In the OpenFlow based split architecture, data-plane forwarding is separated from control and management functions. Forwarding elements make only simple forwarding decisions based on flow table entries populated by the controller. While OpenFlow does not specify how topology monitoring is performed, the centralized controller can use Link-Layer Discovery Protocol (LLDP) messages to discover link and node failures and trigger restoration actions. This monitoring and recovery model has serious scalability limitations because the controller has to be involved in the processing of all of the LLDP monitoring messages. For fast recovery, monitoring messages must be sent with millisecond interval over each link in the network. This poses a significant load on the controller. In this paper we propose to implement a monitoring function on OpenFlow switches, which can emit monitoring messages without posing a processing load on the controller. We describe how the OpenFlow 1.1 protocol should be extended to support the monitoring function. Our experimental results show that data plane fault recovery can be achieved in a scalable way within 50 milliseconds using this function.

Scalable fault management for OpenFlow

A method for resource optimized network virtualization overlay transport in a virtualized data center environment includes an optimized virtualized transport mechanism based on MPLS-TP tunneling technology. The transport mechanism may include a usage monitoring and resource usage advertisement mechanism based on IGP-TE protocol extension. Also, the transport mechanism may include a path computation engine (PCE) based optimal path computation for a virtualized transport tunnel used to carry VM-to-VM traffic across the virtualized data center. Additionally, the transport mechanism may include a SDN controller for provisioning and control of virtualized machines and a virtualized transport system.

Method for resource optimized network virtualization overlay transport in virtualized data center environments

Mechanisms are described by which link state “path” information can be collected from networks and shared with external components, such as routers or centralized controllers or path computation elements, using an exterior gateway protocol, such as the Border Gateway Protocol. That is, the link state information for multiple interior gateway protocol (IGP) routing domains is shared between external components using the exterior gateway protocol, such as BGP. As such, the techniques described herein allow link state information to be shared across different routing domains, such as routing and reachability information shared between different autonomous systems. The extensions described herein allow an exterior gateway protocol to be used to signal explicit path segments within IPG routing domains so as to set up an overall path that spans the multiple IPG routing domains.

BGP link-state extensions for segment routing

Fixed and mobile telecom operators, enterprise network operators and cloud providers strive to face the challenging demands coming from the evolution of IP networks (e.g., huge bandwidth requirements, integration of billions of devices and millions of services in the cloud). Proposed in the early 2010s, Segment Routing (SR) architecture helps face these challenging demands, and it is currently being adopted and deployed. SR architecture is based on the concept of source routing and has interesting scalability properties, as it dramatically reduces the amount of state information to be configured in the core nodes to support complex services. SR architecture was first implemented with the MPLS dataplane and then, quite recently, with the IPv6 dataplane (SRv6). IPv6 SR architecture (SRv6) has been extended from the simple steering of packets across nodes to a general network programming approach, making it very suitable for use cases such as Service Function Chaining and Network Function Virtualization. In this article, we present a tutorial and a comprehensive survey on SR technology, analyzing standardization efforts, patents, research activities and implementation results. We start with an introduction on the motivations for Segment Routing and an overview of its evolution and standardization. Then, we provide a tutorial on Segment Routing technology, with a focus on the novel SRv6 solution. We discuss the standardization efforts and the patents providing details on the most important documents and mentioning other ongoing activities. We then thoroughly analyze research activities according to a taxonomy. We have identified 8 main categories during our analysis of the current state of play: Monitoring, Traffic Engineering, Failure Recovery, Centrally Controlled Architectures, Path Encoding, Network Programming, Performance Evaluation and Miscellaneous. We report the current status of SR deployments in production networks and of SR implementations (including several open source projects). Finally, we report our experience from this survey work and we identify a set of future research directions related to Segment Routing.

Segment Routing: A Comprehensive Survey of Research Activities, Standardization Efforts, and Implementation Results

A method and device are disclosed for opportunistic compression of routing segment identifiers. In one embodiment, the method includes participating in routing of a first data packet through a first node in a network, and subsequently entering into an arrangement with an adjacent node in the network. The first data packet includes a first plurality of routing segment identifiers, and additional data packets to be routed through the first node also include the first plurality of routing segment identifiers. The arrangement entered into includes representation of the first plurality of routing segment identifiers by a single compression identifier. The method further includes participating in routing of at least one of the additional data packets using the compression identifier instead of the first plurality of routing segment identifiers. In an embodiment, the device includes one or more network interfaces and a processor configured to perform the steps of the method.

Opportunistic compression of routing segment identifier stacks

This document specifies an architectural framework for the application
of Multiprotocol Label Switching (MPLS) to the construction of packet-
switched transport networks. It describes a common set of protocol
functions -- the MPLS Transport Profile (MPLS-TP) -- that supports the
operational models and capabilities typical of such networks,
including signaled or explicitly provisioned bidirectional connection-
oriented paths, protection and restoration mechanisms, comprehensive
Operations, Administration, and Maintenance (OAM) functions, and
network operation in the absence of a dynamic control plane or IP
forwarding support. Some of these functions are defined in existing
MPLS specifications, while others require extensions to existing
specifications to meet the requirements of the MPLS-TP. This document
defines the subset of the MPLS-TP applicable in general and to point-
to-point transport paths. The remaining subset, applicable
specifically to point-to-multipoint transport paths, is outside the
scope of this document. This document is a product of a joint
Internet Engineering Task Force (IETF) / International
Telecommunication Union Telecommunication Standardization Sector
(ITU-T) effort to include an MPLS Transport Profile within the IETF
MPLS and Pseudowire Emulation Edge-to-Edge (PWE3) architectures to
support the capabilities and functionalities of a packet transport
network as defined by the ITU-T. This document is not an Internet
Standards Track specification; it is published for informational
purposes.

A Framework for MPLS in Transport Networks

A method and system are disclosed for use of segment routing in monitoring of a network path. In one embodiment, the method includes selecting a plurality of segment identifiers and assembling the segment identifiers into a segment identifier stack, where the segment identifier stack encodes a test path within the network for attempted routing of a test message. The method may further include inserting the segment identifier stack into a header associated with the test message, and forwarding the test message according to an entry in a forwarding table corresponding to the segment identifier at the top of the segment identifier stack. Interior gateway protocol advertisements may be used to communicate segment identifiers for creating or updating of the data structure or the forwarding table. In an embodiment, the system includes one or more network interfaces and a processor configured to perform the steps of the method.

Method and system for path monitoring using segment routing

An apparatus and method is disclosed for segment routing (SR). In one embodiment, the method includes a node creating a segment stack that identifies one segment calculated using a first algorithm and a second segment calculated using a second, different algorithm. The node then attaches this header to a packet and sends it to another node.

Segment Routing Techniques

Many service provider service level agreements (SLAs) depend on the
ability to measure and monitor performance metrics for packet loss and
one-way and two-way delay, as well as related metrics such as delay
variation and channel throughput. This measurement capability also
provides operators with greater visibility into the performance
characteristics of their networks, thereby facilitating planning,
troubleshooting, and network performance evaluation. This document
specifies protocol mechanisms to enable the efficient and accurate
measurement of these performance metrics in MPLS networks. [STANDARDS-
TRACK]

Daniel C. Frost

Papers

A Framework for MPLS in Transport Networks

Opportunistic compression of routing segment identifier stacks

Method and system for path monitoring using segment routing

Segment Routing Techniques

Packet Loss and Delay Measurement for MPLS Networks