Download Challenges within Transport Protocols - COST

Challenges
within Transport
Protocols
Åke Arvidsson, Ph.D., Prof.
Disclaimer
› Few or no new research results (save for Bilbao).
› Focus on (more or less) open problems.
Challenges within Transport Protocols | Ericsson Internal | 2016-08-29 | Page 2
Overview
› Drivers behind challenges:
– Higher cellular uptake.
– Higher bit rates.
– New environments.
› Current research efforts:
– End-to-end control.
– Network assisted control.
– TCP/NC.
– QUIC and HTTP2.
– MPTCP.
Challenges within Transport Protocols | Ericsson Internal | 2016-08-29 | Page 3
Overview
› Not discussed:
– Data centres.
– SDN and service chaining.
– Internet of Things.
– SCTP track.
– Security aspects.
– Middle box issues.
– ...
Challenges within Transport Protocols | Ericsson Internal | 2016-08-29 | Page 4
Challenges
› Quality Engineering for a Reliable Internet of Services.
– Quality in terms of experience and reliability.
› Continuous improvements:
– Improve experience.
– Increase utilisation.
– More flexibility.
– ...
› Had enough?
– Too much of a good thing can be wonderful. [Mae West]
– Besides, conditions have changed.
Challenges within Transport Protocols | Ericsson Internal | 2016-08-29 | Page 5
Drivers
› Higher cellular uptake:
Source: Ericsson Mobility Report June 2016.
Challenges within Transport Protocols | Ericsson Internal | 2016-08-29 | Page 6
DRIVERS
› Technological evolution:
› Source: Performance of Wireless Networks, Chapter 7, O’Reilly.
Challenges within Transport Protocols | Ericsson Internal | 2016-08-29 | Page 7
DRIVERS
› Technological evolution:
5G
0.01–10 Gb/s
1 ms
› Additional source: Ericsson White Paper 2016.
Challenges within Transport Protocols | Ericsson Internal | 2016-08-29 | Page 8
DRIVERS
› Technology adoption:
Source: Ericsson Mobility Report June 2016.
Challenges within Transport Protocols | Ericsson Internal | 2016-08-29 | Page 9
Drivers
› Integrated services:
– Real time (voice, gaming, …).
› Data centres:
– Short distances.
› Software defined networks:
– Service chaining.
Challenges within Transport Protocols | Ericsson Internal | 2016-08-29 | Page 10
HIGH
VOLTE
Overall Target
› Make the most out of new technology.
› Support demands from new services.
› Maximum goodput.
– Only useful bytes contribute to user experience.
› Minimum queuing.
– Real time, handover, abandonment (cf. above).
› Basic problem:
– Achieve both at the same time.
Challenges within Transport Protocols | Ericsson Internal | 2016-08-29 | Page 11
End-to-end Control
› Some attempts to exercise end-to-end control:
Source: ”TCP ex Machina: Computer-Generated Congestion Control”, Keith Winstein et al., MIT Computer Science and Artificial
Intelligence Laboratory (2014).
Source: ”TCP Congestion Avoidance Algorithm Identification”, Peng Yang et al. , IEEE/ACM Trans. Netw., vol. 22, no. 4 (2014).
Challenges within Transport Protocols | Ericsson Internal | 2016-08-29 | Page 12
End-to-end Control
› Loss-based, delay-based, hybrid, …
› Are we done?
› No:
– Recent papers point to several problems.
› So:
– Beat TCP by opening multiple, parallel connections.
– Beat TCP by tweaking slow start.
– Beat TCP by adding pacing.
– Give up and design yourself.
Challenges within Transport Protocols | Ericsson Internal | 2016-08-29 | Page 13
End-to-end Control
› Improvements:
– Reduce sensitivity to RTT variations.
– E.g., Cubic hybrid slow start.
› Development:
– Use static pre-information?
– Use temporary pre-information?
– Fast start instead of slow start?
– Are two phases necessary?
› Only packet format is standardised.
Challenges within Transport Protocols | Ericsson Internal | 2016-08-29 | Page 14
Network assisted
control
› Some attempts to provide network assisted control:
Source: ”TCP ex Machina: Computer-Generated Congestion Control”, Keith Winstein et al., MIT Computer Science and Artificial
Intelligence Laboratory (2014).
Challenges within Transport Protocols | Ericsson Internal | 2016-08-29 | Page 15
Network assisted
control
› Renewed interest in ECN, explicit congestion notification.
› Congestion flags propagated back to the source.
› Flags set based on AQM, active queue management.
– RED (random early discard): Based on queue length.
– CoDel (controlled delay): Based on minimum delay in time window.
– ...
› Work on both ECN, AQM and their interworking to be done.
› Different track: DASH-friendly transport (support or enable
rate estimation).
Challenges within Transport Protocols | Ericsson Internal | 2016-08-29 | Page 16
Network coding
› Simplified idea:
– For a file of N packets, compute M  N linear combinations.
– Send new combinations until N packets have been received.
– Re-compute packets from combinations.
› Example:
– PAP1+P2, PBP1-P2, PCP1+2*P2
– P12*PA-PC, P2PC-PA
› Benefits:
– Packets are replaceable.
– No need to identify lost packets.
– No need to maintain packet order.
Challenges within Transport Protocols | Ericsson Internal | 2016-08-29 | Page 17
SPDY, HTTP/2 and Quic
› SPDY allows parallel objects over single (TCP) flows.
› HTTP/2 adds server push and standardises these ideas.
› QUIC adds encryption and more to a complete protocol.
› Congestion control, wireless and middle boxes...
Challenges within Transport Protocols | Ericsson Internal | 2016-08-29 | Page 18
MPTCP
› Multi-path TCP.
› Let different packets follow different paths.
– Normally invisible to end points.
– Split and reassembly handled by gateways.
› Load distribution for optimal throughput.
› Load distribution for temporary (cost based) offload.
› Minimise reordering at receiver.
Challenges within Transport Protocols | Ericsson Internal | 2016-08-29 | Page 19
”Controlled
environments”
› Access networks (in particular cellular):
– Under control of (largely) a single operator.
– High efficiency (bit rate/queuing) more important.
› Bridging functionality between gateway (GGSN or PGW)
and base station (Node B or eNode B).
– Split transport (faster feedback; higher rate and more accurate).
– Limited uncertainty (path may be more or less known); better CC.
– New features (limited need for compatibility); ECN, NC, MPTCP,
Rate notification…
› No need to feel constrained by ossification.
– Large enough gains are always interesting!
Challenges within Transport Protocols | Ericsson Internal | 2016-08-29 | Page 20
SOME Recent IETF
Publications
› Duke et al., ”A Roadmap for Transmission Control Protocol (TCP)
Specification Documents”, IETF RFC 7805 (2015).
› Kuehlewind et al., “Problem Statement and Requirements for Increased
Accuracy in Explicit Congestion Notification (ECN) Feedback”, IETF
RFC 7560 (2015).
› Baker et al., ”IETF Recommendations Regarding Active Queue
Management”, IETF RFC 7567 (2015).
› Detchart et al., ”Tetrys, an On-the-Fly Network Coding protocol”, IETF
Draft (2016).
› Hamilton et al., “QUIC: A UDP-Based Multiplexed and Secure
Transport”, IETF Draft (2016).
› Bagnulo et al., “Analysis of Residual Threats and Possible Fixes for
Multipath TCP (MPTCP)”, IETF RFC 7430 (2015).
Challenges within Transport Protocols | Ericsson Internal | 2016-08-29 | Page 21