Segment Routing

This chapter covers the following exam topics:

3.3 Describe segment routing

• 3.3.a Segment types

• 3.3.b SR control plane (BGP, OSPF, IS-IS)

• 3.3.c Segment routing traffic engineering

• 3.3.d TI-LFA

• 3.3.e PCE-PCC architectures

• 3.3.f Flexible algorithm

• 3.3.g SRv6 (locator, micro-segment, encapsulation, interworking gateway)

Segment Routing represents a cutting-edge technology designed to enhance and optimize the use of MPLS-based and IPv6 networks. This innovative approach introduces a suite of tools and concepts that not only simplify network operations but also significantly enhance the flexibility available to network operators. By allowing for more granular control over packet paths, Segment Routing empowers network operators to efficiently navigate the intricacies of modern networks, adapt to dynamic requirements, and minimize the challenges associated with traditional MPLS-based architectures.

In essence, Segment Routing is a beacon of progress in the networking realm, offering a robust set of solutions to meet the most demanding network requirements. Its advent marks a transformative shift in how networks are managed, providing operators with a versatile toolkit to navigate the complexities of traffic engineering, and ensuring that networks can dynamically respond to changing conditions in real time. By simplifying the routing paradigm and enhancing the scalability of MPLS-based networks, Segment Routing emerges as a pivotal technology, poised to play a crucial role in the evolution of modern network architectures.

“Do I Know This Already?” Quiz

The “Do I Know This Already?” quiz allows you to assess whether you should read this entire chapter thoroughly or jump to the “Exam Preparation Tasks” section. If you are in doubt about your answers to these questions or your own assessment of your knowledge of the topics, read the entire chapter. Table 15-1 lists the major headings in this chapter and their corresponding “Do I Know This Already?” quiz questions. You can find the answers in Appendix A, “Answers to the ‘Do I Know This Already?’ Quizzes and Review Questions.”

Table 15-1 “Do I Know This Already?” Section-to-Question Mapping

1. Which of the following are viable options for assigning SRGB ranges? (Select all that apply.)

   1. Globally

   2. Per IGP

   3. Dynamically

   4. Statically

2. Which labels cannot be a part of SRGB? (Select all that apply.)

   1. 15999

   2. 16000

   3. 24999

   4. 1,048,576

3. Which TLVs play an important role in Segment Routing? (Select all that apply.)

   1. 22

   2. 41

   3. 135

   4. 163

4. Which of the following is not an option for the SR Control Plane?

   1. RSVP-TE

   2. IS-IS

   3. OSPF

   4. BGP

5. Which of the following is not a viable option to supply SR policy to the ingress router?

   1. NETCONF

   2. FIB

   3. CLI

   4. PCEP

6. Which behavior properly describes an SR policy?

   1. An SR policy uses Network Service Orchestrator (NSO) to program its data plane.

   2. SR-PCE will use BGP-LS to program an SR policy into the ingress node.

   3. An SR policy encodes the list of constraints into the MPLS headers.

   4. An SR policy will use BSID entries to program its forwarding table.

7. Which of the following describes TI-LFA functionality? (Select all that apply.)

   1. TI-LFA must rely on LDP functionality to provide double-segment protection.

   2. TI-LFA uses next-hop neighbor as the point of local repair.

   3. TI-LFA preprograms the post-convergence path into a router’s data plane.

   4. TI-LFA can use P space to calculate the post-convergence path.

8. Viable repair tunnel endpoints are found at which intersections?

   1. At midpoints of extended spaces

   2. At the intersection of point of local repair and double segments

   3. At the intersection of PQ nodes

   4. At the intersection of P and Q spaces

9. Which component serves the needs of long-term network engineering and capacity planning?

   1. Crosswork Network Controller

   2. Crosswork Optimization Engine

   3. WAN Automation Engine

   4. Crosswork Cloud

10. Which of the following protocols are used by PCEP to calculate network paths? (Select all that apply.)

    1. IS-IS

    2. BGP-LS

    3. RSVP-TE

    4. OSPF