1 Path Splicing Author: Murtaza Motiwala, Megan Elmore, Nick Feamster and Santosh Vempala Publisher: SIGCOMM’08 Presenter: Hsin-Mao Chen Date:2009/12/09

2 Outline Introduction Design Goals Path Splicing Main Idea Intradomain Path Splicing Interdomain Path Splicing Evaluation

3 Introduction Single path routing. Multipath routing provides nodes access to multiple paths for each destination. Two obstacles have hindered many multipath routing solution. 1.Scalability 2.Control

4 Design Goals High reliability Fast recovery Small stretch Control to end systems

5 Path Splicing Main Idea A new routing primitive called path splicing. 1.Generate many alternate paths by running multiple routing protocol instances. 2.Allow traffic to switch between paths at intermediate hop. 3.Give end systems the control to switch paths.

6 Intradomain Path Splicing Conventional shortest paths routing is designed to route traffic along low-cast. Path splicing creates routing trees that are base on random link-weight perturbation. Degree-base perturbations of link weights

7 Intradomain Path Splicing

8 End systems insert a “shim” splicing header in between the network and transport headers. The size of the splicing header is n ‧ lg(k) k is the number of slices. n is the number of the hops along the network path.

9 Interdomain Path Splicing BGP select only a single best route for each destination prefix. Instead, a router could select the best k routers and push them into the forwarding table. An n-hop AS path requires 2n ‧ lg(k) routing bit.

10 Interdomain Path Splicing

11 Evaluation Reliability Intradomain Sprint backbone network topology inferred from Rocketfuel[29]

12 Evaluation Reliability Interdomain C-BGP[25]

13 Evaluation Recovery Intradomain

14 Evaluation Recovery Interdomain

15 Evaluation Stretch Intradomain

16 Evaluation Novelty Intradomain

17 Evaluation Comparison to Routing Deflections[32]

18 Evaluation Incremental Deployability

19 Evaluation Minimal Disruption to Traffic Abilene network(11 nodes, 14 links)