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

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201netdev-linux module that abstracts interaction between ofproto and Linux networkdevices(like Ethernet ports).We tested our implementation of the MPLS data-plane using the OFTest framework[121,122] shown in Fig.5.11b. OFTest includes a data-plane interface that allows sendingand receiving packets to a switch-under-test (OVS in this case). It also includes a controlplaneinterface that implements a light-weight OpenFlow controller that can be used tointeract with the switch-under-test using the OpenFlow protocol. In our case thiscontroller communicates with the ofproto module in OVS. We used OFTest to write testscriptsthat verified the correct functionality of the MPLS data plane.Control-Plane: The control-plane was hosted in a server running NOX [15]. NOXwas modified to include our changes to version 1.0 of the OpenFlow protocol, therebyenabling control of an MPLS data-plane [123].Fig. 5.12 MPLS-TE NOX Software ArchitectureThe software architecture is shown in Fig. 5.12. We use NOX’s basic event engineand connection-handlers to the switches that are collectively referred to as nox-core. Wealso use NOX’s link discovery module to discover IP links and construct the annotatedtopology-map. And we include several data-bases for packet-flows, tunnels and MPLS-
202 CHAPTER 5. INTRODUCING SDN CONTROL IN MPLS NETWORKSlabel information. Together with the switch and network-APIs, these modules presentapplications with a map-abstraction.The first set of network-applications involves TE functionality. The TE-LSPconfiguration module is responsible for reading tunnel configuration files or alternatelyresponding to config-messages from a GUI. Tunnels are configured by specifying thehead-end and tail-end routers; the desired bandwidth and tunnel priority; the type oftraffic the tunnel is designated for; and whether Auto-Bandwidth is enabled on the tunnelor not. With this information the config module uses the TE-LSP routing module to find apath between head-end and tail-end routers that satisfy all the constraints (bandwidth,priority, traffic-class). Once a path is found, the config module uses the network-API toestablish the tunnel in the data-plane by inserting flow-entries for the LSP which includeslabel information. If Auto-Bandwidth has been configured on the tunnel, it also activatesthe polling process for LSP usage information in the TE-LSP statistics module. Thisinformation is used by the Auto-Bandwidth module to periodically change the tunnelreservation and update the TE-LSP database. But before such an update happens, theAuto-Bandwidth module checks the CSPF module to make sure that the new-bandwidthreservation is possible along the existing tunnel path. If it is possible but requires reroutinglower priority tunnels or re-routing the tunnel itself, it processes such change byinvoking methods in the network-API.Together the TE applications create, manage, re-route, and tear-down TE-LSPs(tunnels) in the data-plane. As explained in the previous section, our map-abstractionallows us to create another map above the TE applications (see Fig. 5.9). This latter maprepresents the TE tunnels as unidirectional links, on which packet-flow routing can beperformed in an automated and programmatic way. We create three routing-modules forpacket-flow routing. The default SPF routing-module uses NOX’s built-in all pairsshortest-path routing module. The only difference is that instead of using this moduledirectly on the IP topology, we use it on the topology that includes the IP links as well asthe tunnels represented as unidirectional links. The default routing module is used for all
Page 1: Chapter 5Introducing SDN Control 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
Page 20 and 21: 191This latter point can best be ex
Page 22 and 23: 193different customer’s traffic d
Page 24 and 25: 195the start of the tunnel, to the
Page 26 and 27: 197forwarding traffic-type (or clas
Page 28 and 29: 199controller, as well as link-stat
Page 32 and 33: 203packet-flow routing. The other t
Page 34 and 35: 205In Fig. 5.14 we show two tunnels
Page 36 and 37: 207forced to route along a less-uti
Page 38 and 39: 209tunnel carries both video and Vo
Page 40 and 41: 211former include (i) our implement
Page 42 and 43: 213these backup tunnels usually do
Page 44 and 45: 215annotated fiber topology, on whi
Page 46: 217of magnitude fewer than implemen

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