课程: MPLS Segment Routing

Understanding source routing and segment routing

课程: MPLS Segment Routing

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Understanding source routing and segment routing

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- [Instructor] In this session, we will learn about source routing and segment routing. We will explore the fundamentals of these routing techniques, their segment types, and how they operate within a network. Let's get started. Source routing is a routing technique where the center of a packet specifies the route that the package should take through the network. Instead of relying on each router along the path to determine the next stop, the entire road is predefined by the source. This metric provides greater control over the path, enabling efficient traffic management and optimization. However, it can also increase complexity since the source must be aware of the entire network topology. Segment routing or SR builds on the principles of source routing, but introduces segments to simplify and enhance routing. In segment routing, the path is broken down into a series of segments, which are instructions encoded within the packet header. Each segment represents either a topological instruction, like a node or a link, or a service-based instruction. This approach reduces the need for complex signaling protocols and simplifies network operations. Segment routing defines various types of segments to direct traffic through a network efficiently. Let's focus on the two most frequently used types, prefix segment, adjacency segment. A prefix segment, also known as a node segment, represents a specific destination prefix or node within the network. It's globally unique within the network domain and direct package to a particular endpoint. When a packet encounters a prefix segment, it's routed to the corresponding node associated with the prefix. This segment is essential for directing traffic to known locations, such as servers, data centers, or any specific device within the network. Prefix segments are fundamental to segment routing as they simplify routing decisions. Each packet carries its destination as part of the segment list, allowing routers to forward the packet based on the encoded segments without needing additional routing information. An adjacency segment is a strict forwarding instruction that creates a single hop tunnel between two nodes. It represents a specific link or adjacency between two nodes in the network. When a packet encounters an adjacency segment, it's directed to traverse the specified link associated with an interior gateway protocol or IGP adjacency, regardless of the link's cost. This means that the packet will always follow the predefined path through that specific link, providing precise control over the packet's route. Adjacency segments are particularly useful for traffic engineering, allowing network operators to manage and optimize the flow of traffic through a specific path. This is crucial in scenarios where certain links need to be used for load balancing or to ensure quality of service. Segment routing can operate over different forwarding planes, primarily MPLS, multiprotocol label switching, and IPv6. Each forwarding plane type has its own advantage and use cases. In the MPLS forarding planes, segments are represented as labels, while in the IPv6 forwarding plane, segments are represented as IPv6 addresses. This flexibility allows segment routing to be implemented in various network environments, leveraging existing infrastructure. In conclusion, source routing and segment routing are powerful techniques for managing network traffic. By understanding the different segment types, prefix, node, and adjacency segment, and their forwarding planes, network operators can achieve greater control, flexibility, and efficiency.

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