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Behavioral model targets

The targets below are not listed in alphabetical order, but roughly by the order of recommendation of their use, from most recommended to least.

simple_switch

This target is a software switch, running on a general purpose CPU such as Intel/AMD/etc., that can execute most P4_14 and P4_16 programs, with only a few restrictions on the features used by those P4 programs.

It implements the P4 features listed below. They correspond to the P4_14 language specification, and also with P4_16 plus the v1model architecture, which is intended to match the architecture defined in the P4_14 language specification:

  • counters
  • meters
  • registers
  • action profiles
  • action selectors
  • several hash and checksum functions
  • pseudo-random number generation
  • digest messages generated by the data plane, sent to the control plane
  • A switch architecture with ingress parser, ingress control, packet buffer with packet replication engine, egress control, and egress deparser.
    • multicast replication
    • cloning/mirroring of packets
    • resubmit packets, from end of ingress back to start of ingress
    • recirculate packets, from end of egress back to start of ingress

This target can accept TCP connections from a controller, where the format of control messages on this connection is defined by a Thrift API. The P4 program loaded into this target can change while it is running, and the target executable need not be recompiled in order to use the new control plane messages for that new P4 program, i.e. the control plane API is program independent (PI).

References:

simple_switch_grpc

This target is based on the simple_switch target described above. The primary difference is that simple_switch_grpc can also accept TCP connections from a controller, where the format of control messages on this connection are defined by the P4Runtime API specification.

simple_switch_grpc can still also accept connections from controllers using the Thrift API, but this is primarily intended for debug purposes. It is recommended that you do not attempt to have multiple controllers controlling the same target device, one controller using the Thrift API, and another using the P4Runtime API. This is not intended to be a useful mode of operation.

psa_switch

This target is similar to the simple_switch described above, except that psa_switch does not use the v1model P4_16 architecture, but instead the Portable Switch Architecture (PSA).

As of November 2018 the implementation is not yet complete. Anyone interested in helping to complete the implementation (which also requires additional work in the P4 compiler p4c) should create an issue in this Github repository, or the one for p4c.

simple_router and l2_switch

These targets were introduced to illustrate how the bmv2 library can be leveraged to implement different architectures. They support much smaller sets of standard metadata, and simple_router does not have an egress control flow. There is no good reason to use these targets over simple_switch as of November 2018, and they cannot be used with P4_16 programs.