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Communication Reference Models
• Layer Models
• ISO 7 layer Model
• IEEE Model
• DOD Model
• ATM
• TCP Protocol Suit
Layer Models General
Upper Layer
protocol
Service
Service
Service
delivery
request
Service Layer
Peer Layer
request
protocol
Alternative implementations
Service Layer
Service
delivery
Layer Message Format
Layer 3
payload
Layer 2
H2
payload
t2
Layer 1
H3
H2
payload
t2
t3
ISO 7-layer model
– 1 physical
transmit signals
– 2 data link
reliable point to point
– 3 network
routing
– 4 transport
end to end
– 5 session
logon, security
– 6 presentation
integers,characters
– 7 apps --> ftp, email, telnet,WWW
IEEE model
• for LANs
• compatible with ISO; more detail for
specific type of networks
-> Application
ISO
LAYER
7,6,5,3
-> LLC - logical link control
2
-> MAC - medium access control
2
-> physical layer/medium
1
LANs : local area networks
• ethernet, or CSMA/CD : IEEE 802.3
– most widely used LAN; more than half of all LANs in
the world
– broadcast-contention protocol
– data rates of 10,100,1000 Mbps
– physically configured as bus or a star
– can use coax cable (thick or thin), twisted pair, or
optical fiber.
– utilization of 30-50%, roughly
ethernet
• ethernet topology: original topology was bus, as
above. Signals broadcast in both directions to all
receivers.
• can also be configured as tree, but uses same
protocol.
LANs : local area networks
• token ring : IEEE 802.5
–
–
–
–
2nd most used in internet; 20-25% of all LANs.
physical ring, logical broadcast; no collisions.
data rates 4,16,100 (FDDI)
throughput 90-95% entirely possible
token ring
• data flows in 1 direction around the ring, from
station to station
• only 1 station, which possesses token,
allowed to transmit; all others repeat.
DOD Model
• Internetworking
ISO
LAYER
– applications : email, FTP, telnet, WWW
7,6,5,
– host-host --> transport layer: TCP,UDP
4
– internet layer : IP
3
– network interface --> to lower layered
networks; eg, ethernet, token ring, FDDI,
MILNet, etc.
2
– Physical
1
TCP/IP protocol suite
telnet, FTP, etc.
apps
TCP
ICMP
ARP
TFTP, other apps.
UDP
IP
LAN/WAN
media
IGMP
RARP
ATM model
• ATM: asynchronous transfer mode
• high speed network
• layers:
physical -- based on optical fiber
ATM layer -- switching
ATM adoption layer - interface
user layers