Why I do get error 101? How is my DNS involved?

If you are getting those kind of errors it means that either, your IPv6 connection was unstable, or the servers were dead, or the file was not found. Right now is working through:

http://[2001:67c:1562::13]/ubuntu/dists/raring-security/multiverse/binary-i386/

What you can see in the output is that your machine is trying to connect using IPV6 addresses (e.g. 2001:67c:1562::13 ) which are distinguishable from IPv4 addresses (e.g 192.168.0.1). You could have two approaches here. One - disable IPv6 following these steps:

1. Open your /etc/sysctl.conf with any text editor ( you'll need sudo for that ). I personally would do something like sudo nano /etc/sysctl.conf ( nano is easiest ) or sudo vi /etc/sysctl.conf.

2. add these lines

   net.ipv6.conf.all.disable_ipv6 = 1
   net.ipv6.conf.default.disable_ipv6 = 1
   net.ipv6.conf.lo.disable_ipv6 = 1
   

3. Run sudo sysctl --load to apply changes

Second way would be to use IPv6 DNS. For instance, click on network indicator in top panel, select Edit Connections, and for your specific wifi or ethernet connection, use 2620:0:ccc::2 dns, which OpenDNS IPv6 server. Make sure you select "Address only" option