Introduction : Crome//Net-Internals/#Dns
In the realm of web browsing and network diagnostics, Google Chrome stands out with its array of built-in tools that provide users and developers with insights into various aspects of browser performance and network activity. One such tool is the Net-Internals feature, specifically its DNS section. This guide aims to demystify the Net-Internals/#DNS tool in Google Chrome, explaining its functions, how it can be utilized, and its benefits for troubleshooting and optimizing network performance.
Introduction to Chrome’s Net-Internals
Google Chrome’s Net-Internals is a powerful diagnostic tool designed to help users and developers analyze and troubleshoot network-related issues within the browser. By navigating to chrome://net-internals in Chrome’s address bar, users can access a variety of network statistics, logs, and diagnostics features. The DNS (Domain Name System) section of this tool is particularly useful for understanding how Chrome handles DNS resolution and for diagnosing related issues.
What is DNS?
Before delving into the specifics of Chrome’s DNS tool, it’s essential to understand what DNS is and why it’s important.
a. Definition and Function
The Domain Name System (DNS) is like the phonebook of the internet. It translates human-friendly domain names (like www.example.com) into IP addresses (like 192.0.2.1) that computers use to identify each other on the network. When you enter a URL into your browser, DNS servers work to resolve that URL into an IP address so that your browser can connect to the appropriate server.
b. Importance of DNS
Efficient DNS resolution is crucial for smooth internet browsing. Slow or failed DNS lookups can lead to delays, inaccessible websites, and overall poor browsing experience. Therefore, understanding and troubleshooting DNS issues is key to maintaining optimal internet performance.
Navigating to the DNS Section in Chrome
To access the DNS section of Chrome’s Net-Internals:
- Open Google Chrome.
- Type
chrome://net-internals/#dnsinto the address bar and press Enter.
This will take you directly to the DNS section of the Net-Internals tool, where you can view various options and logs related to DNS.
Key Features of the DNS Section
The DNS section of Net-Internals offers several features that can be instrumental in diagnosing DNS-related issues:
a. DNS Cache
- View DNS Cache: This feature displays the list of DNS records that Chrome has cached. Caching DNS records improves performance by reducing the need for repeated DNS lookups. However, sometimes stale or incorrect cache entries can cause issues. Viewing the DNS cache allows users to see what domains and IP addresses are currently stored.
- Clear DNS Cache: Clearing the DNS cache can resolve issues related to outdated or incorrect DNS records. This action forces Chrome to refresh its DNS cache and perform new lookups, potentially fixing connectivity problems.
b. DNS Lookup
- Perform DNS Lookup: This feature lets you manually perform a DNS lookup for a specific domain. Entering a domain name into the provided field and clicking “Resolve” will show you the IP addresses associated with that domain. This can be useful for checking if DNS resolution is functioning correctly for a particular domain.
c. Host Resolver Cache
- View Host Resolver Cache: Similar to the DNS cache, the host resolver cache contains resolved IP addresses of hostnames. This feature provides insights into the resolver cache and helps identify any discrepancies between the expected and actual resolved addresses.
What network bugs can net-internals help you identify?
There’s several network issues or bugs this can help you identify. Here’s a good list from the Chromium Project:
- Cache hits for DNS resolves
- Reads/writes from disk cache
- Queueing delay to schedule DNS resolves to threads
- Stalls due to chrome extensions pausing requests
- Stalls due to exceeding socket pool limits
- Speculative DNS resolves
- Proxy resolution
- Attempts to do a TCP connect to an IP address
- Network change events
- Proxy configuration change events
- Other Errors
The Chromium Project goes a bit further and states that this is not a replacement for packet captures like tcpdump but it’s actually used for “application level logic and caches” that are not known at lower layers. It can also capture bytes sent and/or received over sockets.
Using Net-internals to Get Network Data for Bug/Error Reports
If you have an issue and need to send it to a developer to fix, here’s how you can gather the network data from net-internals:
- Start a new browser window and go to chrome://net-internals
- If you need byte-level data, select “Capture” from the drop down menu that’s in the top left, then check “Include the actual bytes sent/received.”
- Replicate the network problem in another tab in the same browser window. Do this after opening Chrome’s net-internals
- In the net-internals tab, enter some information regarding the issue into the open text box and click “Save to File.” If you switched to the “Capture” page in step 2 then you’ll first need to select “Export” from the top-left.
- (OPTIONAL) Edit the log to remove any personal information, but make sure the code is still usable
- Either attach the log to a bug in crbug.com, or send email to the bug investigator. Include any relevant data or URLs.
- If the problem occurs very early and you cannot enable logging through chrome://net-internals, you can add a command line argument to Chrome to start logging as early as possible:
–log-net-log=C:\some_path\some_file_name.txt
For info about adding command line options see command-line-flags
Using net-internals to visualize captured events
You can visualize many events with net-internals as well. This includes open sockets, in-use sockets, DNS jobs, URL requests and bytes sent/received.
This gives you a pretty good understanding of what is happening as you replicate a process. It’s worth noting this will capture events for every open tab, so only have issue-causing tabs open. Yep, that means close down those cat videos.
Conclusions on using chrome://net-internals
Net-internals is a good way to debug your network. As always, make sure if you’re sharing your logs or data with people outside your organization to remove personally identifiable information