the output of sudo apt-get update command are below:
Hit:9 http://ppa.launchpad.net/ubuntu-mozilla-daily/ppa/ubuntu xenial InRelease
Get:11 http://archive.ubuntu.com/ubuntu xenial-backports InRelease [102 kB]
Hit:12 http://ppa.launchpad.net/ubuntu-wine/ppa/ubuntu xenial InRelease
Hit:13 http://ppa.launchpad.net/webupd8team/brackets/ubuntu xenial InRelease
Err:14 http://dell.archive.canonical.com/updates xenial-dell InRelease
Could not connect to dell.archive.canonical.com:80 (91.189.89.6), connection timed out
Fetched 306 kB in 2min 0s (2,551 B/s)
Reading package lists... Done
W: Failed to fetch http://dell.archive.canonical.com/updates/dists/xenial-dell/InRelease Could not connect to dell.archive.canonical.com:80 (91.189.89.6), connection timed out
W: Some index files failed to download. They have been ignored, or old ones used instead.