diff --git a/CHANGELOG.md b/CHANGELOG.md
index 50f90a1..aa577f7 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,7 @@
+## unreleased
+
+*   warn when connecting via TCP to a known-broken live555 server version.
+
 ## `v0.3.0` (2021-08-31)
 
 *   BREAKING CHANGE: [#30](https://github.com/scottlamb/retina/issues/30):
diff --git a/src/client/mod.rs b/src/client/mod.rs
index 18a4e64..e91417a 100644
--- a/src/client/mod.rs
+++ b/src/client/mod.rs
@@ -216,6 +216,9 @@ pub struct Presentation {
     base_url: Url,
     pub control: Url,
     pub accept_dynamic_rate: bool,
+
+    /// Session-level `a:tool` from SDP.
+    tool: Option<Box<str>>,
 }
 
 /// Information about a stream offered within a presentation.
@@ -908,6 +911,17 @@ impl Session<Described> {
                 "must SETUP before PLAY".into()
             ))
         })?;
+        if let Some(tool) = inner.presentation.tool.as_deref() {
+            if matches!(inner.options.transport, Transport::Tcp) && has_live555_tcp_bug(tool) {
+                warn!(
+                    "Connecting via TCP to known-broken RTSP server {:?}. \
+                       See <https://github.com/scottlamb/retina/issues/17>. \
+                       Consider using UDP instead!",
+                    tool
+                );
+            }
+        }
+
         trace!("PLAY with channel mappings: {:#?}", &inner.conn.channels);
         let (msg_ctx, cseq, response) = inner
             .conn
@@ -1022,6 +1036,17 @@ impl Session<Described> {
     }
 }
 
+/// Checks if the `tool` entry refers to a live555 version affected by
+/// [#17](https://github.com/scottlamb/retina/issues/17).
+fn has_live555_tcp_bug(tool: &str) -> bool {
+    const PREFIX: &str = "LIVE555 Streaming Media v";
+    if !tool.starts_with(PREFIX) {
+        return false;
+    }
+    let version = &tool[PREFIX.len()..];
+    version > "0000.00.00" && version < "2017.06.04"
+}
+
 /// Sends dummy RTP and RTCP packets to punch a hole in connection-tracking
 /// firewalls.
 ///
@@ -1748,4 +1773,13 @@ mod tests {
             println!("{:-40} {:4}", name, size);
         }
     }
+
+    #[test]
+    fn check_live555_tcp_bug() {
+        assert!(!has_live555_tcp_bug("not live555"));
+        assert!(!has_live555_tcp_bug("LIVE555 Streaming Media v"));
+        assert!(has_live555_tcp_bug("LIVE555 Streaming Media v2013.04.08"));
+        assert!(!has_live555_tcp_bug("LIVE555 Streaming Media v2017.06.04"));
+        assert!(!has_live555_tcp_bug("LIVE555 Streaming Media v2020.01.01"));
+    }
 }
diff --git a/src/client/parse.rs b/src/client/parse.rs
index 2ad1a9e..4082de2 100644
--- a/src/client/parse.rs
+++ b/src/client/parse.rs
@@ -417,6 +417,7 @@ pub(crate) fn parse_describe(
         .unwrap_or(Ok(request_url.clone()))?;
 
     let mut control = None;
+    let mut tool = None;
     for a in &sdp.attributes {
         if a.key == "control" {
             control = a
@@ -425,6 +426,8 @@ pub(crate) fn parse_describe(
                 .map(|c| join_control(&base_url, c))
                 .transpose()?;
             break;
+        } else if a.key == "tool" {
+            tool = a.value.as_deref().map(Into::into);
         }
     }
     let control = control.unwrap_or(request_url);
@@ -447,6 +450,7 @@ pub(crate) fn parse_describe(
         base_url,
         control,
         accept_dynamic_rate,
+        tool,
     })
 }
 
@@ -825,6 +829,10 @@ mod tests {
         let base = "rtsp://192.168.5.206/h264Preview_01_main/";
         assert_eq!(p.control.as_str(), base);
         assert!(!p.accept_dynamic_rate);
+        assert_eq!(
+            p.tool.as_deref(),
+            Some("LIVE555 Streaming Media v2013.04.08")
+        );
 
         assert_eq!(p.streams.len(), 2);
 
@@ -967,6 +975,10 @@ mod tests {
         let p = parse_describe(prefix, include_bytes!("testdata/foscam_describe.txt")).unwrap();
         assert_eq!(p.control.as_str(), &(prefix.to_string() + "/"));
         assert!(!p.accept_dynamic_rate);
+        assert_eq!(
+            p.tool.as_deref(),
+            Some("LIVE555 Streaming Media v2014.02.10")
+        );
 
         assert_eq!(p.streams.len(), 2);