P 4 specifying data planes http P 4

P 4: specifying data planes http: //P 4. org netdev 0. 1 Ottawa, February 15, 2015 Mihai Budiu

P 4 Language Consortium • “Open for participation by any individual or corporation” • http: //p 4. org • Language spec v 1. 0. 1 • Coming soon (3/2015): FOSS release of a reference P 4 implementation 2

What do we want to achieve? Switch Currently most useful if you have your own network playground Standard protocols Your own protocols Datacenter 3

Benefits • Implement (new) protocols • Vx. LAN: 175 lines of code • NVGRE: 183 lines of code • Low overhead (high speed) • Flexible forwarding policies • Improved signaling, monitoring, and troubleshooting • Change functionality with software upgrades • Use only what you need 4

P 4 Scope Traditional switch P 4 -defined switch Control plane Data plane Control plane Table mgmt Control traffic Packets P 4 Program P 4 table mgmt Data plane 5

Q: Which data plane? A: Any data plane! Control plane Programmable switches FPGA switches Programmable NICs Software switches You name it… Data plane 6

Data plane programmability Programmable blocks Data plane P 4 P 4 Fixed function 7

How does it work? Programmable parser eth vlan ipv 4 Headers Payload Packet (byte[]) Programmable match-action units eth ipv 4 mtag err port bcast Queueing Metadata Headers eth mtag ipv 4 Programmable reassembly Packet 8

P 4 language Programmable parser State-machine; bitfield extraction Programmable match-action units Table lookup and update; bitfield manipulation; control flow Programmable reassembly Bitfield assembly No: memory (pointers), loops, recursion, floating point 9

Parsing = State machines header_type ethernet_t { fields { dst. Addr : 48; src. Addr : 48; ether. Type : 16; } } Eth VLAN IPv 4 IPv 6 TCP New parser parse_ethernet { extract(ethernet); return select(latest. ether. Type) { 0 x 8100 : parse_vlan; 0 x 800 : parse_ipv 4; 0 x 86 DD : parse_ipv 6; } } 10

Match � table ipv 4_lpm { reads { ipv 4. dst. Addr : lpm; } actions { set_next_hop; drop; } } Lookup key dst. Addr action 0. * drop 10. 0. 0. * set_next_hop 224. * drop 192. 168. * drop 10. 0. 1. * set_next_hop 11

Actions action set_nhop(nhop_ipv 4_addr, port) { modify_field(metadata. nhop_ipv 4_addr, nhop_ipv 4_addr); modify_field(standard_metadata. egress_port, port); add_to_field(ipv 4. ttl, -1); } dst. Addr action 0. * drop 10. 0. 0. * set_next_hop 224. * drop 192. 168. * drop 10. 0. 1. * set_next_hop nhop_ipv 4_addr port 10. 0. 0. 10 1 10. 0. 1. 10 2 12

Control-Flow M/A control ingress { apply(port); M/A if (valid(vlan_tag[0])) { apply(port_vlan); } apply (bridge_domain); M/A if (valid(mpls_bos)) { apply(mpls_label); } M/A retrieve_tunnel_vni(); if (valid(vxlan) or valid(genv) or valid(nvgre)) { apply(dest_vtep); M/A apply(src_vtep); } } 13

Reassembly • Driven by header types • add_header(ipv 6); • remove_header(vlan); 14

Table contents management Control plane Manage tables contents (Tied to P 4 program) Data plane 15

P 4 Summary • Simple language • Parsing, bit-field manipulation, table lookup, control flow, packet reassembly • • • Efficient execution (high speed switching) Simple cost model Abstract resources Portable Expressive: • New protocols, forwarding policies, monitoring and instrumentation 16

Control plane The P 4 Programming. Language Interface Data plane 17