ANSA Trader (Name Server) Extension

The ANSA trader is mainly used as a database of MSNL addresses and names. The IP part of the name service does not make use of it.

It is possible to have multiple network interfaces to a host, with each network interface having an alias and a network address. The trader name extension for the type MachInfo contains all the aliases and network addresses but it does not provide information as to which alias correspond to which address. The following ANSA trader (name server) extension is made to allow this.

In the context of /wanda/machines, a new type, IFInfo, has been added and MachInfo is compatible with it. Thus the current trader interface type directed acyclic graph (as relevant to us) is as:

MachInfo IFInfo wanda

The IFInfo contains properties Name, MSNL, Type and InterfaceId. Only the alternative network interface, e.g. cod-c, will have an entry in this type. The principle entry, cod must always be in the MachInfo type.

When a name to address resolution request (library call of getmsnlhostbyname on Unix or gethostbyname on Wanda) is made (using procedure NS_GET_SAPS_BY_SAPNAME as defined in the NAME_SERVICE interface), the name server performs the following operations:

• Lookup the principle MSNL address which correspond to the name, using a lookup in context /wanda/machines with type of IFInfo and constraint of property Name equal to the name requested.
• If the entry is not in the trader, lookup in a local table. The local table is used to supplement the data in the ANSA trader. This is orginally designed to be a catch-all mechanism to allow entries that do not have entry in the trader. Since it has been decided that both Wanda and Unix machines should have trader entries, this mechanism should not be used other than some exceptional cases.
• If the entry is in the trader, a further lookup to the trader is done to find out about possible additional addresses. The trader lookup the MSNLAliases in context /wanda/machines with type of IFInfo. The constraint is host name in Aliases.

The result returned to the user always has the MSNL address of the requested name listed first.

Similarly, when a address to name request (library call of getmsnlhostbyaddr on Unix or gethostbyaddr on Wanda) is made (using procedure NS_GET_SAPNAMES_BY_SAP as defined in the MSRPC interface), the MSNL name server does:

• Lookup the principle interface name that correspond to the address, using a lookup in context /wanda/machines with type of IFInfo and constraint of property MSNL equal to the requested address.
• If the entry is not in the trader, lookup in a local table.
• If the entry is in the trader, do a further lookup to find out the aliases in context /wanda/machines with type of IFInfo. The constraint is address in MSNLAliases.

Again, the result returned to the user always has the name of the requested MSNL address listed first.

Update the trader

tco(8) and tci(8) are provided to dump and update the MachInfo part of the trader information. Alternatively naclient can be used if you prefer something more direct.

Standard tco/tci will not be able to show/update the IFInfo type. A script iftco(8) and iftci(8) which provides the functionality of tco and tci respectively for the IFInfo interface type.

If you are adding/deleting a network interface from the trader, make sure that you update both IFInfo type and the MSNLAliases & Aliases properties of the MachInfo type.