Have you ever chuckled at a person wearing a full rain coat with the hood but also carrying an umbrella in his hand on a rainy day? Actually, this analogy is no different from your company’s Internet service.
With the demand to provide 100% availability for the internet service, every organization goes for multiple Internet services. However due to cost constraints the speed and the bandwidth may vary between service providers. It is obvious, in terms of backup link because you don’t want your users to browse any social or unproductive web sites when your main service link is down.
Recently, I happen to visit one of our customers for training and implementation. Their Internet Service Provider (ISP) had provided them with 3 types of internet services to ensure 100% uptime for their Internet service i.e.
- An Optical Carrier [OC] based internet – Primary
- A Radio Frequency [RF] based internet – Secondary
- A VSAT based internet – Tertiary – Backup link
With these 3 Internet services, the ISP was able to provide high redundancy and availability of services to this customer at all times. All the 3 internet services were always active at any point of time, with the traffic flowing only across OC link primarily.
In the case of primary link going down, the routing table on the core router uses a static route that switches over to the secondary link without any interfaces coming up or changing the IP. Needless to say the ISP’s SLA for Network uptime is 97% and is always achieved.
The real catch here is the Response time which is very poor for RF and VSAT links when compared to the OC. Especially with VSAT which has a high latency and a minimum Round Trip Time (RTT) as 550 ms.
The customer was unhappy with the slow internet connectivity with its branches, because at times it took more than 20 minutes to complete a business transaction from the branch offices.
Before upgrading the links or contacting their ISP, the IT team wanted to get all the Ws’ right? I mean…
- Who causes the delay? Is it the application or users?
- Whether is it possible to achieve some trade-off in terms of bandwidth usage to provide a better service?
- Where does the latency happen? Is it at the service provider’s end or something internal?
- When and for how long has the high latency been prevailing?
The IT team was able to recognize the answers for the first two questions by using Traffic and bandwidth analysis module; NetFlow from ManageEngine. However, they were not aware of Cisco IP SLAs and how it can help them monitor their WAN links.
Similar to NetFlow, Cisco IP SLAs is also a part of Cisco IOS. Cisco IP SLAs uses active monitoring techniques to let you know how the link is performing! To know about the Cisco IP SLAs features that are supported in the IOS versions click here…More at http://www.cisco.com/en/US/products/ps6602/products_ios_protocol_group_home.html
I had created the WAN RTT monitors from their core router (Cisco 1841, IOS v12.4) to the branch offices and set a threshold of above 150 ms. This is because the link between the Source and the Destination is always the same and only the quality (Latency/ RTT) of the internet connection changes for OC, RF and VSAT.
Now, if the link latency increases beyond the threshold point, an alarm would be raised immediately to the network team. When they receive an alert from OpManager the first thing they verify these days is the HOP graph, which lets them identify where exactly the high latency was induced.They could also deduce the type of internet service that is currently in use by measuring the RTT as well checking the IP addresses in the HOP graph.
OpManager WAN RTT dashboards, lets administrator monitor the response time and availability round-the-clock. To know more about OpManager’s WAN monitoring, click here…
Now, they use OpManager’s WAN RTT monitoring extensively with over 100 WAN links to monitor.
I am sure this use case will give you a fair idea on where and how we can use OpManager’s WAN RTT monitoring to help eliminate & isolate latency,RTT issues across WAN links.
Signing off for now… and Wishing you happy holidays!
– S Arun Kumar
Image courtesy: chumpysclipart.com
