Planning How the AltaVista Tunnel Works

94

6.3.3 The Guts

Lets look at the structure for information provided by the AltaVista Tunnel.

6.3.3.1 AltaVista Tunnel Extranet server

The tunnel server consists of three integral parts that allow it to function as a router for tunnel sessions: Routing tables The routing table maps a range of local physical IP addresses to hosts on the local network that will receive tunnel traffic. A defined route may be set as a default route for all tunnel groups, or dynamically assigned as needed to one or many groups. A default route for all tunnel groups would allow those groups to access the same hosts on the enterprise LAN or WAN, whereas a dynamically assigned configuration would allow certain groups to access specific ranges of IP addresses on the network. The routing table on the tunnel server consists of three parts: • Subnet: This is the subnet of the network addresses on the local network that are part of the tunnel. Traffic destined for these IP addresses will use the tunnel network. • Netmask: This is the Netmask corresponding to the assigned subnet. • Description: A unique designation assigned to this route. Dynamic IP tables Each dynamic range of IP addresses can be routed to the physical IP addresses listed in the tunnel servers routing table. The dynamic IP addresses are virtual. The server assigns one IP address to the client requesting a tunnel session, and a second to the servers end of the tunnel session. The server end of the tunnel session is then routed to the physical IP range configured in the routing table. Each tunnel group has its own range of dynamic virtual IP addresses, and each of these ranges may be routed to the same or different physical IP addresses, as needed. Each dynamic IP address range has five definable parameters: • Range name : This name is arbitrary and assigned by the system administrator for defining the IP range in a manageable way. • Range description : A brief description of the IP range i.e., IPs for the Sales Tunnel. This is useful when managing many dynamic IP ranges on the same server. • First IP : This is the lowest IP address in the dynamic IP range, and thus the first usable IP address within the range. • Total tunnels : This value is the total number of tunnel sessions available at any given time. The total number of IP addresses that can be dynamically assigned is twice that of the Total Tunnels setting one IP address per end of the tunnel. • NetMask : The network mask that corresponds to the total group of usable IP addresses in the dynamic range. 95 Authentication tables Each tunnel group is assigned a specific username, password, and session key. The tunnel client is configured with this authentication information, and transmits it to the server for verification before tunnel traffic can commence. The Extranet server generates the authentication key, user group name, and password as exportable files described in the next section for installation into the Telecommuter Client clients that require access. These files should be treated as confidential information, and should be closely managed. The three parameters presented here are configured for each tunnel group. Configuration of the local firewall is also required for successfully routing tunnel traffic. See Section 6.4 below for details.

6.3.3.2 Security procedures

When you create a tunnel group, the AltaVista Tunnel Extranet server requires you to manually enter a unique username and password. Once the group is configured, the tunnel server creates a unique 1024-bit RSA authentication key for that particular group. Both of these authentication pieces may be extracted into separate ETA and key files. The ETA file contains the user group name and password, and is by default named groupname.eta. The key file is typically named groupname.key. These authorization files are needed by remote clients for connecting to and authorizing tunnel sessions to the tunnel server. Once extracted, these files should be distributed to all authorized remote clients. These security files should be handled as highly confidential information, as anyone with this file will be allowed access to the virtual private network. Distribution by floppy disk or private FTP site are semi-secure ways of distribution, but all transfers should be logged by the system administrator to maintain the integrity of the security system.

6.3.3.3 AltaVista Tunnel Telecommuter Client

The tunnel client software contains a single configuration for each tunnel group to which the client has access. Thus, the user could be a sales forecaster for a manufacturing company, and have access to the Sales group for historical sales data and the Manufacturing group for factory throughput. The following parameters are specific to each group: Username This is the unique tunnel group name as it appears in the tunnel servers authentication tables. This parameter is part of the extractable ETA file from the Extranet server, or it may be entered manually. Server key ID The server key also comes from the tunnel servers authentication tables. Each group has a specific key, which allows the client access to the tunnel group. A copy of this key is provided in the extractable key file from the Extranet server.