RE: MPLS Load balancing

From: Gary Tate (gtate@juniper.net)
Date: Wed Oct 17 2001 - 05:57:13 EDT


Hi Andrew,

If you do a search on Load Balancing in the JunOS 5.0 documentation:
Internet Software Configuration Guide MPLS Applications available on the
web: http://www.juniper.net/techpubs/software.html

You will find the information you need. Hope this is helpful

Gary

Here are some excerpts

Per-Prefix Load Balancing with CSPF
-----------------------------------
When there are multiple equal cost tunnels to a destination, load
balancing can be controlled for each path. Load balancing is
proportional to the configured bandwidth per LSP. If an LSP has a larger
bandwidth associated with it, that LSP will carry a larger number of
prefixes. If
you configure the bandwidth, the prefixes automatically adjust
themselves.

Configure Load-Balancing LSPs without CSPF
------------------------------------------
LSP tends to load-balance its placement by randomly selecting one of the
equal-cost next hops and using it exclusively. The random selection is
made independently at each transit router and is made by comparing IGP
metrics alone. No consideration is given to bandwidth or congestion
levels.

Configure FEC Deaggregation
---------------------------
When an LDP egress router advertises multiple prefixes, the prefixes are
bound to a single label and aggregated into a single Forwarding
Equivalence Class (FEC). By default, LDP maintains this aggregation as
the advertisement traverses the network.

By default, because an LSP cannot be split across multiple next hops and
all of the prefixes are bound into a single LSP, you cannot load-balance
across equal-cost paths.

To change the default to load-balance across equal-cost paths,
deaggregate FECs.

Deaggregating FECs causes each prefix to be bound to a separate label
and become a separate LSP.

To configure deaggregated FECs, include the deaggregate statement:

        deaggregate;

You can configure deaggregated FECs globally for all LDP sessions (at
the [edit protocols ldp] hierarchy level) or for each interface (at the
[edit protocols ldp interface interface-name] hierarchy level).

Deaggregating an FEC allows the resulting multiple LSPs to be
distributed across multiple equal-cost paths and distributes LSPs across
the multiple next hops on the egress segments but installs only one next
hop per LSP.

To aggregate FECs, include the no-deaggregate statement:

        no-deaggregate;

You can configure aggregated FECs globally for all LDP sessions (at the
[edit protocols ldp] hierarchy level) or for each interface (at the
[edit protocols ldp interface interface-name] hierarchy level).

>-----Original Message-----
>From: Andrew Smith [mailto:as160@yahoo.com]
>Sent: 17 October 2001 03:48
>To: juniper-nsp@puck.nether.net
>Subject: MPLS Load balancing
>
>
>All,
>
>For IPV4 we have random and per-packet as load
>balancing options.
>
>What about in MPLS? Any pointers/docs will be great.
>
>TIA
>---andrew
>
>__________________________________________________
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