core(network-analyzer): infer single rtt estimate for h3

core/lib/dependency-graph/simulator/network-analyzer.js

@@ -114,19 +114,25 @@ class NetworkAnalyzer {
   }
 
   /**
-   * Estimates the observed RTT to each origin based on how long the TCP handshake took.
+   * Estimates the observed RTT to each origin based on how long the connection setup.
+   * For h1 and h2, this could includes two estimates - one for the TCP handshake, another for
+   * SSL negotiation.
+   * For h3, we get only one estimate since QUIC establishes a secure connection in a
+   * single handshake.
    * This is the most accurate and preferred method of measurement when the data is available.
    *
    * @param {LH.Artifacts.NetworkRequest[]} records
    * @return {Map<string, number[]>}
    */
-  static _estimateRTTByOriginViaTCPTiming(records) {
-    return NetworkAnalyzer._estimateValueByOrigin(records, ({timing, connectionReused}) => {
+  static _estimateRTTByOriginViaConnectionTiming(records) {
+    return NetworkAnalyzer._estimateValueByOrigin(records, ({timing, connectionReused, record}) => {
       if (connectionReused) return;
 
-      // If the request was SSL we get two estimates, one for the SSL negotiation and another for the
-      // regular handshake. SSL can also be more than 1 RT but assume False Start was used.
-      if (timing.sslStart > 0 && timing.sslEnd > 0) {
+      if (timing.connectEnd > 0 && timing.connectStart > 0 && record.protocol.startsWith('h3')) {
+        // These values are equal to sslStart and sslEnd for h3.
+        return timing.connectEnd - timing.connectStart;
+      } else if (timing.sslStart > 0 && timing.sslEnd > 0) {
+        // SSL can also be more than 1 RT but assume False Start was used.
         return [timing.connectEnd - timing.sslStart, timing.sslStart - timing.connectStart];
       } else if (timing.connectStart > 0 && timing.connectEnd > 0) {
         return timing.connectEnd - timing.connectStart;
@@ -318,7 +324,7 @@ class NetworkAnalyzer {
       useHeadersEndEstimates = true,
     } = options || {};
 
-    let estimatesByOrigin = NetworkAnalyzer._estimateRTTByOriginViaTCPTiming(records);
+    let estimatesByOrigin = NetworkAnalyzer._estimateRTTByOriginViaConnectionTiming(records);
     if (!estimatesByOrigin.size || forceCoarseEstimates) {
       estimatesByOrigin = new Map();
       const estimatesViaDownload = NetworkAnalyzer._estimateRTTByOriginViaDownloadTiming(records);

core/test/audits/__snapshots__/metrics-test.js.snap

@@ -4,20 +4,20 @@ exports[`Performance: metrics evaluates valid input (with image lcp) correctly 1
 Object {
   "cumulativeLayoutShift": 0,
   "cumulativeLayoutShiftMainFrame": 0,
-  "firstContentfulPaint": 3364,
+  "firstContentfulPaint": 3313,
   "firstContentfulPaintAllFrames": undefined,
   "firstContentfulPaintAllFramesTs": undefined,
   "firstContentfulPaintTs": undefined,
-  "firstMeaningfulPaint": 3364,
+  "firstMeaningfulPaint": 3313,
   "firstMeaningfulPaintTs": undefined,
-  "interactive": 6412,
+  "interactive": 6380,
   "interactiveTs": undefined,
-  "largestContentfulPaint": 5578,
+  "largestContentfulPaint": 5621,
   "largestContentfulPaintAllFrames": undefined,
   "largestContentfulPaintAllFramesTs": undefined,
   "largestContentfulPaintTs": undefined,
-  "lcpLoadEnd": 5529,
-  "lcpLoadStart": 5407,
+  "lcpLoadEnd": 5572,
+  "lcpLoadStart": 5449,
   "maxPotentialFID": 160,
   "observedCumulativeLayoutShift": 0,
   "observedCumulativeLayoutShiftMainFrame": 0,
@@ -50,7 +50,7 @@ Object {
   "observedTotalCumulativeLayoutShift": 0,
   "observedTraceEnd": 4778,
   "observedTraceEndTs": 760625421283,
-  "speedIndex": 6339,
+  "speedIndex": 6313,
   "speedIndexTs": undefined,
   "timeToFirstByte": 2394,
   "timeToFirstByteTs": undefined,

core/test/audits/byte-efficiency/render-blocking-resources-test.js

@@ -81,7 +81,7 @@ describe('Render blocking resources audit', () => {
       {
         'totalBytes': 621,
         'url': 'https://fonts.googleapis.com/css?family=Fira+Sans+Condensed%3A400%2C400i%2C600%2C600i&subset=latin%2Clatin-ext&display=swap',
-        'wastedMs': 440,
+        'wastedMs': 465,
       },
       // Due to internal H2 simulation details, parallel HTTP/2 requests are pipelined which makes
       // it look like Montserrat starts after Fira Sans finishes. It would be preferred

core/test/computed/metrics/lcp-breakdown-test.js

@@ -102,8 +102,8 @@ describe('LCPBreakdown', () => {
     const result = await LCPBreakdown.request(data, {computedCache: new Map()});
 
     expect(result.ttfb).toBeCloseTo(2393.7, 0.1);
-    expect(result.loadStart).toBeCloseTo(5407.1, 0.1);
-    expect(result.loadEnd).toBeCloseTo(5529.3, 0.1);
+    expect(result.loadStart).toBeCloseTo(5449.0, 0.1);
+    expect(result.loadEnd).toBeCloseTo(5572.1, 0.1);
   });
 
   it('returns breakdown for a real trace with text LCP', async () => {

core/test/lib/dependency-graph/simulator/network-analyzer-test.js

@@ -29,7 +29,7 @@ describe('DependencyGraph/Simulator/NetworkAnalyzer', () => {
         networkRequestTime: 10,
         networkEndTime: 10,
         transferSize: 0,
-        protocol: 'http/1.1',
+        protocol: opts.protocol || 'http/1.1',
         parsedURL: {scheme: url.match(/https?/)[0], securityOrigin: url.match(/.*\.com/)[0]},
         timing: opts.timing || null,
       },
@@ -143,6 +143,23 @@ describe('DependencyGraph/Simulator/NetworkAnalyzer', () => {
       assert.deepStrictEqual(result.get('https://example.com'), expected);
     });
 
+    it('should infer from tcp and ssl timing when available', () => {
+      const timing = {connectStart: 1, connectEnd: 100, sslStart: 50, sslEnd: 100};
+      const record = createRecord({networkRequestTime: 0, networkEndTime: 1, timing});
+      const result = NetworkAnalyzer.estimateRTTByOrigin([record]);
+      const expected = {min: 49, max: 50, avg: 49.5, median: 49};
+      assert.deepStrictEqual(result.get('https://example.com'), expected);
+    });
+
+    it('should infer from connection timing when available for h3 (one estimate)', () => {
+      const timing = {connectStart: 1, connectEnd: 100, sslStart: 1, sslEnd: 100};
+      const record =
+        createRecord({networkRequestTime: 0, networkEndTime: 1, timing, protocol: 'h3'});
+      const result = NetworkAnalyzer.estimateRTTByOrigin([record]);
+      const expected = {min: 99, max: 99, avg: 99, median: 99};
+      assert.deepStrictEqual(result.get('https://example.com'), expected);
+    });
+
     it('should infer from sendStart when available', () => {
       const timing = {sendStart: 150};
       // this record took 150ms before Chrome could send the request