Dig into MPLS: Transit Tunnel Diversity Yves Vanaubel, Pascal Mérindol, Benoit Donnet , Jean-Jacques Pansiot Plane 1
Agenda • Motivations • Measuring MPLS • LPR • Evaluation • Conclusion AIMS - CAIDA/UCSD - March/April 2015 - Benoit Donnet 2
Motivations • Current studies are mainly about MPLS discovery and its impact on topology discovery B. Donnet, M. Luckie, P. Mérindol, J.-J. Pansiot. Revealing MPLS - Tunnels Obscured from Traceroute . In ACM SIGCOMM Computer Communication Review, 42(2)., pp. 87-93. April 2012 J. Sommers, B. Eriksson, P. Barford. On the Prevalence and - Characteristics of MPLS Deployments in the Open Internet . In Proc. Internet Measurement Conference (IMC). October 2008. T. Flach, E. Katz-Basset, R. Govindan. Quantifying Violations of - Destination-Based Forwarding on the Internet . Proc. Internet Measurement Conference (IMC). November 2012. • Actual usage of MPLS by operators not yet studied AIMS - CAIDA/UCSD - March/April 2015 - Benoit Donnet 3
Motivations (2) • Observation several LSPs may exist for a given <Ingress LER, Egress - LER> LSP 1 : LSP 2 : LSP 1 : Ingress Egress LER LER B D A F C E AIMS - CAIDA/UCSD - March/April 2015 - Benoit Donnet 4
Motivations (3) • Those LSPs between <Ingress LER, Egress LER> can represent load balancing (i.e., ECMP) between the ingress and the - egress LER traffic-engineering - • We want to distinguish 3 types of MPLS tunnels mono-path - transit tunnel without TE - transit tunnel with TE - • We focus on explicit MPLS tunnels - transit tunnels - inter-domain tunnels seems negligible ✓ AIMS - CAIDA/UCSD - March/April 2015 - Benoit Donnet 5
Measuring MPLS • The discovery of MPLS can be based on standard active measurement tools ( [CCR2012] ) ping - traceroute - • Two options are required 1. ICMP extension ( [RFC4950] ) if an MPLS router must forge an ICMP time_exceeded ✓ message, it should quote the MPLS LSE stack in it 2. TTL propagate ( [RFC3443] ) the ingress LER of an MPLS should initialize the LSE-TTL ✓ with the value inside the IP-TTL field (iTTL) the opposite operation is done by the egress LER (oTTL) ✓ AIMS - CAIDA/UCSD - March/April 2015 - Benoit Donnet 6
Measuring MPLS (2) • MPLS Explicit tunnels RFC4950 ∧ RFC3443 - R 1 R 2 R 3 R 4 R 5 Source Ingress Egress Destination LSP PHP LER LER Traceroute output: 1. R 1 2. R 2 - MPLS tag 3. R 3 - MPLS tag 4. R 4 - MPLS tag 5. R 5 6. Destination AIMS - CAIDA/UCSD - March/April 2015 - Benoit Donnet 7
LPR • L abel P attern R ecognition algorithm • Allows to distinguish multi-FEC from IP load balancing • Passive classification method works offline, once the data has been collected - requires no additional probing than traceroute - • Recognizes behaviors of LDP vs. RSVP-TE based on MPLS labels distribution and IP addresses • LPR provides four classes AIMS - CAIDA/UCSD - March/April 2015 - Benoit Donnet 8
LPR (2) • Class 1 MonoLSP - Ingress Egress PHP LER LER L 1 L 2 L 2 L 1 A B C D Trace LSP 1 : Trace LSP 2 : 1. A 1. A 2. B - Label L 1 2. B - Label L 1 3. C - Label L 2 3. C - Label L 2 4. D 4. D Same IP addresses and same Labels AIMS - CAIDA/UCSD - March/April 2015 - Benoit Donnet 9
LPR (3) • Class 2 Multi-FEC - Common IP means an interface Ingress Egress LER PHP LER L 1 B 1 1 2 2 A D E F G L 2 C Trace LSP 1 : Trace LSP 2 : 1. A 1. A 2. … 2. … 3. C - Label 3. B - Label Different labels 4. D 2 - Label 4. D 1 - Label for at least 5. E - Label L 2 5. E - Label L 1 6. … 6. … 1 common IP 7. F 2 - Label 7. F 1 - Label 8. G 8. G AIMS - CAIDA/UCSD - March/April 2015 - Benoit Donnet 10
LPR (4) • Class 3 ECMP Mono-FEC : disjoint routers - Common IP Ingress Egress LER PHP L 2 LER B 1 1 2 2 A D E F G L 2 C Trace LSP 1 : Trace LSP 2 : 1. A 1. A 2. … 2. … 3. C - Label 3. B - Label 4. D 2 - Label L 1 Same label 4. D 1 - Label L 1 5. E - Label L 2 5. E - Label L 2 ∀ common IPs 6. … 6. … 7. F 2 - Label 7. F 1 - Label 8. G 8. G AIMS - CAIDA/UCSD - March/April 2015 - Benoit Donnet 11
LPR (5) • Class 3 (cont.) ECMP Mono-FEC : parallel links - Same labels along all the LSPs Ingress Egress LER L 3 PHP L1 L 2 L 4 LER 1 1 1 2 2 2 A C B F D E L1 L 4 L 2 L 3 Different IPs are aliases! Trace LSP 1 : Trace LSP 2 : 1. A 1. A 2. … 2. … 3. B - Label L 1 3. B - Label L 1 4. C 2 - Label L 2 4. C 1 - Label L 2 5. D 2 - Label L 3 5. D 1 - Label L 3 6. … 6. … 7. E 2 - Label L 4 7. E 1 - Label L 4 8. F 8. F AIMS - CAIDA/UCSD - March/April 2015 - Benoit Donnet 12
LPR (6) • Class 4 Unclassified - • If PHP is used, the Egress LER does not exhibit labels • It may happen that LSPs do not intersect on a common IP address • Those tunnels are arbitrarily tagged as unclassified AIMS - CAIDA/UCSD - March/April 2015 - Benoit Donnet 13
Evaluation • Archipelago platform • First traceroute cycle of each month since 2010 until December 2014 • 60 cycles AIMS - CAIDA/UCSD - March/April 2015 - Benoit Donnet 14
Evaluation (2) • Numbers of tunnels unexplained drop AIMS - CAIDA/UCSD - March/April 2015 - Benoit Donnet 15
Evaluation (3) • AS6453 AIMS - CAIDA/UCSD - March/April 2015 - Benoit Donnet 16
Evaluation (4) • AS1273 AIMS - CAIDA/UCSD - March/April 2015 - Benoit Donnet 17
Evaluation (5) • AS2914 AIMS - CAIDA/UCSD - March/April 2015 - Benoit Donnet 18
Evaluation (6) • AS286 AIMS - CAIDA/UCSD - March/April 2015 - Benoit Donnet 19
Evaluation (7) • Tunnel length AIMS - CAIDA/UCSD - March/April 2015 - Benoit Donnet 20
Evaluation (8) • Tunnel width AIMS - CAIDA/UCSD - March/April 2015 - Benoit Donnet 21
Evaluation (9) • Tunnel symmetry AIMS - CAIDA/UCSD - March/April 2015 - Benoit Donnet 22
Conclusion • New algorithm to reveal TE usage within ASes label distribution - Mono- or Multi-FEC ✓ ECMP load balancing - parallel links or disjoint routers ✓ dynamics - temporal evolution of MPLS deployment and usage ✓ AIMS - CAIDA/UCSD - March/April 2015 - Benoit Donnet 23
Conclusion (2) • Next steps deeper investigation of Multi-FEC class - high frequency traceroute to observe labels behavior ✓ deeper investigation of ECMP class - Paris Traceroute mda mode ✓ providing a library to automatically export MPLS tunnels - usage from CAIDA dataset AIMS - CAIDA/UCSD - March/April 2015 - Benoit Donnet 24
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