Switching:
Circuit switched network(use switch to only forward
message)
Packet switched network(use router to store and forward
network)
Internet: one can connect to internet by various means
- Using telephone lines(Dialup and DSL services
- Using cable networks
- Using wireless network
FCC(federal communication commision has
authority over interstate and international commerce in the communications
field )
Network
Model : Two principles
First, each layer needs to perform two opposite
tasks.
Second, two objects under each layer at both sides
should be identical.
- The OSI model appeared after the TCP/IP protocol suite
Physical Layer
1.
A time-domain graph plots
amplitude as a function of time.
2.
A frequency-domain graph plots each sine wave
peak amplitude against its frequency
3.
a sine wave is defined by
three characteristics: amplitude, frequency, and phase
Analog Signal
- Frequency is number of period completed in a second
- Wavelength is distance a simple signal travel in a
second
- wavelength(lenda)=propagation speed(v)*time(t)
- λ =c*t = c/f(frequency)
- The bandwidth of a composite signal is the difference between the highest and the lowest frequencies contained in that signal
- Only periodic signal can be used in analog data communication
Digital Signal
- Bit rate is number of bits sent in 1 second. Expressed in bits per second(bps)
- Bit length is the distance one bit occupies on the transmission medium
- Bit length = propagation speed * bit duration
- Only non periodic signal can be used in digital data communication
Digital signal can be transmitted using two
method-baseband and broadband
- Baseband transmission means sending a digital signal over a channel without changing the digital signal to an analog signal
- Broadband transmission or modulation means changing the digital signal to an analog signal for transmission.
Transmission Impairment
- Attenuation (loss of energy) db=10*log p2/p1
- Distortion
- Noise
Signal to noise ratio (SNR)=average signal power/average
noise power
Data Rate Limit
Shannon capacity for noise channel =
bandwidth*log2(1+SNR)
Noiseless Channel: Nyquist Bit Rate = 2 *
bandwidth * log2L L is number of signal level
Digital Transmission
Data Rate Versus Signal Rate
The data rate defines the number of data elements (bits)
sent in 1s. The unit is bits per
second (bps). The signal rate is the number of signal
elements sent in 1s. The unit is
the baud. There are several common terminologies
used in the literature. The data rate
is sometimes called the bit rate; the signal rate is
sometimes called the pulse rate, the
modulation rate, or the baud rate.
Three technique to convert digital data to digital
signal.- Line coding,Block coding,Scrambling
Two technique to convert analog signal to digital data-Pulse
code modulation,delta modulation
Transmission Modes--Parallel and
Serial(Synchronous, Asynchronous, Isochronous )
In asynchronous
transmission, we send 1 start bit (0) at the beginning and 1 or more
stop bits (1s) at the end of each byte. In synchronous transmission, we send
bits one after another without
start or stop bits or gaps. It is the responsibility of
the receiver to group the bits.
Analog Transmission
Four techniques to convert digital data to analog
signal-amplitude shift keying (ASK), frequency shift keying (FSK), and
phase shift keying (PSK), Quadrature amplitude modulation
Three techniques to convert analog signal to analog
Data- Frequency modulation,amplitude modulation, Phase modulation
Multiplexing:
FDM-frequency
division multiplexing -FDM is used in AM,FM radio broadcasting
1. A special band
from 530 to 1700 kHz is assigned to AM radio. All radio stations need to share
this band. AM station needs 10 kHz of bandwidth
2. FM has a wider
band of 88 to 108 MHz because each station needs a bandwidth of 200 kHz.
3. Each TV channel
has its own bandwidth of 6MHz
WDM-Wave division multiplexing--WDM is
an analog multiplexing technique to combine optical signals.One application of
WDM is sonnet network
TDM-Time division multiplexing- two
types
Synchronous TDM-allocates time slot for each source even
if source is transmitting any signal
Statistical TDM-allocates time dynamically according to
source requirement
Spreading.privacy and anti jamming can be achieved by
using spreading
Two technique of spreading-frequency hopping spread
spectrum (FHSS), Direct Sequence spread spectrum (DSSS)
Transmission
Media
Guided Media
- Twisted Pair cable(Connector-RJ45 Male and Female)
- Coaxial cable(BNC connector ,BNC T, BNC Terminator)
- Fiber Cable(MT RJ)
Propagation Method
- Ground Propagation(below 2MHz)
- Sky Propagation(2-30MHz)
- Line of sight Propagation(Above 30MHz)
UnGuided Media:wireless transmission can be divided into
three category radio,micro and infrared waves
Radio waves-Omnidirectional (upto 1GHz- used in
Radio,TV,Paging system)
Microwaves-Unidirectional (1-300 GHz-used in Cellular
Phone,Satellite Network, LAN’s)
Infrared waves-(300 GHz to 400GHz) used in short range
communication)
Switching
Switching
Three type of switching
Circuit switching(setup--transfer-tore down)
-used in Physical layer
Packet switching
Virtual Packet Switching-data link layer
Datagram Packet switching -Network Layer
Message Switching -used at application level
Data Link Layer
Three types of address unicast ,multicast(one to
many),broadcast(One to All)
Error
Detection and Correction
Data Link Control
DLC is responsible for framing ,flow and error control
Two protocol to pack data bits into variable frame-character
oriented approach and bit oriented approach
- Byte/Bit stuffing is the process of adding one extra
byte/bit whenever there is a flag or escape character in the text.
HDLC(High Level Data Link Control):
High-level Data Link Control (HDLC) is a bit-oriented protocol for
communication over point-to-point and multipoint links. It implements the
Stop-and-Wait protocol.HDLC provides two types of transfer modes.
NRM-normal response mode:In NRM
,primary station sends command to one more station and secondary station can
only respond.
ABM-Asynchronous balanced mode-used
for point to point communication where both peer can send command and response
HDLC defines three types of frames: information frames
(I-frames), supervisory frames (S-frames), and unnumbered frames (U-frames).
PPP(Point to Point protocol):
Media Access
Control(MAC)
Multiple-access protocols
Random-access protocols
- ALOHA
- Pure Aloha (efficiency is 18.6)
- Slotted Aloha(efficiency is 36.8)
- CSMA/CD
- CSMA
Channelization Protocol
- CSMA/CA
- FDMA
- TDMA
- CDMA
Controlled-access protocols
- Polling
- Token passing
- Reservation
Ethernet
The IEEE 802.3 Standard defines 1-persistent CSMA/CD as the access method for first-generation 10-Mbps Ethernet. The data-link layer of Ethernet consists of the LLC sublayer and the MAC sublayer.
The IEEE 802.3 Standard defines 1-persistent CSMA/CD as the access method for first-generation 10-Mbps Ethernet. The data-link layer of Ethernet consists of the LLC sublayer and the MAC sublayer.
Each station on an Ethernet network has a unique 48-bit
address imprinted on its network interface card (NIC). The minimum frame length for 10-Mbps Ethernet is 64 bytes; the maximum
is 1518 bytes. The common implementations of 10-Mbps Ethernet are
10Base5 (thick Ethernet), 10Base2 (thin Ethernet), 10Base-T (twisted-pair
Ethernet), and 10Base-F (fiber Ethernet).
Other wired network
Telephone Network: Plain old telephone
system(POTS):
LATAs local access transport areas
Dial up service and Digital Subscriber Line is used for
transmitting data over telephone line
Cable Network-community antenna television
(CATV) network
Synchronous Optical Network (SONET) developed
by ANSI- used to connect WAN and higher data transfer
lines SONET defines four layers: path, line,
section(first three incorporated in data link layer), and photonic(Physical
Network). We can roughly divide SONET networks into
three categories: linear, ring, and mesh networks
ATM:Asynchronous Transfer Mode (ATM) is a switched wide area
network based on the cell relay protocol designed by the ATM forum and
adopted by the ITU-T .ATM header is of 5 Byte
and payload is of 48 bytes.
Wireless LANs
802.11(Wireless
LAN also known as Wireless fidelity -wifi)-two types of architecture . two
services: basic service set (BSS) and extended service set (ESS).
Ad Hoc network(without Access point) ,infrastructure
network(with AP)
Bluetooth:A
Bluetooth network is called a piconet, or a small net. A piconet can have up to
eight stations, one of which is called the primary; the rest are called
secondaries . Piconets can be combined to form what is called a scatternet.
Logical Link Control and Adaptation Protocol, or L2CAP (L2 here means LL), is
roughly equivalent to the LLC sublayer in LANs. The baseband layer is roughly
equivalent to the MAC sublayer in LANs. The access method is TDMA .
Radio layer is equivalent to physical layer .
Other Wireless Network
Worldwide Interoperability for Microwave
Access (WiMAX) First, 802.11 is a standard for a wireless
LAN; 802.16 is a standard for a wireless WAN (or MAN). The distance
between a base station and a host in the first is very limited; the base
station and subscriber station in the second may be separated by tens of
kilometers. Project 802.11 defines a connectionless communication; project
802.16 defines a connection- oriented service.
A later revision of IEEE 802.16 created two new standards
called IEEE 802.16d, which concentrates on the fixed WiMAX, and IEEE 802.16e,
which defines the mobile WiMAX.
AMPS-advanced mobile phone system
GSM is
digital cellular phone using TDMA and FDMA and was invented in Europe during
2nd generation
Universal Mobile Telecommunications System (UMTS)
Connecting Devices
Connecting Devices
HUB-
Physical Layer
Switching Network- Physical Layer,Data link Layer
Router-
Physical Layer,Data link Layer,Network Layer
Network Layer
The main services provided by the network layer are
packetizing and routing the packet from the source to the destination. The
network layer in the Internet does not seriously address other services such as
flow, error, or congestion control.
Packet switching. There are two approaches to packet switching: datagram
approach and virtual-circuit approach.
DHCP works at network layer and operate on
port 67,68
Network Address Translation (NAT). A technology that
can provide the mapping between the private and universal addresses, and at the
same time support virtual private networks,is Network Address Translation
(NAT).
Network-Layer Protocols
Four protocol is used in Network layer-IP,ARP,IGMP,ICMP
IP header is of 20-64
bytes and packet length is upto 65536 bytes
ICMPv4-this is designed to compensate error and
host-network management queries
Message is divided in two part-error reporting and query
message
Two tools ICMP uses for debugging-ping and traceroute
Routing
Unicast Routing
Distance vector Routing-Warshall algorithm-Routing
information protocol(RIP)
Link state routing-Dijkstra's Algo-Open shortest path
first(OSPF)
Path vector routing-Spanning tree- Border Gateway
Protocol(BGP)
Multicast Routing
In classless addressing the block
224.0.0.0/4 is used for multicast addressing
Transport Layer
Services provided by transport layer
- Process to Process communication
- Port Addressing(Well known:0-1023,Registered:1024-49151,Dynamic:49152-65535)
- Encapsulation and decapsulation
- Multiplexing and demultiplexing
- Flow control
Combination of port and IP address is called socket
address
Protocol at Transport Layer
- Stop and wait
- Go back N Protocol
- Selective Repeat Protocol
- Piggybacking
UDP: UDP datagram header is of 8 byte(2
byte each for source port and destination port,2 for checksum,2 for packet
length)
UDP is basically used in real time application such as
DNS,SNMP,RIP. It can not be used in FTP,SMTP.
TCP- TCP segment header vary from 8 to 20 bytes .
A connection establishment in TCP is called
three-way-handshaking(Connection establishment,data transfer, connection
termination
Application Layer Applications in the
Internet are designed using either a client-server paradigm or a peer-to-peer
paradigm
Standard Client Server protocol The
idea of the Web was first proposed by Tim Berners-Lee in 1989 at CERN- European
Organization for Nuclear Research.
HTTP(port80) uses the services of TCP
FTP uses two well-known TCP ports: port 21 is
used for the control connection, and port 20 is used for the data connection.
SMTP:used to transfer mail between mail server-25
POP/IMAP4(Internet mail access protocol)-used to
retrieve mail from server-110/143
MIME Multipurpose Internet mail extension
TELNET(Terminal Network)is used for remote login-23
SSH(Secure shell)was designed to replace
telnet and used for remote login and FTP-22
DNS mapping name to address to known as name address resolution-153
SNMP Simple Network Management Protocol (SNMP) 161
is a framework for managing
devices in an internet using the TCP/IP protocol
suite.The five areas comprising network management are configuration
management, fault management, performance management, accounting management,
and security management
Cryptography
Cryptography
Cryptography Algorithms can be categorized into part
Symmetric Cryptography(Secret key) -- Sender and receiver
uses the same key and algorithm
Asymmetric Cryptography(Public key)—Sender uses public
key and receiver private key
Traditional Encryption
Modern Encryption
SYMMETRIC Key Algorithm Types
Data Encryption Standard (DES)
The algorithm encrypts a 64-bit
plaintext block using a 64-bit key
Advanced Encryption Standard (AES)
AES
Configurations
|
||
size
of data block
|
number
of round
|
Key
Size
|
128
bits
|
10
|
128
|
12
|
196
|
|
14
|
256
|
|
ASYMMETRIC Key Algorithm Types
RSA and Diffie-Hellman.
RSA(Rivest, Shamir,and Adleman (RSA).
e and n shared to public and d ,fi kept secret.
P and Q are two large prime
n=P*Q
d*e(random integer)=1mod fi
fi=(P-1)(Q-1)
C=P^e (mod)n
P= C^d(mod)n
A combination of an encryption algorithm and a decryption
algorithm is called a cipher.
Network Security:
Message
- Confidentiality
- NonRepudiation
- Integrity
- Authentication
Entity
- Authorisation
Security in Internet
Internet Engineering Task Force (IETF)
IPSecurity(IPSec) : Applied to network layer
Two modes of IPSec
1.Transport mode: protects only IP payload . applicable
to end to end encryption(host to host)
2.Tunnel mode: protects to whole IP packet.applicable to
router to router or router to host or host to router
Two types of protocol
Two types of security protocol
- Authentication Header Protocol(AH):provide authentication at IP level
- Encapsulating Security Protocol:provide authentication and encryption at IP level
Application of ISec is VPN which uses
ESP protocol
Transport layer Security(SSL/TSL)
Ssl is designed to provide security and
compression services to Transport layer protocol.ssl use four protocol to
accomplish its task
1.handshake protocol
2.ChangeCipherSpec Protocol
3.Alert Protocol
4.Record Protocol
Application Layer Security(PGP
and S/MIME)
Pretty Good Privacy
(PGP). (PGPs invented by Phil Zimmermann to provide)
Secure/Multipurpose Internet Mail Extension
(S/MIME). The protocol is an enhancement of the Multipurpose Internet Mail
Extension (MIME)
Firewall:A firewall is a device
(usually a router or a computer) installed between the internal network of an
organization and the rest of the Internet. It is designed to forward some
packets and filter (not forward) others
Two types of firewall
Packet Filter firewall Filter only network and Transport Layer
Proxy Filter Firewall (Application Gateway) filter the application layer
Cryptographic Message Syntax (CMS)
Internet Key Exchange (IKE)
Internet Security Association and Key
Management Protocol (ISAKMP)
Points
1.
combination of key exchange, hash, and
encryption algorithms defines a Cipher suite
