Bart Salaets – is Solutions Architect in F5 Networks specifically focusing on service providers in the EMEA region. Prior to this, he has held IP consulting and technical leadership positions in Juniper Networks, Redback Networks and Alcatel-Lucent, giving him more than 15 years of experience in both fixed and mobile broadband IP network design. Bart Salaets was born and still lives in Belgium and holds a Masters degree in Electrical Engineering from the Catholic University of Leuven, Belgium and an MBA from Flanders Business School in Antwerp, Belgium. Topic of Presentation: Optimising TCP in today’s changing network environment Language: English Abstract: The need to juggle performance across wired, wireless and wi-fi networks is a challenge as each of these paths has very different characteristics when it comes to TCP. Tuning the TCP stack to be optimized for the varying degrees of packet loss, latency and congestion on the different connection types is a challenge. This session will cover tuning several aspects of your network and the underlying TCP stack to deliver an optimized application experience for all users. Topics will include: Choosing the correct Congestion Control algorithm Optimizing TCP with techniques like TCP buffering and adjusting TCP window sizes Rate-based pacing to help multiple request/responses over a single connection

1. Optimizing TCP in Today’s
Changing Network Environment
Bart Salaets, Solution Architect, F5 Networks
September 2014

2. Agenda
• Market Trends – Network and Content Optimization
• TCP Technology Review
• TCP Optimization in Mobile Networks
• Test Results
• Summary
© F5 Networks, Inc 2

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 connections
RISE 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 3

4. SPDY – Load Web Pages Faster
• HTTP inefficient and outdated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
© F5 Networks, Inc 4

5. 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
© F5 Networks, Inc 5

6. TCP Protocol Review
• 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
© F5 Networks, Inc 6

7. Bandwidth-Delay Product – Determining Ideal Window Size
• Ideal size = Bandwidth * Delay Product (BDP)
Receiver
Bandwidth = 1Mbps, RTT = 1 second (BDP = 1M bits)
100K
BITS
100K
BITS
100K
BITS
• What if window size < BDP ?
100K
BITS
• Inefficiency (wasted bandwidth)
Sender
• What if window size > BDP ?
• Queuing at intermediate routers
• Increased RTT due to queuing delays
• Potentially, packet loss
THE BDP SPECIFIES THE TOTAL AMOUNT OF DATA THE PIPE CAN
9
100K
BITS
100K
BITS
100K
BITS
100K
BITS
100K
BITS
100K
BITS
HOLD
© F5 Networks, Inc 9

8. TCP Congestion Control Algorithms
• 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)
RENO CUBIC
ILLINOIS
© F5 Networks, Inc 10

9. Impact of Latency – Web Page Load Times
Source: Ilya Grigorik, Google
© F5 Networks, Inc 11

10. Impact of Packet Loss – Throughput Degradation
• TCP designed to probe the network to figure out available capacity
• TCP slow start is a feature, not a bug
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 12

11. Ideal TCP Stacks Would Result In …
High Effective Faster Web
Flow Fairness
Throughput
Page Loading
HOW DO WE ACHIEVE THIS IN 2G, 3G, AND 4G NETWORKS ?
© F5 Networks, Inc 13

12. TCP Optimization on Gi LAN Using TCP Proxy
WITH F5
PGW/
GGSN
Content
Server
Radio
Access
Internet
TCP-SYN
TCP-SYN/ACK
TCP-ACK
TUNE SEND/RECEIVE BUFFERS TO INTERNET
CHOOSE CONGESTION CONTROL TO INTERNET
ENABLE S-ACK FOR ALL TCP CONNECTIONS
ENABLE OTHER TCP OPTIONS
TCP-SYN
TCP-SYN/ACK
TCP-ACK
Cell-optimized TCP connection
TUNE SEND/RECEIVE BUFFERS TO RADIO
CHOOSE CONGESTION CONTROL TO RADIO
ENABLE RATE PACING TO RADIO
ENABLE S-ACK FOR ALL TCP CONNECTIONS
ENABLE LOSS FILTER
ENABLE OTHER TCP OPTIONS
TYPICALLY USES
STANDARD TCP
SETTINGS OF THE
OPERATING SYSTEM
WAN-optimized TCP connection
© F5 Networks, Inc 14

13. TCP Optimization Deals with Specifics of Radio Networks
BDP differences between
Radio/WAN
Random packet loss
Buffer bloat issues
Mobility and inter-RAT handovers
TCP buffer tuning and buffer mgmt
Intelligent congestion control (loss
filters)
TCP buffer tuning and TCP rate pacing
Loss- and delay-based congestion
control
© F5 Networks, Inc 15

14. Traditional Optimization Architecture
PGW/
GGSN
RTR Internet
Data Center
TCP
Optimization
Video
Optimization
DPI Firewall/CGNAT
All Port 80 traffic (HTTP only) forwarded
to optimization platforms
Transparent
Caching
RAN
Optimization platforms can be
standalone or consolidated
© F5 Networks, Inc 16

15. Next-Generation Optimization Architecture
Inline TCP optimization with intelligent steering consolidated
PGW/
GGSN
RTR
PCRF
Diameter Gx
DPI Firewall/CGNAT Internet
Traffic
Steering
Context-aware and policy-driven
traffic steering and service chaining
TCP
Optimization
Data Center
Video
Optimization
Transparent
Caching
CONTEXT-AWARE
STEERING
Subscriber
Device-type
RAT-type
Content (Video, URI, ...)
Congestion
Content optimization platforms
© F5 Networks, Inc 17

16. TCP Test Results – Throughput & Web Page Load Times
200%
180%
160%
140%
120%
100%
80%
60%
40%
20%
0%
3G 4G
HTTP large
download
196% 95% 22% 14%
Poor coverage Good coverage
40%
35%
30%
25%
20%
15%
10%
5%
0%
Large download: HTTP page with large images (throughput test)
Small download: HTTP page with small objects (web page load time test)
HTTP large
download
38% 33% 20% 28%
Poor coverage Good coverage
TCP OPTIMIZATION BENEFITS INCREASE UNDER POOR RADIO COVERAGE
© F5 Networks, Inc 18

17. HTTPS/SPDY Performance Tests
1.8
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
0
Impact SPDY/Optimizer
Non-SPDY SPDY Non-SPDY-OPT
SPDY-OPT
Series1 1.64 1.46 1.27 1.16
Page Download Time Seconds
Ref test: duckduckgo.com (25 samples on 4G)
35%
30%
25%
20%
15%
10%
5%
0%
Impact SPDY/Optimizer
Non-SPDY SPDY Non-SPDY-OPT
SPDY-OPT
Series1 0% 11% 23% 31%
Gain in Download Time %
TCP OPTIMIZATION PROVIDES ADDITIONAL BENEFITS ON TOP OF SPDY
BENEFITS
© F5 Networks, Inc 19

18. TCP Optimization Helps Avoid Buffer Bloat
RTT 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 20

19. 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
© F5 Networks, Inc 21

20. Solutions for an Application World.