Build and Measure Routing Systems

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BUILD AND MEASURE ROUTING SYSTEMS

COMPUTING AND MONITORING THE PATH FORWARD

Soutenance HDR Pascal Mérindol September 4, 2022

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HDR DEFENSE

Build and Measure Routing Systems

Habilitation à Diriger des Recherches

Présentée par Pascal Mérindol le 11/07/2022 devant le jury composé de :

Griffin Tim Rapporteur

Magnien Clémence Rapporteur

Schmid Stefan Rapporteur

Pelsser Cristel Garant Bastoul Cédric Président Bonaventure Olivier Examinateur

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SECTION I: OVERALL INTRODUCTION

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PROFESSIONAL RECORDS

2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023

My Ph.D. thesis (ULP) Post-Doc UCLouvain

Associate Professor Unistra

Ph.D. Thesis of François Clad

Ph.D. Thesis of Yves Vanaubel (Ulg)

Ph.D. Thesis of Julian Del. Fiore

Ph.D. Thesis of Loic Miller

Ph.D. Thesis of Renato Neto

Ph.D. Thesis of Jean-Romain Luttringer Responsible of a Master degree (first year)

Responsible of a Bachelor degree (first year)

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PROJECTS, PH.D. THESIS & PUBLICATIONS

Research Projects

EU FP7 Trilogy (participant, 2008-10), GEANT GN4-2 (local leader, 2016-19), ANR JCJC (leader, 2019-22).

Ph.D. Thesis

Six co-supervisions: 1 withJean-Jacques Pansiot(F. Clad), 1 withBenoit Donnet (Y. Vanaubel, Ulg), 1 withFabrice Theoleyre(R. Neto, ANR Nanonet) and 3 withCristel Pelsser(J-D. Fiore, IdEx ICube, L. Miller, Cisco Foundation, and J-R. Luttringer).

International Publications

I 13 journals: 5 Computer Networks (Q1), 2 ToN (Q1), 2 TNSM (Q1) and 1 CCR...

I 28 conferences: 5 IMC (A), 3 PAM, 2 NCA, 1 INFOCOM (A*), 1 ICNP (A) and 1 ICCCN...

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THESIS TOPICS & PUBLICATIONS

Ph.D. Student Keywords Topic Publications

FrançoisClad

Routing Algorithms Disruption-free Routing 1 ICNP, 2 ToN Yves

Vanaubel IP Measurements Revealing and Characterizing MPLS 3 IMC, 1 PAM, 1 TNSM

Julian Del.

Fiore IP Measurements Hidden Broken Pieces of the Internet 1 TMA, 1 CCR, 1 TNSM

LoicMiller Cloud Networks Security Securing Microservices with Meta- graphs

2 HPSR, 1 MDPI

RenatoNeto IoT Networks Privacy Privacy-aware Aggregation of IoT Streams

1 LCN, 1 NCA, 1 IWCMC, 1 ISCC Jean-Romain

Luttringer Routing Algorithms Hot-Potato & Delay Constrained Paths 1 INFOCOM, 1 NCA, 1 COMNET 4

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NUMEROUS COLLABORATIONS

2011-14 2012-18 2017-21 2018-22 2019-22 2019-22

F. Clad Y. Vanaubel J-D. Fiore L. Miller R. Neto J-R. Luttringer

Routing Algorithms: IP Measurements: IP Measurements: Security Privacy Routing Algorithms:

reconfigurations MPLS detours in Cloud Networks in IoT networks reliability and latency

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NUMEROUS COLLABORATIONS

2011-14 2012-18 2017-21 2018-22 2019-22 2019-22

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NUMEROUS COLLABORATIONS

2011-14 2012-18 2017-21 2018-22 2019-22 2019-22

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MAIN RESEARCH CONTRIBUTIONS

Three Main Research Topics to Improve the Internet

Routing, routing and... routing but from three distinct perspectives

1. Routing Algorithms & Protocols:Compute and Deploy Valuable IP Routes I Fast and correct convergence for several change models

I Multi-metric paths for traffic engineering

2. IP Measurementsin Transit Networks:Topology Discovery & Large Scale Monitoring I Reveal Hidden Tunnels and Forwarding Detours

I Troubleshoot Internet Service Provider Networks 3. Energy and Privacyin Edge & Cloud Networks

I Constrained Networks Life-Time I Privacy Aware Architectures

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AGENDA

1. Context, Motivation & Background 2. Building Routing Systems

3. Measuring Routing Systems 4. Conclusion & Research

Perspectives

p₁ n₁ a

n2

if_a

Prefix BGP NH IGP NH Interface

p2

A hierarchical forwarding model

A sample of the Internet 7

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INTERNET: THE WORLDWIDE DISTRIBUTED SYSTEM

I Large scale: soon 100,000 Domains (including≈[100...10,000]routers), 1MIP prefixes and much more end-devices than human beings!

I Complex: numerous heterogeneous hardware and software components

I Innovation is difficult and challenging:

I The universal common technology for connecting all devices lies in theIP data-plane I TheIP control-plane (i.e. the routing)provides means toinstall and manage

forwarding routes, e.g. with MPLS or Segment Routing (SR) w.r.t. the type of service

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INTERNET: THE WORLDWIDE DISTRIBUTED SYSTEM

I Large scale: soon 100,000 Domains (including≈[100...10,000]routers), 1MIP prefixes and much more end-devices than human beings!

I Complex: numerous heterogeneous hardware and software components

I Innovation is difficult and challenging:

I The universal common technology for connecting all devices lies in theIP data-plane I TheIP control-plane (i.e. the routing)provides means toinstall and manage

forwarding routes, e.g. with MPLS or Segment Routing (SR) w.r.t. the type of service

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TWO SCALES AND SEVERAL TECHNOLOGIES

Two scales of routing operations:

I inter-domain or AS-wide level:BGP

I intra-domain or router level within an AS:IGP

Several technologies and paradigms: I Hop-by-hoppacket forwarding (for best-effort traffic),

orloose source routing, e.g. withSR or MPLS tunnels

I With packet encapsulation, one can enableTraffic Engineering (TE)for premium flows, or deployLoad Balancing (LB) and Fast-ReRoute(FRR) for all services. A single deviation from the best-effort usual IP forwarding schemeis often enough

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TWO SCALES AND SEVERAL TECHNOLOGIES

Tier-1 AS

Transit AS

Transit AS IGP

eBGP

Edge Networks

2

2 4

Stub Networks ISP 2 relying on tunneling technologies

(e.g. MPLS or SRv6) ISP 3

ISP 1

Ingress Provider Edge Router

CDN p2p

c2p

p2p

p2p iBGP

Egress Provider Edge Router

p2p

MED 10

c2p

Several technologies and paradigms: I Hop-by-hoppacket forwarding (for best-effort traffic),

orloose source routing, e.g. withSR or MPLS tunnels

I With packet encapsulation, one can enableTraffic Engineering (TE)for premium flows, or deployLoad Balancing (LB) and Fast-ReRoute(FRR) for all services. A single deviation from the best-effort usual IP forwarding schemeis often enough

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TWO SCALES AND SEVERAL TECHNOLOGIES

Tier-1 AS

Transit AS

Transit AS IGP

eBGP

Edge Networks

2

2 4

Stub Networks ISP 2 relying on tunneling technologies

(e.g. MPLS or SRv6) ISP 3

ISP 1

CDN p2p

c2p

p2p

p2p iBGP

Egress Provider Edge Router

p2p

MED 10

c2p

Several technologies and paradigms:

I Hop-by-hoppacket forwarding (for best-effort traffic), orloose source routing, e.g. withSR or MPLS tunnels

I With packet encapsulation, one can enableTraffic Engineering (TE)for premium flows, or deployLoad Balancing (LB) and Fast-ReRoute(FRR) for all services.

A single deviation from the best-effort usual IP forwarding schemeis often enough ⁹

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BACKGROUND: INTERNET ROUTING PROTOCOLS

Two respective paradigms for inter- and intra-domain routing:

I with BGP, preferences are local and selfish:the path vector protocol may diverge I sufficient conditions for convergence a priori met in practice (valley freeroutes and usual

economical incentives)

I within IGP link-state routing protocols (e.g. OSPF, IS-IS),the objective is globally consistent, typically aminimum functionapplied on anadditive metric:(min,+) I convergence is granted (thanks to theisotonicity&monotonyof routing operations),

butanomalies, e.g. forwarding loops and path sub-optimality,still occur during transient periods of change

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ROUTING CHANGES: ILLUSTRATION IN RENATER

TheDCARTproject deployed in the French Educational & Research Network

paris1a lyon1a paris1 paris2a marseille1 lyon2 marseille2 bordeaux orsay paris2 nantes rennes clermont evry jussieu quimperorleanslannionpoitierslorient stbrieucvannescachanbrest cadarachetoulousenancytouloncaen ...

13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 02 04 06 08 10 12 14 16 18 20 22 24 26 28 30

Links(perrouterandsortedbydegree)

Time (Week Number 2015-2016) Isolated events Flap events

Topological changes are common and links are oftenflapping ¹¹

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ROUTING CHANGES: ILLUSTRATION IN RENATER

0 100 200 300 400 500 600

1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8 3

7541552

AbsoluteQuantity(truncatedwhen>500)

Duration of losses with their loops (seconds) AllLosses

0 100 200 300 400 500 600

1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8 3

7541552

Duration of losses with their loops (seconds) LossesreportedtoUPevents

0 100 200 300 400 500 600

1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8 3

7541552

Duration of losses with their loops (seconds) LossesreportedtoDOWNevents

0 100 200 300 400 500 600

1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8 3

7541552

Duration of losses with their loops (seconds) LoopsreportedtoUPevents

0 100 200 300 400 500 600

1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8 3

7541552

Duration of losses with their loops (seconds) LoopsreportedtoDOWNevents

x

y z

d

2

×

A not so simple ECMP forwarding loop Forwarding loops do occur, in particular when routers reboot!

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FROM PRACTICAL NETWORK PROBLEMS TO GRAPHS

An illustration of an usual simplegraph transformation:

s

p2c

iBGP Egress Provider

Edge Router I

c2p MED 50

Egress Provider Edge Router II

Prefix P

c2p MED 10

x y

z

x

s z

y P

⇒Existence of 2

node-disjoint pathss→P?

From Operational Technological Challenges to Graph Problems Minimize the signaling overhead and the operational cost

To ensure lightweight processing & incremental heterogeneous deployment

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ROUTING & MEASUREMENTS

Control-Plane Routing Graphs

Measu

rem

ne ts

,L TE

,MB

PLS ,SR

BGC P,CL IG,DP,FRR

uoR

ting

Data-Plane Forwarding Systems ¹⁴

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SECTION II: BUILDING ROUTING SYSTEMS

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SEVERAL RESEARCH QUESTIONS

Routing Data Packets in Resilient IP Networks

Ensurereliability, i.e. provide protection, forthree types of changes

1. Compute and Deploy Alternate Paths for Local Failures

I Post-Convergence Loop-Free Paths

2. Graceful Router-wide Convergence for Planned Events

I Minimal Sequence of Weights Updates

3. Avoid Superfluous Hot-Potato

Convergencefor BGP Routing Updates I Rank BGP routes into MED-aware sets

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ADJUSTED GREEDY BACKWARD ALGORITHM

AGBA

Goal

Safe convergence, i.e. free of intermediary changes, packet losses and forwarding loops, forrouter-wide planned events(e.g. reconfigurations, maintenance, reboot)

Challenge and Originality

Using only Link State Advertisement (LSA) control messages, i.e.not requiring protocol changesor complex management system

The Algorithm in a Nutshell

I Incremental updates: progressively shift the traffic from the node to be shut, or respectively attract it for the node addition

I Find correct and minimal sequences

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PROBLEM STATEMENT: THE NODE SHUT

AGBA

0

1 3

b d

2

a e

c 4

1 1

1 10 1

10 2

5 20

5

1

1 1

5 10

5 0

1 3

b d

2

a e

c 4

0

1 3

b d

2

a e

c 4

10

10 2

5 20

5

1 1

1 5

10 5

Pre-convergence paths The merged graph:P∪P⁰ Post-convergence paths P=RSPDAG(G,4) ~0→

3 1 3 0

→∞~ P⁰=RSPDAG(G⁰,4) Satisfy theloop constraintsinduced by suchtransient circuitswith increasing vectors ₁₇

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MAIN THEORETICAL RESULTS

AGBA

The Node-Shut Problem

I Given a set of (static) loop constraints to safely remove node 0, find the shortest sequence satisfying all of them

I Deal with side effects: dynamic loops!

Theorem 1: optimal strictly increasing sequences

GBA computes the minimal strictly increasing sequence for shutting a node 0. It requires tofreeze the data-planeof router 0.

Theorem 2: optimal weakly uniform sequences

AGBA computes the minimal weakly uniform sequence for shutting a node 0, i.e. it logicallyprevent forwarding changesof router 0.

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OPTIMAL PROTECTION TECHNIQUE

FOR INTER-INTRA DOMAIN CONVERGENCE (OPTIC)

Goal

Fast optimalBGP convergence for IGP events Challenge and Originality

OPTIC solves thehot-cold potato problemwhile existing schemes only mitigate it; with enoughiBGP visibilityforstable deterministic MED&IGP diversityforhot-potato routing, definesufficient conditions to optimally protecteach IP prefix for any IGP event The Algorithm in a Nutshell

I Stack enough MED-aware Rounded (MR) sets to ensurek-node connectivity (k>1)

−→Optimal Protecting Rounded (OPR) set

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PROBLEM STATEMENT: PROTECT THE POTATO

OPTIC

AS 2 AS 3

AS 1

AS 5

AS 4 AS 6 2

s

5

a b 2

2

5

2

c d

2

n1 n2 n3 n4 n5

n6 c2p n7

p2p p2p

p2c p2c p2c p2c p2c

p

e

R1

I Optimally protect the traffic froms, the ingress PER, towards external prefixp:

I considering any single internal failure I as well as the failure of the egress PER I Which routessneeds to protectp(OPR)?

I obviously, the best routeR₁:vian₁at AS 1 I but alsoallthe routes thatmay turn to bethe

best afteranysingle event:vian₂andn₃

I Current deployed approaches (e.g., PIC+Add-Path) neglect several aspects

I no explicit check for k-node disjoint paths I intermediary transient sub-optimal routes I insufficient diversity for MED re-convergence

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PROBLEM STATEMENT: PROTECT THE POTATO

OPTIC

AS 2 AS 3

AS 1

AS 5

AS 4 AS 6 2

s

5

a b 2

2

5

2

c d

2

n1 n2 n3 n4 n5

n6 c2p n7

p2p p2p

p2c p2c p2c p2c p2c

p

e

R1

I Optimally protect the traffic froms, the ingress PER, towards external prefixp:

I considering any single internal failure I as well as the failure of the egress PER I Which routessneeds to protectp(OPR)?

I obviously, the best routeR₁:vian₁at AS 1 I but alsoallthe routes thatmay turn to bethe

best afteranysingle event:vian₂andn₃ I Current deployed approaches (e.g.,

PIC+Add-Path) neglect several aspects I no explicit check for k-node disjoint paths I intermediary transient sub-optimal routes I insufficient diversity for MED re-convergence 20

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SECTION III: MEASURING ROUTING

SYSTEMS

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SEVERAL TECHNICAL CHALLENGES

I Topology Discovery

I Reveal hidden MPLS tunnels (with TNT)

I Internet maps and network analysis (e.g. with MERLIN) I Network Monitoring and Analysis

I Detect forwarding detours & default routes

I Finely monitor intra- and inter-domain traffic (e.g. with DCART)

Originality with respect to the related works

First active measurement methodsin the field for layer-2 and MPLS discovery: novel probing tools and methods exploiting the TTL of ICMP error replies

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THE HIDDEN TUNNEL PROBLEM

Goal

Detect & reveal hidden IP hopswithin invisible MPLS tunnels

Originality and Challenges

Rely on ICMP error replies and theirTTL signaturesbefore launching additional active probing accordingly (limit the probing budget)

The Method in Practice

I analyse pairs of subsequent initial TTLs in active traces (traceroute) I according to the signature, classify MPLS tunnels andtrigger novel probesif

necessary

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MPLS DISCOVERY IN A NUTSHELL

THE PROBLEM OF HIDDEN TUNNEL

P1

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LSP

<latexit sha1_base64="0/GmCo+DoY+h/91tHLLlSOWbp/Q=">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</latexit><latexit sha1_base64="0/GmCo+DoY+h/91tHLLlSOWbp/Q=">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</latexit><latexit sha1_base64="0/GmCo+DoY+h/91tHLLlSOWbp/Q=">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</latexit><latexit sha1_base64="0/GmCo+DoY+h/91tHLLlSOWbp/Q=">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</latexit>

Invisible UHP

Explicit Implicit

Invisible PHP

MPLS Discovery Classification

Four categories of tunnels:Explicit,Implicit,Opaque&Invisible.

The two first are easy to retrieve with passiveindicatorssuch as qTTL and UTURN. For the two last, we rely ontriggersand active probing!

23

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MPLS DISCOVERY IN A NUTSHELL

THE PROBLEM OF HIDDEN TUNNEL

P1

LSP

<latexit sha1_base64="0/GmCo+DoY+h/91tHLLlSOWbp/Q=">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</latexit><latexit sha1_base64="0/GmCo+DoY+h/91tHLLlSOWbp/Q=">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</latexit><latexit sha1_base64="0/GmCo+DoY+h/91tHLLlSOWbp/Q=">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</latexit><latexit sha1_base64="0/GmCo+DoY+h/91tHLLlSOWbp/Q=">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</latexit>

Invisible UHP

Explicit Implicit

Invisible PHP

MPLS Discovery Classification

Four categories of tunnels:Explicit,Implicit,Opaque&Invisible.

The two first are easy to retrieve with passiveindicatorssuch as qTTL and UTURN.

For the two last, we rely ontriggersand active probing! ²³

(35)

FROM SIGNATURES TO REVELATION TECHNIQUES

TNT: TRACE THE NAUGHTY TUNNELS

P1

LSP<latexit sha1_base64="0/GmCo+DoY+h/91tHLLlSOWbp/Q=">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</latexit><latexit sha1_base64="0/GmCo+DoY+h/91tHLLlSOWbp/Q=">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</latexit><latexit sha1_base64="0/GmCo+DoY+h/91tHLLlSOWbp/Q=">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</latexit><latexit sha1_base64="0/GmCo+DoY+h/91tHLLlSOWbp/Q=">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</latexit>

Invisible UHP

Explicit Implicit

Invisible PHP

Triggers for Invisible Tunnels: I FRPLA: capture asymmetry to infer the

minof the return path (Cisco routers) I RTLA: detect theminthanks to distinct

iTTL (Juniper routers)

Revelation Techniques: I BRPR: Backward Recursive Path

Revelation

I DPR: Direct Path Revelation

24

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FROM SIGNATURES TO REVELATION TECHNIQUES

TNT: TRACE THE NAUGHTY TUNNELS

P1

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Invisible UHP

Explicit Implicit

Invisible PHP

Triggers for Invisible Tunnels:

I FRPLA: capture asymmetry to infer the minof the return path (Cisco routers) I RTLA: detect theminthanks to distinct

iTTL (Juniper routers)

Revelation Techniques:

I BRPR: Backward Recursive Path Revelation

I DPR: Direct Path Revelation

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THE PROBLEM OF FORWARDING DETOURS

ASBR₂

ASBR₃ ASBR₁

1

3 2

4

P_B

ASBR2

Pfx BGP NH Int PR 𝑠𝑒𝑙𝑓 𝑖0 PG ASBR3 𝑖1 PB ASBR3 𝑖1 0/0 𝑠𝑒𝑙𝑓 𝑖0

ASBR1

Pfx BGP NH Int PR ASBR2 𝑖0 PG ASBR3 𝑖1

0/0 ASBR2 𝑖0 P_G

𝑖₀ 𝑖₁

P_R 𝑖₀ 𝑖₁

Partial FIBs and Detours:

I ASBR₁uses ASBR₂as a default next-hop... I ...but, instead of sending the traffic externally,

ASBR₂then considers ASBR₃for prefix P_B I thedefault routeof ASBR₁visible because of

theForwarding Detour (FD)to reach ASBR3

I for prefixes P_Gand P_B, traffic is forwarded differently⇒multi-path forwarding pattern Detect and quantify FD by distinguishing them from LB and TE

Partial FIB and default routes result in FD, but severalLoadBalancing flavors (ECMP variants) andTrafficEngineering practices may result in the same effects at first glance

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THE PROBLEM OF FORWARDING DETOURS

ASBR₂

ASBR₃ ASBR₁

1

3 2

4

P_B

ASBR2

ASBR1

0/0 ASBR2 𝑖0 P_G

𝑖₀ 𝑖₁

P_R 𝑖₀ 𝑖₁

I ASBR₁uses ASBR₂as a default next-hop...

I ...but, instead of sending the traffic externally, ASBR₂then considers ASBR₃for prefix P_B I thedefault routeof ASBR₁visible because of

I for prefixes P_Gand P_B, traffic is forwarded differently⇒multi-path forwarding pattern

Detect and quantify FD by distinguishing them from LB and TE

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THE PROBLEM OF FORWARDING DETOURS

ASBR₂

ASBR₃ ASBR₁

1

3 2

4

P_B

ASBR2

ASBR1

0/0 ASBR2 𝑖0 P_G

𝑖₀ 𝑖₁

P_R 𝑖₀ 𝑖₁

I ASBR₁uses ASBR₂as a default next-hop...

I ...but, instead of sending the traffic externally, ASBR₂then considers ASBR₃for prefix P_B I thedefault routeof ASBR₁visible because of

I for prefixes P_Gand P_B, traffic is forwarded differently⇒multi-path forwarding pattern Detect and quantify FD by distinguishing them from LB and TE

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CONCLUSION & RESEARCH PERSPECTIVES

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SUMMARY

I Severalrouting contributions: algorithms for safe and fast convergence to deal with several type of IGP events, i.e. failures, updates with AGBA and, optimal hot & cold potato routing for the BGP transit traffic with OPTIC

I Severalmeasurements toolsto reveal hidden MPLS tunnels and forwarding detours, ormonitoring systemslike DCART to finely probe IGP networks

I Preliminary works in other fields such asedge and cloud networks:energy and privacyconcerns in particular

I Severalongoing research perspectivesincluding:

I an unified convergence solution for symmetric networks enabling data-plane updates I energy-efficient multi multi-hop wireless communications with wake-up radios

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SUMMARY

I Severalrouting contributions: algorithms for safe and fast convergence to deal with several type of IGP events, i.e. failures, updates with AGBA and, optimal hot & cold potato routing for the BGP transit traffic with OPTIC

I Severalmeasurements toolsto reveal hidden MPLS tunnels and forwarding detours, ormonitoring systemslike DCART to finely probe IGP networks

I Preliminary works in other fields such asedge and cloud networks:energy and privacyconcerns in particular

I Severalongoing research perspectivesincluding:

I an unified convergence solution for symmetric networks enabling data-plane updates I energy-efficient multi multi-hop wireless communications with wake-up radios

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THE SYMMETRIC CONVERGENCE

Goal

Anunified solutionfor optimal safe and fast IP convergence handling all type of events (e.g. link or node failures and planned reconfigurations)

With a symmetry assumption, simplify the optimal re-routing problem:avoid the use of timers and explicit messages

The Algorithmical Sketch

I Opportunistic loop detectionsafety net(ingoing port = outgoing port):

loopy packets are reactively detoured with SR

I Data-plane updates: prevent loops with pro-active (and/or reactive detours) on new next-hops−→data packets detoured with SR used as control messages!

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OPPORTUNISTIC IMPLICIT UPDATES

MAIN OUTCOMES

Not only asymmetric valuationmitigates theoverhead of SR deploymentand thepath computation complexity, but we have:

Theorem (all loops are made of size 2 circuits with ECMP)

With a symmetric valuation and ECMP, each edge of each circuit exists in both directions in the merged pre- and post-convergence graph.

x

y z

d 2

×

^{With a}loop detectionsafety net& the use ofdata-plane updates:

I mitigate transient sub-optimal states

I avoid distant loops (nottransitively adjacentto the failure)

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THE NODE PROTECTION PROBLEM

f_k s

s1

s2 d

1 1

1

3 3

1. Compute allnode protecting paths for each neighborf_kofs

2. Encode them as SR segment lists 3. Evaluate the cost in terms of#seg

(w.r.t. to the theoretical bound)

Conjecture: the cost of node protection depends on the failed node degree

Withfk∈succ(s), the neighbor node detected as failed froms, and#segthe maximal number of segments required to optimally detour the traffic fromf_k, we have

#seg<deg(f_k)for any destination,if the link valuation is symmetric.

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THE MULTI MULTI-HOPS PROBLEM

For energy efficiency,each device embeds two radios, &their two graphs are merged

3 4

1 5

2

0 LR range and

best paths LR/WUR

devices

WUR range and best paths The sink

1. one graph for theLong Rangeradio:LR

I in sleep mode by default, used for the standard convergecast communications (n-to-1)

2. one graph for theWake Up Radio:WUR I n-to-n unicast distances as the second metric I if WUR edges⇒LR ones:

WUR connectivity⇒LR connectivity

3. consider the two graphs as a multi-metric one I Deploy this WUR-LR structure efficiently

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THE MULTI MULTI-HOPS PROBLEM

For energy efficiency,each device embeds two radios, &their two graphs are merged

3 4

1 5

2

0 LR range and

best paths LR/WUR

devices

1. one graph for theLong Rangeradio:LR

I in sleep mode by default, used for the standard convergecast communications (n-to-1)

2. one graph for theWake Up Radio:WUR I n-to-n unicast distances as the second metric I if WUR edges⇒LR ones:

WUR connectivity⇒LR connectivity

3. consider the two graphs as a multi-metric one I Deploy this WUR-LR structure efficiently

3 4

1 5

2 0

LR range and best paths LR/WUR

devices

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TOWARDS AN ENERGY EFFICIENT ROUTING SCHEME

Goal

Deploy WUR-LR() routes with an energy-efficient signaling protocol

Build and evaluate the deployment of a multi multi-hop near optimal routing scheme not requiring WUR flooding

Several Algorithms to Explore

I Deploy near optimal LR routes with various strategies I Relay WUR topological information within LR messages

I Consider constraints and simplifications to limit the LR broadcast

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NEXT STEPS

Supervise Ph.D. students on my own!

I First, on routing and measurement topics. In particular, looking atdistributed systemsproblems and their relations with routing algorithms: towardsgeneral adversarial models, e.g.byzantinerather thanfail stop& self-stabilization algorithms I Second, I aim to performextensive experimentationswith our recent hardware

enablingflexible data-plane updates

Several novel research questions to tackle:

I what are the routing features to operate at line-rate within the packet pipeline? I what should be measured and operated within the data-plane, and which and how

information should be shared between the two planes?

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NEXT STEPS

Supervise Ph.D. students on my own!

I First, on routing and measurement topics. In particular, looking atdistributed systemsproblems and their relations with routing algorithms: towardsgeneral adversarial models, e.g.byzantinerather thanfail stop& self-stabilization algorithms I Second, I aim to performextensive experimentationswith our recent hardware

enablingflexible data-plane updates Several novel research questions to tackle:

I what are the routing features to operate at line-rate within the packet pipeline?

I what should be measured and operated within the data-plane, and which and how information should be shared between the two planes?

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THANKS!

2014 2018 2021 2022 2022 2022

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ROUTING & MEASUREMENTS

Control-Plane Routing Graphs

Measu

rem

ne ts

,L TE

,MB

PLS ,SR

BGC P,CL IG,DP,FRR

uoR

ting

Data-Plane Forwarding Systems ³⁴

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BACKUP SLIDES

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BACKGROUND: GRAPHS & PATH COMPUTATION

The usual network model is adirected weighted graphG(V,E,w)whereVdenotes the set ofnodes(|V|=n),Ethe set of (bi-directionnal)edges(|E|=m) andw:E−→Nthe valuation functionapplied on them.

The main goal of a routing protocol is tocompute the set of best pathsp1(s,d)(and their next-hopsn₁(s,d)) according to an additive metric applied from a sources∈Vtowards all destinationsd∈V.

Two mainShortest Path Computation(SPC) algorithms exist to retrieve such aShortest Path Tree(SPT¹):

I TheBellmann-Fordalgorithm:O(nm)// detect negative absorbing circuits I TheDijkstraalgorithm:O(nlogn+m)// positive weights only but efficient

1Considering Equal Cost Multi-Paths (ECMP), the SPT becomes aDirected Acyclic Graph, aDAG.

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BACKGROUND: GRAPHS & PATH COMPUTATION

The usual network model is adirected weighted graphG(V,E,w)whereVdenotes the set ofnodes(|V|=n),Ethe set of (bi-directionnal)edges(|E|=m) andw:E−→Nthe valuation functionapplied on them.

The main goal of a routing protocol is tocompute the set of best pathsp1(s,d)(and their next-hopsn₁(s,d)) according to an additive metric applied from a sources∈Vtowards all destinationsd∈V.

Two mainShortest Path Computation(SPC) algorithms exist to retrieve such aShortest Path Tree(SPT¹):

I TheBellmann-Fordalgorithm:O(nm)// detect negative absorbing circuits I TheDijkstraalgorithm:O(nlogn+m)// positive weights only but efficient

1Considering Equal Cost Multi-Paths (ECMP), the SPT becomes aDirected Acyclic Graph, aDAG.