This document summarizes a panel discussion on tackling connectivity diversity for constrained radio networks and devices. The panel discussed the disconnect between how applications are developed and how they are used across different devices and networks. This can lead to issues with varying data rates, latency spikes from error correction and power management, and intermittent connectivity from features like discontinuous reception. Going forward, networks aim to improve data rates and reduce latency further, though maintaining low loss rates will still be important. The panel debated whether it is better for applications to use multiple interchangeable protocols, or single protocols with wide applicability. They also considered design principles for addressing restricted connectivity and interactions between power and connectivity management.

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Tackling Connectivity Diversity:
Protocol Challenges for Constrained Radio
Networks and Devices
Olaf Kolkman, Moderator
Chief Internet Technology Officer
The Internet Society
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We are…
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Not at the IETF
 Taking discussion up a level
 Taking any identified work items to the appropriate
IETF WGs
“On the air”
 Streaming
 Recording
Stopping at 12:45pm so you can all get back to
the IETF…

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Agenda outline
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Overview
Panelists’ introduction
Framing discussion
Open mic

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The Panel
Olaf Kolkman (Moderator)
Ted Hardie
Blake Matheny (Facebook)
Henning Wiemann (Ericsson)

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Today’s discussion
Disconnect between application development
environments and application use environments
 Handsets
 Networks
Does infrastructure need to change?
Is this a transient condition?
Is there a need for better design to cope with
connectivity diversity?
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Global Internet Report
Some charts from the Internet Society’s Global Internet
Report 2015
More at:
http://www.internetsociety.org/globalinternetreport/
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Proportion of population covered by at least 3G
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The Digital Divide
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Panelists’ introduction
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12. Characteristics of
Mobile Broadband Connections
… as seen from IP and above
Henning Wiemann
Ericsson Research
3GPP RAN2 Chairman

13. Characteristics of Mobile Broadband | Public | © Ericsson AB 2015 | 2015-07-20 | Page 13
› Packet Loss Rate seen on IP layer: < 10-6
– ARQ to avoid that TCP interprets transmission losses as congestion
› Latency (RTT) in the order of tens of ms
– Spikes due to error correction (ARQ)
– Spikes due to Connection Establishment and DRX (see next slide)
› Data Rates vary depending on channel conditions, network
load, total carrier bandwidth, deployed features…
– LTE today: ~100 kbps (at the coverage edge) to ~300 MBps
(specs allow already much higher rates)
Performance
Data Rates, Latency, Loss Rate
Be prepared for varying data rates!
Latency is low but shows some spikes!

14. Characteristics of Mobile Broadband | Public | © Ericsson AB 2015 | 2015-07-20 | Page 14
› Discontinuous Reception (DRX) to save UE battery
– Allows UE to switch-off receiver chain after short inactivity
– Network initiated traffic observes additional delays (typically 0.05 to 1s)
› Radio Connection released upon longer inactivity
– Further decreases battery consumption and control signaling
– But requires additional control signaling and delays when
connection is established again for the next packet burst
Power Consumption
Impact to Performance & Reachability
Every “Keep-Alive” is costly if it forces the UE to wake-up from
DRX or to establish a new Radio Connection!

15. Characteristics of Mobile Broadband | Public | © Ericsson AB 2015 | 2015-07-20 | Page 15
› Data Rates will still vary
– Aiming at high data rates in wider areas (e.g. massive beamforming)
– Connectivity in very challenging coverage conditions
(at least for low data rate Internet-of-Things applications)
– Even higher peak data rates (up to several tens of GBps)
› Latency Reductions
– Aiming initially at a reduction by a factor ~5-10
– Even lower latency is targeted for latency critical applications
› Low loss rates should remain to be low
– To ensure that TCP can utilize the high data rates
– But costly in terms of memory (Packet-Delay-Budget)
And in Future?

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Blake Matheny
Facebook
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17. Tension among competing optimizations

18. Tension among competing optimizations

19. Building blocks
Is it better for applications or
systems to use multiple building
block protocols that can be
swapped in and out, or single
protocols with a wide range of
applicability?

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Some aspects to consider
Approaches taken by application developers to deal
with terminal and connectivity diversity
Considerations for protocol developers
The impact of restricted connectivity on user behavior
Design principles that could be extrapolated from the
data and the technical responses to date
Interactions between power management and
connectivity management

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The Panel
Olaf Kolkman (Moderator)
Ted Hardie
Blake Matheny (Facebook)
Henning Wiemann (Ericsson)