Transcript Networking Basics and Internet Protocol Stack

Networking Basics: A Review
Carey Williamson
iCORE Chair and Professor
Department of Computer Science
University of Calgary
Communications Networks
• Historically, there have been two different
philosophies guiding the design, operation,
and evolution of communication networks
– the “telco” view (i.e., telecommunications networks
to support voice telephony and other emerging
services, such as fax, data, location, etc.)
– the “data networking” view (i.e., the Internet)
• While the two approaches share some similar
goals and challenges (e.g., scale, geography,
heterogeneity), they often have quite different
underlying assumptions
CPSC 641
Winter 2011
Copyright © 2005 Department of Computer Science
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Telco Networks (1 of 2)
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About 100 years old
Circuit-switched network
Designed for transmission of human voice
Twisted pair copper wire for residential access
– “cheap”, adequate bandwidth, easy to handle...
• Aggregation of multiple calls at toll office for
multiplexing/demultiplexing using TDM
• Low bandwidth required per call (e.g., 64 Kbps)
• Fixed bandwidth required per call
CPSC 641
Winter 2011
Copyright © 2005 Department of Computer Science
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Telco Networks (2 of 2)
• Call routing and circuit allocation decided once per
call at time of call arrival
• End to end path allocation, with dedicated circuit
(reserved bandwidth) per active call
• All bits travel same path; stay in same order
• Call state information crucial in network switches
• Busy signal if no path possible (blocking <= 2%)
• Billing model based on time used (in minutes)
• Single class of service; high reliability (99.99%)
• New services: faxes, modems, mobility, ...
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Winter 2011
Copyright © 2005 Department of Computer Science
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The Internet (1 of 2)
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About 30 years old
Packet-switched network
Variable size packets permitted
Designed for transmission of data
Wide range of access technologies
Wide range of user and application behaviour
Bursty, variable bandwidth required per call
Aggregation of traffic at routers/switches
Transmission links shared on stat mux basis
CPSC 641
Winter 2011
Copyright © 2005 Department of Computer Science
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The Internet (2 of 2)
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Connection-less network layer protocol (IP)
“Best effort” datagram delivery model
Packet routing decided on a per packet basis
No end to end path allocation; no reserved
bandwidth per active call
Packets can travel any path; packets can be
delayed, lost, duplicated, re-ordered
Minimal state info in network switches
Single class of service
Billing model? (hours? pkts? bytes? bandwidth?)
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Winter 2011
Copyright © 2005 Department of Computer Science
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Asynchronous Transfer Mode (1of2)
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About 20 years old
Packet-switched network
Small fixed-size packets (53 bytes)
Designed for integrated services (voice, video,
data, imaging, interactivity,…)
High speed network technologies (optical)
Wide range of user and application behaviour
Bursty, variable bandwidth required per call
Aggregation of traffic at switches
Transmission links shared on a stat mux basis
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Winter 2011
Copyright © 2005 Department of Computer Science
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ATM (2 of 2)
• Connection-oriented
• Allocates a virtual channel (VC) per active call
• End to end path allocation determined at time of
call arrival; reserved bandwidth per active call
• All packets travel same path (order preserved)
• Crucial state info in ATM switches
• Multiple classes of service (priority levels)
• Offers end to end QOS guarantees (SLAs)
• Billing model? (cells? bandwidth? time?)
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Winter 2011
Copyright © 2005 Department of Computer Science
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Internet Protocol Stack
• Application: supporting network
applications and end-user services
– FTP, SMTP, HTTP, DNS, NTP
• Transport: end to end data transfer
Application
Transport
– TCP, UDP
• Network: routing of datagrams from
source to destination
– IPv4, IPv6, BGP, RIP, routing protocols
• Data Link: hop by hop frames,
channel access, flow/error control
– PPP, Ethernet, IEEE 802.11b
Network
Data Link
Physical
001101011...
• Physical: raw transmission of bits
CPSC 641
Winter 2011
Copyright © 2005 Department of Computer Science
9
Internet Protocol Stack
Application
Application
Transport
Transport
Network
Network
Data Link
Data Link
Physical
Core
Network
CPSC 641
Winter 2011
Copyright © 2005 Department of Computer Science
Physical
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Internet Protocol Stack
Application
Application
Application
Transport
Transport
Transport
Network
Network
Network
Data Link
Data Link
Data Link
Physical
Physical
Physical
Router
CPSC 641
Winter 2011
Copyright © 2005 Department of Computer Science
11
Internet Protocol Stack
Application
Application
Application
Transport
Switch
Transport
Transport
Network
Network
Network
Data Link
Data Link
Data Link
Physical
Physical
Physical
CPSC 641
Winter 2011
Copyright © 2005 Department of Computer Science
12