Nextelco:Application Server

Application Server

The application server is a combination of different services which are necessary for the management of user accounts and devices which provide connectivity to end-users. This are the services offered by the application server:

• AAA server: provides end-users and devices Authentication, Authorization and Accounting.
• Billing server:
• DHCP server: provides different range IP addresses depending on the requesting device.
• DNS server: provides easy to remember names for devices which compose the service network. Specially interesting for device management and maintenance.
• Web server: this service will provide the necessary interface to deal with the voucher system.
• DB server: data base service is necessary to keep all accounting information in a centralized place and access it whatever the service we are using to manage users.
• Management server: composed by Network Management System (NMS) for Radio Access Network (RAN) and RCMS for Base Station (BS) view and configuration.
• Maintenance server: different and necessary services for network maintenance such as TFTP, SYSLOG, Time service (NTP), Speed test and File sharing.

The Application Server could be one or a combination of several physical servers. Each server could hold just one machine or a combination of different virtual machines. This will be decided depending on physical servers availability as well as their resources.

System installation

The application server has the following hardware characteristics:

• Intel Xeon 3.2GHz x 4
• 4GB RAM
• Three network interfaces
  • Two Ethernet copper
  • One fiber
• Two 36GB identical hard drives

Regarding the software, it is based on Debian GNU/Linux 7.5 (wheezy) distribution. Due to fact that the server has two equal hard drives, during Debian installation software based RAID1 has been set up. These are the partitions:

• 1 -> 100MB /boot
• 2 -> 8 GB swap
• 3 -> Rest /

The configuration of RAID1 has been done according to this web page RAID on debian. However there are more useful web pages:

• Setting up RAID
• GRUB on RAID

After Debian installation it is important to set up GRUB on both hard drives. To do that this is the command that has been used:

#dpkg-reconfigure -plow grub-pc

Additionally, if we want to check RAID status we use this command:

#cat /proc/mdstat

It is convenient to install a SSH server in order to access the server remotely for any reason. These are the steps followed to install the SSH server:

1. Install openssh-server together with blacklisted RSA and DSA keys

#apt-get install openssh-server openssh-blacklist openssh-blacklist-extra

2. It is convenient to set up shared keys based log in. This increases the security level together with the deny of root login and password-based authentication.
1. Generate in the local machine a RSA key pair.

$ssh-keygen -t rsa

2. Copy on the server the generated public key.

$scp path_to_RSA_key username@server:/home/username/.ssh/authorized_keys

3. Edit openssh-server configuration

#vi /etc/ssh/sshd_config
-- change
#AuthorizedKeysFile  %h/.ssh/authorized_keys
-- to
 AuthorizedKeysFile  %h/.ssh/authorized_keys
-- change: 
 #PasswordAuthentication yes
-- to
 PasswordAuthentication no
-- change
PermitRootLogin yes
-- to
PermitRootLogin no

4. Restart sshd server

#invoke-rc.d ssh restart

3. In order to access the server through SSH this is the necessary command.

$ssh -i path_to_id_rsa(private) username@server

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