diff --git a/src/netsleuth/probes/icmp_win.py b/src/netsleuth/probes/icmp_win.py
index 1b242f5..b7a61a7 100644
--- a/src/netsleuth/probes/icmp_win.py
+++ b/src/netsleuth/probes/icmp_win.py
@@ -1,6 +1,7 @@
 from __future__ import annotations
 
 import struct
+from dataclasses import dataclass
 from typing import NamedTuple
 
 IP_SUCCESS = 0
@@ -22,6 +23,16 @@ class IcmpReply(NamedTuple):
     ttl: int
 
 
+@dataclass
+class IcmpRequest:
+    dest: str
+    ttl: int
+    timeout_ms: int
+    payload: bytes = b"netsleuth"
+    source_ip: str | None = None
+    df: bool = False
+
+
 def classify_status(status: int) -> str:
     if status == IP_SUCCESS:
         return "ok"
@@ -128,23 +139,16 @@ def _handle():
     return iphlpapi, handle
 
 
-def echo_once(
-    dest: str,
-    ttl: int,
-    timeout_ms: int,
-    payload: bytes = b"netsleuth",
-    source_ip: str | None = None,
-    df: bool = False,
-) -> IcmpReply:
+def echo_once(req: IcmpRequest) -> IcmpReply:
     iphlpapi, handle = _handle()
     try:
         options = _IpOptionInformation(
-            Ttl=ttl, Tos=0, Flags=IP_FLAG_DF if df else 0, OptionsSize=0, OptionsData=None
+            Ttl=req.ttl, Tos=0, Flags=IP_FLAG_DF if req.df else 0, OptionsSize=0, OptionsData=None
         )
         buffer = ctypes.create_string_buffer(_REPLY_BUFFER_SIZE)
-        address = struct.unpack("<I", socket.inet_aton(dest))[0]
-        if source_ip:
-            source = struct.unpack("<I", socket.inet_aton(source_ip))[0]
+        address = struct.unpack("<I", socket.inet_aton(req.dest))[0]
+        if req.source_ip:
+            source = struct.unpack("<I", socket.inet_aton(req.source_ip))[0]
             count = iphlpapi.IcmpSendEcho2Ex(
                 handle,
                 None,
@@ -152,12 +156,12 @@ def echo_once(
                 None,
                 ctypes.c_uint32(source),
                 ctypes.c_uint32(address),
-                payload,
-                ctypes.c_ushort(len(payload)),
+                req.payload,
+                ctypes.c_ushort(len(req.payload)),
                 ctypes.byref(options),
                 buffer,
                 ctypes.c_uint32(_REPLY_BUFFER_SIZE),
-                ctypes.c_uint32(timeout_ms),
+                ctypes.c_uint32(req.timeout_ms),
             )
         else:
             count = iphlpapi.IcmpSendEcho2(
@@ -166,12 +170,12 @@ def echo_once(
                 None,
                 None,
                 ctypes.c_uint32(address),
-                payload,
-                ctypes.c_ushort(len(payload)),
+                req.payload,
+                ctypes.c_ushort(len(req.payload)),
                 ctypes.byref(options),
                 buffer,
                 ctypes.c_uint32(_REPLY_BUFFER_SIZE),
-                ctypes.c_uint32(timeout_ms),
+                ctypes.c_uint32(req.timeout_ms),
             )
         if count == 0:
             return IcmpReply(address=None, status=IP_REQ_TIMED_OUT, rtt_ms=None, ttl=0)
@@ -189,7 +193,9 @@ def ping_samples_win(
     for index in range(count):
         if index:
             time.sleep(interval)
-        reply = echo_once(dest, ttl=128, timeout_ms=timeout_ms, source_ip=source_ip)
+        reply = echo_once(
+            IcmpRequest(dest=dest, ttl=128, timeout_ms=timeout_ms, source_ip=source_ip)
+        )
         samples.append(reply.rtt_ms if classify_status(reply.status) == "ok" else None)
     return samples
 
@@ -212,7 +218,9 @@ def trace_hops_win(
     for ttl in range(1, max_hops + 1):
         if time.monotonic() >= deadline:
             break
-        reply = echo_once(address, ttl=ttl, timeout_ms=per_hop_timeout_ms, source_ip=source_ip)
+        reply = echo_once(
+            IcmpRequest(dest=address, ttl=ttl, timeout_ms=per_hop_timeout_ms, source_ip=source_ip)
+        )
         hops.append((ttl, reply))
         if classify_status(reply.status) == "ok":
             break
diff --git a/src/netsleuth/probes/pmtud.py b/src/netsleuth/probes/pmtud.py
index 2c572db..38f9f77 100644
--- a/src/netsleuth/probes/pmtud.py
+++ b/src/netsleuth/probes/pmtud.py
@@ -69,13 +69,22 @@ def supports_df() -> tuple[bool, str]:
 async def _probe_windows(
     resolved_ip: str, size: int, timeout: float, source_ip: str | None
 ) -> tuple[bool, bool]:
-    from netsleuth.probes.icmp_win import classify_status, echo_once
+    from netsleuth.probes.icmp_win import IcmpRequest, classify_status, echo_once
 
     payload = b"\x00" * max(0, size - _IPV4_ICMP_OVERHEAD)
     timeout_ms = int(timeout * 1000)
 
     def _run():
-        return echo_once(resolved_ip, ttl=64, timeout_ms=timeout_ms, payload=payload, source_ip=source_ip, df=True)
+        return echo_once(
+            IcmpRequest(
+                dest=resolved_ip,
+                ttl=64,
+                timeout_ms=timeout_ms,
+                payload=payload,
+                source_ip=source_ip,
+                df=True,
+            )
+        )
 
     reply = await asyncio.to_thread(_run)
     kind = classify_status(reply.status)
diff --git a/tests/test_icmp_win_trace.py b/tests/test_icmp_win_trace.py
index 2bbcc2b..17034bd 100644
--- a/tests/test_icmp_win_trace.py
+++ b/tests/test_icmp_win_trace.py
@@ -3,7 +3,7 @@ from __future__ import annotations
 import time
 from unittest.mock import patch
 
-from netsleuth.probes.icmp_win import IP_REQ_TIMED_OUT, IcmpReply, trace_hops_win
+from netsleuth.probes.icmp_win import IP_REQ_TIMED_OUT, IcmpReply, IcmpRequest, trace_hops_win
 
 
 def _fake_gethostbyname(host: str) -> str:
@@ -19,9 +19,9 @@ def test_trace_hops_win_total_elapsed_is_bounded_by_the_total_budget_not_hops_ti
     # to the 100ms total budget.
     call_timeouts: list[int] = []
 
-    def fake_echo_once(dest: str, ttl: int, timeout_ms: int, payload: bytes = b"netsleuth", source_ip=None) -> IcmpReply:
-        call_timeouts.append(timeout_ms)
-        time.sleep(timeout_ms / 1000.0)
+    def fake_echo_once(req: IcmpRequest) -> IcmpReply:
+        call_timeouts.append(req.timeout_ms)
+        time.sleep(req.timeout_ms / 1000.0)
         return IcmpReply(address=None, status=IP_REQ_TIMED_OUT, rtt_ms=None, ttl=0)
 
     with (
@@ -43,8 +43,8 @@ def test_trace_hops_win_total_elapsed_is_bounded_by_the_total_budget_not_hops_ti
 def test_trace_hops_win_per_hop_timeout_is_capped_even_for_a_huge_total_budget():
     call_timeouts: list[int] = []
 
-    def fake_echo_once(dest: str, ttl: int, timeout_ms: int, payload: bytes = b"netsleuth", source_ip=None) -> IcmpReply:
-        call_timeouts.append(timeout_ms)
+    def fake_echo_once(req: IcmpRequest) -> IcmpReply:
+        call_timeouts.append(req.timeout_ms)
         return IcmpReply(address=None, status=IP_REQ_TIMED_OUT, rtt_ms=None, ttl=0)
 
     with (
@@ -62,9 +62,9 @@ def test_trace_hops_win_per_hop_timeout_is_capped_even_for_a_huge_total_budget()
 def test_trace_hops_win_happy_path_hop_count_and_ok_break_are_unchanged():
     from netsleuth.probes.icmp_win import IP_SUCCESS
 
-    def fake_echo_once(dest: str, ttl: int, timeout_ms: int, payload: bytes = b"netsleuth", source_ip=None) -> IcmpReply:
-        if ttl < 3:
-            return IcmpReply(address=f"10.0.0.{ttl}", status=IP_REQ_TIMED_OUT, rtt_ms=None, ttl=0)
+    def fake_echo_once(req: IcmpRequest) -> IcmpReply:
+        if req.ttl < 3:
+            return IcmpReply(address=f"10.0.0.{req.ttl}", status=IP_REQ_TIMED_OUT, rtt_ms=None, ttl=0)
         return IcmpReply(address="203.0.113.1", status=IP_SUCCESS, rtt_ms=5.0, ttl=64)
 
     with (