65 lines
2.1 KiB
Markdown
65 lines
2.1 KiB
Markdown
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# Module 7: Traffic Engineering
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> **Course**: [ISP Backbone Lab Course](../README.md)
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> **Previous**: [Module 6: Segment Routing](06-segment-routing.md)
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> **Next**: [Module 8: Attack & Defense](08-attack-defense.md)
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---
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## Network Diagram
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*SR-TE explicit path steering — default shortest path vs policy-driven SID stack path with Flex-Algo*
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---
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## Why TE?
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By default, IS-IS picks the shortest path. But what if:
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- The shortest path is congested?
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- You want to send VoIP traffic on a low-latency path and bulk data on a high-bandwidth path?
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- A fiber cut takes out the shortest path and you need a pre-computed backup?
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**Traffic Engineering** lets you define explicit paths through the network.
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## SR-TE (Segment Routing Traffic Engineering)
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With SR, TE is just a **stack of SIDs**. Want traffic to go P1 → P2 → P-CORE → P4 instead of the direct path? Push labels `[16002, 16005, 16004]` onto the packet. Done. No RSVP tunnels, no signaling protocol, no state in the core.
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## Lab 7 Config: SR-TE Policy
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**PE-EDGE1 (force traffic to PE-EDGE4 via a specific path):**
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```
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segment-routing traffic-eng
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segment-list PATH-VIA-P2-PCORE
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index 10 mpls label 16002 ! P2
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index 20 mpls label 16005 ! P-CORE
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index 30 mpls label 16014 ! PE-EDGE4
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!
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policy STEER-TO-PE4
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color 100 end-point 10.0.0.14
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candidate-paths
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preference 200
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explicit segment-list PATH-VIA-P2-PCORE
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```
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## Flex-Algo (Advanced)
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Flex-Algo lets you define **multiple topologies** on the same physical network. For example:
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- **Algorithm 0** (default): Shortest path by metric
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- **Algorithm 128**: Low-latency path (uses delay metric)
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- **Algorithm 129**: High-bandwidth path (avoids congested links)
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Each algorithm creates a separate set of SIDs, so you can steer traffic into different topologies without explicit path lists.
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## Understanding Check
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1. How does SR-TE compare to RSVP-TE? What makes it simpler?
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2. What is a SID stack and how does it define a path?
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3. What is Flex-Algo and when would you use it over explicit SR-TE?
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---
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> **Next Module**: [Module 8: Attack & Defense Labs →](08-attack-defense.md)
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