COMPLETE COMPUTER NETWORK

Computer Networks
LMR

WWW.AMARPANCHAL.COM

What is….. It ?
• A computer network consists of end systems,
which are sources of information, which are
sources of information, which communicate
through the transit systems interconnecting
them. The transit system is also called an
interconnect subsystem or a subnetwork.

Topology:
– Topology refers to the way the network is laid out,
either physically or logically. Two or more devices
connect to a link, two or more links form a
topology.
A

B

A

E

E

B

B

HUB

Central
Controller
D

D

C

A

HUB

HUB

C
C

D

D

D

D

F

F

A
A

B

A
Ring interface
unit

A
C

D

A

A

Asymmetrical DSL (ADSL)
• ADSL divides up the available frequencies in a
line on the assumption that most Internet
users look at, or download, much more
information than they send, or upload.
– Under this assumption, if the connection speed
from the Internet to the user is three to four
times faster than the connection from the user
back to the Internet, then the user will see the
most benefit (most of the time).

Asymmetrical DSL (ADSL)
• ADSL is an adaptive technology.
• The system uses a data rate based on the
condition of the local loop line.
• Speed:
Most existing local loops can handle
bandwidths up to 1.1 MHz.

OTHER TYPES OF DSL:
• Symmetric DSL (SDSL)
• High-bit-rate DSL (HDSL)
• Very high bit-rate DSL (VDSL)

Symmetric DSL (SDSL)
• Used mainly by small businesses & residential
areas
• Bit rate of downstream is higher than
upstream

High-bit-rate DSL (HDSL)
• Used as alternative of T-1 line
• Uses 2B1Q encoding
• Less susceptible to attenuation at higher
frequencies
• Unlike T-1 line (AMI/1.544Mbps/1km), it can
reach 2Mbps @ 3.6Km

Very high bit-rate DSL (VDSL)
• Uses DMT modulation technique
• Effective only for short distances(300-1800m)
• Speed:
downstream : 50 - 55 Mbps
upstream
: 1.5-2.5 Mbps

DATA LINK LAYER
• chacter count

• Starting and ending characters with character
stuffing

• Starting end ending flags with bit stuffing.

Flow Control
• STOP N WAIT
• SLIDDING WINDOW
– SLIDDING WINDOW GO BACK N ARQ
– SELECTIVE REJECT ARQ

Error control :
• Cyclic redundancy check :
•
If Original Data to be transmitted is 110101010
•
Divisor is 10101
•
The data is appended with 4 zeros and divided by the divisor.
•
The remainder is added to the dividend in order to obtain the
data to be transmitted.
•
1101010100000
•
1011
•
1101010101011
•
Therefore, transmitted data : 1101010101011

10101 1101010100000
10101
11111
10101
10100
10101
11000
10101
11010
10101
11110
10101
1011

REMANIDER

Taxonomy of Networks
• Communication networks can be classified based on
the way in which the nodes exchange information:
Communication
Network

Circuit-Switched
Network

Frequency
Division
Multiplexing

Packet-Switched
Network

Datagram
Network

Time Division
Multiplexing

Wavelength
Division
© Jörg Liebeherr, Multiplexing

CS757

Virtual Circuit
Network

Circuit Switching
• In a circuit-switched network, a dedicated
communication path (“circuit”) is established
between two stations through the nodes of the
network
• The dedicated path is called a circuit-switched
connection or circuit
• A circuit occupies a fixed capacity of each link for the
entire lifetime of the connection. Capacity unused
by the circuit cannot be used by other circuits
• Data is not delayed at the switches
© Jörg Liebeherr,

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Circuit Switching
• Circuit-switched communication involves three
phases:
1. Circuit Establishment
2. Data Transfer
3. Circuit Release

• “Busy Signal” if capacity for a circuit not available
• Most important circuit-switching networks:
•
•

Telephone networks
ISDN (Integrated Services Digital Networks)

© Jörg Liebeherr,

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Circuit Switching

circuit 2

C

B

D
1

2
3
5

4
A

circuit 1

© Jörg Liebeherr,

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6

E

Implementation of Circuit-Switching
• There are two ways to implement circuits
– Frequency Division Multiplexing (FDM)
– Time Division Multiplexing (TDM)
– Wavelength Division Multiplexing (WDM)

• Example: Voice in (analog) telephone network:
Needed bandwidth:
3000 Hz
Allocated bandwidth:
4000 Hz
Therefore, a channel with 64 kHz can carry 16 voice conversations
© Jörg Liebeherr,

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Frequency Division Multiplexing (FDM)


Approach: Divide the frequency spectrum into logical
channels and assign each information flow one logical
channel
Channel 1 (f1)

Source 1

1
Source 2
Source 3
Source 4
Source 5
Source 6

© Jörg Liebeherr,

Channel 2 (f2)
S
w
i
t
c
h

Channel 3 (f3)
Channel 4 (f4)
Channel 5 (f5)
Channel 6 (f6)
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S
w
i
t
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h

3
4
5
6

Frequency Division Multiplexing (FDM)
Endsystem

Endsystem

Circuit
Switch

Circuit
Switch

Endsystem

Endsystem

• A circuit switch bundles (multiplexes) multiple voice calls on a high-bandwidth
link
• Frequency-Division-Multiplexing (FDM): Each circuit receives a fixed bandwidth.
The frequency of each call is shifted, so that multiple calls do not interfere
© Jörg Liebeherr,

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Time Division Multiplexing (TDM)


Approach: Multiple signals can be carried
on a single transmission medium by
interleaving portions of each signal in time
Source 1

1

Source 2
Source 3

M

M

3

Source 4

U

Source 5

12345612

X

U
X

Source 6

© Jörg Liebeherr,

2

4
5
6

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Time Division Multiplexing (TDM)
endsystem

Circuit
Switch

endsystem

endsystem

slots

Circuit
Switch

endsystem

frames

• Time is divided into frames of fixed length
• Each frame has a fixed number of constant-sized
“slots”
• Each circuit obtains one or more “slots” per frame
© Jörg Liebeherr,

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Circuit Switch
switch
fabric

memory

•A circuit switch relays a circuit from an input to an output link
•A switch may reassign frequencies (FDM) or time slot allocation (TDM)
•No queueing delays are experienced
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© Jörg Liebeherr,

Packet Switching
•
•

Data are sent as formatted bit-sequences, so-called packets
Packets have the following structure:
Header

Data

Trailer

• Header and Trailer carry control information
• Each packet is passed through the network from node to node along some
path (Forwarding/Routing)
• At each node the entire packet is received, stored briefly, and then
forwarded to the next node (Store-and-Forward Networks)
• Packet transmission is never interrupted (no preemption)
• No capacity is allocated for packets

© Jörg Liebeherr,

CS757

A Packet Switch
input
queues

output
queues
switch
fabric

memory

© Jörg Liebeherr,

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Statistical Multiplexing
• Packet transmission on a link is referred to as
statistical multiplexing
– There is no fixed allocation of packet
transmissions
– Packets are multiplexed as they arrive
Packets from different
streams

Transmission
line

1

2

1

N

2

output buffer
N

© Jörg Liebeherr,

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1

Datagram Packet Switching
• The network nodes process each packet
independently
If Host A sends two packets back-to-back to Host B over a datagram packet
network, the network cannot tell that the packets belong together In fact,
the two packets can take different routes

• Packets are called datagrams
• Implications of datagram packet switching:
• A sequence of packets can be received in a different order
than it was sent
• Each packet header must contain the full address of the
destination
© Jörg Liebeherr,

CS757

Virtual-Circuit Packet Switching
• Virtual-circuit packet switching is a hybrid of
circuit switching and packet switching
– All data is transmitted as packets
– Emulates a circuit-switched network

• All packets from one packet stream are sent along
a pre-established path (=virtual circuit)
– Guarantees in-sequence delivery of packets
– Note: Packets from different virtual circuits may be
interleaved
© Jörg Liebeherr,

CS757

• Communication with virtual circuits (VC) takes place in
three phases:
1.
2.
3.

VC Establishment
Data Transfer
VC Disconnect

• Note: Packet headers don’t need to contain the full
destination address of the packet
• Circuit-switched and virtual-circuit packet-switched
networks are said to provide a connection-oriented
service.
© Jörg Liebeherr,

CS757

Packet Forwarding and Routing
• There are two parts to the routing problem:
1. How to pass a packet from an input interface to the
output interface of a router (packet forwarding)?
2. How to calculate routes (routing algorithm)?

• Packet forwarding is done differently in
datagram and virtual-circuit packet networks
• Route calculation is similar in datagram and
virtual-circuit packet networks
© Jörg Liebeherr,

CS757

Datagram Packet Switching
C
B

C.1

1

2
C.1

C.2

A.1
A.3 A.2

4
A

A.1
C.1 A.2
C.2 A.3

C.2

A.1
A.2
A.3

© Jörg Liebeherr,

5

D

3

A.1
A.3 C.2
A.2

A.2

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A.2

6

E

C.2

VC 2

B

C

A.1
C.1 A.2
C.2 A.3

C.1

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2
C.2

3

C.1

5
4
A A.1

VC 1

C.1
C.2 A.1
A.3 A.2

A.1
A.3 A.2

7

A.2
A.3

© Jörg Liebeherr,

D

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6

E

Packet Forwarding of Datagrams
• Recall: In datagram networks, each packet
must carry the full destination address
• Each router maintains a routing table which
has one row for each possible destination
address
Routing Table of node v
• The lookup yields the address of the next hop
to
(next-hop routing)
w
v
n
d
via
(next hop)

x
d

n

© Jörg Liebeherr,

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Packet Forwarding of Datagrams
• When a packet arrives at an incoming link, ...
1. The router looks up the routing table
2. The routing table lookup yields the address of the
next node (next hop)
3. The packet is transmitted onto the outgoing link
that Table of node v
Routing goes to the next hop
to

via
(next hop)

d
w

d
v

n
x

d

n

© Jörg Liebeherr,

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d

To
A

Next
hop

To

Next
hop

Forwarding
Datagrams
-

A

A

B

B

-

C

C

D

D

C

D

D

E

B

E

E

X

C

X

D

B
C

To

E

Next
hop

To

Next
hop

E

E

E

A

C

B

C

C

C

D

C

E

C

A

A

A

B

X

-

B

-

B

B

C

D

C

C

D

D

D

-

E

D

E

B

X

E

X

C

X

© Jörg Liebeherr,

C
To

D
To

Next
hop

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Next
hop

B
B
B
-

X

E

B
D

E

B

E

B

A
C

A

E

B

Packet Forwarding with Virtual Circuits
• Recall: In VC networks, the route is setup in
the connection establishment phase
• During the setup, each router assigns a VC
number (VC#) to the virtual circuit
• The VC# can be different for each hop
• Routingis written into the packet headers
VC# Table of node v
path of virtual
circuit

from

VC#

to

VC#

2

w

3

1

v

n
x

w

2

© Jörg Liebeherr,

d

3

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d

Packet Forwarding of Virtual Circuits
• When a packet with VCin in header arrives from router
nin, ...
1. The router looks up the routing table for an entry with
(VCin, nin)
2. The routing table lookup yields (VCout, nout)
3. The router updates the VC# of the header to VCout and
transmits the packet to nout
Routing Table of node v
from

VC#

to

2

VC#

2

w

3

path of virtual
circuit

1

3

1

v

n
x

w

2

© Jörg Liebeherr,

d

3

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Forwarding with VCs
Part 1: VC setup
from X to E
nin

Vin

nout

-

C

Vin

D

5

nout

Vout

E

3

A

Vout

-

nin

B

E

5

nin

Vin

nout

B

X

C
nin
X

© Jörg Liebeherr,

Vin
5

3

nout

Vout

B

5

D

nout

Vout

D

3

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nin
C

Vin
3

Vout

-

-

Forwarding with VCs
Part 2: Forwarding
the packet
nin

Vin

nout

-

C

Vin

D

5

nout

Vout

E

2

A

Vout

-

nin

2

B

5

5
5
X

X

© Jörg Liebeherr,

Vin
5

nin

Vin

nout

B

3
C

nin

E

3

nout

Vout

B

5

D

nout

Vout

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nin
C

Vin
3

Vout

-

-

Comparison
Datagram Packet
Switching

Circuit Switching












Dedicated
transmission path
Continuous
transmission
Path stays fixed for
entire connection
Call setup delay
Negligible
transmission delay
No queueing delay
Busy signal overloaded
network
Fixed bandwidth for
each circuit
No overhead after call
setup

© Jörg Liebeherr,











No dedicated
transmission path
Transmission of
packets
Route of each packet
is independent
No setup delay
Transmission delay
for each packet
Queueing delays at
switches
Delays increase in
overloaded networks
Bandwidth is shared
by all packets
Overhead in each
packet
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VC Packet
Switching










No dedicated
transmission path
Transmission of
packets
Path stays fixed for
entire connection
Call setup delay
Transmission delay
for each packet
Queueing delays at
switches
Delays increase in
overloaded networks
Bandwidth is shared
by all packets
Overhead in each
packet

HDLC Overview
Broadly HDLC features are as follows:
• Reliable protocol
– selective repeat or go-back-N

• Full-duplex communication
– receive and transmit at the same time

• Bit-oriented protocol
– use bits to stuff flags occurring in data

• Flow control
– adjust window size based on receiver capability

• Uses physical layer clocking and synchronization to
send and receive frames

HDLC Overview
• Defines three types of stations
– Primary
– Secondary
– Combined

• Defines three types of data transfer mode
– Normal Response mode
– Asynchronous Response mode
– Asynchronous Balanced mode

• Three types of frames
– Unnumbered
– information
– Supervisory

HDLC
• The three stations are :
– Primary station
• Has the responsibility of controlling the operation of data flow the
link.
• Handles error recovery
• Frames issued by the primary station are called commands.

– Secondary station,
• Operates under the control of the primary station.
• Frames issued by a secondary station are called responses.
• The primary station maintains a separate logical link with each
secondary station.

– Combined station,
• Acts as both as primary and secondary station.
• Does not rely on other for sending data

HDLC
Unbalanced Mode

Commands
Primary
Responses
Secondary

Secondary

Balanced mode

Combined

Combined
commands/Responses

HDLC
• The three modes of data transfer operations are
– Normal Response Mode (NRM)
• Mainly used in terminal-mainframe networks. In this case,
• Secondaries (terminals) can only transmit when specifically instructed by
the primary station in response to a polling
• Unbalanced configuration, good for multi-point links

– Asynchronous Response Mode (ARM)
• Same as NRM except that the secondaries can initiate transmissions
without direct polling from the primary station
• Reduces overhead as no frames need to be sent to allow secondary nodes
to transmit
• Transmission proceeds when channel is detected idle , used mostly in
point-to-point-links

– Asynchronous Balanced Mode (ABM)
• Mainly used in point-to-point links, for communication between
combined stations

Data Link Control HDLC frame structure
(a) Frame
Format

(b) Control
field
format

11-7 POINT-TO-POINT PROTOCOL

Although HDLC is a general protocol that can be used
for both point-to-point and multipoint configurations,
one of the most common protocols for point-to-point
access is the Point-to-Point Protocol (PPP). PPP is a
byte-oriented protocol.

Figure 11.32 PPP frame format

11.54

Note
PPP is a byte-oriented protocol using byte stuffing with the escape byte 01111101.

11.55

Figure 11.33 Transition phases

11.56

Routing :
•
•
•
•

1)
2)
3)
4)

Centralized Routing :
Distributed Routing :
Static Routing or Non-adaptive routing :
Dynamic Routing or Adaptive Routing :

• 1.Shortest path routing algorithm:

• . The count-to-infinity problem.

• Link State Routing
– Discover its neighbors and learn their network
addresses.
– Measure the delay or cost to each of its neighbors.
– Construct a packet telling all it has just learned.
– Send this packet to all other routers.
– Compute the shortest path to every other router.

CIDR Addresses
• Identifying a CIDR block requires both an address and a mask
– Slash notation
– 128.211.168.0/21 for addresses 128.211.168.0 – 128.211.175.255
• Here the /21 indicates a 21 bit mask

– All possible CIDR masks can easily be generated
• /8, /16, /24 correspond to traditional class A, B, C categories

• IP addresses are now arbitrary integers, not classes
• Raises interesting questions about lookups
– Routers cannot determine the division between prefix and suffix just by
looking at the address
• Hashing does not work well
• Interesting lookup algorithms have been developed and analyzed
CS 640

62

CIDR – A Couple Details
• ISP’s can further subdivide their blocks of
addresses using CIDR
• Some prefixes are reserved for private
addresses
– 10/8, 172.16/12, 192.168/16, 169.254/16
– These are not routable in the Internet

CS 640

63

Congestion control
• In Virtual-Circuit
– Admission control

• In Datagram Subnets
– The Warning Bit
– Choke Packets
– Hop-by-Hop Choke Packets
– Load Shedding
– Jitter Control

Connecting Devices and the OSI Model

Connecting Devices
Repeaters
Hubs
Bridges
Two-Layer Switches

Repeaters
• A repeater (or regenerator) is an electronic device that
operates on only the physical layer of the OSI model.
• A repeater installed on a link receives the signal before it
becomes too weak or corrupted, regenerates the original
pattern, and puts the refreshed copy back on the link.

Repeaters
• A repeater does not actually connect two LANS; it connects
two segments of the same LAN.
• A repeater forwards every frame; it has no filtering capability.

Hubs
• A Hub is a multiport repeater. It is normally used to create
connections between stations in a physical star topology.

Bridges
• Bridges operate in both the physical and the data link
layers of the OSI model.

Bridges
• Bridges can divide a large network into smaller segments. They
contain logic that allows them to keep the traffic on each segment
separate. When a frame (or packet) enters a bridge, the bridge not
only regenerates the signal but checks the destination address and
forwards the new copy only to the segment the address belong.

Bridges
• A bridge operates in both the physical and the data link layers.
• As a physical layer device, it regenerates the signal it receives.
• As a data link layer device, the bridge can check the physical
(MAC) address (source and destination) contained in the
frame.
• A bridge has filtering capability. It can check the destination
address of a frame and decide if the frame should be
forwarded or dropped. If the frame is to be forwarded, the
decision must specify the port.
• A bridge does not change the physical (MAC) addresses in a
frame.
• A bridge has a table used in filtering decisions.

Types of Bridges
• To select between segments, a bridge must have a look-up
table that contains the physical addresses of every station
connect to it. The table indicate to which segment each
station belongs.
Simple Bridge
• The address table must be entered manually, before a
simple bridge can be used.
• Whenever a new station is added or removed, the table
must modified.
• Installation and maintenance of simple bridges are timeconsuming and potentially more trouble than the cost
savings are worth.

Routers
• Routers have access
to network layer
addresses and
contain software that
enables them to
determine which of
several possible paths
between those
addresses is the best
for a particular
transmission.
• Routers operate in
the physical, data link,
and network layers of
the OSI model.

• Routers relay packets among multiple interconnected
networks. They route packets from one network to any of
a number of potential destination networks on an
internet.

Gateways
• Gateways potentially operate in all seven layers of the OSI
model.

Gateways
• A gateway is a protocol converter. A router by itself
transfers, accepts, and relays packets only across networks
using similar protocols.
A gateway can accept a packet formatted for one protocol
(e.g. AppleTalk) and convert it to a packet for another
protocol (e.g. TCP/IP).

Gateways
• A gateway is generally software installed within a router.
The gateway understands the protocols used by each
network linked into the router and is therefore able to
translate from one to another.

What is SONET?
•

Synchronous Optical Network standard

SONET
Network
Element

•
•
•
•
•

Digital
Tributaries

SONET
Network
Element
Digital
Tributaries

Defines a digital hierarchy of synchronous signals
Maps asynchronous signals (DS1, DS3) to synchronous format
Defines electrical and optical connections between equipment
Allows for interconnection of different vendors’ equipment
Provides overhead channels for interoffice OAM&P

SONET Rates

Level

Optical
Designation

Bit Rate
(Mb/s)

STS-1

OC-1

51.840

STS-3

OC-3

155.520

STS-12

OC-12

622.080

STS-48

OC-48

2,488.320

STS-192

OC-192

9,953.280

STS
OC

= SYNCHRONOUS TRANSPORT SIGNAL
= OPTICAL CARRIER
(“..result of a direct optical conversions of the STS after
synchronous scrambling” - ANSI)

SONET Network Layers
Services
DS3, DS1, etc

Path

Line

Section

• Map Services & POH Into SPE
• Path Protection/Restoration
• Other Path OA&M Functions

Path

• Combine SPE & LOH
• Sync & Mux For Path Layer
• Line Protection/Restoration
• Other Line OA&M Functions

Section

• Add SOH & Create STS Signal
• Framing, Scrambling
• Section OA&M Functions

Physical • E/O Conversion
(Photonic) • Line Code

• Physical Signal
[No additional overhead]

Line

Line

DS3
etc

MUX

LTE

Section

Regen

Section

Regen

SONET ADM

Section

LTE

LTE

MUX

DS3
etc

Functional Description of SONET Layers
Function
Path Layer

Information
Payload

Line
OH

Line Layer

Section
Layer

Photonic
Layer

Path
OH

Section
OH

E/O Conversion

Transmission over OC-N

Payload Mapping
Error Monitoring
Synchronization
Multiplexing
Error Monitoring
Line Maintenance
Protection Switch
Order Wire
Framing
Scrambling
Error Monitoring
Section Maintenance
Orderwire
E/O Conversion
Pulse Shaping
Power Level
Wavelenght

OH: Overhead

Internet Protocol (IP)
• Features:
– Layer 3 (Network layer)
– Unreliable, Connectionless, Datagram
– Best-effort delivery

• Popular version: IPv4
• Major functions
– Global addressing
– Datagram lifetime
– Fragmentation & Reassembly

IPv4 companion protocols (1)
• ARP: Address Resolution Protocol
– Mapping from IP address to MAC address

• ICMP: Internet Control Message Protocol
– Error reporting & Query

• IGMP: Internet Group Management Protocol
– Multicast member join/leave

• Unicast Routing Protocols (Intra-AS)
– Maintaining Unicast Routing Table
– E.g. RIP, OSPF (Open Shortest Path First)

IPv4 companion protocols (2)
• Multicast Routing Protocols
– Maintaining Multicast Routing Table
– E.g. DVMRP, MOSPF, CBT, PIM

• Exterior Routing Protocols (Inter-AS)
– E.g. BGP (Border Gateway Protocol)

• Quality-of-Service Frameworks
– Integrated Service (ISA, IntServ)
– Differentiated Service (DiffServ)

Why IPv6?
• Deficiency of IPv4
• Address space exhaustion
• New types of service  Integration
– Multicast
– Quality of Service
– Security
– Mobility (MIPv6)

• Header and format limitations

Advantages of IPv6 over IPv4
•
•
•
•
•
•
•

Larger address space
Better header format
New options
Allowance for extension
Support for resource allocation
Support for more security
Support for mobility

Header: from IPv4 to IPv6
Changed

Removed

Advantages of IPv6 over IPv4 (1)
Feature
Source and
destination address
IPSec
Payload ID for QoS in
the header

Fragmentation
Header checksum

Resolve IP address to
a link layer address

IPv4

IPv6

32 bits

128 bits

Optional

required

No identification

Using Flow label field

Both router and the
sending hosts

Only supported at the
sending hosts

included

Not included

broadcast ARP
request

Multicast Neighbor
Solicitation message

Advantages of IPv6 over IPv4 (2)
Feature

IPv4

IPv6

Determine the
address of the best
default gateway

ICMP Router
Discovery(optional)

ICMPv6 Router
Solicitation and
Router Advertisement
(required)

Send traffic to all
nodes on a subnet

Broadcast

Link-local scope allnodes multicast
address

Configure address

Manually or DHCP

Autoconfiguration

(IGMP)

Multicast Listener
Discovery (MLD)

Manage local subnet
group membership

Bluetooth Overview
• Wireless technology for short-range voice and
data communication
• Low-cost and low-power
• Provides a communication platform between
a wide range of “smart” devices
• Not limited to “line of sight” communication

Motivation
Digital Camera

Computer

Scanner

Inkjet
Printer

Home Audio System

PDA
Cell Phone

Cordless Phone
Base Station

Bluetooth Applications
• Automatic synchronization between mobile
and stationary devices
• Connecting mobile users to the internet using
bluetooth-enabled wire-bound connection
ports
• Dynamic creation of private networks

Ad Hoc Networks
• Up to 8 devices can be actively connected in
master/slave configuration
• Piconets can be combined to form scatternets
providing unlimited device connectivity

Bluetooth Radio
• Uses 2.4 GHz ISM band spread spectrum radio
(2400 – 2483.5 MHz)
• Advantages
– Free
– Open to everyone worldwide

• Disadvantages
– Can be noisy (microwaves, cordless phones,
garage door openers)

Frequency Hopping
•
•
•
•

In order to mitigate interference, Bluetooth
implements frequency hopping
1600 hops per second through 79 1MHz
channels
Spreads Bluetooth traffic over the entire ISM
band
All slaves in piconet follow the master for
frequency hop sequence

Establishing Piconets
• Whenever there is a
connection between two
Bluetooth devices, a piconet is
formed
• Always 1 master and up to 7
active slaves
• Any Bluetooth device can be
either a master or a slave
• Can be a master of one piconet
and a slave of another piconet
at the same time (scatternet)
• All devices have the same
timing and frequency hopping
sequence

Scatternets
• Formed by two or
more Piconets
• Master of one piconet
can participate as a
slave in another
connected piconet
• No time or frequency
synchronization
between piconets

Berkeley Sockets
The socket primitives for TCP.

COMPLETE COMPUTER NETWORK

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