Parallelizing Downloads Across Hostnames
Domain sharding can have a negative effect on performance if not done right. This is because it adds DNS request time as well as connection time to each new concurrent connection on the shard. However, if utilized correctly as illustrated below, you can drastically improve resource load time.
How to Improve Resource Load Time with Domain Sharding
You can parallelize downloads across hostnames with MaxCDN by creating multiple custom domains (CNAME records) and pointing them to the CDN URL (e.g. myzone.yourcompanyname.netdna-cdn.com).
It’s recommended you create between two to four custom domains (see CNAME records tutorial). After creating CNAME records, they need to be added under zone settings within “Custom Domains List” in your MaxCDN Control Panel.
There is a propagation time for DNS records that you can monitor with online tools like the Global DNS Propagation Checker.
The sample below shows a single domain being used to load assets. As you can see, parallel downloading is severely limited.
The chart below illustrates how files are downloaded when domain sharding or hostname parallelization is implemented. (The difference is quite obvious.)
