Next Hop selection based on packet rate

[sudiptad4]

Dear All,

I wanted to check if there is a way we can track a flow (say DNS request), and based on rate we can forward it to particular next hop.

----(ingress interface)|Router| (Egress Interface 2) -----

                             (Egress Interface 1)

                                      |

                                      |

Say we are tracking DNS traffic on ingress interface(via ACL)

1. If traffic is less than equal to 1000 packet/second, it sends it to Next hop Egress interface 1.

2. If traffic is greater than 1000 packet/second, it sends it to Next hop Egress interface 2.

I tried ABF, but for tracking option, I couldn't find traffic rate based tracking option.

Please do let me know, if there is any method we can use to achieve this scenario.

Thanks and Regards,

Sudipta

[Philip D'Ath]

I've never tried this exact combination, but you should look into Pfr (Performance Based Routing).

https://www.cisco.com/c/en/us/products/ios-nx-os-software/performance-routing-pfr/index.html

[sudiptad4]

Hi Philip,

Thanks for the reply.

Although I am looking for IOS-XR. Looks like PFR doesn't support it (from one of the thread)

https://supportforums.cisco.com/t5/xr-os-and-platforms/pfr-for-ios-xr/td-p/2901976

Any other way we can achieve this?

Thanks and Regards,

Sudipta

[Aleksandar Vidakovic]

hi Sudipta,

have you considered the WAN Automation Engine (WAE) for this? It is true that there is no easy solution for this on a single device level. On network level WAE should be the way to go.

If you are looking for a forwarding decision on a packet-by-packet basis, this could lead to out of sequence packets. Not an issue with UDP, but it can cause lots of retransmission with TCP. Whatever solution you go for, it should ensure that a complete flow is always taking the same path.

/Aleksandar

[sudiptad4]

Hi Aleksandar,

Thanks for the reply.

Yes, this is specific for UDP (DNS) traffic.

Looks like I am new to WAE, need to do some research on this area.

Any solution with QOS or similar?

Thanks and Regards,

Sudipta

[Aleksandar Vidakovic]

If you think of it, there can be no device-level reliable solution for this because it may lead to traffic loops in the network because the downstream device may decide to send the traffic back, using a similar dynamic algorithm. The only reliable solution is at network level.