RSSI Protocol

RSSI (Reliable Streaming Service Interface) provides reliable, in-order stream delivery over lower layers that are not inherently reliable (for example UDP). Rogue’s RSSI implementation uses sequence/acknowledge exchange, retransmission, timeout handling, and negotiated link parameters to maintain a stable stream. Conceptually, RSSI is based on the Reliable Data Protocol lineage defined by RFC 908 and RFC 1151.

Protocol documentation

RSSI protocol reference: https://confluence.slac.stanford.edu/x/1IyfD
Additional SLAC RSSI notes: https://confluence.slac.stanford.edu/x/xovOCw

The protocol reference links to the relevant RFC background used by RSSI’s reliability model (sequencing, acknowledgments, retransmission, and timeout behavior).

How RSSI classes fit together

The rogue::protocols::rssi classes are layered as follows:

Client / Server: convenience wrappers that instantiate and wire the full stack for each role.
Controller: the protocol state machine; performs handshake, negotiation, ACK handling, retransmission policy, and flow-control decisions.
Transport: lower stream edge carrying RSSI frames to/from the underlying transport link.
Application: upper stream edge carrying payload frames to/from application protocols.
Header: helper codec/container for parsing and encoding RSSI frame headers.

Typical stream topology:

[Underlying link] <-> Transport <-> Controller <-> Application <-> [Upper protocol]

Python usage example

In most PyRogue applications, RSSI links are created with pyrogue.protocols.UdpRssiPack. This helper bundles UDP socket transport, RSSI protocol endpoints, and packetizer wiring into a single object. It is implemented as a pyrogue.Device, so RSSI link/status variables are exposed directly in the PyRogue tree. For wrapper details, see Network Wrapper. For typical FPGA-facing links, instantiate it in client mode (server=False).

import pyrogue as pr
import pyrogue.protocols
import rogue.protocols.srp

class MyRoot(pr.Root):
    def __init__(self):
        super().__init__(name='MyRoot')

        self.add(pyrogue.protocols.UdpRssiPack(
            name='Net',
            server=False,
            host='10.0.0.5',
            port=8192,
            jumbo=True,
            packVer=2,
            enSsi=True,
        ))
        self.addInterface(self.Net)

        srp = rogue.protocols.srp.SrpV3()
        self.Net.application(dest=0) == srp

        # Example device using SRP as memBase
        # self.add(MyDevice(name='Dev', offset=0x0, memBase=srp))

For advanced debugging or custom wiring, you can still instantiate each layer explicitly. The following pattern is used in wrappers such as python/pyrogue/protocols/_Network.py:

import rogue.protocols.udp
import rogue.protocols.rssi
import rogue.protocols.packetizer

# Server side
s_udp = rogue.protocols.udp.Server(0, True)
s_rssi = rogue.protocols.rssi.Server(s_udp.maxPayload() - 8)
s_pack = rogue.protocols.packetizer.CoreV2(True, True, True)

s_udp == s_rssi.transport()
s_rssi.application() == s_pack.transport()

# Client side
c_udp = rogue.protocols.udp.Client("127.0.0.1", s_udp.port(), True)
c_rssi = rogue.protocols.rssi.Client(c_udp.maxPayload() - 8)
c_pack = rogue.protocols.packetizer.CoreV2(True, True, True)

c_udp == c_rssi.transport()
c_rssi.application() == c_pack.transport()

# Start RSSI state machines (Python binding names)
s_rssi._start()
c_rssi._start()

RSSI Protocol

Protocol documentation

How RSSI classes fit together

Python usage example

See also