Transcript Chapter 3 slides

From Coulouris, Dollimore, Kindberg and Blair
Distributed Systems:
Concepts and Design
Edition 5, © Addison-Wesley 2012
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Introduction
Networking Issues for Distributed Systems
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Type of Network
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Performance, Scalability, Reliability, Security, Mobility, QoS, Multicasting
 PANs, LANs, WANs, MANs, WLANs, WMANs, WWANs, Internetwork, Network
errors.
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Network Principle
◦
Packet Transmission, Data Streaming, Switching Schemes.
Protocols
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Routing
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 Layers, Suites, Packet Assembly, Ports, Addressing, Packet Delivering.
 Simple routing Algorithm.
Congestion Control
Internetworking
 Routers, bridges, hubs, switch, tunneling
Internet Protocols: IP addressing – P protocol – IP routing –IPV6
– Mobile IP – TCP, UDP – Domain Name – Firewalls
Case Study: Ethernet – Wifi and Bluetooth.
The networks used in distributed systems are built from
a variety of transmission media, hardware devices, and
software components.
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functionality and performance available to distributed
system and application programs is affected by all of
these.
communication subsystem: refer to the collection of
hardware and software components that provide the
communication facilities (Host & Node).
communication subsystem is strongly influenced by
◦ characteristics of the operating systems.
◦ characteristics of the Networks and media
◦ characteristics of the applications.
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Performance:
means affecting the speed of individual messages
that transferred between two interconnected computers.
◦ Speed: Determine by (Latency & Data Transfer Rate).
◦ Latency: delay time occurs before data starts to arrive to
destination computer. (software overheads, routing delays and a
load-dependent)
◦ Data Transfer Rate: speed of data transferred between two
computers in the network. (bits/second) (Physical characteristics)
◦ So, Time required to transfer a message containing length bits
between two computers is:
Message transmission time = latency + length ⁄ data transfer rate
◦ This equation valid only for specific message length. Longer
messages are segmented.
◦ Latency or data transfer rate (which & why effect performance?)
◦ Throughput: total system bandwidth of a network. Effected by
network technology.
km
Instructor’s Guide for Coulouris, Dollimore, Kindberg and Blair, Distributed Systems: Concepts and Design Edn. 5
© Pearson Education 2012
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Scalability:
growth in the number of host computers, networks,
and web servers connected to the Internet.
◦ In realistic, expect to include several billion nodes and hundreds of
millions of active hosts.
◦ These numbers indicate the future changes in size and load that
the Internet must handle.
◦ network technologies cope with that or not?
◦ substantial changes should be given to the addressing and routing
mechanisms.
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Reliability: error-free communication (No Failure).
◦ Detection of communication errors and their correction is often best
performed by application-level software.
◦ reliability of most physical transmission media is very high.
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Security: requirements and techniques for achieving security.
◦ A firewall: creates a protection boundary between the organization’s
intranet and the rest of the Internet
.
◦ cryptographic techniques:
◦ virtual private network (VPN)
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Mobility:
◦ Mobile devices are moved frequently between locations and
reconnected at convenient network connection points or even used
while on the move.
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Multicasting: one-to-many communication.
◦ network technologies support the simultaneous transmission of
messages to several recipients.
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Quality of service:
ability to meet deadlines when transmitting
and processing streams of real-time multimedia data.
◦ Applications that transmit multimedia data require guaranteed
bandwidth and bounded latencies for the communication channels
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Personal area networks (PANs):
◦ a subcategory of local networks where various digital devices carried by a user are
connected by a low-cost, low-energy network. (e.g. Bluetooth, OnAir).
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Local area networks (LANs):
◦ LANs carry messages at relatively high speeds between computers connected by a
single communication medium.(e.g. twisted copper wire, coaxial cable, or optical
fibre.) using
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Wide area networks (WANs)
◦ WANs carry messages at lower speeds between nodes in different organizations and
may be separated by large distances.
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Metropolitan area networks (MANs)
◦ based on the high bandwidth copper and fibre optic cabling recently installed in
some towns and cities.
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Wireless local area networks (WLANs)
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Wireless metropolitan area networks (WMANs)
Wireless wide area networks (WWANs)
Internetworks
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Network errors:
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loss data, packets ( why?)
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Communication is asynchronous: messages arrive at their destination after a
delay depending on time that packets take to travel through the network.
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Packet transmission: logical units of information, or messages
subdivided into packets.
◦ sufficient buffer storage to hold the largest possible incoming packet; avoid the
undue delays that would occur in waiting for communication channels
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Data streaming: The transmission and display of audio and video in
real time is referred to as streaming.
Switching schemes: A network consists of a set of nodes connected
together by circuits.
◦ Broadcast: Everything is transmitted to every node.
◦ Circuit switching: local exchange was connected by an automatic switch at
the exchange to the pair of wires connected to the other party’s. (Phone)
◦ Packet switching: brought processing and storage. construct a different kind of
communication network called a store-and-forward network.
◦ Frame relay: They overcome the delay problems by switching small packets
(called frames) on the fly.
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