Deployment Guide

Whatever routing policy a switch is using applies to the VE_Ports as well. For more information on
VE_Ports, refer to the Fabric OS FCIP Administrator's Guide.
Exchange-based routing
The choice of routing path is based on the Source ID (SID), Destination ID (DID), and Fibre Channel
originator exchange ID (OXID) optimizing path utilization for the best performance. Thus, every
exchange can take a different path through the fabric. Exchange-based routing requires the use of the
Dynamic Load Sharing (DLS) feature; when this policy is in effect, you cannot disable the DLS feature.
Exchange-based routing is also known as Dynamic Path Selection (DPS). For more information on DPS
refer to Dynamic Path Selection on page 107.
Device-based routing
Device-based routing optimizes routing path selection and utilization based on the Source ID (SID) and
Destination ID (DID) of the path source and destination ports. As a result, every distinct flow in the fabric
can take a different path through the fabric. Effectively, device-based routing works the same as
exchange-based routing but does not use the OXID field. This helps to ensure that the exchanges
between a pair of devices stay in order.
NOTE
Device-based routing requires the use of Dynamic Load Sharing (DLS); when this policy is in effect, you
cannot disable the DLS feature.
Device-based routing is also a form of Dynamic Path Selection (DPS). For more information on DPS
refer to Dynamic Path Selection on page 107.
NOTE
Device-based routing is supported in FICON environments, and in open environments only when
FICON coexists.
Dynamic Path Selection
DPS assigns communication paths between end devices in a fabric to egress ports in ratios proportional
to the potential bandwidth of the ISL, ICL, or trunk group. When there are multiple paths to a
destination, the input traffic is distributed across the different paths in proportion to the bandwidth
available on each of the paths. This improves utilization of the available paths, thus reducing possible
congestion on the paths. Every time there is a change in the network (which changes the available
paths), the input traffic can be redistributed across the available paths. This is a very easy and non-
disruptive process when the exchange-based routing policy is engaged.
Route selection
Selection of specific routes can be dynamic, so that the router can constantly adjust to changing
network conditions; or it may be static, so that data packets always follow a predetermined path.
Exchange-based routing
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