Specifications

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LSP there is no possibility for parallel paths. However, there could be multiple
LSPs configured between the same pair of routers. In this case, either of the
algorithms described above could be applied to the operation of the edge Label-
Switching Router (LSR), though once an LSP is chosen by that LSR the packet
will take exactly one path through the core.
3.2.11 Equal Cost Load Balancing with The Internet Processor II
The challenge with equal cost load balancing is twofold:
§ 1) The load balancing should spread traffic equally across all interfaces.
§ 2) The load balancing should not send packets from the same TCP flow
across different links because there is a danger of packet reordering, which
diminishes TCP performance.
The Internet Processor II meets both challenges.
First, The Internet Processor II supports load balancing on a per-packet basis,
meaning that individual packets are mapped to each of the links across which the
load is balanced. An alternative is to map traffic based on destination prefix.
Packet-based mapping ensures a better balance, particularly when the number of
destination prefixes is small.
Secondly, the Internet Processor II supports per-packet load sharing without
reordering of packets within a TCP flow because the assignment of packets to
links is deterministic. Packets are assigned based on a hash calculation of
header fields (ie source/destination TCP port), ensuring that all the packets within
a TCP flow are assigned to the same path and hence, not reordered.
Equal-cost paths
Port 1
Port 2
Prefixes A-F
R
A prefix is associated with multiple
next hops.
A
Hash computed to share load
deterministically so packets within a
flow are sent down the same link.