9. Manageability Considerations
9. Manageability Considerations
In SR-enabled networks, the path the packet takes is encoded in the header. As the path is not signaled through a protocol, OAM mechanisms are necessary in order for the network operator to validate the effectiveness of a path as well as to check and monitor its liveness and performance. However, it has to be noted that SR allows to reduce substantially the number of states in transit nodes; hence, the number of elements that a transit node has to manage is smaller.
SR OAM use cases for the MPLS data plane are defined in [RFC8403]. SR OAM procedures for the MPLS data plane are defined in [RFC8287].
SR routers receive advertisements of SIDs (index, label, or IPv6 address) from the different routing protocols being extended for SR. Each of these protocols have monitoring and troubleshooting mechanisms to provide operation and management functions for IP addresses that must be extended in order to include troubleshooting and monitoring functions of the SID.
SR architecture introduces the usage of global segments. Each global segment MUST be bound to a unique index or address within an SR domain. The management of the allocation of such an index or address by the operator is critical for the network behavior to avoid situations like misrouting. In addition to the allocation policy/tooling that the operator will have in place, an implementation SHOULD protect the network in case of conflict detection by providing a deterministic resolution approach.
When a path is expressed using a label stack, the occurrence of label stacking will increase. A node may want to signal, in the control plane, its ability in terms of size of the label stack it can support.
A YANG data model [RFC6020] for SR configuration and operations has been defined in [SR-YANG].
When SR is applied to the IPv6 data plane, segments are identified through IPv6 addresses. The allocation, management, and troubleshooting of segment identifiers is no different than the existing mechanisms applied to the allocation and management of IPv6 addresses.
The DA of the packet gives the active segment address. The segment list in the SRH gives the entire path of the packet. The validation of the source-routed path is done through inspection of DA and SRH present in the packet header matched to the equivalent routing table entries.
In the context of the SRv6 data plane, the source-routed path is encoded in the SRH as described in [IPv6-SRH]. The SRv6 source-routed path is instantiated into the SRH as a list of IPv6 addresses where the active segment is in the DA field of the IPv6 packet header. Typically, by inspecting, in any node, the packet header, it is possible to derive the source-routed path to which it belongs. Similar to the context of the SR-MPLS data plane, an implementation may originate path control and monitoring packets where the source-routed path is inserted in the SRH and where each segment of the path inserts in the packet the relevant data in order to measure the end-to-end path and performance.