Overblog Suivre ce blog
Editer l'article Administration Créer mon blog
20 août 2012 1 20 /08 /août /2012 10:52

The configuration of the load balancing parameters is done at the forwarding-option level. There are 2 parts, each one is related to a type of hardware:

 

- hash-key : for Ichip based platforms on MX or T series FPC

- enhanced-hash-key : for Trio based platforms

 

The 2 configurations may be present at the same time in case of chassis with a mix of cards.

 

1/ DPC:

 

On MX, for DPC cards, you can configure the following parameters to overide the default configuration (see part 1):

 

hash3

As you can see above, the common configuration for IPv4 and IPv6 traffic is very simple. You can just add TCP/UDP fields within the key buffer. For MPLS traffic, you can analyse until 3 labels.

 

Note: before activate the mpls payload analysis you must specified the maximum number of labels analysed (ie. label-1 label-2 ....).  You can specify to analyse the mpls payload for IP or Ethernet traffic (conveyed over MPLS)

 

2/ MPC:

 

On MX, for MPC cards, you can configure the following parameters to overide the default configuration (see part 1):

 

hash4

 

Here you have a specific configuration for IPv4 and IPv6. You can add the IIF index of the incoming port, deactivate the layer-4 fields and add the TOS field.

 

For MPLS traffic, you can disable the payload (that is activated by default - see part 1), add the IIF like IP traffic and add the EXP field of the label 1 within the key buffer.

 

3/ Example:

 

Below, it's a simple configuration that tries to homogenize the hashing parameters on a chassis with a mix of DPC and MPC cards. In other words, I try to have the same parameters within the key buffer in function with the default parameters of each type of card.

 


forwarding-options {
    hash-key {
        family inet {
            layer-3;
        }
        family mpls {
            label-1;
            label-2;
            payload {
                ether-pseudowire;
                ip {
                    layer-3-only;
                }
            }
        }
    }
    enhanced-hash-key {
        family inet {
            incoming-interface-index;
            no-destination-port;
            no-source-port;
        }
        family inet6 {
            incoming-interface-index;
            no-destination-port;
            no-source-port;
        }
       

        family mpls {
            incoming-interface-index;
        }
    }
}


 

In my example, I expect to have within the key buffer :) :

 

- For inet and inet6 traffic : src-ip address + dst-ip address + IP protocol + IIF index

- For MPLS traffic : at least Label 1 and Label 2 (by default MPC supports until 5 labels) + IIF index + MPLS payload (IP + Ethernet)

 

Option:

 

In some configurations with multiple next-hop (aka ECMP) or in case of multiple aggregated next-hop with an equal cost you can experience a bad load sharing among with the diffirent links.

 

To have a better load balancing, you can add the knob (indexed-load-balance or indexed-next-hop - depends on the version). This mechanism introduces a second layer of hashing within the multiple next hop, whereby an index table based on 3 bits of the destination address points to a unique, permuted ordering of the original nexthop list.

 

The knob is:

 


set forwarding-options load-balance indexed-load-balance or indexed-next-hop


 

David.

 


Partager cet article

Repost 0
Published by junosandme - dans Posts
commenter cet article

commentaires