diff --git a/hptp-send/src/main.rs b/hptp-send/src/main.rs
index 5461f73..dbd7a98 100644
--- a/hptp-send/src/main.rs
+++ b/hptp-send/src/main.rs
@@ -119,9 +119,11 @@ where
         }
     }
 
-    fn ack(&mut self, seg_idx: SegIdx) {
-        self.unacked_segs.remove(&seg_idx);
-        // TODO: update bounds
+    /// `seg_idxs` should be distinct and in increasing order.
+    fn ack(&mut self, seg_idxs: &[SegIdx]) {
+        for seg_idx in seg_idxs {
+            self.unacked_segs.remove(seg_idx);
+        }
     }
 }
 
@@ -149,13 +151,12 @@ where
 
     let mut store = SegmentStore::new(inp);
     let mut deadline = Instant::now();
-    const DELAY_MS: u64 = 250;
+    const DELAY_MS: u64 = 100;
 
     let mut to_send = vec![];
 
     loop {
         let timer = tokio::time::delay_until(deadline);
-
         let evt = tokio::select!(
             _ = timer => Evt::Timer,
             Ok(m) = peer.recv() => Evt::Recv(m),
@@ -173,15 +174,13 @@ where
                         });
                         Action::Continue
                     }
-                    None => {
-                        log.completed().await;
-                        Action::Quit
-                    }
+                    None => Action::Quit,
                 }
             }
 
-            Evt::Recv(m) => {
-                log.debug_msg(format!("{:?}", m)).await;
+            Evt::Recv(DownMsg::Ack { idxs }) => {
+                log.debug_msg(format!("got acks: {:?}", idxs)).await;
+                store.ack(&idxs);
                 Action::Continue
             }
         };