[ndnSIM] About environment building of ndnSIM

[CHOU Ro]

Hello,

Recently I am building an environment of ndnSIM on my VMWare which is 
running Ubuntu v 14.04.3 LTS.

When I try to execute:

git clone -b master-v1 git://github.com:named-data/ndnSIM.git 
ns-3/src/ndnSIM

but it returns me

Cloning into 'ns-3/src/ndnSIM'...
fatal: unable to connect to github.com:
github.com: Servname not supported for ai_socktype

Does anyone who knows how to solve this please? NTP is correctly 
configured under /etc/services.

Thanks in advance.

BR

Lu