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Network Layered
Protocols
I VPR
Institute for Visualization and Perception Research
© Copyright 1998 Haim Levkowitz
1
Layered protocol models
...
• Protocol message contents ...
• Identities
• Sender, receiver
• Message length
• Message data
• Layered protocols ...
• Protocol enveloping ...
• OSI reference model ...
• Internet TCP/IP model ...
• Protocol enveloping in TCP/IP ...
I VPR
Institute for Visualization and Perception Research
© Copyright 1998 Haim Levkowitz
2
Layered protocols ...
• N layers
Computer 1
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Computer 2
Layer N
Layer N – 1
Layer N
Layer N – 1
Layer 1
Layer 1
Institute for Visualization and Perception Research
© Copyright 1998 Haim Levkowitz
3
Protocol enveloping ...
Computer 1
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Computer 2
Layer N
Layer N – 1
Layer N
Layer N – 1
Layer 1
Layer 1
Institute for Visualization and Perception Research
© Copyright 1998 Haim Levkowitz
4
OSI reference model ...
• Open Systems Interconnection
abstract model
• Does not define: PL bindings, OS
bindings, API issues, UI issues
• Defines: 7 protocol layers ...
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Institute for Visualization and Perception Research
© Copyright 1998 Haim Levkowitz
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Defines: 7 protocol layers
...
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Physical ...
Data link ...
Network ...
Transport ...
Session ...
Presentation ...
Application ...
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Application
Presentation
Session
Transport
Network
Data Link
Application-r
elated
services
Network-r
elated
services
Physical
Institute for Visualization and Perception Research
© Copyright 1998 Haim Levkowitz
6
Physical ...
• Network transmission medium
• E.g., coaxial, twisted-pair, fiber-optic
• Raw bit-stream service
• Responsible only for writing / reading
bits to / from physical medium
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Institute for Visualization and Perception Research
© Copyright 1998 Haim Levkowitz
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Data link ...
• Group bits into frames
• Goal: reliable delivery mechanism
• Error detection
• Noise, interference
• Collisions
• Flow control
• Avoid unnecessary frame loss
• Saturated buffers
I VPR
Institute for Visualization and Perception Research
© Copyright 1998 Haim Levkowitz
8
Network ...
• Extend data link layer
• From local to neighboring / distant networks
• E.g., Ethernet, Token Ring
• Incompatible physical and link layers
• ==> Internetworks (networks of networks)
• Topology: routers
• Two network layer services ...
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Institute for Visualization and Perception Research
© Copyright 1998 Haim Levkowitz
9
Two network layer
services ...
• connection-oriented (CO)
• "reliable" / "virtual-circuit"
• well ordered data stream
• guarantee lost, order, duplicate
• connectionless (CL)
• "unreliable" / "datagram"
• no guarantees
I VPR
Institute for Visualization and Perception Research
© Copyright 1998 Haim Levkowitz
10
Transport ...
• higher-level tasks (not end-to-end delivery)
• multiplexing
• OSI: 5 incompatible transport protocols
• CL, w/ CL network
• CL, w/ CO network
• CO, w/ CO network
• CO, w/ CL network
• highest network aware
I VPR
Institute for Visualization and Perception Research
© Copyright 1998 Haim Levkowitz
11
Session ...
• how data exchanged in dialog
• two-way simultaneous (full-duplex)
• two-way alternate (half-duplex)
• one-way (simplex)
• checkpointing
• synch points in data stream
• resume aborted transfer at last
encountered synch point
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Institute for Visualization and Perception Research
© Copyright 1998 Haim Levkowitz
12
Presentation ...
• hide diff in data rep'n
• e.g., ASCII vs. EBCDIC
• generic rep’n w/ ISO ASN.) spec ...
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Institute for Visualization and Perception Research
© Copyright 1998 Haim Levkowitz
13
Generic rep'n w/ ISO
ASN. spec ...
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(Abstract Syntax Notation One)
Boolean
Integer (arb. length)
Real (arb. length & prec.)
Enumerated (days of week, months of year, etc.)
Bit string (arb. length)
Octet (byte) string (arb. length)
Null (any undef'd value)
I VPR
Institute for Visualization and Perception Research
© Copyright 1998 Haim Levkowitz
14
Application ...
• service consumer
• via APIs
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Institute for Visualization and Perception Research
© Copyright 1998 Haim Levkowitz
15
Internet TCP/IP model ...
• 5 layers
• physical, data link, network, transport,
application
• session, presentation
• by application, w/ assistance of API
• Network layer: IP ...
• Transport layer: TCP & UDP ...
• Application layer ...
I VPR
Institute for Visualization and Perception Research
© Copyright 1998 Haim Levkowitz
16
Network layer: IP ...
•
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move data between endpoints
if not on same host ==> routing
IP protocol
IP datagram (packet)
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Institute for Visualization and Perception Research
© Copyright 1998 Haim Levkowitz
17
Transport layer: TCP &
UDP ...
• Transmission Control Protocol (TCP)
• connection-oriented
• User Datagram Protocol (UDP)
• connectionless
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Institute for Visualization and Perception Research
© Copyright 1998 Haim Levkowitz
18
Application layer ...
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FTP
SMTP: Simple Mail Transfer Protocol
NNTP: Network News
HTTP
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Institute for Visualization and Perception Research
© Copyright 1998 Haim Levkowitz
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Protocol enveloping in
TCP/IP ...
• Application data
--> TCP segment
--> IP datagram -> Ethernet frame
Application
FTP, SMTP, HTTP,
TCP
UDP
Protocol Suite
ICMP
IP
Data Link
Ethernet, Token Ring, FDDI
Physical
I VPR
Institute for Visualization and Perception Research
© Copyright 1998 Haim Levkowitz
20