Expand Configuration and Management Manual (G06.24+)

Subsystem Description
Expand Configuration and Management Manual—523347-008
18-69
Mixing Extended and Nonextended Packets
•
The variable packet size feature does not provide any benefit on paths configured
with the L4EXTPACKETS_OFF modifier, which specifies that the extended 64-byte
packet header format not be used. Nonextended frames are not fragmentable and
therefore must use the network-wide FRAMESIZE modifier value.
•
If a large packet encounters a path with a smaller packet size, the Expand line-
handler process automatically breaks the large packet into maximum size packets
for that path. Packet fragmentation occurs as a variable size passthrough packet is
forwarded, but the next hop path has a smaller value for the PATHPACKETBYTES
modifier than does the receiving path. Packet fragmentation is performed in the
outgoing Expand line-handler process since Expand paths have no knowledge of
other paths’ configurations.
•
The value specified for the L2TIMEOUT modifier should be based on the
transmission time required for the configured PATHPACKETBYTES modifier value
rather than on the configured FRAMESIZE modifier value.
Mixing Extended and Nonextended Packets
In Figure 18-21, packets sent from node \A to node \B can use variable-sized packets.
Packets sent from node \B to node \C and from node \A to node \C cannot use
variable-sized packets because the L4EXTPACKETS_OFF modifier causes both
directions of data flow to use nonextended packets. Therefore, if all data is from node
\A to node \C, there is no benefit to enabling the variable packet size feature, because
nonextended packets revert to FRAMESIZE modifier-sized packets.
Figure 18-21. Mixing Extended and Nonextended Packets
033CDT .CDD
Node \A
(D30)
Node \B
(D30)
Node \C
(L4EXTPACKETS_OFF)
Extended
packets
Nonextended
packets
Nonextended
packets