ServerNet Cluster Manual

ServerNet Cluster Description
ServerNet Cluster Manual—520575-003
1-25
Node-Numbering Agent (NNA) FPGA
Modification of the ServerNet IDs
Figure 1-13 illustrates how the node number for a ServerNet packet is modified as a
packet moves from one node to another in a cluster:
1. ServerNet packets from \A destined for \B leave the local node through the single-
mode, fiber-optic PIC installed in port 6 of the MSEB in group 01. As the packets
pass through the PIC, the node-numbering agent (NNA) FPGA modifies the SID of
each packet, replacing the default internal-routing SID with the external-routing
SID.
2. The packets travel along the fiber-optic cable until they reach the ServerNet II
Switch. (The ServerNet II Switch is the main component of the cluster switch.)
Because the PICs installed in the ServerNet II Switch do not contain an NNA
FPGA, the packets pass through these PICs unmodified and are routed to their
destination ID by the router-2 ASIC within the ServerNet II Switch.
3. When they reach the single-mode, fiber-optic PIC in the MSEB at \B, the ServerNet
packets are modified again. The NNA FPGA modifies the DID for each packet,
replacing the external-routing DID with the default internal-routing DID.
Figure 1-13. ServerNet Addressing Scheme for External Fabrics
VST034.VSD
\A \B
NonStop Himalaya
Cluster Switch
External Fabric
Packet
\A Node Numbers
Internal Routing: 0
External Routing: 2
MSEB
(Group 01)
MSEB
(Group 01)
\B Node Numbers
Internal Routing: 0
External Routing: 4
DID SID
4 0
DID SID
4 2
Packet
DID SID
0 2
Packet
NNA
Modifies
SID
NNA
Modifies
DID
Internal Fabric
Internal Fabric
Legend
DID - Destination ID
SID - Source ID
NNA - Node-Numbering Agent
MSEB - Modular ServerNet
Expansion Board
Data Data Data