Load balancing in OSPF

OSPFLoad Balancing

Sharif University of TechnologyDepartment of Computer Engineering

Winter 2016

By: Arash Pourdamghani

Arash PourdamghaniWinter 2016 2

Update: OpenSignal’s New Report

November 2016

Iran


Review of OSPFStands for Open Shortest Path First

Inside Autonomous Systems(Intra-AS)

Local Link-State(Dijkstra) algorithm

in order to find shortest path

Version 2 -> IPv4 , Version 3 -> IPv6


Load Balancing ProblemOptimize Networking!

Layaer-4 switching

NAT-like function


Solution: ECMPEqual-Cost Multiple Routes

Equally split traffic over multiple paths

ECMP is available only for Linux in UNIX world

http://www.cs.princeton.edu/courses/archive/spring11/cos461/


Benefits of ECMPLoad balancing

Improve bandwidth utilization

Mitigate congestion


Source DAGEach Router has set of next hops

http://courses.cs.washington.edu/courses/csep561/13au


ECMP ForwardingRandom

AllocationRound-Robin Hash-

Threshold

Informatio

nRandom! Per-packet

Header based

Balanced Complete Near-Optimal Partial

Disruption High High Low

TCP-

FriendlyNo No Yes


Traditional ECMP drawback

Link capacity = 1


Weighted ECMPOptimize end-to-end delay

Distributes based pre-determined ratios

Use heuristic algorithm

Obtain the near-optimal weight configuration


Weighted ECMP advantage


ReferencesJ. Moy, (April 1998). "OSPF Version 2". The Internet

Society. OSPFv2. Retrieved 2007-09-28.

J. Kurose, K. Ross, “Computer Network Top-Down

Approach”,6th edition, Pearson Education Inc., 2013

A. Tanenbaum, D. Wetherall, “Computer Networks”,

5th edition, Pearson Education Inc., 2011


References(cont’d)C. Hopps, “Analysis of an Equal-Cost Multi-Path

Algorithm(RFC 2992), The Internet Society”, 2000

J. Zhang, K. Xi, L. Zhang , “Optimizing Network

Performance using Weighted Multipath Routing”,

NYU Tandon School of Engineering


Thank You