Next hop subnetwork
A router, by its nature, must be connected to multiple subnetworks. Each subnetwork is
connected to a separate port on that router. The Next Hop Port identifies the
subnetwork to exit this node for the next hop towards the destination.
For the DSwT IP router entity, there are two types of port/subnetwork:
1. LAN: This is the Ethernet (common subnetwork type for IP routers).
2. CLNP-Tunnel: This is a logical subnetwork created by the OSI CLNP network
itself. From the IP router perspective, this subnetwork is seen as a “Non-Broadcast
Multiple Access” (NBMA) subnetwork. The IP router simply sees all the neighbor
IP router entities connected together to this NBMA. It does not see any of the OSI
CLNP nodes inside this network.
Next hop node
Once the correct exit port (subnetwork) has been identified, the correct node on that
subnetwork must be identified by its SNPA. This could be an Ethernet address (for a
LAN), or an X.121 address for an X.25 subnetwork. When the subnetwork is a
point-to-point link then there is no need to identify the Next Hop. There are various
ways to identify the Next Hop Node, and they depend on the type of subnetwork that
node is attached to. The following table provides an overview:
Subnetwork Type Next Hop Node (Identity Type)
LAN IP address or none if the destination is actually on this LAN (there is
no Next Hop Node).
CLPN-Tunnel NSAP
Management communication setup
Dual stack with tunneling (DSwT)
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4-22
Alcatel-Lucent - Proprietary
See notice on first page
365-312-807R7.2
Issue 4, May 2007
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