1. P4 (Programming Protocol-independent Packet Processors)
Seyeon Jeong
DPNM lab, Dept. of CSE, POSTECH

2. Introduction OpenFlow was simple Over the past years
A single flow rule table
Matching on any of 12 fields of the incoming packet
MAC addr., IP addr., Transport protocol, …
Over the past years
Still not enough to support many encapsulation techniques
Version
Date
# header fields
OF 1.0
Dec 2009
12 (Ethernet, TCP, IPv4)
OF 1.1
Feb 2011
15 (MPLS, inter-table meta data)
OF 1.2
Dec 2011
36 (ARP, ICMP, IPv6, etc.)
OF 1.3
Jun 2012 40
OF 1.4
Oct 2013 41
OF 1.5
Dec 2014 45

3. Introduction OF switches must be updated to support
Latest features of the newest version
Difficulties in maintenance, compatibility, …
Where does it stop?
People think that future SDN(/OpenFlow) switches must have
Configurable packet parser
Not tied to a specific header format (protocol)!
Flexible match+action tables
General packet-processing primitives

4. Introduction New generation of switch ASICs
Intel FlexPipe
RMT [SIGCOMM’ 13]
Cisco Doppler
But, programming these chips is hard
Custom, vendor-specific interface
Low-level programming like microcode
We need a higher-level interface!
P4 (Programming Protocol-independent Packet Processors) language + P4 compiler

5. P4 language
P4 language
Provides a single means of configuration to packet forwarding
Based on an abstract forwarding model
With a programmable parser
Allows the definition of arbitrary headers and fields
Provides a context for match+action definitions

6. P4 language

7. P4 language Header and Fields
Fields have a (bitwise) width and other attributes
Headers are collections of fields
Like an instantiated class in Java

8. P4 language Parser Extracts header instances
Selects a next “state” by returning another parser function

9. P4 language Match + Action table
Parsed representation of headers give context for processing of the packets
An action function consists of several primitive actions

10. P4 as Open Source Project

11. OpenFlow + P4 “Classic” OpenFlow 1.x OpenFlow 2.0 SDN Control Plane
“Classic” OpenFlow 1.x
OpenFlow 2.0
SDN Control Plane
SDN Control Plane
Configuring:
Parser, tables, and control flow
(P4 program)
Populating:
Installing and querying rules
Installing and querying rules
Parser &
Table conf.
Rule Translator
P4 Compiler
Target Switch
Target Switch

12. Conclusion P4 in a nutshell An alternate future of OpenFlow 1.x
Protocol independence
Target independence
Reconfigurability in the field
Simple language
Programmable parser
Match + Action tables
Control flow (packet processing pipeline)
C-like syntax
Multiple companies have written the compilers

13. Q&A