UWB

Equal Cost Multipath Routing in FOKUS OpenSDNCore

Hai Dinh Tuan

Next Generation Networks & Future Internet Technologies Projects

• Introduction – ECMP & SDN

• Problems

• Solutions

• Demo

• Remark

Agenda

The separation of

control plane (routing

functionalities) and

data plane (forwarding

functionalities)

Introduction - SDN

Source: SDNCentral

Shortest path first (SPF) algorithm calculates the single shortest path

from a source node to a destination is used in Link-state protocols

such as OSPF and IS-IS.

Equal Cost Multipath is a Traffic Engineering technique that enables

using several equal cost paths in IP routing

Introduction - ECMP

Introduction – ECMP (2)

Which path(s) is used for packet forwarding from A to G?

Shortest Path First

Only 1 path {A,D,G} is stored in forwarding table

Equal Cost Multipath Routing

Multiple paths {A,D,G}, {A,E,D,G}, {A,E,F,G} are used for forwarding

Routing

Problems in this project

IMPLEMENT ECMP IN OPENSDNCORE

Controller-switch communication

Forwarding

How to calculate all possible paths

How to implement all paths in switches

How to choose path for packet forwarding

Controller Switch

Routing Problems

“Set each link’s cost along the shortest path to infinite, and run the

shortest path calculation again each time”

Arc cutting method

How it works (1)

A single shortest part is discovered by Dijkstra's algorithm as normal

How it works (2)

Delete one link of shortest path by setting its weight to infinitive

How it works (3)

Execute Dijkstra's algorithm one more time and compare path cost

How it works (4)

Delete another link of shortest path

How it works (5)

Continue using Dijkstra's algorithm

How it works (6)

Finally, multiple equal cost paths are discovered

Communication Problems

What type of messsages to be transfered between controller

and swiches?

• FlowMod message

• GroupMod message

How to implement all posible paths?

• FlowMod “Add Flow Entry” message

• GroupMod “Add Bucket”message

Message types

Forwading Problems

Which path selection scheme should be used?• Random?

• Round Robin?

• Hash-based?

Packet forwarding

Which path selection scheme should be used?• Random

• Round Robin?

• Hash-based

Packet forwarding

Random ECMP

CONTROLLER SIDE

SWITCH SIDE

ENTRY LOOKUP OPERATION

Hash based ECMP

CONTROLLER SIDE

SWITCH SIDE

ENTRY LOOKUP OPERATION

Comparison

Random ECMP Hashed based ECMP

Advantages

Simple, implement only on the Controller

Deterministic behavior

Work well with any switchProvides control over

path selection

Disadvantages

Possible congestionRequire more

computing resources

Possible congestion

Demo Topology

Remark

Expected outcomes Results

Successful implementation of ECMP in OpenSDNCore

Detailed documentation

Efficient communication between supervisor and student

Gather experiences

Remark

Expected outcomes Results

Successful implementation of ECMP in OpenSDNCore

Detailed documentation (to be submitted)

Efficient communication between supervisor and student

Gather experiences

UWBTHANK YOUHai Dinh Tuan

Next Generation Networks & Future Internet Technologies Projects