Computer networking (nnm)
Transcript of Computer networking (nnm)
NETWORKING OF COMPUTERS
What is computer network? Why we need a computer network ? How a computer network works ? Network models IP Addressing Network Topology Different type of network Requirements for network Applications Security
WHAT IS NETWORK ?
Interconnection of computers
How to interconnect ?
Links required for interconnecting „N‟ nodes
Suitable ?
Solution ?
GOALS OF THE NETWORKING
Resource Sharing
Information/Data Sharing
Centralized Computing
Remote Computing
Communication – Mail, Video Conferencing
Improving Security
Managing Tasks and Applications
SOME BASICS
Why a computer network is required ? Data transfer
How to identify a node in network ? IP address
How data flows in networks ? Packet form
What is Packet switching ? Statistical Multiplexing
ReceiverSenderPacket
Transmission
SOME BASICS……..
Channel capacity = Maximum data rate for a channel Nyquist Theorem:
Bandwidth = W Data rate =< 2W
Bilevel encoding: Data rate = 2 X Bandwidth
Multilevel encoding: Data rate = 2 X Bandwidth X log 2 M
For example if M = 4, Capacity = 4 X Bandwidth Shannon‟s Theorem:
Maximum number of bits/sec = W log2 (1+S/N) For telephone line: S/N = 30 dB, W = 3K; Capacity =
30Kbps
TREND: TRAFFIC > CAPACITY
Expensive Bandwidth Cheap Bandwidth
Sharing No sharing
Multicast Unicast
Needs QoS QoS is not an issue
Wireless LAN Possible in LAN
OSI REFERENCE MODEL
The seven layers
Each layer hides complexity of lower layer
Layering enforces modularity
End-to-end layer: top 4 OSI layers
Network layer: OSI network layer
Link layer: bottom 2 OSI layers
A-P-S-T are implemented in software
N-D-P are implemented in hardware
THE SEVEN LAYERS
THE SEVEN LAYERS ………….
Physical layer Transmission of bit stream over physical medium Coding scheme, connector shape and size, bit-level
synchronization
Data link layer Reliable transfer of information across the physical link Sends blocks - frames Medium access control (MAC): data link-layer address and access
to the medium Logical link control: link error control and flow control Ethernet card: physical and data link layers
THE SEVEN LAYERS ………….
Network layer Concatenate logically a set of links to form an end-to-
end link.
Compute a route
Segmentation and reassembly
Unique network-wide addresses : IP address
The beauty of IP is that we can layer it over any data link layer technology
Type-of-service in the IP
THE SEVEN LAYERS ………….
Transport layer Create the abstraction of an error-controlled,
and flow-controlled, end-to-end link
Multiplex multiple applications to the same end-to-end connection
Port number
THE SEVEN LAYERS ………….
Best-effort network layer- drops packets- delays packets- reorders packets- corrupts packet contents
Many applications want reliable transport- all packets reach receiver……in order they were sent- no data corrupted- “reliable byte stream”
Need a transport protocol, e.g., Internet‟s Transmission Control Protocol (TCP)
PRINCIPLES OF RELIABLE DATA TRANSFER
Important in application, transport, and link layers Top-10 list of important networking topics!
Sending Process
Receiving Process
Reliable Channel
Sending Process
Receiving Process
Unreliable Channel
RDT protocol
(sending side)RDT protocol
(receiving side)
Application Layer
Network Layer
Transport Layer
Characteristics of unreliable channel will determine complexity of reliable data transfer protocol
THE SEVEN LAYERS ………….
Session layer provides the control structure for communication between
applications The Internet does not have a standard session layer protocol.
Presentation layer deals with data encrypt data The Internet does not support a standard presentation layer.
Application layer Provides access to the users WWW: browser, server, navigation file transfer using TCP real-time audio and video retrieval using UDP
TCP/IP MODEL
TCP/IP protocol consists of four/five layers The lower layers correspond to the layer of the
OSI model. The application layer of the TCP/IP model
represents the three topmost layers of the OSI model
TCP/IP is based on two principles IP Over everything end to end
TCP/IP MODEL………..
TCP – Transmission Control Protocol IP – Internet Protocol (Routing)
TCP/IP Model TCP/IP Protocols OSI Ref Model
Physical
Datalink
Network
Transport
Session
Presentation
Application
Physical
Datalink
Network
Transport
Session
Presentation
Application
Host to
Network
Network
Transport
Application
Host to
Network
Network
Transport
Application
UDP
HTTPTelnet
Point
- to -
Point
Packet
RadioEthernet
IP
TCP
FTP
UDP
HTTPTelnet
Point
- to -
Point
Packet
RadioEthernet
IP
TCP
FTP
ADVANTAGE OF TCP/IP MODEL
Open Protocol Standards Independent of actual physical network &
Computer hardware or software. Run over Ethernet/ Token Ring/ Modems/ Unix/ Windows PCs
Uses Common Global address scheme (IP addressing) that enables global connectivity
IP ADDRESSING
IP addressing scheme is integral to the process of routing IP datagram through an internetwork.
Each IP address has specific component and follows a basic format.
These IP addresses can be subdivided and used to create addresses for sub networks.
Each host on a TCP/IP network is assigned a unique 32-bit logical address that is divided into two main parts: the network number and the host number.
The network number identifies a network and must be assigned by the internet Network Information Center (InterNIC) if the network is to be part of the internet.
IP ADDRESSING
An Internet Service Provider (ISP) can obtain blocks of network addresses from InterNIC and can itself assign address space as necessary.
The host number identifies a host on a network and is assigned by the local network administrator.
COMPONENTS OF A NETWORK
Server :Computer that provides shared resources to network users.
Clients :Computer that access shared network resources provided by server.
Media : Way of connecting computers. e.g. Cable, fiber optics, telephone line.
Resources: Files, printers or other items to be used by network users.
CLIENT-SERVER ARCHITECTURE
server: always-on host permanent IP address
clients: communicate with
server may be intermittently
connected may have dynamic IP
addresses do not communicate
directly with each other
client/server
P2P ARCHITECTURE
no always-on server
users directly communicate
peers are intermittently connected and change IP addresses
Highly scalable but difficult to manage
peer-peer
HYBRID OF CLIENT-SERVER AND P2P
Skype voice-over-IP P2P application centralized server: finding address of remote
party client-client connection: direct (not through
server)
Instant messaging chatting between two users is P2P centralized service: client presence detection
user registers its IP address with central server when it comes online
user contacts central server to find IP addresses of buddies
NETWORK TOPOLOGY
Defines the way in which computers, printers, and other devices are connected.
Describes the layout of the wire and devices as well as the paths used by data transmissions.
BUS TOPOLOGY
All the devices on a bus topology are connected by one single cable
At a time only one host can send messages
Passive topology. Hosts on the bus are not responsible for moving data
Failure of any host doesn‟t affect the Network
STAR & TREE TOPOLOGY
Commonly used architecture in Ethernet LAN
Larger networks use the extended star topology also called tree topology
IEEE 802 STANDARDS
802.1 Network management and bridging 802.2 Logical link control 802.3 Ethernet and fast Ethernet 802.4 Token bus 802.5 Token ring 802.7 Broadband 802.8 Fiber – optics 802.9 Integrate data and voice 802.10 Security and privacy 802.11 Wireless LAN 802.16 WiMAX (Broadband Wireless Access)
DIFFERENT TYPES OF NETWORKS
Local Area Network (LAN)
Metropolitan Area Network (MAN)
Wide Area Network (WAN)
LOCAL AREA NETWORK (LAN)
A network confined to a single location e.g. one building or one complex
Used for Sharing Hardware e.g. Printers
Software
Data Maximum distance limited by signal strength
METROPOLITAN AREA NETWORK (MAN)
A network that covers an entire city
Usually Cable is signal carrier
Maximum range of about 75 kilometers (45 miles) or so, and with high-speed transmission capabilities
T3 = 45 megabits per second (Mbps)
Unlike LANs, MANs generally include provisions for both voice and data transmissions.
WIDE AREA NETWORK (WAN)
A Network spread over wide areas such as across cities, states or countries
High speed data lines used to connect LANs in separate geographical locations
Communication using telephone lines, satellite or Microwave links
WANs can be centralized or distributed
More accurately wide-area internetworks(WAIs)
REQUIREMENTS FOR NETWORK
Server – Win NT/2000/2003, Unix/Linux, Netware
Client – Win XP, Win NT/2000, Linux, DOS NIC – Ethernet Transmission media – twisted pair, coaxial
cables, fiber optics Topology – bus, ring, star, tree Protocol – TCP/IP Interconnection devices – Hub, switch, router,
bridge, gateway
APPLICATIONS
Internet
Downloads
E - Commerce
Group Chatting
Internet Telephony (VoIP)
Video Conferencing
IPTV
Internet Radio
Server based audio & video services
TYPES OF MALWARE
Viruses: Code that attaches itself to programs, disks, or memory to propagate itself
Worms: Installs copies of itself on other machines on a network, e.g., by finding user names and passwords
Trojan horses: Pretend to be a utility. Convince users to install on PC
Spyware: Collect personal information Hoax: Use emotion to propagate, e.g., child's last
wish