Transcript Media Access and Internet Workingx

MEDIA ACCESS AND INTERNETWORKING
BY
SUBASHINI.G
 Sub
layer of datalink layer.
 Provides
addressing and channel access control
mechanism.
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IEEE 802.3 formed a standard technology
called Ethernet.
Uses CSMA/CD technology.
Ethernet standard found in 1972.
802.3 extended for 100 Mbps called fast
ethernet.
1000 Mbps- GigaBit Ethernet
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Carrier Sense Multiple Access.
Set of nodes send and receive frames.
Nodes can distinguish between an idle and busy link.
Uses packet radio network as a rout protocol.
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Implemented on a coaxial cable of 500 metres.
Host connect to an ethernet.
Transceiver- device attached to the tape.
It receives incoming signal.
It connected to ethernet adapter which is plugged into
the host.
transceiver
ethernet
cable
adapter
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Multiple ethernet segment can be joined by repeaters.
Device that follows signals in all outgoing segments.
Signal is propagated in both directions.
Manchester encoding is used here.
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Several point to point segments coming out of a
multiwave repeater.
HUB
HUB
HOST
ETHERNET HUB
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Algorithm that controls access to a shared ethernet link.
Implemented as hardware in the network adapter.
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64
48
48
preamble Dest
add
Src
add
16
46-1500 32
type
body
CRC
Preamble(64 bits): allows receiver to synchronize the
signal.
Host and destination address(48 bits).
Packet type(16 bits):acts as demux key and identify the
higher level protocol.
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Each host on the ethrnet has a unique ethernet address.
Address belongs to the adapter not the host.
A sequence of six number separated by colon(ie) 6*1/2
Ex 8:0:2b:e4:b1:2
Every adapter has a unique address .
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Unicast – frame is transmitted to the ethernet.
Broadcast - we are going to set all the bits as 1.
Multicast – the first bit set to 1.
Ethernet adapter accepts all frames and accepts.
Frames address to its own address
Frames address to the broadcast address
Frames address to the multicast address if it has been instructed
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Wireless signal uses electromagnetic signals.
Use of particular frequency allocated by FCC-Federal
Communication Commission- USA
Three categories:
Some bands for government use.
Some bands for AM Radio,FM Radio,
telivision,satellite communication.
Some bands for individual organization in
certain area.
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BLUETOOTH
WI-FI
WI MAX
3G CELLULAR NETWORKS
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Nodes are peers.
Designed for limited geographical area.
Signal propagation through space.
802.11 using two technologies
Frequency hopping- MHz(or)GHz
Direct sequence- MHz
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A and c are said to be hiden nodes because they re not
aware of collision
B
A
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C is called exposed node to B
C
D
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802.11 packet format
16
16
48
48
48
16
48
0-18496 32
control dest add1 add2 add3 seq add4 Pay CRC
load
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Used for short range communication inbetween mobile
phones, PDA
Going to operate on 2.45 GHz
Distance is 10 meters
Speed is 2.1 Mbps
Based on piconet
We have advanced technology called Zigbee
HUB
 REPEATER
 SWITCH
 BRIDGE
 ROUTER
 GATEWAY
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- PHYSICAL LAYER
- PHYSICAL LAYER
- DATA LINK LAYER
- DATA LINK LAYER
- NETWORK LAYER
- TRANSPORT LAYER
DATAGRAM APPROACH(OR) CONNECTIONLESS
 VIRTUAL CIRCUIT(OR) CONNECTION
ORIENTED
 SOURCE ROUTING
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Host can send packet anywhere at anytime
Does not care the delivery of data
To decide how to forward a packet a routing table is
used
TWO STAGES Connection setup
Data transfer
Also called packet switching or virtual circuit
Virtual circuit making virtual connection in between
sender and receiver
Accept LAN frames in their inputs and forward them to
all other outputs
A
B
C
BRIDGE
X
Y
Z
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Keeps all the vertices of the original graph but throws
some of the edge
Sub graph that covers all the vertices but contains no
cycle
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No cycle is formed
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Minimum cost and covers all the vertices
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IP PACKET FORMAT
VERSION HLEN
TOS
FLAGS
IDENT
TTL
LENGTH
PROTOCOL
OFFSET
CHECKSUM
SOURCE ADDRESS
DESTINATION ADDRESS
OPTIONS(VARIABLE)
PAD(VARIABLE)
DATA
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VERSION- 4
HLEN- HEADER LEN-4 BITS
TOS- TYPE OF SERVICE
LENGTH-16 BIT-NO OF BYTES IN THE DATAGRAM
IDENT- 16 BITS USED FOR FRAGMENTATION
FLAGS/OFFESET- THERE ARE 16 BITS USED BY
FRAGMENTATION
TTL- NO OF HOPS
PROTOCOL- 8 BITS-DEMUX KEY
CHECKSUM-16 BITS
DESTINAION/SOURCE ADDRESS-32 BITS EACH
OPTIONS& PAD- 16 BITS(VARYING FROM PACKET TO
PACKET)
PACKET DELIVERY MODEL
Each network has some MTU(Maximum
Transmission Unit) ex, Ethernet
FDDI- Fibre Distributed Data Interface
GLOBAL ADDRESSING SCHEME
Global unique address
Combination of network and host
IP address
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The division of network into smaller network called
subnet
 IP Address is 32 bit LAN
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One portion indicates a networlk ID and other portion indicates
host or router
To connect more host we need subnet
16
1
0
Ex:class B 141.14.0.0
NET
16
H
H
Delivery to the site
 Delivery to the sub-net
 Delivery to the host
MASKING:
It is a process that extracts the address of physical
network from an IP address
Masking can be done whether we have subnet or
not
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MASK WITHOUT SUBNETTING
141.14.2.21
IP ADDRESS
N/w ADDRESS
141.14.0.0
MASK
255.255.0.0
• MASK WITH SUBNETTING
141.14.2.21
MASK
255.255.255.0
141.14.2.0
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Also called supernetting
Allocate and specify the internet address used in inter
domain routing
Consists of two groups
◦ To identify a network/subnetwork
◦ To identify a host
ARP PACKET FORMAT
HARDWARE TYPE
H LEN
P LEN
PROTOCOL TYPE
OPERATION
SOURCE HARDWARE ADDRS(BYTE 0-3)
SOURCE HARDWARE
ADDRESS (BYTE 4-5)
SOURCE PROTOCOL
ADDRESS(BYTE 0-1)
SOURCE PROTOCOL
ADDRESS (BYTE 2-3)
TARGET HARDWARE
ADDRESS (BYTE 0-1)
TARGET HARDWARE ADDRESS(BYTE 2-5)
TARGET PROTOCOL ADDRESS(BYTE 0-3)
UNICAST TO
SERVER
DHCP
RELAY
HOST
OTHER
N/W
DHCP
SERVER
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It is responsible for providing configufration
information to host
There is atleast one DHCP server for an administrative
domain
It maintains a pool of available devices
DHCP relay unicast the message to the DHCP server
and waits for response
Defines collection of error messages that are send back to
the source host whenever the router is unable to crosses an
IP datagram
ERRORS:
◦ Destination host unreachable due to link or node failure
◦ Reassembling process failed