Source-linked AI summary
Designing Core Layer in Campus Network Using Software-Defined Networking
Iwan Setiawan, Azis Wisnu Widhi Nugraha, Sauqi Asrorul Zaza
TL;DR
The paper addresses how to provide campus-core interconnectivity and routing while applying traditional IP routing over SDN/OpenFlow. It designs and tests a RouteFlow-based core using OSPF, with Mininet and Open vSwitch for the data plane and RouteFlow with POX for control. The tests found connected hosts and switches, 40-65 ms average RTTs, and shortest-path routing consistent with OSPF’s SPF algorithm.
Problem
Campus core layers must provide highly available interconnectivity and routing, while implementing traditional OSPF over SDN/OpenFlow remains a design challenge.
Method
The paper designs a triangle-topology campus core using RouteFlow and OSPF, and evaluates it in a two-VM virtual SDN testbed.
Results
The tests showed interconnected switches and hosts, 40-65 ms average RTTs, and packet routes matching OSPF’s shortest-path algorithm.
Takeaways & Limitations
The virtual design demonstrated interconnectivity and shortest-path packet routing for the proposed RouteFlow-based campus core.
Takeaways & Limitations
The study remains a virtual testbed evaluation; physical OpenFlow switches and comparison with a physical SDN testbed are proposed for future work.
Abstract
from arXiv · showhide
As one of the layers in campus network, core layer or backbone network should provide interconnectivity and routing between internal and external networks, including other campus networks or the Internet. With that requirement, designing this layer to be highly available to interconnect and route traffic is a high priority. By using software-defined networking (SDN) paradigm, we attempt to design core layer in campus network employing best practices of network topology and routing protocol at the layer with a use case of core layer in a university campus network. We use RouteFlow as the SDN platform supporting a traditional routing protocol, i.e. Open Shortest Path First (OSPF), over OpenFlow (OF) network infrastructure. The experimental testbed/environment consists of two virtual machines (VMs). The first VM is used as the SDN/OF data plane with Open vSwitch in Mininet network emulator, and the second one representing SDN control plane comprising RouteFlow with POX controller. We evaluated the design by testing the interconnectivity using ping for the OF switches in the topology and hosts that are connected to the switches. We also tracked the route of the packets by monitoring traffic passed through all network interfaces of the switches using tcpdump. This case was evaluated since we need to make sure that packets were routed with the shortest path from source to destination using OSPF that was implemented in the virtual network at the top of the SDN platform.
1. Introduction
Campus core layers must provide available interconnectivity and routing between internal and external networks. The paper applies SDN to this setting through RouteFlow, using OSPF over OpenFlow and evaluating a university-campus design.
- Campus-network context: Campus networks use hierarchical core, distribution, and access layers, with the core connecting internal networks to other campuses or the Internet.Interconnectivity and routing are identified as essential core-layer services, with availability as a priority.
- SDN motivation: SDN separates control and data planes by moving control functions to an external controller, while enabling programmable, flow-based forwarding.Traditional networks couple these planes within network devices.
- SDN platform: RouteFlow provides a way to run traditional IP routing over SDN/OpenFlow infrastructure.The paper positions RouteFlow as a framework for experimenting with SDN while retaining traditional routing stacks.
- Related work: Prior studies applied RouteFlow to ISP networks, IS-IS-based QoS and controller evaluations, and OSPF experiments involving QoS and convergence time.These studies establish related uses of RouteFlow across network contexts and routing protocols.
- Paper contribution: This paper designs a triangle-topology campus core using RouteFlow, SDN/OpenFlow, and OSPF, then evaluates interconnectivity and packet routing.The design reflects the core layer of Universitas Jenderal Soedirman.
2. Research Method
The research translates campus core-layer requirements into an SDN/OpenFlow topology and validates the resulting design through interconnectivity and packet-routing tests.
- Method overview: The method identifies core-layer requirements, proposes a simple network-topology architecture, establishes a virtual testbed, and runs interconnectivity and packet-routing tests.The validation targets both connectivity and routing behavior.
2.1. System Design
The system design combines a triangle core topology with OSPF routing and RouteFlow-based SDN/OpenFlow control. The proposed architecture adapts a traditional campus core for a virtual SDN testbed.
- Network topology: Triangle topology is preferred over square topology because it provides equal-cost redundant paths for deterministic convergence.Point-to-point links are also desired for rapid propagation when link states change.
- Case-study topology: The Unsoed campus core uses a triangle connecting three routers at Duren Tiga, Grendeng, and Blater over 1 Gbps links.The topology is presented as the case-study basis for the SDN design.
- Routing protocol: OSPF computes best paths using Dijkstra’s least-cost or shortest-path algorithm for dynamic routing.The protocol is described as an open, widely used intra-AS routing protocol.
- Routing integration: The design addresses the challenge of implementing traditional OSPF routing over SDN/OpenFlow infrastructure.This is stated as the research goal for the core layer.
- RouteFlow architecture: RouteFlow virtualizes IP routing over OpenFlow, using a virtual network and legacy routing engines that support protocols including OSPF.The platform includes RFProxy, RFServer, RFClient, and can use POX or Ryu controllers.
- Controller selection: POX was selected because it is used with Mininet and included in RouteFlow, while requiring only a small functional controller program for this study.The choice is tied to the research scope.
- SDN core design: The proposed SDN/OpenFlow core design places RouteFlow and the POX controller in the SDN controller and adapts the traditional architecture.The experimental network is assembled through software virtualization.
2.2. Experimental Setup
The experimental setup uses virtualized RouteFlow and Mininet components to implement a triangle SDN/OpenFlow core-layer topology with OSPF routing.
- Host: The testbed uses two virtual machines running on a Debian GNU/Linux 9 host.The host laptop uses an Intel Core i5-6200U processor with 2 cores and 12GB memory.
- Host: The virtual machines connect through two TUN interfaces and a virtual bridge, with distinct MAC and IP addresses and host-provided NAT Internet access.These settings provide the virtual network connection between the VMs and the host.
- RouteFlow: RouteFlow with a POX controller forms the SDN control plane and configures three Quagga virtual routers running OSPF in a triangle topology.OSPF hello and dead intervals are configured as 1 second and 4 seconds, respectively, with backbone-area networks.
- Mininet: Mininet provides the SDN data plane with Open vSwitch and OpenFlow switches.The experiment uses Mininet version 2.2.2 and OpenFlow 1.0.
- Mininet: A Python script creates the triangle topology, connects Mininet to the RouteFlow VM, and sets link bandwidth to 1 Gbps.The script also configures host network routes.
3. Evaluation and Results
The design was evaluated for host and switch interconnectivity and for packet-path selection. Ping showed connectivity, while tcpdump analysis indicated that OSPF routed packets along shortest paths.
- 3.1. Interconnectivity: Ping tests between host pairs h1-h2, h2-h3, and h3-h1 evaluated interconnectivity ten times per pair.Tcpdump data was also examined for OpenFlow packet-ins and packet-outs carrying ICMP traffic.
- 3.1. Interconnectivity: 40-65 ms was the range of average RTT values measured in the interconnectivity tests.The paper considers these results normal, although they exceed typical LAN RTT values.
- 3.2. Packet Routing: Tcpdump monitored traffic on every switch interface to trace ICMP packets during packet-routing evaluation.The captured traffic was analyzed to determine which interfaces carried the packets.
- 3.2. Packet Routing: OSPF routed h1-to-h2, h2-to-h3, and h3-to-h1 packets along their shortest paths in the triangle topology.Virtual routers computed the paths, and RFProxy applied the routing information to the Mininet SDN/OpenFlow data plane.
4. Conclusions and Future Work
The study implemented a triangle-topology campus core using OSPF over RouteFlow in a two-VM SDN testbed, then validated connectivity and shortest-path routing. Future work targets failure resilience and physical-testbed validation.
- Conclusions: The design used a triangle topology, OSPF, and RouteFlow across separate SDN control- and data-plane VMs.RouteFlow and POX ran on one VM, while Mininet with Open vSwitch ran on the other.
- Conclusions: Connectivity testing produced average ping RTTs ranging from 40–65 ms across interconnected switches and hosts.Packet traffic was collected from switch interfaces with tcpdump and analyzed using Wireshark.
- Conclusions: Observed packet routes corresponded to OSPF’s SPF algorithm, routing packets along the shortest path from source to destination.The routing check used ICMP packets captured across switch interfaces.
- Future Work: Future experiments will test interconnectivity availability under link failures and measure RTT and convergence time while alternate paths form.The planned scenarios cover each possible link in the topology.
- Future Work: A physical SDN testbed using commodity OpenFlow switches is proposed to assess the design’s real-world application alongside the virtual testbed.The authors expect side-by-side results to provide more valuable insights.