Alcatel-Lucent 7750 Configuration Manual page 123

header in the hashing routine at an LSR for the purpose of spraying labeled IP packets over
multiple equal cost paths in ECMP in an LDP LSP and/or over multiple links of a LAG group in
all types of LSPs.
The user enables the LSR hashing on label stack and/or IP header by entering the following
system-wide command: config>system>load-balancing>lsr-load-balancing [lbl-only | lbl-ip |
ip-only]
By default, the 7x50 LSR falls back to the hashing on label stack only. This option is referred to as
lbl-only and the user can revert to this behavior by entering one of the two commands:
config>system>load-balancing>lsr-load-balancing lbl-only
config>system>load-balancing>no lsr-load-balancing
The user can also selectively enable or disable the inclusion of label stack and IP header in the
LSR hash routine on a specific network interface by entering the following command:
config>router>interface>load-balancing>lsr-load-balancing [lbl-only | lbl-ip | ip-only]
This provides some control to the user such that this feature is disabled if labeled packets received
on a specific interface include non IP packets that can be confused by the hash routine for IP
packets. These could be VLL and VPLS packets without a PW control word.
When the user performs the no form of this command on an interface, the interface inherits the
system level configuration.
The default lbl-only hash option and the label-ip option with IPv4 payload is supported on all
platforms and chassis modes. The ip-only option with both IPv4 and IPv6 payloads as well as the
lbl-ip option with IPv6 payload are only supported on IP interfaces on IOM3/IMM ports.
LSR Default Hash Routine—Label-Only Hash Option
The following is the behavior of ECMP and LAG hashing at an LSR in the existing
implementation. These are performed in two rounds.
First the ECMP hash. It consists of an initial hash based on the source port/system IP address.
Each label in the stack is then hashed separately with the result of the previous hash, up to a
maximum of five labels. The net result will be used to select which LDP FEC next-hop to send the
packet to using a modulo operation of the net result with the number of next-hops. If there is a
single next-hop for the LDP FEC, or if the packet is received on an RSVP LSP ILM, then a single
next-hop exists.
This same net result will feed to a second round of hashing if there is LAG on the egress port
where the selected LDP or RSVP LSP has its NHLFE programmed.
7750 SR Interface Configuration Guide
Interface Configuration
Page 123