Glossary

P4 ecosystem

P4_16

The current major version of the P4 language (the data-plane programming language). p4net only consumes P4_16 sources.

v1model

The reference P4 architecture used by BMv2's simple_switch / simple_switch_grpc. Defines the parser → ingress → traffic-manager → egress → deparser shape p4net assumes.

PSA

Portable Switch Architecture. A more capable v1model successor. p4net does not target PSA in v0.x; see Roadmap.

p4c

The reference P4 compiler. p4net invokes p4c -b bmv2 --p4runtime-files=p4info.txtpb to produce both the BMv2 JSON and the P4Info description.

P4Info

A protobuf message describing a compiled P4 program's tables, actions, counters, registers, and controller-header layouts. Lets a generic P4Runtime client target a specific pipeline by name.

BMv2

Behavioral Model version 2 — the reference software P4 dataplane. simple_switch_grpc is the v1model BMv2 binary with P4Runtime server enabled.

simple_switch_grpc

The specific BMv2 binary p4net uses. Listens on a configurable gRPC port (default 50051) for P4Runtime, plus an optional Thrift port (default 9090) for direct dataplane debugging.

P4Runtime

The standard control-plane protocol for P4 dataplanes. Defined in a protobuf schema; rides on gRPC. Covers pipeline configuration, table CRUD, counter reads, register reads, multicast group management, and a StreamChannel for asynchronous packet I/O.

P4 dataplane primitives

Match-Action Table

A table of (match key) → (action, params) entries. The packet's field values match an entry; the entry's action runs with the stored params.

LPM

Longest Prefix Match. A match-key type used for IP routing tables; entries are (prefix, prefix_length).

Ternary

Match-key type for value-and-mask matches (any subset of bits cared about). Requires a priority field for disambiguation.

Range

Match-key type for value-in-[low, high] matches. Requires a priority.

Exact

Match-key type for exact equality.

Action

A P4 routine that runs when a table entry matches; modifies headers, picks egress port, etc. Can be parameterised (set_egress_port(bit<9> port)).

Counter

A P4-side packet/byte counter. Direct counters are bound to a table; indirect counters are standalone arrays addressed by a 32-bit index.

Control-plane concepts

Control plane

The component(s) that decide what the dataplane should do — install table entries, read counters, react to packet-in events. For p4net, the control plane is your Python topology + setup code.

Data plane

The component that processes individual packets at line rate. For p4net, the dataplane is simple_switch_grpc.

Pipeline

The compiled dataplane program currently running on a switch (parser + controls + deparser). Pushed via P4Runtime's SetForwardingPipelineConfig.

Election ID

A 128-bit number that orders P4Runtime controllers competing for primary mastership. Highest election ID wins. p4net uses millisecond-since-epoch so re-running the same script always claims primary.

Mastership

Which controller holds the primary role for a device. P4Runtime allows one primary writer at a time.

Linux networking

Network namespace (netns)

A kernel-isolated network stack: separate interfaces, routing tables, IP addresses, neighbor caches. p4net puts each host in its own.

veth pair

A pair of virtual Ethernet interfaces wired to each other — packets out one show up on the other. p4net uses these to wire hosts (in their namespace) to switches (in the root namespace).

qdisc

Queueing discipline. Linux's traffic-control state machine on an interface; controls scheduling, shaping, dropping.

netem

Network emulation qdisc — adds configurable delay, jitter, loss, reorder, corruption.

tc

The userspace tool that programs qdisc. p4net shells out to tc qdisc add ... root netem ... from p4net.runtime.apply_netem.

sysctl

The userspace tool that reads/writes kernel /proc/sys knobs. p4net uses sysctl -w net.ipv6.conf.<iface>.disable_ipv6=... for its per-interface IPv6 gate.

Link-local address

A non-routable IPv6 address (fe80::/10) that interfaces auto-generate when IPv6 is enabled. p4net suppresses these on interfaces that don't ask for IPv6.

SLAAC

StateLess Address AutoConfiguration — IPv6 hosts deriving addresses from Router Advertisements. Disabled by default in p4net (accept_ra=0, autoconf=0) so explicitly assigned addresses are the only ones present.

ND (Neighbor Discovery)

IPv6's analogue of ARP. Resolves IPv6 addresses to MACs.

ARP

Address Resolution Protocol. Resolves IPv4 addresses to MACs. p4net's examples seed static ARP entries because BMv2 has no built-in ARP responder.

Tooling and packaging

PyPI

The Python Package Index. p4net publishes wheels here as p4net.

MkDocs

The static-site generator p4net uses for this documentation site.

Material for MkDocs

The MkDocs theme used here. Provides search, dark mode, social cards, and the navigation chrome.

mkdocstrings

The MkDocs plugin that generates the API reference from Python docstrings.

Graphviz DOT

The graph description language Topology.to_graphviz() emits. The dot command renders DOT to PNG/SVG/PDF.