Задумывались ли вы, что стоит между вами и картинкой милого котика в вашем смартфоне? Почему мордочка котика грузится так медленно? Может ли эта картинка может стоить вам разряженой батареи и почему? И что разработчики мобильных приложений могут сделать, чтобы котики и пользователи были счастливы? Это, а возможно и не только, будет интересно и тестировщикам (и мобильных, и веб-приложений) и просто владельцам умного телефона.

1. SMARTPHONE,
INTERNET AND REAL LIFE
Why networking matters
Tetiana Liuliuchenko

2. LOUIS C.K. – EVERYTHING IS
AMAZING
QAFEST 2017

3. ABOUT ME
More than 6 years in testing.
ISTQB certified.
QAFest and SQADays speaker.
Conduct internal smart talks and
trainings.
QAFEST 2017

4. HELLO, INTERNET
QAFEST 2017

5. COMPONENTS OF NETWORK
PERFORMANCE
QAFEST 2017

6. BANDWIDTH - MAXIMUM
THROUGHPUT OF A LOGICAL OR
PHYSICAL COMMUNICATION
PATH
QAFEST 2017
• add more fibers into our fiber-optic links
• deploy more links across the congested routes
• improve the WDM techniques to transfer more data
through existing links

7. LATENCY - THE TIME FROM THE
SOURCE SENDING A PACKET TO
THE DESTINATION RECEIVING IT
QAFEST 2017
Propagation delay
+
Transmission
delay
+
Processing delay
+
Queuing delay
+
…

8. LATENCY – CAN WE BE
FASTER?
The speed of light places a hard limit on the
minimum latency.
We can’t make light move faster, but we can:
 reduce round trips of data;
 move the data closer to the client;
 build applications that can hide the latency through
caching, pre-fetching, and a variety of similar
techniques
QAFEST 2017

9. LAST-MILE LATENCY
QAFEST 2017

10. WIRELESS NETWORKS
QAFEST 2017

11. TYPES OF WIRELESS
NETWORKS
QAFEST 2017
Type Range Applications Standards
Personal area
network (PAN)
Within reach of
a person
Cable
replacement for
peripherals
Bluetooth,
ZigBee, NFC
Local area
network (LAN)
Within a
building
Wireless
extension of
wired network
IEEE 802.11
(WiFi)
Metropolitan
area network
(MAN)
Within a city
Wireless inter-
network
connectivity
IEEE 802.15
(WiMAX)
Wide area
network (WAN)
Worldwide
Wireless
network access
Cellular (UMTS,
LTE, etc.)

12. CHANNEL CAPACITY
C - channel capacity, measured in bits per second.
BW - available bandwidth, is measured in hertz.
S - signal, measured in watts.
N - noise, measured in watts.
QAFEST 2017

13. SIGNAL INTERFERENCE
Near-far problem
Cell-breathing
QAFEST 2017

14. GENERATIONS OF MOBILE
NETWORKS
Generatio
n
Peak data
rate
Data rate Latency
1G No data
2G Kbit/s 100–400
Kbit/s
300–1000
ms
3G Mbit/s 0.5–5 Mbit/s 100–500
ms
4G Gbit/s 1–50 Mbit/s < 100 ms
QAFEST 2017

15. CELLULAR NETWORK
STANDARDS
QAFEST 2017
Generation Organization Release
2G
3GPP GSM
3GPP2 IS-95 (cdmaOne)
2.5G, 2.75G
3GPP GPRS, EDGE (EGPRS)
3GPP2 CDMA2000
3G
3GPP UMTS
3GPP2 CDMA 2000 1x EV-DO Release 0
3.5G, 3.75G,
3.9G
3GPP HSPA, HSPA+, LTE
3GPP2
EV-DO Revision A, EV-DO Revision B,
EV-DO Advanced
4G 3GPP LTE-Advanced, HSPA+ Revision 11+

16. USER EQUIPMENT CATEGORY
QAFEST 2017

17. UMTS/HSPA+/DC-HSDPA (850, 900,
1700/2100, 1900, 2100 MHz)
GSM/EDGE (850, 900, 1800, 1900 MHz)
CDMA EV-DO Rev. A (800, 1900, 2100
MHz)
802.11a/b/g/n/ac Wi-Fi with MIMO
Bluetooth 4.2 wireless technology
FDD-LTE (Bands 1, 2, 3, 4, 5, 7, 8, 12, 13,
17, 18, 19, 20, 25, 26, 28, 29, 30, 66)
TD-LTE (Bands 34, 38, 39, 40, 41)
TD-SCDMA 1900 (F), 2000 (A)
NFC with reader mode
QAFEST 2017
iPhone X (Model
A1865) • UMTS/HSDPA/HSUPA (850, 900,
1900, 2100 MHz);
• GSM/EDGE (850, 900, 1800, 1900
MHz)
• CDMA EV-DO Rev. A (800, 1900
MHz)3
• 802.11b/g/n Wi-Fi (802.11n 2.4GHz
only)
• Bluetooth 4.0 wireless technology
• World phone
iPhone 4S

18. RADIO STATE MACHINE
QAFEST 2017

19. APPS AND THE RADIO STATE
MACHINE
QAFEST 2017

20. OPTIMIZE FOR MOBILE
QAFEST 2017

21. PRESERVE BATTERY POWER
QAFEST 2017

22. REDUCE CONNECTIONS
Eliminate Periodic and Inefficient Data Transfers
Batch Transfers and Connections
Reduce Connections
Idle whenever is possible
QAFEST 2017

23. SAVE DATA IN ADVANCE
Pre-fetch data
Cache things
QAFEST 2017

24. ELIMINATE UNNECESSARY
APPLICATION KEEPALIVES
QAFEST 2017

25. A FEW FACTORS THAT MAY
AFFECT THE PERFORMANCE OF
YOUR WIRELESS NETWORK
Distance between receiver and
sender
Background noise
Interference from users in intra-cell
Interference from users in inter-cell
Available transmit power
Amount of processing power and
the chosen modulation scheme
QAFEST 2017

26. WHAT MAY HAPPEN
Internet router failure
Route change
Router/Link overload (with queues being full)
Router being loaded, but not overloaded. AQM fires in
Traffic Shaper on the way
Last mile – electromagnetic interference
Firewalls
QAFEST 2017
Last mile oversubscription
Modem retrain
Heavy download (overload of last mile downstream)
LTE last mile – poor weather (fog or rain)
Sudden IP change
Poor Wi-Fi
Wi-Fi interference

27. HOW WE MAY OBSERVE IT
100% packet loss
Random packet loss
Burstable packet loss
“Hanged” connections
Long responses
QAFEST 2017

28. TEST IN-LAB
Simulate patterns of packet loss to see how your server can
handle it
Handle “hanged connection” (without forcing user to close-
and-reopen-app)
Prepare to handle “mass disconnects”
QAFEST 2017

29. TEST OUT OF LAB
Go out and have poor connection!
QAFEST 2017

30. CONTACT ME
Facebook: tatyana.lyulyuchenko
LinkedIn: tetiana-liuliuchenko
QAFEST 2017