Guide to Device Link(Connection) Monitoring

When working in a large enterprise or Telecom network, the most difficult part of diagnostics, is finding where the fault happened on the network.

Different network-device vendors like Cisco, HP and more, provide policy configurations on their devices that provide a top-level view on the complete network.

Policies by different vendors:


and more.

I’ll talk specifically about Cisco’s policy, i.e., IPSLA

What is IPSLA?

Its a Service Level Agreement, that uses active traffic monitoring — the generation of traffic in a continuous, reliable, and predictable manner — for measuring network performance.

Why we need it?

Using IPSLAs, service provider customers can measure and provide service level agreements, and enterprise customers can verify service levels, verify outsourced service level agreements, and understand network performance.

How it works?

It sends data across the network to measure performance between multiple network locations or across multiple network paths. It simulates network data and IP services, and collects network performance information in real time.

  • The information collected includes data about response time, one-way latency, jitter (interpacket delay variance), packet loss, voice quality scoring, network resource availability, application performance, and server response time.

Measurement statistics provided by the various IP SLAs operations can be used for troubleshooting, for problem analysis, and for designing network topologies.

How to use it?

Depending on the specific IP SLAs operation, statistics of delay, packet loss, jitter, packet sequence, connectivity, path, server response time, and download time can be monitored within the Cisco device and stored in both CLI and SNMP MIBs.

The packets have configurable IP and application layer options such as a source and destination IP address, User Datagram Protocol (UDP)/TCP port numbers, a type of service (ToS) byte (including Differentiated Services Code Point [DSCP] and IP Prefix bits), a Virtual Private Network (VPN) , “scheduling” option, “threshold” of when it fails, “frequency” for verification, routing/forwarding instance (VRF), and a URL web address.

Metrics that we can measure on:

  • Delay (both round-trip and one-way)


  • Domain Name System (DNS): uses DNS packet to measure RTT, and latency from source and back to source from the dns server.



Get the Medium app

A button that says 'Download on the App Store', and if clicked it will lead you to the iOS App store
A button that says 'Get it on, Google Play', and if clicked it will lead you to the Google Play store
Vinayak Khandelwal

• Software Engineer with years of experience in Software design and Development. Worked on multiple technologies like Nginx, Spring, AWS, Java, Python, etc,