Murari Sridharan murarismicrosoftcom CONEX BOF IETF 76 Hiroshima Its all about the apps Apps have diverse needs P2P VoIP TV online apps games Filling the pipe while being TCP fair Highspeed congestion control Autotuning the receive window host OS including app bottlenecks ID: 591746
Download Presentation The PPT/PDF document "End-host Perspectives on Congestion Mana..." is the property of its rightful owner. Permission is granted to download and print the materials on this web site for personal, non-commercial use only, and to display it on your personal computer provided you do not modify the materials and that you retain all copyright notices contained in the materials. By downloading content from our website, you accept the terms of this agreement.
Slide1
End-host Perspectives on Congestion Management
Murari Sridharan
muraris@microsoft.com
CONEX BOF, IETF 76, HiroshimaSlide2
Its all about the apps
Apps have diverse needs
P2P, VoIP, TV, online apps, games
Filling the pipe while being TCP fair
High-speed congestion control, Autotuning the receive window, host OS (including app) bottlenecks
Low priority scavenger service
Protocols changes to reduce latency
Multipath transport to maximize link capacity, improve resiliencySlide3
End-host view of the network
Mostly works as expected
Establishing connectivity is sometimes problematic
Largely remains a black box
Congestion, bottleneck capacity is implicitly inferred
Network seems change/risk averse
Imposes complex usage requirements
Volume caps, pay-per-use, metered data plans …Slide4
Network’s view of the end-hosts
End-hosts cannot be trusted, need to be explicitly controlled
Application performance needs can be inferred and improved upon by inspecting packets on the wire
End-hosts typically establish connectivity to well-known servers
And the reality is …Slide5
Splitting at the seams
Devices, Devices, Devices …
IGDs/NATs/Firewalls/DPI devices/Load balancers/Soft switches
Layering violations, RFC non-conformance, no future proofing
Backwards compatibility
Thanks to deep packet inspection you can’t even touch padding bits!
Hampered ECN deployment
New protocols hard or impossible to deploy
No changes to protocol on the wire
Takes time for apps to move to using new APIs
Not all apps need TCP, but only TCP passes reliably E2E
Tunneling, feedback loops & TCP over TCP issues
Network traffic management is a nightmare due to increased appetite for large volumesSlide6
CONEX: Things to consider
Let’s please stop inferring each other.
How can the end-host learn about network policy?
Explicit feedback to/from the network
OS has tons of context than the small amount reflected in the packets
Wireless/Cellular network operators are moving towards usage based models
Tactically, policy based routing/interface selection is the high-order bit
How does the end-host learn about the network policy?Slide7
CONEX: Things to consider
Incremental deployment & incentives
Bottleneck is largely within the home and/or last mile
Congestion exposure doesn’t add any benefit but shouldn’t make it worse
Primal-dual congestion control
Performance is a function of source rate controller, AQM, marking thresholds, congestion measure
Measure of congestion, feedback of congestion measure, and use of congestion measure by the source controller are
all
important.
Beyond TCP – UDP(DCCP) + ECN