Optimising Streaming Systems with SDN/P4/NetFPGA T. Khoa Phan University College London NetFPGA Summit, Cambrige, April 2017.

Facebook Livestream System Origin server Edge cache Live stream server INTERNET Edge cache Origin server Looking at this pic, the bottle neck now is between the edge cache and users because the edge cache has to send every stream for every user. Given almost 2 billions active FB users, this scalability is still not enough. The question is can we design a network protocol for the edge cache to serve users in a more efficient way. To do that, let me zoom in the connection between the edge cache and users. Facebook livestream system – Content Delivery Network [1] Each edge cache can serve up to 200,000 users simultaneously [1] https://code.facebook.com/posts/1653074404941839/under-the-hood-broadcasting-live-video-to-millions/

Unicast vs. Multicast Network Edge cache Today’s unicast network Edge cache IP Multicast Edge cache Xcast Treemap First standardized in 1986. One stream for all receivers. Need multicast routers everywhere (or complex tunneling techniques). Can work for any streaming systems. Source code: github.com/ptkhoa1984/Xcast6_Treemap

Xcast treemap part (optional) What is Xcast Treemap? S A B C D E Breath-first tree traversal A B C D E List of IP addresses 2 Treemap Sender S creates packets: A B C D E Src: S, Dest: A Payload 2 Unicast part Xcast treemap part (optional) Today router only understands unicast part. Xcast router lookups and forwards for each IP in the list.

How Xcast Treemap works? Unicast routing table at R3 Dest Next hop C D E Full Xcast packet header created by S: D A B A | A B C D E D | D B | B S C Today routers don’t see the list of destination. To sum up: for today Internet, if users install Xcast Treemap in the computers, it will send data like the overlay tree defined by the sender. R1 R2 R3 C | C D E E | E C | C D E Dest Next hop A B, C, D, E R2 E Today router Fig. 1: only today routers Unicast routing table at R1

How Xcast Treemap works? Unicast routing table at R3 Dest Next hop C D E Full Xcast packet header created by S: B D A A | A B C D E D | D B | B C | C S C R1 R2 R3 C doesn’t need to forward ptk to D and E. It has been done automatically by Xcast router and network layer multicast is much better than P2P My messages: no matter if there’re Xcast router on the network or not. If there are, no matter where they are, Xcast guarantee that all hosts will receive the pkt correctly. Xcast Treemap is a stateless protocol: no states at routers and no state at end-hosts, everything is in the packet header. C | C D E E | E C | C D E Dest Next hop A B, C, D, E R2 E Xcast router Today router Unicast routing table at R1 Fig. 2: mixture of Xcast and today routers

Facebook Livestream System current system with Xcast Treemap Edge cache server and users

Xcast Treemap with SDN S A B C S A B C Shortest path routing SDN controller S B A C R2 R1 S A X3 B C Overlay tree by SDN controller Traffic engineering for Xcast traffic

Future work with P4/NetFPGA Current approach for Xcast router: Plugin additional network cards for a computer Install Xcast router software on FreeBSD Future work for Xcast router: P4/C#/NetFPGA Xcast router Other possible platforms?

Deployment Scenarios With Xcast NetFPGA gateway Only with Xcast end-hosts With Xcast backbone routers

Thank you!!! Email: t.phan@ucl.ac.uk

Xcast Treemap Evaluation In P2P, packet loss happens when end-hosts leave (e.g. A leaves and B replaces A in the tree – hosts need to update fwd table in their memory). Without Xcast router: sender S sends pkt with new treemap header, there’s no fwd table at hosts. With all Xcast router: pkts are replicated at routers, no pkt loss when hosts join/leave. S A P2P system B C P2P system Xcast: without Xcast router All routers are Xcast routers

Xcast Treemap with SDN S A B C S A B C Shortest path routing SDN controller S B A C R2 R1 S A X3 B C Overlay tree by SDN controller Traffic engineering for Xcast traffic