Networks and Protocols CE00997-3 Week 1a. Staff Module leader/lectures: Mr Chris Howard – Room:...

Networks and Protocols CE00997-3

Week 1a

Staff

• Module leader/lectures: Mr Chris Howard– Room: K216– Email: [email protected]– Tel: 01785 35 (3304)

• Tutorials: Mr John Cowley– Room: K216– Email: [email protected]– Tel: 01785 35 (3304)

mailto:[email protected]

Course scheduleWeek Lecture 1 Lecture 21 Intro to module and networks OSI 7 layer model Vs TCP/IP

2Network Hardware (routers, hubs, Switches) LAN's CSMA/CD, Bus, Star, Ring etc…

3 ARP, HTTP etc… ARP, HTTP etc… cont 4 Classful addressing Classless Addressing 5 WAN overview ISDN Frame Relay, ATM 6 Wireless, Cellular Routing - general, flow control… 7 Distance vector routing link state routing 8 Project brief Project surgery 9 Network Management SNMP 10 Security, firewalls VPN, Remote access 11 network design Network design 12 Surgery In class test

All slides will be hosted on blackboard, please do not print off to many weeks in advance

Delivery

• 1 x 2 hour lectures per week• 1 x 2 hour tutorials per week• Attendance is required at all classes

• If you have any questions, PLEASE ask, do not leave then until week 12!

Assessment

• 1 x in-class test– This will be in week 12 in the last lecture

• 1 x project (individual) submitted in week 12– If the work is submitted let it attracts a score of

zero unless extenuating circumstances are upheld

Inter & intra network systems

Heterogeneous environments

Microsoft TCP/IP

Internet Resources Windows NT

(Including RAS)Windows for Workgroups

TCP/IP-BasedPrinters

Apple MacintoshSystems

IBM Mainframes UNIX Host

LAN Manager

LAN Managerfor UNIX Host

DEC Pathworks for VMSNFS Hosts

Definition of a Network

• What quantifies a network?• 2 more computers that can utilise data

communications (peer to peer)

Definition

• Is the previous definition correct?• Partially• It does not have to be 2 computers• It is 2 devices that share data and/or

information.• Information is processed data!

LAN connections

• Are 2 x PC’s that are connected with a piece of cable, Network cards and appropriate software a network?

• Are 3 truck drivers with CB radios a network?• Are mobile phone owners a network?

Networks• The answer to all of the questions is YES• The computers are a simple peer-to-peer LAN,

It does not have to be stored! The PC’s have text, images, sounds…

• The truck drivers are part of a wireless public network, the truck drivers are sharing information verbally

• The mobile phone users are also part of a wireless public network, the phones uses can be sharing information verbally, additionally text and graphics (phone & network dependant)

LAN• Typically described as a number of data sharing

nodes (computers normally) in a small geographical area

• E.g. a workstation and a CD jukebox• Normally more than 3 machines going through a

connection point e.g. Hub• Local area network - communication network – Interconnects a variety of data communicating devices

within a small geographic area – Broadcasts data at high data transfer rates with very low

error rates• Since the local area network first appeared in the

1970s, its use has become widespread in commercial and academic environments

Primary Function of a LAN

•To provide access to hardware and software resources that will allow users to perform one or more of the following activities:

•File serving - large storage disk drive acts as a central storage repository

•Print serving - Providing authorization to access a particular printer, accept and queue print jobs, and user access to print queue to perform administrative duties

Other LAN functions

•Video transfers - High speed LANs are capable of supporting video image and live video transfers

•Manufacturing support - LANs can support manufacturing and industrial environments

•Academic support – In classrooms, labs, and wireless

•E-mail support

•Interconnection between multiple systems

Advantages of LANs

•Ability to share hardware and software resources•Individual workstation might survive network failure•Component and system evolution are possible•Support for heterogeneous forms of hardware and software•Access to other LANs and WANs (Figure 7-1)•Private ownership•Secure transfers at high speeds with low error rates

LAN

PC

PC

PC

CD jukebox

Network printer

Disadvantages of LANs

•Equipment and support can be costly•Level of maintenance continues to grow•Private ownership?•Some types of hardware may not interoperate•Just because a LAN can support two different kinds of packages does not mean their data can interchange easily•A LAN is only as strong as it weakest link, and there are many links

Basic Local Area Network Topologies

Local area networks are interconnected using one of three basic configurations:

1. Bus/tree

2. Star-wired bus

3. Wireless

Bus/Tree Topology•The original topology

•Workstation has a network interface card (NIC) that attaches to the bus (a coaxial cable) via a tap

•Data can be transferred using either:

•Baseband digital signals

•Bidirectional, outward transmitting from the workstation in both directions

•Broadband analog signals

•Usually uni-directional, special wiring considerations needed

Bus/Tree Topology

Bus/Tree Topology operation

Star-Wired Bus Topology

•Logically operates as a bus - physically looks like a star

•Star design based on hub•All workstations attach to hub

•Unshielded twisted pair usually used to connect workstation to hub•Hub takes incoming signal and immediately broadcasts it out all connected links•Hubs can be interconnected to extend network size


•Modular connectors and twisted pair make installation and maintenance of star-wired bus better than standard bus

•Hubs can be interconnected with twisted pair, coaxial cable, or fiber optic cable

•Biggest disadvantage: when one station talks, everyone hears it called a shared network

•All devices are sharing the network medium

Star-Wired Bus Topology operation

Wireless LANs•Not really a specific topology

•Workstation in wireless LAN can be anywhere as long as within transmitting distance to access point

•Several versions of IEEE 802.11 standard defines various forms of wireless LAN connections

•Workstations reside within a basic service set

•Multiple basic service sets create an extended service set

Wireless LANs•Two basic components necessary:

•Client Radio - usually PC card with integrated antenna installed in a laptop or workstation•Access Point (AP) - Ethernet port plus transceiver

•AP acts as bridge between wired and wireless networks

•Can perform basic routing functions•Workstations with client radio cards reside within a basic service set•Multiple basic service sets create extended service set

Wireless LANs

Wireless LANs• With directional antennae designed for point-to-point

transmission (rare), 802.11b can transmit for more than 10 miles

• With an omni-directional antenna on a typical AP, range may drop to as little as 100 feet

• IEEE 802.11a – One of the more recent standards, capable of transmitting data at 54 Mbps using 5 GHz frequency range

• IEEE 802.11g – The other recent standard, also capable of transmitting data at 54 Mbps but using the same frequencies as 802.11b (2.4 GHz)– Backwards compatible with 802.11b

Wireless LANs•HiperLAN/2 (European standard, 54 Mbps in 5 GHz band)•To provide security, most systems use either Wired Equivalent Privacy (WEP)

•Provides either 40- or 128-bit key protection•Or a more advanced standard such as WPA (more on security in Chapter Thirteen)•Wireless LANs may also be configured without access point

•These configurations are called “ad-hoc”

Comparison of Bus, Star-Wired Bus,Star-Wired Ring, and Wireless Topologies

WAN connectivity

Types of Communications Networks

•Circuit switched network:

•Network in which a dedicated circuit is established between sender and receiver

•All data passes over this circuit

•Telephone system is a common example

•Connection is dedicated until one party or another terminates the connection

Circuit-Switched Network

Packet-Switched Network•Packet switched network:

•Network in which all data messages are transmitted using fixed-sized packages, called packets•More efficient use of a telecommunications line since packets from multiple sources can share the medium.•One form of packet switched network is the datagram •With a datagram, each packet is on its own and may follow its own path•Virtual circuit creates a logical path through the subnet

•All packets from one connection follow this path

Broadcast Network

•Broadcast network: •Network typically found in local area networks but occasionally found in wide area networks

•A workstation transmits its data and all other workstations “connected” to the network hear the data

•Only the workstation(s) with the proper address will accept the data

Summary of Network Structures

The Internet

• US Department of Defence, Advanced Research Projects Agency (ARPA).

• End of 1960’s not enough power• Late 1970’s Internetworking was main focus• 1990’s commercial success

Growth of the Internet

Internet

• The Internet can be thought of as the ultimate WAN. Thousands of LANS connected to form a WAN

• Main point to consider, there is no regulatory body, except for addressing

• Some people use the cloud analogy

Cloud

The Internet

World Wide Web• WWW can be thought of as an application, I.e.

how to source info• Large scale, online repository of information• Can search using an application – browser• Distributed Hypermedia system• LANS’s, WAN’S, the internet and WWW all have

commonalities• All are designed to share data/information• All must follow some sort of standard, Protocols• ISO (international Standards Organisation)

Ports & Sockets (TCP/IP model)

Transport

Application

Internet

Network

TFTPServer

WebServer

0 . . . 65536 0 . . . 65536

TCP Ports20,21

UDP Port69

TCP Port80

Windows Sockets Interface

WebBrowser

TCP Port1210

TCP UDP

IP

Windows SocketsApplications

FTPServer

Port numbers• Between 0 and 65,536• Client side app port numbers are

dynamically assigned• Well known server side apps have port

numbers assigned by IANA (Internet Assigned Numbers Authority

• Numbers below 255 - for public applications

• Numbers from 255-1023 - assigned to companies for marketable applications

• Numbers above 1023 - are unregulated

Browser operation• When a browser opened the default home

launched (site connected)• Browser loads files into clients memory &

disconnects from web server• When new URL entered connection established to

new web server• Web server transfer files to clients browser, then

stored in clients memory, web server disconnects• If next page on same website, client must re-

establish connection

Satellite and Microwave Configurations

• Long distance wireless connections

• Many types of applications including long distance telephone, television, radio, long-haul data transfers, and wireless data services

• Typically expensive services but many companies offer competitive services and rates

Satellite and Microwave Configurations

Connection-Oriented vs. Connectionless Network Applications

•The network structure is the underlying physical component of a network

•What about the software or application that uses the network?

•A network application can be either connection-oriented or connectionless


•A connection-oriented application requires both sender and receiver to create a connection before any data is transferred

•Applications (such as large file transfers) and sensitive transactions (such as banking and business) are typically connection-oriented

•A connectionless application does not create a connection first but simply sends the data

•Electronic mail is a common example


•A connection-oriented application can operate over both a circuit switched network or a packet switched network

•A connectionless application can also operate over both a circuit switched network or a packet switched network

•However, a packet switched network may be more efficient

Locating a Document on the Internet

•Every document on the Internet has a unique uniform resource locator (URL)

•All URLs consist of four parts:

1. Service type

2. Host or domain name

3. Directory or subdirectory information

4. Filename

Uniform Resource Locator (URL)


•When a user, running a web browser, enters a URL, how is the URL translated into an IP address?

•The Domain Name System (DNS) is a large, distributed database of URLs and IP addresses

•The first operation performed by DNS is to query a local database for URL/IP address information

•If the local server does not recognize the address, the server at the next level will be queried


•Eventually the root server for URL/IP addresses will be queried

•If root server has the answer, results are returned

•If root server recognizes domain name but not the extension in front of the domain name, the root server will query the server at the domain name’s location

•When the domain’s server returns results, they are passed back through the chain of servers (and their caches)

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