svchost is a windows component, it does tasks like renewing your IP or making DNS queries.
renewign your IP: if you suddenly lose connection to your ISP, it tries to get you back online by requesting an IP via DHCP.
DNS: gets the IP from hostnames (like www.otcentral.com), if you oftenly get messages that hosts can't be found is because you are blocking the access of svchost to make DNS queries.