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ICA Browsing Using DNS with TCP/IP+HTTP
One additional very important new benefit of this method of ICA browsing is its integration with DNS. By default, when you browse for ICA services from a client using TCP/IP+HTTP, it will first try to browse for list of services from whatever Citrix MetaFrame server resolves to the hostname ica. This functionality is very important to understand when you set up your Citrix MetaFrame server farm.
As an administrator, you have several options for pointing the ica hostname to a particular Citrix MetaFrame server on your network. You could set up the hostname in WINS, DNS, the local LMHOST file, or a local HOST file. However, the best option for most environments is normally to set up the hostname for ica in DNS. However you set it up, the goal is simple. When the ica hostname is set up correctly on all your clients, you should be able to go to the command prompt on any of the clients, run the command ping ica, and be able to get a response from the Citrix MetaFrame server to which you set the ica hostname to point. Normally you should point ica to your dedicated data collector if you have one. Otherwise, point it to one of your production MetaFrame servers.
Listing 1—Pinging by the ICA Hostname
E:\WINNT\system32\drivers\etc>ping ica Pinging ica [192.168.10.251] with 32 bytes of data: Reply from 192.168.10.251: bytes=32 time=120ms TTL=126 Reply from 192.168.10.251: bytes=32 time=110ms TTL=126 Reply from 192.168.10.251: bytes=32 time=110ms TTL=126 Reply from 192.168.10.251: bytes=32 time=110ms TTL=126
When you create the hostname ica on your internal or external DNS servers, it will automatically append your domain name to ica. If you put the hostname into the acme.com primary DNS domain, for instance, you should be able to immediately ping ica.acme.com from any station that has access to this DNS server. ica.acme.com is referred to as the fully qualified domain name (FQDN) for ica.
If you ping only ica and not the not the FQDN ica.acme.com, it might or might not resolve correctly depending on what domain your workstation is a member of. By default, any Windows workstation will automatically append its domain name to any hostname that you ping. That is why it is important to ensure that your DHCP servers are assigning the correct domain names to your workstations.
If in the network settings of your client's workstation or using DHCP you assign your clients to the acme.com domain, for example, when they attempt to browse for ICA services they will first try to retrieve the list from whatever device is assigned to ica.acme.com.
To see where this is set, try creating a custom ICA connection. During the setup of the connection, select TCP/IP+HTTP for the protocol, and then click the Server Location button. Take the check off of Use Default, and then look at the default setting for the TCP/IP+HTTP protocol. It will be set to (ica). Remember from the previous discussion that the default setting for just TCP/IP is (Auto), meaning that if you choose TCP/IP (port 1604), you will send out a broadcast to locate your ICA services. If you choose TCP/IP+HTTP, however, you will send out a directed packet to ica.[client domain name] instead.
As an administrator, this makes TCP/IP+HTTP browsing very easy to set up and control for an enterprise both for internal and external access. To set it up properly, follow these steps:
Assign a standard domain name to all of your workstations either manually or preferably through DHCP. You can determine what DNS domain a workstation belongs to using the ipconfig /all command for Windows NT 4.0/2000 and the winipcfg command for Windows 95/98/Me.
On your internal DNS server, create a host entry for ICA on this domain name. Point this entry to the internal address of your data collector or master browser. For example, you would create a host entry for ICA in the acme.com domain.
Make sure ICA clients use TCP/IP+HTTP for establishing connections by default rather than TCP/IP.
For ease of TCP/IP+HTTP browsing from the Internet to internal Citrix MetaFrame servers, follow these steps:
Assign a standard domain name manually to home workstations in the Network Properties, DNS settings area.
On your external DNS servers, create a host entry for ICA on this domain name. Point this entry to the external address of your data collector or master browser. If the external address differs from the internal address because of Network Address Translation, you will need to use the alternate address functionality within Citrix.
Make sure clients use TCP/IP+HTTP for establishing connections, not TCP/IP. Also you might need to check the Use Alternate Address, by clicking the Firewall button when setting up the connection.
Another advantage of the TCP/IP+HTTP approach is disaster recovery.