1. Networking
B.Ramamurthy
Chapter 3
1/11/2019
B.Ramamurthy

2. Introduction
Distributed systems use local area networks, wide area networks and internet for communication.
Performance, reliability, scalability, mobility, and quality of service (qos) impact the design.
Changes in user requirements have resulted in emergence of wireless and qos guarantees.
Principles: protocol layering, packet switching, routing, data and behavior streaming.
We will study: Ethernet, Asynchronous Transfer Mode (ATM), IEEE wireless network standard.
1/11/2019
B.Ramamurthy

3. Networking Issues Performance: Scalability:
Latency: delays at the switches and routers.
Data transfer rate (bits/sec) : raw data
Bandwidth: total volume of traffic that can be transferred across the network in a given time.
Scalability:
How does a system handle increase in the number of users? Increase in the size of the system? Increase in load and traffic?
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B.Ramamurthy

4. Networking Issues (contd.)
Security: requirements and techniques for achieving security. Firewall, Virtual Private Network (VPN).
Mobility: Support for moving devices. Not necessarily wireless.
QoS: Bandwidth and latency bounds.
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B.Ramamurthy

5. Types of Networks
Characterized by speed, communication medium, size, geographical distances, bandwidth, latency, technology.
LAN :
Single medium such as twisted pair of copper wires, coaxial cables, or optical fibers.
Technology: Ethernet, token rings, slotted rings.
WAN:
Set of comm circuits (coax, satellite) linked by dedicated computers called routers.
Technology: Switching.
1/11/2019
B.Ramamurthy

6. Types of Networks MAN: Wireless:
High bandwidth copper or fiber optic cables. (phone lines, DSL, cable modem)
Technology: Ethernet, IEEE802.6, ATM
Wireless:
Radio frequency, infrared,
Technology: IEEE (wavelan), CDPD, GSM, bluetooth (proximity)
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B.Ramamurthy

7. Figure 3.1 Network types Range Bandwidth (Mbps) Latency (ms) LAN
1-2 kms
1-10
WAN
worldwide
MAN
2-50 kms
1-150 10
Wireless LAN km
2-11
5-20
Wireless WAN
worldwide
Internet
worldwide
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B.Ramamurthy

8. Internetworks
Communication subsystem in which several networks are linked together to provide a data communication facilities that conceal the technologies and protocols of individual components.
Gateways, switches, routers, compute and data servers.
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B.Ramamurthy

9. Networking Fundamentals
Packet transmission
Data Streaming
Switching schemes
Broadcast, circuit switching, packet switching, frame relay (ATM)
Protocols
Protocol layers
Protocol suites
Packet assembly
Ports
Addressing
Packet delivery
1/11/2019
B.Ramamurthy

10. Networking Fundamentals (contd.)
Routing
Tables and algorithms
Congestion control
Internetworking
IP address, protocol
Routers
Hubs
Bridges
Switches
Tunnelling
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B.Ramamurthy

11. Conceptual layering of protocol software
Message sent
Message received
Layer n
Layer 2
Layer 1
Sender
Communication
Recipient
medium
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B.Ramamurthy

12. Encapsulation as it is applied in layered protocols
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B.Ramamurthy

13. Protocols
The term protocol refers to a well-known set of rules and formats to be used in order to perform a task. For example, a task of communicating between processes.
Parts of a protocol:
A specification of a sequence of messages that must be exchanged.
A specification of the format of the data in the messages.
Existence of well-known (standard) protocols enables the separate components of the distributed systems to be developed independently in different languages and on different platforms.
1/11/2019
B.Ramamurthy

14. ISO’s OSI Framework/Model
ISO : International Standards Organization
OSI : Open Systems Interconnection
Services, interfaces, protocols
Protocol Suite: Complete set of protocol layers is referred to as protocol stack or protocol suite.
OSI Model defines the layers. For a protocol suite to be compliant with OSI it has defined a protocol for each of the layers specified in OSI model.
1/11/2019
B.Ramamurthy

15. OSI Protocol Layers
Application: Communication requirements. Ex: HTTP, FTP, SMTP, CORBA IIOP
Presentation: Bridges the data representation difference in the network and the computers; Encryption. Ex: Secure Sockets (SSL).
Session: Reliability; Detection of failures and recovery. Ex: Checkpointing and recovery.
Transport: Facilitates peer to peer process conversation. Port address concept. Ex: TCP (Transmission Control Protocol), UDP (User Datagram Protocol).
Network: Transfers packets. Packet format that includes routing info. Ex: IP, ATM.
Data Link: Responsible for data transfer between directly connected nodes (routers, hosts). Ex: PPP (Point-to-Point Protocol)
Physical: The hardware circuits and binary transfer of data (optic, radio, microwave freq). Ex: ISDN (Integrated Service Digital Network), Cable modem.
1/11/2019
B.Ramamurthy

16. Ports and Addresses
Ports are destination points within a host computer.
Processes are attached to the ports, enabling them to communicate.
Transport layer addresses are composed of network address of the host computer and a port number.
In the Internet every host is assigned a unique IP number which is used in routing.
In an Ethernet each host is responsible for recognizing that the messages meant for it.
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B.Ramamurthy

17. Routing in WAN Routers are computers with dedicated functionality.
They determine the route of the packets using routing algorithms.
A routing algorithm has two goals:
It must make decisions that determine route taken by each packet as it travels through the network.
It must dynamically update its knowledge of the network based on the traffic monitoring and detection of configuration changes or failures.
Fine example of a distributed algorithm.
We will examine a Router Information Protocol (RIP)
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18. Routing in a wide area network
Hosts
Links
or local
networks A D E B C 1 2 5 4 3 6
Routers
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19. Routing tables for the network in Last Slide
Routings from A
Routings from B
Routings from C To
Link
Cost A B C D E
local 1 3 2 4 5
Routings from D
Routings from E To
Link
Cost A B C D E 3 6
local 1 2 4 5
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B.Ramamurthy

20. Pseudo-code for RIP routing algorithm
Send: Each t seconds or when Tl changes, send Tl on each non-faulty outgoing link.
Receive: Whenever a routing table Tr is received on link n:
for all rows Rr in Tr {
if (Rr.link < > n) {
Rr.cost = Rr.cost + 1;
Rr.link = n;
if (Rr.destination is not in Tl) add Rr to Tl;
// add new destination to Tl
else for all rows Rl in Tl {
if (Rr.destination = Rl.destination and
(Rr.cost < Rl.cost or Rl.link = n)) Rl = Rr;
// Rr.cost < Rl.cost : remote node has better route
// Rl.link = n : remote node is more authoritative }
1/11/2019
B.Ramamurthy

21. Internetworking Local networks are built using Ethernet and ATM.
Wide area networks are built using telephone lines, satellite links, wide-area ATM, ISDN, etc.
Internetworking is connecting all these subnets of differing technologies.
Issues?
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B.Ramamurthy

22. Problems in Internetworking
A unified internetwork addressing scheme that enables packets to be addressed to any host connected to any subnet.
A protocol defining the format of internetwork packets and giving rules according to which they are to be handled.
Interconnecting components that route packets to their destinations.
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B.Ramamurthy

23. Solutions provided by the Internet
For the Internet,
Problem 1) is solved by IP addresses
Problem 2) is addresses by IP protocol
Problem 3) is performed by components called Internet Routers.
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B.Ramamurthy

24. Simplified view of the QMW Computer Science network
file
compute
dialup
hammer
henry
hotpoint
bruno
router/
sickle
/29
copper
firewall
web
/29
server
desktop computers xx
subnet
Eswitch
custard
hub
Student subnet
Staff subnet
other
servers %
1000 Mbps Ethernet
Eswitch: Ethernet switch
100 Mbps Ethernet
file server/
gateway
printers
Campus
router xx
1/11/2019
B.Ramamurthy