Optimizing TCP in Today’s Changing Network EnvironmentBart Salaets, Solution Architect, F5 Networks

September 2014

© F5 Networks, Inc 2

• Market Trends – Network and Content Optimization

• TCP Technology Review

• TCP Optimization in Mobile Networks

• Test Results

• Summary

Agenda

© F5 Networks, Inc 3

A Changing Environment

SSL / SPDY INCREASE

• In Europe, SSL traffic (HTTPS and SPDY) on mobile networks is currently reaching around 50% of total Internet traffic

• Top web sites such as Google, Facebook, and Twitter use SPDY

• HTTP 2.0 being standardized in IETF with browsers requiring TLS encryption when setting up HTTP 2.0 connectionsRISE OF ADAPTIVE BIT RATE VIDEO STREAMING

• Top video sites such as YouTube, Netflix, Hulu, and BBC iPlayer have all embraced ABR video technology

• Video is encoded at different bit rates, client dynamically chooses or changes appropriate bit rate based on network conditions

• ABR video can be "optimized" using bandwidth control techniques

© F5 Networks, Inc 4

• HTTP inefficient and outdated • HTTP protocol inefficiencies have a negative

impact on mobile web browsing experience• Due to higher latencies in mobile networks

• SPDY: New app layer protocol developed by Google• Overcomes inherent inefficiencies with HTTP• Improved performance (~ 20-50%)• Good for low bandwidth / high latency mobile

networks• Forms the basis for HTTP 2.0 in IETF

SPDY – Load Web Pages Faster

HTTP

SPDY

SSL

TCP

Application

Transport

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Impact on Optimization Technologies

Transparent Caching

TCP Optimization

and Bandwidth Control

Video and Web Optimization

Increase of SSL and SPDY on the web are reducing

the benefits of this technology

Will continue to provide benefits to majority of

traffic as > 90% of all traffic rides on top of TCP

(including SSL/SPDY)

Increase of video encryption and ABR video are reducing the benefits

of this technology

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• TCP is a connection-oriented protocol• Client and server must establish a connection before any data can be

transfered

• TCP provides reliability• Knows that data it sends is correctly received by the other end• Acknowledgements confirm delivery of data received by TCP receiver• Ack for data sent only after data has reached receiver

• TCP implements flow control and congestion control• Sender can not overwhelm a receiver with data• Sender will "back off" when under congestion

TCP Protocol Review

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• Ideal size = Bandwidth * Delay Product (BDP)

• What if window size < BDP ?• Inefficiency (wasted bandwidth)

Bandwidth-Delay Product – Determining Ideal Window Size

9

Receiver

Bandwidth = 1Mbps, RTT = 1 second (BDP = 1M bits)

100K

BITS

100K

BITS

100K

BITS

100K

BITS

100K

BITS

100K

BITS

100K

BITS

100K

BITS

100K

BITS

100K

BITS

Sender

THE BDP SPECIFIES THE TOTAL AMOUNT OF DATA THE PIPE CAN HOLD

• What if window size > BDP ?• Queuing at intermediate routers• Increased RTT due to queuing delays• Potentially, packet loss

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• Loss-based algorithms• Reno, New Reno, High-Speed,

Scalable, BIC, CUBIC

• Delay-based algorithms• Vegas

• Bandwidth-estimating algorithms• Westwood, Westwood+

• Hybrid delay/loss algorithms• Illinois, Woodside (F5)

TCP Congestion Control AlgorithmsRENO CUBIC

ILLINOIS

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Impact of Latency – Web Page Load Times

Source: Ilya Grigorik, Google

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• TCP designed to probe the network to figure out available capacity

• TCP slow start is a feature, not a bug

Impact of Packet Loss – Throughput Degradation

Avg HTTP response size 16 kB (3 round

trips)

In mobile networks packet loss does not

necessarily imply congestion

Source: Ilya Grigorik, Google

© F5 Networks, Inc 13

Ideal TCP Stacks Would Result In …

Faster Web Page Loading

Flow FairnessHigh Effective

Throughput

HOW DO WE ACHIEVE THIS IN 2G, 3G, AND 4G NETWORKS ?

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TCP Optimization on Gi LAN Using TCP Proxy WITH F5

PGW/GGSN

ContentServer

RadioAccess

Internet

TCP-SYN

TCP-SYN/ACK

TCP-ACK

TCP-SYN

TCP-SYN/ACK

TCP-ACK

TUNE SEND/RECEIVE BUFFERS TO RADIO

CHOOSE CONGESTION CONTROL TO RADIO

ENABLE RATE PACING TO RADIOENABLE S-ACK FOR ALL TCP

CONNECTIONSENABLE LOSS FILTER

ENABLE OTHER TCP OPTIONS

TUNE SEND/RECEIVE BUFFERS TO INTERNET

CHOOSE CONGESTION CONTROL TO INTERNET

ENABLE S-ACK FOR ALL TCP CONNECTIONS

ENABLE OTHER TCP OPTIONS

TYPICALLY USES STANDARD TCP

SETTINGS OF THE OPERATING

SYSTEM

Cell-optimized TCP connection

WAN-optimized TCP connection

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TCP Optimization Deals with Specifics of Radio Networks

BDP differences between Radio/WAN

Random packet loss

Buffer bloat issues

Mobility and inter-RAT handovers

Loss- and delay-based congestion control

TCP buffer tuning and TCP rate pacing

Intelligent congestion control (loss filters)

TCP buffer tuning and buffer mgmt

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Traditional Optimization Architecture

PGW/GGSN

InternetRTR

Data Center

TCPOptimization

VideoOptimization

TransparentCaching

All Port 80 traffic (HTTP only) forwardedto optimization platforms

DPI Firewall/CGNAT

RAN

Optimization platforms can be

standalone or consolidated

© F5 Networks, Inc 17

Next-Generation Optimization ArchitectureInline TCP optimization with intelligent steering consolidated

PGW/GGSN

RTR

Data Center

VideoOptimization

Transparent Caching

Context-aware and policy-driven traffic steering and service chaining

CONTEXT-AWARE STEERINGSubscriberDevice-typeRAT-typeContent (Video, URI, ...)Congestion

InternetDPI Firewall/CGNAT

PCRF

Diameter Gx

s /WZ/K E WůĂƚĨŽƌŵ

TrafficSteering

TCPOptimization

Content optimization platforms

© F5 Networks, Inc 18

Large download: HTTP page with large images (throughput test)Small download: HTTP page with small objects (web page load time test)

TCP Test Results – Throughput & Web Page Load Times

Poor coverage Good coverage0%

20%

40%

60%

80%

100%

120%

140%

160%

180%

200% HTTP large down-load

Poor coverage Good coverage0%

5%

10%

15%

20%

25%

30%

35%

40% HTTP large down-load

3G 4G

TCP OPTIMIZATION BENEFITS INCREASE UNDER POOR RADIO COVERAGE

20% 28%38% 33%22% 14%196%95%

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Ref test: duckduckgo.com (25 samples on 4G)

HTTPS/SPDY Performance Tests

TCP OPTIMIZATION PROVIDES ADDITIONAL BENEFITS ON TOP OF SPDY BENEFITS

Non-SPDY SPDY Non-SPDY-OPT SPDY-OPT

Series1 0 0.11 0.23 0.31

3%

8%

13%

18%

23%

28%

33%

Impact SPDY/Optimizer

Gain

in D

ow

nlo

ad T

ime %

Non-SPDY SPDY Non-SPDY-OPT

SPDY-OPT

Series1 1.64 1.46 1.27 1.16

0.1

0.3

0.5

0.7

0.9

1.1

1.3

1.5

1.7

Impact SPDY/Optimizer

Page D

ow

nlo

ad T

ime S

eco

nds

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TCP Optimization Helps Avoid Buffer BloatRTT graphs are based on two file downloads under good 3G coverage

NON-OPTIMIZED (11 Mbps)(up to 2.5 seconds latency)

OPTIMIZED (11 Mbps)(constant 200 ms latency)

LATENCY MAY NOT DESTROY THROUGHPUT, BUT WILL DEGRADE BROWSING EXPERIENCE

© F5 Networks, Inc 21

TCP Optimization – Summary

Increases “goodput” on radio network and keeps latency under control

Works for > 90% of all Internet traffic regardless of encryption or encoding

Lengthens life span of radio infrastructure and enhances user experience

Deployed inline on Gi LAN, optionally consolidated with other L4-7 functions

Solutions for an Application World.