Some Current Research/Challenges

04/23/2008

Admin.

Multimedia applications and QoS slides are linked on the schedule page

Programming assignment 3 Due on May 5

Office hours during break please send email to Antonis and me for

appointments

Objectives

A brief introduction to some computer networking projects we are working on here at Yale disclaimer: some projects I describe are not

Yale projects

More importantly, focus on perspectives that challenge what we have covered in class

Objectives of Networking Research

Faster More efficient More reliable More ubiquitous Safer

Faster

“Within five years, all media will be delivered across the Internet.”

- Steve Ballmer, CEO Microsoft, D5 Conference, June 2007

The Internet is increasingly being used for content and media delivery

Rising Content Distribution Demand

Some speculation

Rising Bandwidth Demand

“Desperate Housewives” 210MB/hour

for 320x240 H.264 Video iTunes image

assume 10,000,000 households downloads

How long will that take to download? 3 days @ 64Gbps non-stop !

HD video is 7~10 times larger than non-HD video AT&T predicts 50-fold increase in broadband to

2015 (75% per year)

http://www.pbs.org/cringely/pulpit/pulpit20060302.html

http://dynamic.abc.go.com/streaming/landing?lid=ABCCOMGlobalMenu&lpos=FEP

Internet Bandwidth Growth

Source: TeleGeograph Research

What Determines Transmission Rate?

Service: transmit a bit stream from a sender to a receiver

Encodingchannel

Decodingoutput bit stream

input bit stream

sender receiver

Question to be addressed: how much can we send through the channel ?

Basic Theory: Channel Capacity The maximum number of bits that can be

transmitted per second (bps) by a physical media is:

where W is the frequency range, S/N is the signal noise ratio. We assume Gaussian noise.

)1(log2 NSW

Fourier Transform

Suppose the period of a data unit is f (=1/T), then the data unit can be represented as the sum of many harmonics (sin(), cos()) with frequencies f, 2f, 3f, 4f, …

A reasonably behaved periodic function g(t), with minimal period T, can be constructed as the sum of a series of sines and cosines:

11

21 )2cos()2sin()(

nn

nn nftbnftactg

dtnfttgb

dtnfttga

dttgc

Tf

T

Tn

T

Tn

T

T

)2cos()(

)2sin()(

)(

/1

0

2

0

2

0

2

nnn barms char “b”

Signal Attenuation

The quality of signal will degrade when it travels loss, frequency passing

)1(log2 NSW

Frequency Dependent Attenuation

The received signal will be distorted even when there is no interference and the transmitted signal is “perfect” square waveform

Example: Voltage-attenuation magnitude ratios of Category 5 cable. For example, 500 feet of cable attenuates a 10-MHz, 1-V signal to 0.32 V, which corresponds to about –9.90 dB

Example

Example: W=3000Hz, S/N 4000

kbpsbandwidth 36)40001(log3000max 2

telephone networksender modem

ModemModulation

(digit->analog)

3Khz bandwidth(add white noise)

ISPdemodulation

output bit stream

input bit stream

Analog to Digital quantization

for transmitting throughthe digital telephone

backbone

ISP modem

V.34 (33.6kbps Dialup Modem)

channel

Example: ADSL Spectrum allocation:

divided into a total of 256 downstream and 32 upstream tones, where each tone is a standard 4kHz voice channel

During initial negotiation, a tone is used only if the S/N is above 6 db (4)

kbpsup

Mbpsdown

297)41(log4000*32

4.2)41(log4000*256

2

2

The Wire: Fiber

A look at a fiber

How it works?

A graded index fiber

The Wire: Fiber

Wide spectrum at low loss: ~0.3db/km (c.f. copper ~190db/km @100Mhz), 30-100km without repeater bit error rate 10-15

(c.f. copper 10-4-10-8) bandwidth of a single fiber

commercial: 1.6Tbps using 169 channels lab: 10 Tbps theoretical: 100-200Tbps

http://www.trnmag.com/Stories/080101/Study_shows_fiber_has_room_to_grow_080101.html

Lightweight: 33 tons of copper to transmit the same amount of information carried by ¼ pound of optical fiber

Advantages of Fibers

How to Do Switching?

Optical-Electrical-Optical Optical switch: optical micro-electro-mechanical systems

(MEMS)

Optical path One optical switch

http://www.qwest.com/largebusiness/enterprisesolutions/networkMaps/preloader.swf

Example: MEMS Optical Switch Using mirrors, e.g. Lambda Router

Implications

Fine-grained switching may not be feasible

What is the architecture of optical networks: packet switching, circuit switching, or others?

Higher Efficiency

Integrating P2P into Internet Content Distribution

Initially standalone applications rogue technology (e.g., copyright issues)

Recent development becomes part of content delivery

infrastructure integrated P2P + servers solutions some projects

• BBC's iPlayer (tremendously popular), Joost, Pando and NBC, MSN video

• Verizon P2P, Thomson/Telephonica nanoData Center

Edge Network

Regional Routers

Internet Transit

Traditional content distribution

P2P, e.g., BT

More Viewers =Worse performance

Higher cost

P2P Efficiency

- Network oblivious peering -> scattered traffic

- Higher financial cost

- Inefficiency

P2P Problem I: Bandwidth Usage

Cache Logic Research: Internet Protocol Breakdown 1993 - 2006

P2P Problem II: Increased Operational Costs

Violating Internet economics (bypass BGP): relay traffic between providers

increased network operational costs

provider

customer

provider

provider tocustomer

An iterative process between two sets of adaptation: ISP: traffic engineering to change

routing to shift traffic away from higher utilized links

• current traffic pattern new routing matrix

P2P: direct traffic to better performing peers

• current routing matrix new traffic pattern

P2P Problem III: Inefficient Interactions

ISP optimizer interacts poorly with P2P.

ISP Traffic Engineering+ P2P Latency Optimizer

- red: P2P adjust alone; fixed ISP routing- blue: ISP traffic engineering adapt alone; fixed P2P communications

P2P Countermeasures

• use random ports

• encrypt traffic

• ...

Attempts to Address P2P Efficiency Problems

ISPs Address P2P

• upgrade network infrastructure

• deploy P2P caching devices

• terminate user connectivity

• rate-limit P2P traffic

• ...

Network neutrality argument

The Fundamental Problem Traditional Internet architectural feedback

to application efficiency is limited: routing (hidden) rate control through coarse-grained TCP

congestion feedback To achieve better efficiency, needs explicit

communications between network resource providers and applications a network resource provider can be a

traditional ISP (AT&T, Verizon) or a content distribution ISP such as Akamai, or a caching provider

P4P Objective Design a framework to enable better providers and

applications cooperation

ISP perspective: guide applications to achieve more efficient resource usage avoid undesirable (expensive/limited capacity) links to more

desirable (inexpensive/available capacity) links

Resource providers such as caching, CDN providers perspective provide applications with better, on-demand

resources/quality

P2P perspective: better performance for users decrease incentives for ISPs to “manage” applications

P4P Framework – Design Goals

Performance improvement Scalability and extensibility: support

diverse ISP objectives and applications scenarios in large networks

Privacy preservation Ease of implementation Open standard: any ISP, provider,

applications can easily implement it

The P4P Framework

Data plane

control plane iTracker: a portal for each network service

provider iTracker of a provider can be identified in

multiple ways• e.g., through DNS SRV records

An iTracker provides multiple interfaces so that others can interact

• each provider decides the interfaces it provides• each interface is encoded in Web Service Definition Language

(WSDL) for extensibility

Control Path Interfaces provider capabilities interface: request QoS,

CoS, servers participation in content distributions

topology interface: topology and connectivity

ISP policy and guideline interface: e.g., traffic balance ratio for inter-AS peering links, time of day preference

…

P4P Control Path : Request Capability

ISP B

1: pTracker [content provider] requests ISP B’s participation in content distribution2: Provider B allocates servers to accelerate content distribution

3: pTracker includes ISP B’s servers in returned peering sets to peers

ISP A

pTracker

a

iTracker BiTracker

A

b

2

3

1

pTracker/content provider requests ISP capabilities to accelerate content distribution.

The Virtual Topology Interface

An interface to guide peer selection

An interface as an optimization decomposition interface guidance through “virtual costs”

Background: Peer Selection

pTracker

webserveruser

“register”

ID1 169.237.234.1:6881ID2 190.50.34.6:5692ID3 34.275.89.143:4545…ID50 231.456.31.95:6882

list of peers

Peer 40Peer 2 Peer 1

…BitTorrent as an example

HTTP GET MYFILE.torrent

MYFILE.torrent

ISP A

Control Path: Virtual Topology Interface

1 4

3

2pTracker

iTracker

peer

Information flow:1. peer queries

pTracker 2. pTracker asks

iTracker for guidance (occasionally)

3. iTracker returns high-level peering suggestions

4. pTracker selects and returns a set of active peers, according to the suggestions

iTracker can be run by trusted third parties, P2P network, or ISPs for security/privacy

The Virtual Topology Interface: Network

PID: set of Points of Presence (PoP)

E: set of links connecting PoPs

ce: the link capacity of link e

Ie(i, j): indicator if link e is on the route from PoP i to PoP j

be: amount of background traffic on link e

The Virtual Topology Interface: P2P

Assume K applications running inside the ISP we call each running P2P application a swarm

Let Tk be the set of acceptable demands for swarm k tk in Tk specifies traffic demand tk

ij from each pair of source-destination PoPs (i,j)

The Virtual Topology Interface

Consider an example: ISP wants to minimize utilization of the highest utilized link the utilization of the highest utilized link is

called the Maximum Link Utilization (MLU)

k

ek ji

ekije

Ee

Ttts

cjiItb

k :k ..

/)),((maxmin

ISP MLU: Transformation

kk

ek ji

ekije

Ttk

cjiItbets

:

),(:..

min

ISP MLU: Dual

Introducing pe (≥ 0) for the inequality of each link e

To make the dual finite, need

)(min)(:;

ee k

keee

Ttke ctbppD

kk

e

eecp 1

ISP MLU: Dual Then the dual is

where pij is the sum of pe along the path from PoP i to PoP j

)(min)(:

e k

keee

Ttke tbppD

kk

e

kee

e kTt

ee tpbpkk

min

ji

kijij

e kTt

ee tpbpkk

min

e k

kee

eTt

ee tpbpkk

min

ISP MLU Dual : Interpretation

Each swarm k chooses tk in Tk to minimize weighted sum of tij

The interface between a swarm and the ISP is the “shadow prices” {pij}

ji

kijij

e kTt

eee tpbppDkk

min)(

Topology with Costs (Illustration)

PID1 PID2

PID3PID6

PID5 PID4

70

2030

10

60

Each PID has:• IP “prefix”

Each link has•“Price”Prices are directional

ISP Update

At update m+1, calculates

eeee

S

See

pcp

mmmpmp

}0;1:{p :S

Sset toprojection:[]

})D({p ofent supergradi :

size step :

)]()()1([)1(

e

e

P2P Operations

Each swarm optimizes its own performance, then picks ISP-friendly peering

For example, selects

where is tolerance, say 80%.

Example: Multihoming

Multihoming A common way of

connecting to Internet

Smart routing Intelligently distribute

traffic among multiple external links

Improve performance Improve reliability Reduce cost

User

ISP 1

ISP K

InternetISP 2

Interdomain Topo

PID1 PID2

PID3PID6

PID5 PID4

70

2030

10

60

Provider1

Provider 2

Provider 3

Cost?

Cost?

Cost?

Integrating Cost Min with P4P

kk

ek ji

ekijee

ek ji

ekije

Ttk

vjiItbEe

cjiItbEe

ts

:

),(:

),(:

..

min0

Field-Tests

So far integrated with BitTorrent on PlanetLab Pando: a P2P software (18 million downloads) Maze: about 5 million users

Run iTrackers Verizon at Yale Telephonica at its own location

Collect data from Feb. 21 to March 2

ISP Perspective: Overall

Traffic within Verizon

Average Hop Each Bit Traverses

Why less than 1: many transfers are in the same metro-area; also same metro-area peers are utilized more by tit-for-tat.

P2P Perspective: Download Rates

Current Status

P4P-WG Next step

wider integration IETF standard

• AT&T• Bezeq Intl• BitTorrent• CacheLogic• Cisco Systems• Grid Networks• Joost• LimeWire• Manatt• Oversi• Pando Networks• PeerApp• Telefonica Group• VeriSign• Verizon• Vuze• Univ of Washington• Yale University

• Abacast• AHT Intl• Akamai• Alcatel Lucent• CableLabs• Cablevision• Comcast• Cox Comm• Juniper Networks• Microsoft• MPAA• NBC Universal• Nokia• RawFlow• Solid State

Networks• Thomson• Time Warner Cable• Turner Broadcasting

Higher Reliability

Is the Internet Reliable?

A key design objective of the “Internet” (i.e., packet-switched networks) is robustness

Does the Internet infrastructure achieve the target reliability objective of a highly reliable system (99.999%)?

Perspective

911 Phone service (1993 NRIC report +) 29 minutes per year per line 99.994% availability

Std. Phone service (various sources) 53+ minutes per line per year 99.99+% availability

…what about the Internet? Various studies: about 99.5% Need to reduce down time by 500 times to

achieve five nines; 50 times to match phone service

Threats to Internet Availability: Operator Errors

- 80% IT budget spent on maintaining status quo

- human configuration errors account for about 60% of all network outages.

Zeus Kerravala, Yankee Group

Shadow Configurations as a Network Management Primitive

Shadow Configurations as a Network Management Primitive

Threats to Internet Availability: Accidents

Stockton

Rialto

El Paso

Oroville

- 675,000 excavation accidentsSprint Backbone: Jan. 9, 2006

Reliability as an Interdomain Service

ISPs pool resources to form an “insurance” pool implications?

Resilient routing reconfiguration

Threats to Internet Availability: Natural Disasters

Unreachable Networks: 10 days

Internet Disaster Recovery Response

Why slow response? the cable repairing is slow: not until 21 days

after quake BGP is not designed to create business

relationship

Objective a meta-BGP to facilitate discovery and

creation of BGP business relationship

More Ubiquitous Connectivity

Goal of Network Access

“People and their machines should be able to access information and communicate with each other easily and securely, in any medium or combination of media – voice, data, image, video, or multimedia – any time, anywhere, in a timely, cost-effective way.”

Dr. G. H. Heilmeier, Oct 1992

Network Access: Ubiquitous Access Goals

be connected whenever possible via the “best” available network

• ubiquitous• location-aware, e.g.

– what services (e.g., printers) are available “here”?– where is the “nearest” database/cache?– where is the “nearest” ATM?

handle multiple network interfaces• may operate at the same time

support the application’s graceful adaptation to the available bandwidth and latency

transparent handoff of user sessions among different devices/networks

Example: wireless overlay may take off if we can combine

cellular and WLAN

Motorola CN 620

Access: Build an Access Network Fast: Ad-Hoc Networks

Faster Wireless

Recap: Traditional Routing

So far, all routing protocols in wireless also use the framework of traditional Internet routing we covered in class a graph representation of underlying network

• point-to-point graph edges with costs select a lowest-cost route for a src-dest pair commit to a specific route before forwarding

A Simple Motivating Scenario

Assumes independent loss Internet architecture computes routing with one pre-

committed route

Implications?

How about Using Multiple Paths?

Traditional Routing3 forwarders

4 links

Opportunistic:7 forwarders

18 links

Opportunistic Coding

Motivating Scenario

A sends 1 packet to B; B sends packet 3 to A

If R has both packets 1 and 3, it can combine them and explore coding and broadcast nature of wireless

A BR

Faster Wireless: Summary

Both approaches dispose the point-to-point Internet link abstraction

Both approaches take advantage of opportunities and leverage broadcast nature of wireless medium to its advantage

New Access: Connecting the Physical World

Mark Weiser from Xerox: transparent computing is the ultimate goal computers should disappear into the

background

Network Access: Sensors

N

S

EW 2 Axis Magnetic Sensor

2 Axis Accelerometer

Light Intensity Sensor

Humidity Sensor

Pressure Sensor

Temperature Sensor

COTS sensors embedded microprocessor RF transceiver

• 916MHz, ~20m range, 4800 bps 1 week fully active, 2 yr @1% recharge by solar, wind, …

Course Summary

The field is moving fast, broad and not well-defined !

Driven by Technology, Infrastructure, Applications, and Understanding: technology

• e.g., wireless/optical communication technologies and device miniaturization (sensors)

infrastructure• e.g., global infrastructure

applications• e.g., P2P, content distribution, sensing, grid computing, VoIP,

IPTV understanding

• e.g., resource sharing principle, routing principles, mechanism design, and randomized access