of the destination computer

Options Contains special processing instructions

Padding Ensures the IP header is a multiple of 32 bits

Data Contains the sent data

IP DatagramSKIP SLIDE


E-Mail Subprotocols

• Sending and receiving e-mail requires a mail server and mail client (application)

• A mail server is a computer that supports both storage and forwarding of e-mail

• A mail client is an application that can access a mail server to retrieve and send e-mail

• TCP/IP supports the e-mail subprotocols — SMTP, POP3, and IMAP4


SMTP

• Simple Mail Transfer Protocol is standard e-mail protocol on the Internet

• It defines the message format and the message transfer agent (MTA), which stores and forwards the mail to SMTP, POP3, and IMAP4 servers

• Supports MIME (multipurpose Internet mail extensions) and other encoding methods to enable program and multimedia files to be attached to e-mail messages


POP3

• Post Office Protocol 3 mail server is commonly used on the Internet

• Provides message storage for incoming e-mail until users log on to download

• A simple system with little selectivity, all pending messages and attachments are downloaded at the same time

• POP3 servers use the SMTP messaging protocol


IMAP4

• Internet Messaging Access Protocol is more sophisticated than POP3

• Messages can be archived in folders

• Mailboxes can be shared

• Users can access multiple mail servers

• Better integration with MIME


E-Mail Clients

• Client e-mail programs, such as Eudora or Outlook, are mail user agents (MUA or UA)

• MUAs submit e-mail messages to SMTP servers and receives messages from either POP3 or IMAP4 servers

• MUAs retrieve/submit e-mail from/to the message store (MS) on a mail server

• The MS holds the mail until it is selectively retrieved and deleted


Internet Protocol (IP) Addresses

• Logical address for identifying computers and devices on the Internet

• 32-bit number composed of four 8-bit octets:

255.255.255.255


Categories of IP addresses

• Public IP addresses can be accessed from the Internet

• Private IP addresses (such as a LAN behind a firewall) cannot be accessed from the Internet

• Static IP addresses are assigned to a specific host and remain unchanged

• Dynamic IP addresses are assigned when a computer logs on to a network and expires at log off


Logical Port Addressing

• Client/Server applications use logical port addressing to connect with specific applications across an IP network

• There are 65,536 logical ports available on an IP network


Well-Known Port Addresses

• Protocol port number that is widely used for a certain type of data on the network

– Port 21: File Transfer Protocol

– Port 25: Outgoing e-mail (SMTP)

– Port 80: Web pages (HTTP services)

– Port 110: Incoming e-mail (POP3)

– Port 443: Encrypted Web pages


Domain Names

• Text-based addressing scheme to locate data on the Internet

• Domain name addresses correspond to a specific IP address:

ICANN.ORG

192.0.34.65


Organizing Domains

• Top-level domains identify major domains (such as “.com”, “.org”. “.gov”)

• Subdomains identify computers by organization function (such as “baba.org”)

• Subdomains are divided by function (such as “mail.baba.org”


The Domain Name System

• Uses name servers that contain databases of domain names and their equivalent IP addresses

• Translates domain names into IP addresses, also called “resolving a domain name”


Domain Name System

• 13 root servers contain the top level domains (TLDs)

• IP address downloaded regularly to thousands of Domain name resolvers

• Name servers at ISP resolves addresses upon receipt of a request from a Web client


Registering a Domain Name

• Internet Corporation for Assigned Names and Numbers (ICANN) manages Domain Name registration

• Domains can be registered through ICANN or through a Shared Registration System (SRS) partner, such as Register.com or VeriSign

http://www.icann.org/

http://www.verisign.com/


Registration process

1. Contact ICANN or an accredited registrar

2. Search the database of registered domains to determine the availability of the desired domain name

3. Select the domain name, and record the required accounting information

4. Provide the IP address of host ISP’s primary and secondary domain name servers

5. Pay the fee


Uniform Resource Locators (URLs)

• A URL is a short text address used with a Web browser to retrieve a Web page and its related files

• A URL includes the TCP/IP subprotocol, host name, domain name, and the path to the Web page file including any subfolders and the filename


Internet Corporation for Assigned Names and Numbers

• Internet Corporation for Assigned Names and Numbers (ICANN) manages Domain Name registration

• Assigns and tracks IP addresses

• Polices bad Internet practices, such as cybersquatting


World Intellectual PropertyOrganization (WIPO)

• Operates under United Nations mandate

• Provides global enforcement for copyrights and trademarks

• WIPO plays an increasing role in resolving international domain name disputes


Internet Society (ISOC)

• ISOC supports the development of Internet standards and protocols through member groups such as the Internet Engineering Task Force (IETF) and the Internet Architecture Board (IAB)

• Membership includes more than 150 organizations and over 6,000 individual members


World Wide Web Consortium (W3C)

• W3C promotes standardization and interoperability on the Web to assure that Web languages such as HTML and XML and protocols such as HTTP are compatible with any hardware and software used to access the Web


Request for Comment(Setting the Standards)

• An RFC is a tool used by Internet scientists to help publicize or improve an idea for a new system or function

• Scientist develops the proposed function, and then submits an RFC document to the appropriate standards body

• The RFC is then assigned a unique number and posted for review and comment

• RFC is refined, reviewed, refined again, and reviewed again, until agreement is reached on a new or revised Internet standard

e-business technologies1 chapter 3 internetworking basics

Documents

network packets

private network public

ebusiness technologies4

network segments

ebusiness technologies6

ebusiness technologies8

data packets

data specialized computers