Avaya Configuring APPN Services Uživatelský manuál stáhnout pdf (Strana 36)

Configuring APPN Services

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Automatic Network Routing

Automatic network routing (ANR) minimizes storage and processing

requirements for routing packets through intermediate nodes. ANR functions

include:

• Fast packet switching

• Session transparency

• Source routing

Fast Packet Switching

ANR operates at the Data Link Control layer of the SNA architecture. Operating

at a lower layer than APPN ISR improves packet switching performance in the

intermediate nodes. Functions typically performed at the intermediate node, such

as link-level recovery, segmentation, flow and congestion control, are performed

at the RTP connection endpoints.

Session Transparency

Intermediate nodes are not aware of the SNA sessions or the RTP connections

established across the nodes. This eliminates the need for storing routing tables

and consuming resources (memory and buffers) at the intermediate nodes.

Source Routing

ANR uses a source routing algorithm. ANR carries the routing information in the

network header of each packet. For each activated link, an ANR label is

dynamically assigned to the packet. As a packet traverses the network, each node

strips off the information it uses in the packet header before forwarding it,

allowing the next node to easily find its routing information at a fixed place in the

header. This allows faster switching through a node. Additionally, there is no

ANR restriction on the number of hops in the network.

Figure 1-10

illustrates how ANR routes packets over an APPN HPR network. The

intermediate network node strips the first routing label (A1) from the network

header before forwarding the packet on the A1 link. C5 represents the endpoint in

the last HPR node.

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Avaya Configuring APPN Services Uživatelský manuál Strana 36