OSF DCE Administration Guide--Core Components

Managing Intercell Naming
5
6
LEGEND
Success!
widget.com
cell root is
at Node E
CDS clerk
GDA
CDS server
DNS server
1
2
3
4
7
8
9
Node B
Node C Node D
Node E
Client
Node A
CDS server
10
?
?
?
= Request path
= Response path
GDA is at
Node C
The following steps summarize the name search that is illustrated in the preceding figure:
1. The client application passes the name /.../widget.com/printsrv1 to the CDS clerk.
2. The clerk passes a lookup request to a CDS server that it knows about on Node B.
3. The server’s clearinghouse contains a replica of the cell root directory, so the
server looks up the CDS_GDAPointers attribute and returns the address of Node
C, where a GDA is running.
4. The clerk passes the lookup request to the GDA.
5. The GDA recognizes that the name is a DNS-style name, so it assumes that the
second component is a cell name that is defined in DNS. It passes that portion of
the name (widget.com) to DNS. For simplicity, the figure shows only one DNS
server; more than one DNS server can actually be involved in resolving a global
cell name.
Note: Although this example concerns the lookup of a DNS-style name,
the sequence and execution of operations is nearly identical for a
GDS name or a hierarchical cell name. If the GDA recognizes that a
name is a GDS-style name, it passes the name to a GDS server,
rather than to a DNS server. If the GDA recognizes that a name is a
hierarchical cell name, it passes it to the CDS server of the topmost
cell in the hierarchy, which is registered in one of the global
namespaces. The CDS server in this cell ‘‘walks down’’ the cell
hierarchy to locate the name.
124243 Tandem Computers Incorporated 22−3