Checking path consistency and reachability in multipath networks - - PowerPoint PPT Presentation

▶

Oct 28, 2023 151 likes •290 views

Checking path consistency and reachability in multipath networks using Batfish Ari Fogel 1 Stanley Fung 1 Todd Millstein 1 Ratul Mahajan 2 Ramesh Govindan 3 Luis Pedrosa 3 1 University of California, Los Angeles 2 Microsoft Research 3 University of

SLIDE 1

Checking path consistency and reachability in multipath networks using Batfish

Ari Fogel1 Stanley Fung1 Todd Millstein1 Ratul Mahajan2 Ramesh Govindan3 Luis Pedrosa3

1University of California, Los Angeles 2Microsoft Research 3University of Southern California

SoCal 2013

1 / 12

SLIDE 2

IP Networks

IP Networks forward traffic from point A to point B

Implement policy Forward desired traffic Drop undesired traffic Fault tolerance

2 / 12

SLIDE 3

Router-based networks

Router-based network paradigm: Decentralized configurations (per-node) Configuration is program in DSL Routing protocols run to fixed point, compute forwarding tables Most commonly deployed

3 / 12

SLIDE 4

Network Abstraction: Data Plane

Data Plane Runtime forwarding state

f network

Dynamically computed Dictates what to do with received traffic Partitioned into forwarding tables at each node

4 / 12

SLIDE 5

Problem Characterization

Policy violations correspond to bad runtime forwarding state Can be detected by analyzing dynamic snapshot Easy given snapshot Dynamic snapshot expensive to obtain Dynamic snapshot may not have converged Can only find problems that are already present

5 / 12

SLIDE 6

Better Approach, New Challenges

We want to find problems before they occur Can ask what-if questions Perform static analysis by looking at configurations Configuration analysis is complicated and difficult: Have to model multiple routing protocols, intricacies Often heterogeneous devices, configuration languages, firmware versions, etc. (e.g. UCLA) Dissimilar configuration paradigms across vendors

6 / 12

SLIDE 7

Batfish

Vendor Configurations Static Forwarding Rules Control Plane Data Plane Network Topology Test flows Queries

Introducing: Batfish Static analysis tool Compiles configs into vendor-independent representation Implements control plane declaratively using LogiQL

Naturally express fixed-point logic Modular Easy to construct queries

7 / 12

SLIDE 8

Network Problems

Misconfigurations cause deviation from policy

Black holes Firewall leaks Forwarding loops

Multipath routing

Multiple paths to destination Path choice unpredictable Policy deviations may be path-specific

8 / 12

SLIDE 9

Path Consistency

Node A Node B Node C Node D int0 int1 int2 int0 int0 int1 int0 int1 int1 int2

Want to ensure Path Consistency: Delivery of flow not contingent on path taken Every flow always dropped or always arrives Defined in terms of per-flow reachability, loops Desired property of multipath networks

Single-path networks trivially path-consistent

9 / 12

SLIDE 10

Related Work

Dynamic analysis

Header space (Hassel) [Kazemian et al., NSDI 2012] Anteater [Mai et al., SIGCOMM 2011]

Check reachability, etc. for data plane snapshot

Static analysis

rcc [Feamster and Balakrishnan, NSDI 2005]

checks configs for inconsistencies

C-BGP [Quoitin and Uhlig, Network, IEEE 19, 6 (2005)]

limited control plane model single paths only

10 / 12

SLIDE 11

Summary

Batfish can statically analyze networks Declarative model for control plane Introduce and decide Path Consistency for multipath networks. Future Work

Run on real, large-scale networks Automatically generate interesting test flows

11 / 12

SLIDE 12

Questions

Questions? Paper: Checking path consistency and reachability in multipath networks using Batfish http://www.cs.ucla.edu/~arifogel/papers/ wqe-f2013-batfish.pdf Slides: http://www.cs.ucla.edu/~arifogel/papers/ socal-2013-batfish-slides.pdf Ari Fogel (arifogel@cs.ucla.edu)

12 / 12