Cluster over WAN verify link support

[J_Vansen_S]

hi All,

We are in the process of deploying UC infras based on 2 qty of BE6000,

• BE6k box is to be deployed 1 unit each at 2 sites. Site A and Site B.
• Our application consist of CUCM, Unity & CCX.
• So ill suppose to have 1 publisher at site A, 1 sub at site B?
• Intersite has an existing leased line bandwidth of 10mb subscribed from telco, where all their data traffic are routed across.

Our objective is to verify the 10mb leased line, whether if it can support our cucm,unity,ccx cluster over it.

we understand that there's a strict requirement of 80ms RTT.

What is the best way to verify that the link is sufficient with our cluster requirement, as we are also sharing the data traffic across?

Does just a simple ping test from the access switch to and across to the site B's access switch works? an interval time ping test, eg during high traffic during the day?

What do most ppl do?

appreciate any advise

[Manish Gogna]

Hi,

A few important considerations from the SRND for clustering over the WAN:

A minimum of 1.544 Mbps (T1) bandwidth is required for Intra-Cluster Communication Signaling (ICCS) traffic between sites.

In addition to the bandwidth required for Intra-Cluster Communication Signaling (ICCS) traffic, a minimum of 1.544 Mbps (T1) bandwidth is required for database and other inter-server traffic between the publisher and every remote subscriber node.

Minimum of 1.5 Mbps or greater WAN link speeds. Video is not recommended on WAN connections that operate at speeds lower than 1.5 Mbps.

For example, if a site serving 20 users is connected with 1.5 Mbps of bandwidth to the rest of the system, the site's voice, presence, instant messaging, email, and video services can readily be hosted at a remote datacenter site. If that same site is hosting 1000 users, some of the services would best be hosted locally to avoid saturating the comparatively limited bandwidth with signaling and media flows. Another alternative is to consider increasing the bandwidth to allow services to be delivered across the WAN from a remote datacenter site.

The influence of latency on design varies, based on the type of Unified Communications service considered for remote deployment. If a voice service is hosted across a WAN where the one-way latency is 200 ms, for example, users might experience issues such as delay-to-dialtone or increased media cut-through delays. For other services such as presence, there might be no problem with a 200 ms latency.

http://www.cisco.com/c/en/us/td/docs/voice_ip_comm/cucm/srnd/collab10/collab10/models.html

Manish

[J_Vansen_S]

Thanks for the detailed reply. 

Noted on the bandwidth requirements but really how do I test the link out? 

Would merely as ping test from pc at from both side's LAN determine the results? Ie as long as I see less than 80 RTT my setup would be good to go?

[Mohammed al Baqari · Accepted solution]

Hi,

The best way to do this is to run IP SLA ICMP-Jitter operation for 1 week and use a tool such as Solarwinds VQM which can capture IP SLA data and generate reports. Once you confirm that the link can match the condition of 80 msec RTT with all BW requirements, you should be good to go.

[J_Vansen_S]

Thanks Mohammaed, i will try your method, but ill first need to familiarized myself with the Solarwinds Voip Network Quality Manager. Have u personally used this for such inter site test?

[Mohammed al Baqari · Accepted solution]

Hi,

I used it and it is very useful and user friendly. You can use the demo version for 60-days.

I believe you need a solid one week report to conclude link stability. It is important to make sure that you don't have spikes in RTT due to link flapping, over utilization, etc. These can't be seen in couple of pings. You need solid tool to do it.

It is important to have consistent RTT. Spikes can cause DB replication to break and impact entire cluster operation. I have seen this happening many times in CoW.

Also, it is important to have the right QoS in place to guarantee BW for voice, signaling ICCS, corporate apps, etc. 10 Mbps is a good pipe if deployed with right QoS. You can have a look at QoS SRND to find out the right model which suites you .

Another important point is to make sure that you have multiple CoS from your MPLS provider. Voice bearer ideally should be on CoS1 to avoid provider dropping your MPLS packets on jammed international links. ICCS should be ideally on CoS 2 or CoS3 with guaranteed latency. Then based on your applications you can go with your provider in minimum 3 x CoS model or higher

Keep in mind the cost factor and tweak things properly. The more sophisticated the solution, the higher the cost and you might lose the deal :)

[Ayodeji Okanlawon]

I believe a ping should be fine. You can also put load on a ping to see how the link respond to increase traffic. 

In addition you can do what Mohammed suggested. I personally have just done ping tests or believe the customer that the link is what it is. Your responsibility is to provide the requirements to them, in a documentation etc and there's is to ensure they provide the infrastructure detailed in that documentation. 

[J_Vansen_S]

Thanks for providing your personal insight and test uve performed.

Would u be able to elaborate how u did your ping test? 2 PCs one at each site on the planned UC segment. And do a quick ping/pathping during high traffic of the day?

My customer has provided a single10mb shared link via the 2 sites, and its my responsibility to verify if it is sufficient to built my cucm, ccx boxes on top of it.

[Ayodeji Okanlawon]

Yes a ping test across the link to confirm a 80ms rtt. The srnd says you need 1.5mb and you have 10mb..So I don't understand your worry. Are you saying you want to verify the customer has the 10mb? Well that will not be my responsibility. If you don't trust your customer, then you need to invest in a reliable tool that can verify the size of the link. Do what Mohammed suggested. I am sure there will be a cost to this. Who will pay for that? 

[J_Vansen_S]

Hi Ayodeji

Yea my worry is that is current 10mb link is also being used by the data traffic across the 2 sites.

Will try both methods as suggested

[Ayodeji Okanlawon]

Of course the link will be used for data traffic. You can't have a link dedicated for voice. Is thus your first deployment? 

[J_Vansen_S]

thanks for the verification~
Yes 1st cluster over wan deployment.