diff --git a/alts/src/generated/main/grpc/io/grpc/alts/internal/HandshakerServiceGrpc.java b/alts/src/generated/main/grpc/io/grpc/alts/internal/HandshakerServiceGrpc.java
index 792ab80d99..58789fb447 100644
--- a/alts/src/generated/main/grpc/io/grpc/alts/internal/HandshakerServiceGrpc.java
+++ b/alts/src/generated/main/grpc/io/grpc/alts/internal/HandshakerServiceGrpc.java
@@ -94,8 +94,12 @@ public final class HandshakerServiceGrpc {
 
     /**
      * <pre>
-     * Accepts a stream of handshaker request, returning a stream of handshaker
-     * response.
+     * Handshaker service accepts a stream of handshaker request, returning a
+     * stream of handshaker response. Client is expected to send exactly one
+     * message with either client_start or server_start followed by one or more
+     * messages with next. Each time client sends a request, the handshaker
+     * service expects to respond. Client does not have to wait for service's
+     * response before sending next request.
      * </pre>
      */
     public io.grpc.stub.StreamObserver<io.grpc.alts.internal.Handshaker.HandshakerReq> doHandshake(
@@ -136,8 +140,12 @@ public final class HandshakerServiceGrpc {
 
     /**
      * <pre>
-     * Accepts a stream of handshaker request, returning a stream of handshaker
-     * response.
+     * Handshaker service accepts a stream of handshaker request, returning a
+     * stream of handshaker response. Client is expected to send exactly one
+     * message with either client_start or server_start followed by one or more
+     * messages with next. Each time client sends a request, the handshaker
+     * service expects to respond. Client does not have to wait for service's
+     * response before sending next request.
      * </pre>
      */
     public io.grpc.stub.StreamObserver<io.grpc.alts.internal.Handshaker.HandshakerReq> doHandshake(
diff --git a/alts/src/generated/main/java/io/grpc/alts/internal/Handshaker.java b/alts/src/generated/main/java/io/grpc/alts/internal/Handshaker.java
index 63f1b29e88..03d7887687 100644
--- a/alts/src/generated/main/java/io/grpc/alts/internal/Handshaker.java
+++ b/alts/src/generated/main/java/io/grpc/alts/internal/Handshaker.java
@@ -2103,7 +2103,7 @@ public final class Handshaker {
     /**
      * <pre>
      * (Optional) Endpoint information of the remote server, such as IP address,
-     * port number, and network protocool.
+     * port number, and network protocol.
      * </pre>
      *
      * <code>.grpc.gcp.Endpoint remote_endpoint = 7;</code>
@@ -2112,7 +2112,7 @@ public final class Handshaker {
     /**
      * <pre>
      * (Optional) Endpoint information of the remote server, such as IP address,
-     * port number, and network protocool.
+     * port number, and network protocol.
      * </pre>
      *
      * <code>.grpc.gcp.Endpoint remote_endpoint = 7;</code>
@@ -2121,7 +2121,7 @@ public final class Handshaker {
     /**
      * <pre>
      * (Optional) Endpoint information of the remote server, such as IP address,
-     * port number, and network protocool.
+     * port number, and network protocol.
      * </pre>
      *
      * <code>.grpc.gcp.Endpoint remote_endpoint = 7;</code>
@@ -2615,7 +2615,7 @@ public final class Handshaker {
     /**
      * <pre>
      * (Optional) Endpoint information of the remote server, such as IP address,
-     * port number, and network protocool.
+     * port number, and network protocol.
      * </pre>
      *
      * <code>.grpc.gcp.Endpoint remote_endpoint = 7;</code>
@@ -2626,7 +2626,7 @@ public final class Handshaker {
     /**
      * <pre>
      * (Optional) Endpoint information of the remote server, such as IP address,
-     * port number, and network protocool.
+     * port number, and network protocol.
      * </pre>
      *
      * <code>.grpc.gcp.Endpoint remote_endpoint = 7;</code>
@@ -2637,7 +2637,7 @@ public final class Handshaker {
     /**
      * <pre>
      * (Optional) Endpoint information of the remote server, such as IP address,
-     * port number, and network protocool.
+     * port number, and network protocol.
      * </pre>
      *
      * <code>.grpc.gcp.Endpoint remote_endpoint = 7;</code>
@@ -4291,7 +4291,7 @@ public final class Handshaker {
       /**
        * <pre>
        * (Optional) Endpoint information of the remote server, such as IP address,
-       * port number, and network protocool.
+       * port number, and network protocol.
        * </pre>
        *
        * <code>.grpc.gcp.Endpoint remote_endpoint = 7;</code>
@@ -4302,7 +4302,7 @@ public final class Handshaker {
       /**
        * <pre>
        * (Optional) Endpoint information of the remote server, such as IP address,
-       * port number, and network protocool.
+       * port number, and network protocol.
        * </pre>
        *
        * <code>.grpc.gcp.Endpoint remote_endpoint = 7;</code>
@@ -4317,7 +4317,7 @@ public final class Handshaker {
       /**
        * <pre>
        * (Optional) Endpoint information of the remote server, such as IP address,
-       * port number, and network protocool.
+       * port number, and network protocol.
        * </pre>
        *
        * <code>.grpc.gcp.Endpoint remote_endpoint = 7;</code>
@@ -4338,7 +4338,7 @@ public final class Handshaker {
       /**
        * <pre>
        * (Optional) Endpoint information of the remote server, such as IP address,
-       * port number, and network protocool.
+       * port number, and network protocol.
        * </pre>
        *
        * <code>.grpc.gcp.Endpoint remote_endpoint = 7;</code>
@@ -4357,7 +4357,7 @@ public final class Handshaker {
       /**
        * <pre>
        * (Optional) Endpoint information of the remote server, such as IP address,
-       * port number, and network protocool.
+       * port number, and network protocol.
        * </pre>
        *
        * <code>.grpc.gcp.Endpoint remote_endpoint = 7;</code>
@@ -4380,7 +4380,7 @@ public final class Handshaker {
       /**
        * <pre>
        * (Optional) Endpoint information of the remote server, such as IP address,
-       * port number, and network protocool.
+       * port number, and network protocol.
        * </pre>
        *
        * <code>.grpc.gcp.Endpoint remote_endpoint = 7;</code>
@@ -4399,7 +4399,7 @@ public final class Handshaker {
       /**
        * <pre>
        * (Optional) Endpoint information of the remote server, such as IP address,
-       * port number, and network protocool.
+       * port number, and network protocol.
        * </pre>
        *
        * <code>.grpc.gcp.Endpoint remote_endpoint = 7;</code>
@@ -4412,7 +4412,7 @@ public final class Handshaker {
       /**
        * <pre>
        * (Optional) Endpoint information of the remote server, such as IP address,
-       * port number, and network protocool.
+       * port number, and network protocol.
        * </pre>
        *
        * <code>.grpc.gcp.Endpoint remote_endpoint = 7;</code>
@@ -4428,7 +4428,7 @@ public final class Handshaker {
       /**
        * <pre>
        * (Optional) Endpoint information of the remote server, such as IP address,
-       * port number, and network protocool.
+       * port number, and network protocol.
        * </pre>
        *
        * <code>.grpc.gcp.Endpoint remote_endpoint = 7;</code>
@@ -6076,7 +6076,7 @@ public final class Handshaker {
     /**
      * <pre>
      * (Optional) Endpoint information of the remote client, such as IP address,
-     * port number, and network protocool.
+     * port number, and network protocol.
      * </pre>
      *
      * <code>.grpc.gcp.Endpoint remote_endpoint = 5;</code>
@@ -6085,7 +6085,7 @@ public final class Handshaker {
     /**
      * <pre>
      * (Optional) Endpoint information of the remote client, such as IP address,
-     * port number, and network protocool.
+     * port number, and network protocol.
      * </pre>
      *
      * <code>.grpc.gcp.Endpoint remote_endpoint = 5;</code>
@@ -6094,7 +6094,7 @@ public final class Handshaker {
     /**
      * <pre>
      * (Optional) Endpoint information of the remote client, such as IP address,
-     * port number, and network protocool.
+     * port number, and network protocol.
      * </pre>
      *
      * <code>.grpc.gcp.Endpoint remote_endpoint = 5;</code>
@@ -6491,7 +6491,7 @@ public final class Handshaker {
     /**
      * <pre>
      * (Optional) Endpoint information of the remote client, such as IP address,
-     * port number, and network protocool.
+     * port number, and network protocol.
      * </pre>
      *
      * <code>.grpc.gcp.Endpoint remote_endpoint = 5;</code>
@@ -6502,7 +6502,7 @@ public final class Handshaker {
     /**
      * <pre>
      * (Optional) Endpoint information of the remote client, such as IP address,
-     * port number, and network protocool.
+     * port number, and network protocol.
      * </pre>
      *
      * <code>.grpc.gcp.Endpoint remote_endpoint = 5;</code>
@@ -6513,7 +6513,7 @@ public final class Handshaker {
     /**
      * <pre>
      * (Optional) Endpoint information of the remote client, such as IP address,
-     * port number, and network protocool.
+     * port number, and network protocol.
      * </pre>
      *
      * <code>.grpc.gcp.Endpoint remote_endpoint = 5;</code>
@@ -7545,7 +7545,7 @@ public final class Handshaker {
       /**
        * <pre>
        * (Optional) Endpoint information of the remote client, such as IP address,
-       * port number, and network protocool.
+       * port number, and network protocol.
        * </pre>
        *
        * <code>.grpc.gcp.Endpoint remote_endpoint = 5;</code>
@@ -7556,7 +7556,7 @@ public final class Handshaker {
       /**
        * <pre>
        * (Optional) Endpoint information of the remote client, such as IP address,
-       * port number, and network protocool.
+       * port number, and network protocol.
        * </pre>
        *
        * <code>.grpc.gcp.Endpoint remote_endpoint = 5;</code>
@@ -7571,7 +7571,7 @@ public final class Handshaker {
       /**
        * <pre>
        * (Optional) Endpoint information of the remote client, such as IP address,
-       * port number, and network protocool.
+       * port number, and network protocol.
        * </pre>
        *
        * <code>.grpc.gcp.Endpoint remote_endpoint = 5;</code>
@@ -7592,7 +7592,7 @@ public final class Handshaker {
       /**
        * <pre>
        * (Optional) Endpoint information of the remote client, such as IP address,
-       * port number, and network protocool.
+       * port number, and network protocol.
        * </pre>
        *
        * <code>.grpc.gcp.Endpoint remote_endpoint = 5;</code>
@@ -7611,7 +7611,7 @@ public final class Handshaker {
       /**
        * <pre>
        * (Optional) Endpoint information of the remote client, such as IP address,
-       * port number, and network protocool.
+       * port number, and network protocol.
        * </pre>
        *
        * <code>.grpc.gcp.Endpoint remote_endpoint = 5;</code>
@@ -7634,7 +7634,7 @@ public final class Handshaker {
       /**
        * <pre>
        * (Optional) Endpoint information of the remote client, such as IP address,
-       * port number, and network protocool.
+       * port number, and network protocol.
        * </pre>
        *
        * <code>.grpc.gcp.Endpoint remote_endpoint = 5;</code>
@@ -7653,7 +7653,7 @@ public final class Handshaker {
       /**
        * <pre>
        * (Optional) Endpoint information of the remote client, such as IP address,
-       * port number, and network protocool.
+       * port number, and network protocol.
        * </pre>
        *
        * <code>.grpc.gcp.Endpoint remote_endpoint = 5;</code>
@@ -7666,7 +7666,7 @@ public final class Handshaker {
       /**
        * <pre>
        * (Optional) Endpoint information of the remote client, such as IP address,
-       * port number, and network protocool.
+       * port number, and network protocol.
        * </pre>
        *
        * <code>.grpc.gcp.Endpoint remote_endpoint = 5;</code>
@@ -7682,7 +7682,7 @@ public final class Handshaker {
       /**
        * <pre>
        * (Optional) Endpoint information of the remote client, such as IP address,
-       * port number, and network protocool.
+       * port number, and network protocol.
        * </pre>
        *
        * <code>.grpc.gcp.Endpoint remote_endpoint = 5;</code>
diff --git a/alts/src/main/proto/handshaker.proto b/alts/src/main/proto/handshaker.proto
index f8b45809c8..9350f63d41 100644
--- a/alts/src/main/proto/handshaker.proto
+++ b/alts/src/main/proto/handshaker.proto
@@ -71,7 +71,7 @@ message StartClientHandshakeReq {
   Endpoint local_endpoint = 6;
 
   // (Optional) Endpoint information of the remote server, such as IP address,
-  // port number, and network protocool.
+  // port number, and network protocol.
   Endpoint remote_endpoint = 7;
 
   // (Optional) If target name is provided, a secure naming check is performed
@@ -114,7 +114,7 @@ message StartServerHandshakeReq {
   Endpoint local_endpoint = 4;
 
   // (Optional) Endpoint information of the remote client, such as IP address,
-  // port number, and network protocool.
+  // port number, and network protocol.
   Endpoint remote_endpoint = 5;
 
   // (Optional) RPC protocol versions supported by the server.
@@ -198,8 +198,12 @@ message HandshakerResp {
 }
 
 service HandshakerService {
-  // Accepts a stream of handshaker request, returning a stream of handshaker
-  // response.
+  // Handshaker service accepts a stream of handshaker request, returning a
+  // stream of handshaker response. Client is expected to send exactly one
+  // message with either client_start or server_start followed by one or more
+  // messages with next. Each time client sends a request, the handshaker
+  // service expects to respond. Client does not have to wait for service's
+  // response before sending next request.
   rpc DoHandshake(stream HandshakerReq)
       returns (stream HandshakerResp) {
   }