Campus Networks

Does SDN Have a Role in Campus Networks?

by Jim Metzler on ‎09-29-2014 04:31 PM - last edited on ‎09-30-2014 10:36 AM by (3,859 Views)

The vast majority of the discussion about SDN to date has focused on the data center. Since the network is a lot bigger than just its data center LAN that begs the question “Does SDN have a role in campus networks?”


A document I published late last year[1] reported on the results of a survey in which the respondents were asked “If your organization is likely to implement SDN sometime over the next two years, where are you likely to implement it?” It shouldn’t surprise you that the most common answer was the data center. It might surprise you that the second most common answer was the branch and/or campus network [2].

While I have no doubt that supporting the dynamic movement of VMs in a data center is an important use case, I also see several important use cases for SDN in campus networks.

One key use case is the ability of SDN to support dynamic QoS and traffic engineering and hence improve the performance of delay sensitive applications such as Unified Communications (UC). Without dynamic QoS and traffic engineering, when a user makes a UC call to another user there is nothing in the call setup to indicate that the UC traffic should have higher priority than other traffic. If SDN has been deployed in the campus, it is possible for the UC application to communicate with an SDN application running on the SDN controller. The SDN application then informs the SDN controller that the priority level for traffic between the two users needs to be set to high and that this traffic should run over non-congested links. The SDN controller determines the optimal path between the users and pushes the necessary information to each of the OpenFlow-enabled switches.


Another key use case for SDN in the campus is role based access. If SDN has been deployed in the campus, when a user is finished authenticating a message is sent to a role-based resource allocation SDN application that contains information about the user, including their role. The application then finds the user in a previously configured capabilities list. The capabilities which are appropriate for this user are converted to a network resource message that is sent to the SDN controller. The SDN controller then communicates with the appropriate network device and configures the OpenFlow tables on that device to ensure the appropriate priority setting for the user’s traffic, the appropriate bandwidth, and instructions to drop flows to restricted addresses.

In spite of all of the momentum behind SDN very few IT organizations have currently deployed SDN and that situation is unlikely to change any time soon. IT organizations realize they don’t have to wait until they have implemented SDN to reap the benefits of SDN in campus networks. Virtual LANs (VLANs) and Virtual Private Networks (VPNs) are two forms of virtualization that are currently well-established and widely used to isolate different types of traffic that share a common physical network. Multiprotocol Label Switching (MPLS) is also well-established and it is widely used to provide traffic engineering and traffic separation. One ongoing change in the use of MPLS is that while many users have historically purchased an MPLS service from their providers, users are increasingly coming to realize that they can implement label switching within their private networks. Another form of network virtualization that is ready for campus networks today is a virtual, or software-based, router that performs in the same way as a typical hardware-based router. One of the primary use cases for a virtual router is to have the virtual router segment the traffic that goes between virtualized servers.


Does SDN Have a Role in Campus Networks? SDN definitely has a big role to play in campus networks. IT organizations don’t have to wait until they have implemented SDN in campus networks in order to realize the benefits of virtualization. VLANs, VPNs, MPLS and virtual routers are production ready today. In order to successfully implement the current generation of virtualization functionality and have the capability to easily evolve to the virtualization functionality enabled by SDN, organizations must ensure that whatever network equipment they are currently buying will support SDN when they are ready to deploy it. Click here learn more about the immediate benefits of SDN in campus networks .

[1] Part 1: Introduction and Network Virtualization
[2] 54% or the respondents indicated data center and 26% indicated branch and/or campus


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