Chapter 5 Introducing SDN Control in MPLS Networks - High ...

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199controller, as well as link-state for reservable bandwidth at eight priority levels. CSPF isperformed in the Controller; tunnel-priorities are taken into consideration; and anyresultant pre-emption is achieved using OpenFlow messages to add, delete or modifyflow-entries in LSRs corresponding to TE tunnels.5.3.2 MPLS-TE PrototypeIn this section we discuss a prototype implementation of MPLS Traffic-Engineering in anSDN based network (MPLS-TE). There are two goals of this implementation: First, wedemonstrate that our approach is capable of reproducing existing services offered byMPLS network today, while validating the simplicity of our approach compared to theexisting IP/MPLS control plane; and second, as described in the previous section, weshow how the implementation of the features can be made different from the traditionalimplementation in ways that either, greatly simplifies the feature or provides a featurethat MPLS-TE cannot provide.Data-Plane: At the time this work was done (late 2010), handling of MPLS labelswas just being introduced into the OpenFlow protocol (version 1.1[117]). As a result,there weren’t any OpenFlow enabled switches (or controllers) that supported MPLS dataplanecapabilities via OpenFlow.We added MPLS data-plane capabilities to a software switch called Open vSwitch(OVS[118]) that fully supported version 1.0 of the OpenFlow protocol. We also had tochange the OpenFlow protocol (v1.0) to add the capability of controlling an MPLS dataplane.To accomplish the latter, we borrowed the MPLS related features from v1.1 of theprotocol and added it to v1.0 † .† We chose not to implement the entire v1.1 spec as it includes a number of other features like groups andmultiple-tables, which were not essential to this experiment.
200 CHAPTER 5. INTRODUCING SDN CONTROL IN MPLS NETWORKS(a)(b)Fig. 5.11 (a) Open vSwitch Software Architecture [119] (b) OFTest Framework [120]Fig. 5.11a shows the OVS software architecture. Details can be found in [119]. Herewe focus on the parts we changed to add MPLS data-plane capabilities. OVS can be usedpurely as an OpenFlow switch, or it can be used with added functionality that is part ofOVS. We chose to use it as an OpenFlow switch using the ovs-openflowd programinstead of the ovs-vswitchd program. The former does not require communication withan ovsdb-server. Next in the stack shown in Fig. 5.11a, the ofproto module communicateswith an external Controller. We changed this module to work with our additions toversion 1.0 of the OpenFlow protocol borrowed from version 1.1 (for MPLS support).The ofproto module communicates with the switch using the ofproto-dpif interface.The OVS switch datapath can be in kernel space (as shown in the figure) or inuserspace. We chose the userspace datapath implemented in the dpif-netdev module,which also instantiates the datapath-interface (dpif) provider class. We added support forthe MPLS data plane in the dpif-netdev module [120]. This included the ability to matchon the outermost MPLS label (id and traffic-class bits) and perform the actions ofpushing, changing and popping off multiple labels from packets together with TTLmanipulations. Since our software switch was hosted in Linux, we used the built-in
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Page 10 and 11: 181routers make decisions on LSP pa
Page 12 and 13: 183benefits of the map-abstraction
Page 14 and 15: 185all upgraded at the same time. M
Page 16 and 17: 187However the tunnel’s reserved
Page 18 and 19: 189Admission-Control: The MPLS cont
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Page 26 and 27: 197forwarding traffic-type (or clas
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Page 34 and 35: 205In Fig. 5.14 we show two tunnels
Page 36 and 37: 207forced to route along a less-uti
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