[nsp] Unusual load balancing with policing...

From: ivac+cisco-nsp@iskon.hr
Date: Thu Apr 11 2002 - 08:33:41 EDT


Hello,
I'd like to here your thoughts about this problem. Idea is to make
special kind of load balancing over two (or more) links but with
predefined bandwidth limits. Below is example

                ------ ------
               | | a s1| |
10.0.0.0/24 - | RA |----------| RB | - NetX
               | |X | |
                ------ ------
                   \ /
                    \ /
                     \ ------ /
                    c \ | | / b
                       \| RC |/
                        | |Y
                         ------

Packets from NetX to 10.0.0.0/24 should go through link "a" when
bandwidth is below 1Mb/s, and everything above 1Mb/s should go through
link "b" (and than through "c").

What I came up is combination of policy-map and route-map:
(I am aware that this puts significant burden on cpu)

Router RB:

class-map match-all Limit
  match access-group 100
!
policy-map Limit
  class Limit
     police 1000000 50000 50000 conform-action set-prec-transmit 5 exceed-action set-prec-transmit 6
!
interface Serial 6/0
 ip policy route-map Limit
 service-policy input Limit
!
access-list 100 permit ip any 10.0.0.0 0.0.0.255
access-list 100 deny ip any any
!
access-list 101 permit ip any 10.0.0.0 0.0.0.255 precedence 5
access-list 101 deny ip any any
!
access-list 102 permit ip any 10.0.0.0 0.0.0.255 precedence 6
access-list 102 deny ip any any
!
route-map Limit permit 10
 match ip address 101
 set ip next-hop X
!
route-map Limit permit 15
 match ip address 102
 set ip next-hop Y

Unfortunately this doesn't work, because route-map doesn't match
precedences set by policy-map (probably order of operation is first
route-map then policy-map; can someone confirm this??).

One solution is to mark packets in NetX, before they enter RB and then
route them according to precedence flag.

Can you advise better (less cpu intensive) solution?



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