Monitoring an SDN, Part 1 (Monitoring the Data Plane)

Terry Slattery
Principal Architect

I just posted a blog at titled Monitoring a Software Defined Network, Part 1. In it, I discuss the basic network monitoring functions that will be needed. Most of these functions are no different than those that have historically been required. I then discuss some additions that will be very useful for determining the source of a problem, or at least determining which systems are affected. While creating NetMRI’s functionality, I often found that I could often detect an error, but that sometimes there was insufficient information available to determine the systems that were involved or determine the root cause of the error.

Most of these errors are where a packet makes it part of the way across the network before an error is detected. The errors tend to be failures in the forwarding systems, causing the packet to be dropped. For example, TTL Exceeded causes a packet to be dropped and an ICMP message generated to the source of the packet. But it would be extremely valuable for the network management system to know that this error has occurred and why it was generated. Was it due to a traceroute being run, or was it due to a routing loop? In today’s networks, we can only look at the total count of TTL Exceeded errors and try to determine how many errors might indicate that a periodic routing loop exists. It would be extremely valuable to be able to retrieve the header information of the failed packet. Knowing the source and destination would be very valuable in the failure analysis.

Since SDN is relatively new, it may be possible to get some very valuable information storage defined that would facilitate troubleshooting many common problems. I would very much like to see that we use this opportunity to integrate valuable network monitoring and management functions in SDN, so that our networks become more reliable.



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Nick Kelly

Cybersecurity Engineer, Cisco

Nick has over 20 years of experience in Security Operations and Security Sales. He is an avid student of cybersecurity and regularly engages with the Infosec community at events like BSides, RVASec, Derbycon and more. The son of an FBI forensics director, Nick holds a B.S. in Criminal Justice and is one of Cisco’s Fire Jumper Elite members. When he’s not working, he writes cyberpunk and punches aliens on his Playstation.


Virgilio “BONG” dela Cruz Jr.

CCDP, CCNA V, CCNP, Cisco IPS Express Security for AM/EE
Field Solutions Architect, Tech Data

Virgilio “Bong” has sixteen years of professional experience in IT industry from academe, technical and customer support, pre-sales, post sales, project management, training and enablement. He has worked in Cisco Technical Assistance Center (TAC) as a member of the WAN and LAN Switching team. Bong now works for Tech Data as the Field Solutions Architect with a focus on Cisco Security and holds a few Cisco certifications including Fire Jumper Elite.


John Cavanaugh

CCIE #1066, CCDE #20070002, CCAr
Chief Technology Officer, Practice Lead Security Services, NetCraftsmen

John is our CTO and the practice lead for a talented team of consultants focused on designing and delivering scalable and secure infrastructure solutions to customers across multiple industry verticals and technologies. Previously he has held several positions including Executive Director/Chief Architect for Global Network Services at JPMorgan Chase. In that capacity, he led a team managing network architecture and services.  Prior to his role at JPMorgan Chase, John was a Distinguished Engineer at Cisco working across a number of verticals including Higher Education, Finance, Retail, Government, and Health Care.

He is an expert in working with groups to identify business needs, and align technology strategies to enable business strategies, building in agility and scalability to allow for future changes. John is experienced in the architecture and design of highly available, secure, network infrastructure and data centers, and has worked on projects worldwide. He has worked in both the business and regulatory environments for the design and deployment of complex IT infrastructures.