Presentation - Columbia University

Transcript Presentation - Columbia University

How Green is IP-Telephony?

Salman Abdul Baset*, Joshua Reich

, Jan Janak**, Pavel Kasparek**, Vishal Misra*, Dan Rubenstein*, Henning Schulzrinne* Department of Computer Science, Columbia University* Tekelec Corporation**

Traditional Telephony

• Place call (

Signaling

) • Directory lookup • Circuit reservation • Talk (

Connectivity

) • Transfer voice data (analog, digital) • Variations on these themes • Multi-party conferencing • Voicemail 2

IP-Based Communication Systems

Telephony • Place call (

Signaling

) • Directory lookup • Packet switched routes • Talk (

Connectivity

) • Direct packet routing • Media relaying • PSTN/mobile gateways And More • Video • IM • Status / buddy list 3

Trends & Implications

• Trend away from traditional telephony infrastructure • Vonage, Packet8, Verizon FiOS • Skype • Mobile • To single infrastructure (IP) for all data/voice/etc.

• More efficient (one system to maintain, improve) • Much less expensive (for now) • More fragile (one system to fail) • More complex

So what does this mean energy wise?

Our Questions

1) Where is energy consumed?

2) How do different design choices effect energy consumption?

3) How we can make IP-telephony more energy efficient?

Outline

• IP-Telephony and power consumption • Answering our questions: 1) Where is energy consumed?

2) How do different design choices effect energy consumption?

3) How we can make IP-telephony more energy efficient?

• Conclusion & Future Work 6

Outline

• IP-Telephony and power consumption • Answering our questions: 1) Where is energy consumed?

2) How do different design choices effect energy consumption?

3) How we can make IP-telephony more energy efficient?

• Conclusion & Future Work 7

IP Communication Flavors

Client-Server (

C/S

) Peer-to-Peer (

P2P

) 8

IP Communication Flavors

Traditional Telephony Replacement Communication Addendum 9

How Does C/S IP-Telephony Work?

SIP registrar / proxy server server IP-PSTN gateway REGISTER (1) signaling (ip addr) (ip addr)

PSTN / Mobile

User agent (2) media (voice, video, IM) User agent

Utopian Internet No NATs or firewalls

And In The Real World…

SIP registrar / proxy / presence / server media server NAT / firewall NAT / firewall User agent User agent 11

Media Servers Bypass Firewalls

SIP registrar / proxy / presence / server (1) signaling NAT / firewall (2) media (voice, video, IM) (UDP or TCP) (1) signaling media server NAT / firewall IP-PSTN gateway

PSTN / Mobile

User agents User agents 12

How Does P2P IP-Telephony Work?

media relay (or relay) (4) media node

NAT / firewall network address (3) media (TCP) (2) (1) (3) signaling

P2P

node

(2) signaling

PSTN / Mobile

(1) NAT / firewall (1) P2P / PSTN gateway node

node

node = user agent (2) signaling node

• • •

nodes form an overlay share responsibilities for message routing, signaling, media relaying super nodes, ordinary nodes

Sources of Energy Consumption

• End-point – Handsets – VoIP conversion boxes – PCs • Core – Signaling / directory – Media relaying – PSTN / mobile gateways • Network 14

Assessing Energy Consumption

• Data (from C/S VoIP provider) • Power Meters – 100 K users (mostly business) – 15 calls per second (CPS) – ~5K calls in system – NAT keep-alive traffic – All calls relayed • Modeling – C/S – P2P – Wattsup – Killawatt • Hardware Measurements – SIP Server – Relay Server – Desktop clients – Laptop clients – Hardware SIP phones – Software phones – Skype peers 15

Outline

• IP-Telephony and power consumption • Answering our questions: 1) Where is energy consumed?

2) How do different design choices effect energy consumption?

3) How we can make IP-telephony more energy efficient?

• Conclusion & Future Work 16

Where is Energy Consumed?

PSTN replacement • VoIP servers consume less than 0.04% of total!

– >10K users, voice traffic – a server can handle signaling workload for 500k users – a server can handle media workload for 50k users – even after a redundancy factor of 2, and conservative PUE of 2!

Where is Energy Consumed?

Non-PSTN replacement • More complicated • If softphone draws little additional power – Still likely that end-point biggest component – But may not dominate consumption • If users leave PCs on just as phones – Possibly even worse than PSTN!

User / hardware study needed.

How Do Design Choices Effect Power Consumption?

SIP registrar / proxy / presence / server INVITE media (voice, video, IM) (UDP or TCP) INVITE User agents User agents media relay (or relay) node

NAT / firewall (3) media (TCP) node

(2) signaling

P2P

node

(1) NAT / firewall of node E?

(2) signaling • C/S Inefficiencies node

node

– Power utilization efficiency – (PUE) • Ratio of data center power draw to IT power draw • e.g., cooling, network equipment, etc. – Idle power consumption (can be addressed in larger systems by techniques such as Somniloquy or Sleep Proxy – Percentage of user population that requires relaying major determinant of core energy consumption.

How Do Design Choices Effect Power Consumption?

SIP registrar / proxy / presence / server INVITE media (voice, video, IM) (UDP or TCP) INVITE User agents User agents media relay (or relay) node

NAT / firewall (3) media (TCP) node

(2) signaling

P2P

node

(1) NAT / firewall of node E?

(2) signaling • P2P Consumption node

node

– Avoids these overheads by using machines that are already on • In theory general user population • In practice appears to be heavily subsidized by university machines • What happens when machines are idling less… – Incurs small additional energy use for signaling and relaying • But how small?

Comparing C/S and P2P

• Compare under same load – Active calls – Call duration – Percentage of PSTN calls • Generic C/S and P2P – Both use standard VoIP (e.g., not Skype) • Isolate only services that differ between P2P, CS – Directory service – Call signaling – Media session – Presence 21

Modeling P2P and C/S

• C/S model – C/S power consumption = #servers

Watts/server

redundancy factor * PUE • P2P model – –

S p s

super nodes active super node consumption

P2P energy efficient when:

S * p s

< C/S power consumption

• One active super node per relayed call.

• Media server fully loaded.

• 100% calls relayed

p s

P2P may consume more than C/S!

Caveats

• Peers – External meters do not provide sufficient resolution to determine

p s

w/ confidence – Will be in different states when relay starts • Medium load unlikely to incur much extra overhead • Low or high loads,

p s

could conceivably be large • Consequently, prior distribution effects efficiency • Servers – Energy usage not linear w/ load – Lower utilization hurts energy efficiency 23

Making IP-Telephony Greener

• Make phones energy efficient – LCD, processor, WOL for phones?

• NATs & Firewalls – Get rid of NATs or rearchitect them – Use TCP to avoid NAT keep-alive – Make firewalls VoIP-friendly.

• Set up SIP user agents on gateways • PC wakeup on receiving calls 24

Outline

• IP-Telephony and power consumption • Answering our questions: 1) Where is energy consumed?

2) How do different design choices effect energy consumption?

3) How we can make IP-telephony more energy efficient?

• Conclusion & Future Work 25

Conclusions

• VoIP endpoints dominate total energy consumption in PSTN replacement systems • P2P not necessarily more energy efficient than C/S.

• NATs and firewalls create the need for media relaying, one of the biggest components of core energy consumption.

Future Work

• Obtain data on PSTN power consumption • Work on accurately measuring

p s

• Measure path length / routing differences between of direct and media-relayed calls.

• Study user behavior viz-a-vis softphone use – How much extra time are machines left on – Power draw during those periods • Develop WOL capable hard-phones 27