Computer Networks · free preview
Router Implementation
A router is a machine that moves packets from input ports to output ports, the software design buffers every packet in main memory under a general processor and is bounded by memory bandwidth and by the per-packet processing rate, the hardware design hands the per-packet work to a network processing unit with fast static memory, ternary content-addressable match tables, and a programmable pipeline of match-action stages forwarding terabits per second, and the clean separation between the per-packet data plane and the background control plane that runs the routing protocols is the idea that software-defined networking turns into an industry-wide architecture.
1. The Software Switch
The Software Switch
2. Two Planes
Two Planes
3. The Hardware Path
The Hardware Path
4. Software-Defined Networking
Software-Defined Networking
5. The two bottlenecks
What limits a router built from a general-purpose computer with several network interfaces?
6. Small packets
Why must switch designers plan for minimum-size packets rather than average traffic?
7. The planes
A router recomputes its forwarding table after a topology change while continuing to forward packets. Which plane does each activity belong to?
8. The ternary table
What does ternary content-addressable memory give a forwarding pipeline that an ordinary table lookup does not?
9. The pipeline
How does a network processing unit sustain tens of terabits per second when each packet needs several lookups?
10. Bare metal
What changed when high-performance switches became bare-metal commodity hardware?
11. Packet budget
A processor forwards 40 million packets per second and traffic arrives as minimum-size 64-byte packets. About how many gigabits per second of aggregate throughput does that allow?
12. The match table
Which memory technology lets a forwarding pipeline match header patterns containing wildcards in a single step?
13. The pipeline language
Which domain-specific language programs the match-action pipelines of modern network processing units?
14. The faster memory
Bare-metal switches buffer packets in which memory technology, roughly an order of magnitude faster than the dynamic memory of main memory?
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