Note: TGs for end nodes are not contained in the network topology database, but
are contained in the node’s local topology database. TDUs do not flow
through the network when a connection is established through a Connection
Network or when an end node is made a member of a Connection Network.
Because the connectivity is represented by a TG from a given node to a
Connection Network, normal topology and routing services (TRS) can be used for
the network node server to calculate the direct path between any two nodes
attached to the SATF (withTGs to the same Connection Network). DLC signaling
information is returned from the destination node during the normal locate process
to enable the origin node to establish a connection directly to the destination node.
Therefore, to achieve direct connectivity on an SATF,instead of each node on the
SATF being defined (or connected) to each other,each node is connected to a
Connection Network. The Connection Network is often visualized as a virtual node
on the SATF to which all other nodes are attached.This model is frequently used
and, in fact, the term Virtual Routing Node (VRN) is often interchanged with the
term Connection Network.
When a connection network is defined, it is named. This name then becomes the
CP name of the VRN and must follow all the requirements of any CP name. See
Table23 on page 149 for a list of these requirements.

Restrictions

vThe same connection network (VRN) can be defined on only one LAN. The same
VRN can be defined on multiple ports having the same characteristics to the
same LAN however.
vThere is only one connection network TG from a given port to a given connection
network’s VRN.
vBecause the VRN is not a real node, CP-CP sessions cannot be established with
or through a VRN.
vWhen a connection network is defined on the router network node, a fully
qualified name is specified for the

connection network name

parameter. Only
connection networks with the same network ID as the router network node may
be defined. The network ID of the VRN is then the same as the network ID of the
router network node.
Branch Extender
The Branch Extender (BrNN) function is designed to optimize the connection of a
branch office to anAPPN WAN backbone network. The BrNN isolates all the end
nodes on one or more branch office LANs from the backbone WAN.The domain of
a BrNN may contain only end nodes and cascaded BrNNs. The domain of a BrNN
does not contain network nodes or nodes with DLUR.
When configuring a BrNN, configure link stations to the backbone to be uplinks.
This causes the BrNN to appear as a conventional end node to the backbone. From
the perspective of the backbone, all resources in the domain of the BrNN appear to
be owned by the BrNN, hiding the topology of the BrNN’s domain from the
backbone and reducing the number of broadcast locates in the backbone.
A BrNN presents a conventional network node interface over downlinks. End nodes
in the domain of the BrNN register their resources with the BrNN and use the BrNN
as a conventional network node server.
APPN
Chapter1. APPN 13