not able to upgrade ubuntu 14.4 to 16.4

sudo apt-get update
................
W: Failed to fetch https://esm.ubuntu.com/ubuntu/dists/trusty-infra-security/main/binary-amd64/Packages Failed to connect to esm.ubuntu.com port 443: Network is unreachable
E: Some index files failed to download. They have been ignored, or old ones used instead.

sudo apt-get update
.................
147 additional updates are available with UA Infrastructure ESM.
To see these additional updates run: apt list --upgradable
See https://ubuntu.com/advantage or run: sudo ua status

sudo update-manager -d

(update-manager:3410): GLib-CRITICAL **: g_hash_table_destroy: assertion 'hash_table != NULL' failed

(update-manager:3410): GLib-CRITICAL **: g_hash_table_destroy: assertion 'hash_table != NULL' failed
jishnu@jishnu-Lenovo-H520e:~$ sudo apt-get dist-upgrade
Reading package lists... Done
Building dependency tree
Reading state information... Done
Calculating upgrade... Done
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.