Investigating black holes in segment routing networks: identification and detection

The new Segment Routing paradigm provides the network operator the possibility of highly in- creasing network performance exploiting advanced Traffic Engineering features and novel network programmability functions. Anyway, as any new solutions, SRv6 has a side effect: the introduction of unknown service disruption events. Network Black Holes (BHs) are logical failures that create a service disruption for a subset of traffic flows, generally due to device misconfiguration. Detection of a BH is a hard task due to its specific nature: the infrastructure is up and the disconnection affects a limited number of flows. An example of BH is the one caused by the failure of the Path MTU Discovery procedure in IPv6. The Segment Routing (SR) Architecture is an overlay infrastructure that realizes the source routing. SR exploits the connectivity service offered by the underlay IPv6 (SRv6). Thus SR inherits the problems related to BHs affecting IPv6. In SR this problem is even more stressed due to the encapsulation mechanism that is required to enforce the segment lists on packets. Even worse, existing active probing based tools to detect network BHs for IPv6 are not suitable in SR. In this paper we investigate the problem of detecting SR Black Holes in SR domains. First, we provide an experimental demonstration of the creation of an SR Black Holes. Then we show that existing tools based on active probing are not suitable to detect SR BHs. Then, a pas- sive framework named Segment Routing Black Holes Detection (SR-BHD) is introduced. SR-BHD make use of specific traffic counters available in SR capable nodes to verify the validity of the flow conservation principle on each network element. Experimental evaluation carried out through simu- lation and emulation shows the effectiveness of SR-BHD in detecting the presence of SR BHs. The proposed framework, named Segment Routing Black Holes Detection (SR-BHD) uses a passive ap- proach based on the observation of traffic counters available in SR capable nodes [9]. In particular, the main contributions of this thesis are: • an experimental demonstration of the existence of SR Black Holes and of the possible failure detecting them through an active approach; • the proposition of a passive detection system allowing a reliable identification of a black hole; • a deep performance evaluation of the proposed method through simulation. • a validation of the proposed framework over a real testbed.