Lecture 6 - SDN P4

Question 1

Why Program Data Planes?

Answer 1

• Fixed function ASICs (chips)
• Features are either supported or not
• Slow cycle of innovation (creating new chips)
• “Closed Source”

Question 2

What are some problems that require programming data planes?

Answer 2

• No ASICs for special use-cases
• Expensive “change requests” only the vendor can modify drivers or behavior

Question 3

Which planes are programmable?

Answer 3

Both Control and Data plane

Question 4

What are the traits of FPGAs?

Answer 4

Field Programmable Gate Array
- Any Boolean Logic
- Registers
- Memory
- SerDes capabilities
- Reconfigurable

Question 5

Name some hardware description languages and 2 compilers for FPGS.

Answer 5

• Verilog
• VHDL
• BlueSpec

Compilers:
- C
- P4

Question 6

What’s the P4 language goal?

Answer 6

An open source language allowing the specification of packet processing logic

• Reconfigurability - Change how switches process packets
• Protocol independence - Switches are not to be tied to any specific network protocols
• Target independence - Description packet-processing functionality independent of the underlying hardware

Question 7

What’s the P4_14 reference pipeline?

Answer 7

• Parser and Deparser
• Ingress and Egress Pipeline
  — Used for packet processing
  — P4 Programmable
• Packet buffer

Question 8

What are the disadvantages of P4_14?

Answer 8

• Fixed pipeline
• Only one parser (no deparser)
• Poor expressivity
• Fixed “table->Action” Construct
• No “special functions”

Question 9

Name P4_16 design goals

Answer 9

• Incremental Change
• Expressivity
• Support for many targets
• Simplicity
• Modularity
• Extensibility
• Robustness

Question 10

What’s the P4_16 reference pipeline?

Answer 10

• No fixed pipeline
• N programmable blocks
• P4_14 compatibility? - Yes 2 programmable and 1 fixed function block
• Smart NICs, FPGAs, p4-ASICs…

Question 11

Steps of the P4_16 Parser?

Answer 11

1. Define header types
2. Structure header stack
3. Parse headers