DBUF

A downlink buffering agent for the UP4 architecture.

Running DBUF

go run cmd/dbuf/main.go

Run with -help for a full list of available flags and descriptions.

DBUF client simulator

DBUF comes with a simulated client that connects to the API and sends data plane packets:

go run cmd/dbuf-client/main.go --demo

Controlplane API

The northbound API is defined in dbuf.proto.

Design

DBUF is:

• Golang microservice with gRPC northbound interface

• Per UE, in memory packet buffer

  • No persistence, inspection, filtering or reordering

• Layer 4 service on Linux networking stack (UDP sockets)

  • GTP/UDP/IP encoding for data plane packets from and to Tofino switches

• Exposing telemetry about system and queue state (e.g. load) via prometheus

Terminology

Packet

A sequence of bytes received on the dataplane interfaces.

Queue

A sequential container storing packets for a single UE. Identified by its ID or the UE's IP address.

QueueManager

Manages queues and notifies clients about queue events.

Buffer

TODOs

• Delete unused queues after a timeout
• Maybe introduce a release delay to prevent overloading downstream
• Use strings for IP addresses when possible, e.g. ModifyQueue message, notifications
• Expose dataplane addresses over gRPC
• Expose queue stats in json and prometheus
• Decide if ReleasePackets should be blocking until drained and if it should lock the queue the whole time (blocking new packets)
• Export monitoring statistics
  • Linux interface drop counter
  • Used / free buffers, queues, memory
• Preallocate memory for packets