Performance of Comcast Broadband Internet
On Monday we had Comcast Broadband Internet installed, along with cable television - hello 20th century. The downstream performance with cable internet is marketed as being 4.0 Mb/s. We saw about 3.1 Mb/s while the technician was performing the installation, which more than exceed my wants or expectations. Our old DSL line delivered a steady 1.5 Mb/s downstream, which was great.
But last night (Tuesday), web browsing performance ground to a halt. I haven't experienced such lag since dial-up. After performing some ping's and traceroute's, I figured that the delay originated in the hostname lookup. Hostname translation involves querying a Domain Name Service (DNS) server to obtain the Internet Address (IP) of the host in question. This operation occurs a lot during web browsing, since most popular websites include content served from multiple hosts. So why was hostname lookup taking so long (>100ms, or timeout)?
I googled the problem and learned that many Comcast users complained of similar problems. The Comcast DNS servers generally have horrible response times, particular during peak residential hours (5-10P during week). Most of those who responded remedied the problem by statically setting their DNS server IPs to other provider's DNS servers rather than using the Comcast DNS servers set during the Dynamic Host Configuration Protocol (DHCP) client registration. I've been using the Verizon DNS servers, since they yield consistently better performance:
- 4.2.2.2
- 4.2.2.3
Comcast, what's the story? How could such horrible DNS performance be 'ok' with a residential broadband provider? Most of their customers use broadband strictly for web browsing. Browsing response times are critical to customer/user satisfaction. Hopefully they'll improve DNS performance soon.