SIP Load Balancing


#1

Hey Guys

We have configured a Peplink with an Outbound Weighted Balance Rule to load balance SIP and RTP traffic through the WAN link. When doing a TCP dump on the linux box (Destination) we can see ICMP traffic is being loadbalanced , but the SIP traffic does not load balance. Can you guys please share your thoughts


#2

Single SIP session will route across one of the WAN link based on the Outbound Policy. The RTP sessions will be routed to same WAN link as related SIP session. Also, the SIP devices should send the keepalive SIP packets, so, for example, if the SIP registered through WAN3, as keepalive will be routed to WAN3 also. Similarly, RTP will also route through WAN3


#3

Ok even though we use a weighted balance rule? So if I understand correctly a Single call will be pushed through the WAN link, while that session is active , the next call will be pushed though a different WAN link based on the weighted ratio?


#4

The next call will still be routed the same WAN link, as the SIP session is still active.


#5

Makes sense , ok if we are to use a 2 WAN links, and 3 Outbound Rules. The first outbound rule “enforced” routes all FTP traffic out of WAN link 1 , the second outbound rule routes SIP traffic using “Least Used Algorithm” same goes for RTP traffic. So first we initiate a call and it routes through WAN link 1 , while the call is initiated, FTP session is establish, so the next SIP traffic would be routed through WAN link 2?


#6

I think the issue (excluding FTP) is related specifically to SIP and how it is load balanced. We found that in the following case that the Peplink does not load balance SIP:

  1. The source IP stays the same e.g 192.168.1.100

  2. The destination IP stays the same e.g 41.1.1.1

We tested in the following way:

[Call generator]—>[Peplink310]===(WAN1,WAN2)==[Router]–>[Asterisk]

Call generator IP: 192.168.1.25/24

Peplink LAN IP: 192.168.1.24/24

Peplink WAN1: 192.168.200.1/29 (NAT enabled)

Peplink WAN2: 192.168.201.1/29 (NAT enabled)

Asterisk server IP: 192.168.10.1/24

The Peplink rules have been configured with weighted balance (10:10:0) for any UDP traffic (SIP or any other UDP traffic). If we generate 10 VOIP calls we found all 10 calls via WAN1. Does not load balance. If we use a data generator and generate 10 UDP streams we found the Peplink to load balance correctly. It seem that the Peplink pushes all SIP traffic out a single WAN