1

Introduction to Networking

• What is a computer network?

• Why do you want to take Csci 5211?

• Internet Architecture

• Statistical multiplexing and packet switching

• Connection-oriented vs Connectionless

• Fundamental issues in computer networking

• Readings

– Sections 1.1-1.5

2

What is a Computer Network?

• Network provides connectivity

– A set of computers/switches connected by communication links

• Many topologies possible

• Many different physical media

– Coaxial cable, twisted pair, fiber optic, radio, satellite, wireless

• Local area networks vs Wide area networks

• Emerging systems area network, home network, storage area network, and wireless network

How do you deliver a string of

bits from one end to another?

• Why networking is hard?

• What are the possible problems for

delivering data?

– Fault-tolerance, availability, reliability, etc.

• Is delivering data from one end to another is

the purpose of computer networks?

3

4

Elements of a Network

• hosts, end-systems

– pc’s, workstations, servers

– PDA’s, phones, toasters

running network apps

• communication links

– Point-to-point, multi access

– fiber, copper, radio, satellite

• Switches and routers:forward packets (chunks) of data

thru network

• internet: network of networks

• Internet is a specific internet

local ISP

companynetwork

regional ISP

router workstationserver

mobile

5

What is The Internet?

• The Internet :

– collection of networks and routers that span the world and use the

TCP/IP protocols to form a single, cooperative virtual network

• intranet:

connection of different LANs within an organization

– private

– may use leased lines

– usually small, but possibly hundreds of routers

– may be connected to the Internet (or not), often by firewall

6

Internet Architecture

LANs

International

lines

ISP ISPcompany university

national

network

regional

network

NAP

on-line

services

companyaccess via

modem

7

NAPs, NSPs, ISPs

• NSP: National Service Provider (Tier 1 Backbones)

– Example: Internet MCI, Sprint Link, UUNET

• NAP: National Access Point

NAPNAP

NAP

NAP

National Provider

National Provider Regional

Provider

POP

customers

8

NAP and Private Peering

9

InternetNetwork

Leveraging Sprint’s SONET-based,

gigabit switch Internet backbone

PrivatePeering

PrivatePeering

PrivatePeering

MAE-WestExchange Point

Pacific BellExchange Point

PrivatePeering Ameritech

Exchange Point

PrivatePeering

PrivatePeering

SprintExchange Point

PrivatePeering

MAE-EastExchange Point

PrivatePeering

10

SprintNetwork

Click here for

a closer look

at the Sprint

network on the

East Coast

Click here for

a closer look

at the Sprint

network in

Northern

CaliforniaPearl City in Hawaii isa future network location

Click here for a closer look at the

Sprint network in Washington state

Legend DS3

OC3

OC12

OC48

Seattle

Atlanta

Chicago

Roachdale

Stockton

San Jose

Anaheim

Fort Worth

Orlando

Kansas City

CheyenneNew York

PennsaukenRelay

Wash. DC

Tacoma

11

UUNET North America

Backbone

• Evolving Networks are Complex

•1980 •1999•1970

6 September 2015 13

•Bridge Monitoring

•Building

•Environment

•Controls

•Earthquake

•Monitoring

•Elder Care

•Factories

•Fire Response

•First Responders

•Forest Management

•Soil Monitoring

•Supply Chain

•Wind Response

•… and more more

•Instrument and Connect the World !

6 September 2015 14

The monitors and sensors include embedded

software systems which can autonomously detect

events of concern:

– Wearable sensors

• Fall sensors

• Heart rate/pulse monitors

– Stationary sensors

• Motion detectors

• Camera systems

An individual sensor may not have sufficient

accuracy, but the combination thereof may

Smart Sensors, People, and Pervasive Computing

System Miniaturization

and Integration for 3D

Stacked SiP by

TUT/ELE

15 OOPSLAJeannette M. Wing

•Smart Cars

•Lampson’s Grand Challenge:

•Reduce highway traffic deaths to zero.

•[Butler Lampson, Getting Computers to Understand,Microsoft, J. ACM 50, 1 (Jan. 2003), pp 70-72.]

•Cars drive themselves

•Credit: PaulStamatiou.com

•A BMW is “now actually a network of computers”

•[R. Achatz, Seimens, Economist Oct 11, 2007]

•Smart parking

16 CPS Luncheon Jeannette M. Wing

Smart Fliers

•An airplane is a network of computers.

•smart helicopters

•smart insects

•Credit: Boeing

•Credit: Harvard university

•Credit: NASA/JPL

17 IBM Research Jeannette M. Wing•17•IBM Research •Jeannette M. Wing

Embedded Medical Devices

•infusion pump

•pacemaker

•scanner

•Credit: Baxter International

•Credit: Siemens AG

Tele-Surgery

Bridge Monitoring & Prognostic

Intelligent Transportation Systems

20

21

•ITS (1/4)

22

•ITS (2/4)

23

•ITS (3/4)

24

•ITS (4/4)

6 September 2015 25

Example: EarthScope

A Continental-Scale Network• 15-year effort to understand earthquakes, volcanism, and

plate movements in N. America

– 400 seismometers, 1000 GPS stations, 180 strainmeters

http://www.earthscope.org

6 September 2015 26

NEON:

National Ecological Observatory Network

Inadequacy of Current Internet ?

(Your Observations)

27

6 September 2015 28

Current Cyber Space

•“A domain characterized by the use of electronics and the electromagnetic spectrum to store, modify, and exchange data via networked systems and associated physical infrastructure.”

Inside the ‘Net: A Different Story…

• Closed equipment

– Software bundled with hardware

– Vendor-specific interfaces

• Over specified

– Slow protocol standardization

• Few people can innovate

– Equipment vendors write the code

– Long delays to introduce new features29

Do We Need Innovation Inside?•Many boxes (routers, switches, firewalls, …) with different interfaces and not programmable.

Proposed SDN Solution

•Control Plane

•Data Plane

•Standard API to Enable

Programmable

•Separation of Control Plane and Data Plane

•Logically Centralize

d Controller

•Open API

Seamless Mobility• See host sending traffic at new location

• Modify rules to reroute the traffic

32

Server Load Balancing• Pre-install load-balancing policy

• Split traffic based on source IP

•src=0*,

•dst=1.2.3.4

•src=1*,

•dst=1.2.3.4

•10.0.0.1

•10.0.0.2

Example SDN Applications

• Seamless mobility and migration

• Server load balancing

• Dynamic access control

• Using multiple wireless access points

• Energy-efficient networking

• Adaptive traffic monitoring

• Denial-of-Service attack detection

• Network virtualization

34•See http://www.openflow.org/videos/

Network Function Virtualization (NFV)

•Slide from: http://

Use Case: vWOC （virtualized

WAN Optimization Controller）

6 September 2015 37

Future Internet Requirements

Be worthy of our society’s trust

– Especially for managing and operating critical infrastructures

Provide a bridge between physical and virtual worlds

– Via instrumented and managed sensorized physical environment

Support pervasive computing

– From netted smart devices to supercomputers

– From wireless channels to all optical light-paths

Enable further innovations in S&E research

– Seamless access to networked instruments, supercomputers, storage,

databases, collaboratories, etc.

Create a social world in which we would want to live

38

Multiplexing Strategies

• Sharing of network resources among multiple users

• Common multiplexing strategies

• Time Division Multiplexing (TDM)

• Frequency Division Multiplexing (FDM)

• These two strategies are circuit switching technology

39

Circuit Switched Networks

• All resources (e.g. communication links) needed by a call

dedicated to that call for its duration

– Example: telephone network

40

Statistical Multiplexing

• Time division, but on demand rather than fixed

• Reschedule link on a per-packet basis

• Packets from different sources interleaved on the link

• Buffer packets that are contending for the link

• Buffer buildup is called congestion

• This is packet switching, used in computer networks

41

Packet Switched Networks

• Data entering network is divided into chunks called “packets”

• Store-and-forward approach: packets buffered before transmission

• Packets traversing network share resources with other packets

– On demand resource use: statistical resource sharing

• Fewer resources: queuing delay, packet loss

42

Why Statistically Share Resources

• Efficient utilization of the network

• Example scenario

– Link bandwidth: 1 Mbps

– Each call requires 100 Kbps when transmitting

– Each call has data to send only 10% of time

• Circuit switching

– Each call gets 100 Kbps: supports 10 simultaneous calls

• Packet switching

– Supports many more calls with small probability of contention

• 35 ongoing calls: probability that > 10 active is < 0.0017!

43

Circuit Switching vs Packet Switching

Item Circuit-switched Packet-switched

Dedicated “copper” path Yes No

Bandwidth available Fixed Dynamic

Potentially wasted bandwidth Yes No

Store-and-forward transmission No Yes

Each packet follows the same route Yes No

Call setup Required Not Needed

When can congestion occur At setup time On every packet

Effect of congestion Call blocking Queuing delay

44

Connection-Oriented Service

• Sender

– Requests “connection” to receiver

– Waits for network to form connection

– Leaves connection in place while sending data

– Terminates connection when no longer needed

• Network

– Receives connection request

– Establishes connection and informs sender

– Transfers data across connection

– Removes connection when sender requests

45

Connectionless Service

• Sender

– Forms packet to be sent

– Places address of intended recipient in packet

– Transfers packet to network for delivery

• Network

– Uses destination address to forward packet

– Delivers the packet to destination

46

Connection-Oriented vs Connectionless

• Connection-Oriented• Telephone System, Virtual Circuit Model

– Path is setup before data is sent

– Data identifies the connection

– All data follows the same path

• Connectionless• Postal System, Datagram Model

– No path setup before transmitting data

– Packet contains identification of destination

– Each packet handled independently

47

Connection-Oriented vs. Connectionless

• Connection-Oriented

– Connection setup overhead

– State in packet switches

– Can reserve bandwidth

• Connectionless

– Stateless and less overhead

– Resource reservation not possible

– Allows broadcast/multicast

48

Fundamental Issues in Networking

• Naming/Addressing

– How to find name/address of the party (or parties) you would like

to communicate with

– Address: byte-string that identifies a node

– Types of addresses

• Unicast: node-specific

• Broadcast: all nodes in the network

• Multicast: some subset of nodes in the network

• Routing/Forwarding: process of determining how to send

packets towards the destination based on its address

– Finding out neighbors, building routing tables

49

Fundamental Problems in Networking

• What can go wrong?

– Bit-level errors: due to electrical interferences

– Packet-level errors: packet loss due to buffer overflow/congestion

– Out of order delivery: packets may takes different paths

– Link/node failures: cable is cut or system crash

• What can be done?

– Add redundancy to detect and correct erroneous packets

– Acknowledge received packets and retransmit lost packets

– Assign sequence numbers and reorder packets at the receiver

– Sense link/node failures and route around failed links/nodes

• Goal: to fill the gap between what applications expect and what underlying technology provides

50

Summary

• The pieces of a network

– Internet architecture and Future Internet

• Packet switching vs. circuit switching

– Statistical multiplexing

• Connection-oriented vs connectionless

• Fundamental issues in networking

– Addressing/Naming and routing/forwarding

– Error/Flow/Congestion control