router-level internet topology mapping
DESCRIPTION
Router-level Internet Topology Mapping. By Talha OZ. Outline. Introduction Internet Topology Collection Basic Techniques Some Measurement Projects & Platforms Issues in Topology Collection Issues in Topology Construction Resolving Anonymous Routers Resolving Alias IP Addresses - PowerPoint PPT PresentationTRANSCRIPT
Router-level Internet Topology Mapping
By Talha OZ
Outline Introduction
Internet Topology Collection• Basic Techniques• Some Measurement Projects & Platforms• Issues in Topology Collection
Issues in Topology Construction• Resolving Anonymous Routers • Resolving Alias IP Addresses• Resolving Genuine Subnets
Summary2Internet Topology Discovery
My stress on this presentation
Will be explained in detail in the next presentation
Outline Introduction
• Internet as a Complex Network• Motivations on Internet Topology Measurement
Internet Topology Collection• Basic Techniques• Some Measurement projects & platforms• Issues in Topology Collection
Issues in Topology Construction• Resolving Anonymous Routers • Resolving Alias IP Addresses• Resolving Genuine Subnets
Summary3Internet Topology Discovery
Internet Topology Discovery 4
Web of interconnected networks• Grows with no central authority• Autonomous Systems optimize local communication efficiency• The building blocks are engineered and studied in depth• Global entity has not been characterized
Most real world complex-networks have non-trivial properties.
Global properties can not be inferred from local ones• Engineered with large technical diversity• Range from local campuses to transcontinental backbone
providers
Internet
Once the graph is built, one can study its characteristics• Essential to design, implement, protect, and operate underlying network
technologies, protocols, services, and applications
Capture graph’s theoretic resilience to failure or say something about its efficiency for routing
Realistic simulation environment for developed products
Comprehend spreading of worms/viruses (Burch and Cheswick’s proposal)
Improve QoS for the multimedia content• Where to store the data in replicated servers distributed across the internet
ISPs are not willing to share their topology information
Motivation on Internet Topology Measurement
5Internet Topology DiscoveryLumenta Jan 06
Types of Internet topology maps• Autonomous System (AS) level maps• Point of presence (PoP) level • Router level maps• IP interface level
A router level Internet map consists of• Nodes: End-hosts and routers • Links: Point-to-point or multi-access links
Router level Internet topology discovery• A process of identifying nodes and links among them
Internet Topology Measurement
6Internet Topology DiscoveryLumenta Jan 06CAIDA Jan 08CAIDA Jan 00
Outline Introduction Internet Topology Collection
• Basic Techniques• Some Measurement projects & platforms
• Issues in Topology Collection
Issues in Topology Construction• Resolving Anonymous Routers • Resolving Alias IP Addresses• Resolving Genuine Subnets
Summary
7Internet Topology Discovery
Internet topology measurement studies Involves topology collection / construction / analysis
How to collect ? Work on IP layer, leverage header information IETF’s RFCs determine the behavior of the nodes Send ICMP, UDP, TCP packets and wait ... Ideal case and issues ...
Internet Topology MeasurementTopology Collection
8Internet Topology Discovery
IETFThe Internet Engineering Task Force (IETF)
develops and promotes Internet standards
RFCAn Internet Standard is a special
Request for Comments (RFC) or set of RFCs.
http://tools.ietf.org/html/rfc792
Internet Topology MeasurementTopology Collection – Who sets the rules ?
9Internet Topology Discovery
Internet Topology MeasurementHow to collect
Internet Topology Discovery 10
Direct probing
Indirect probing
A DB C
Internet Topology MeasurementsProbing
IPB TTL=64
IPB
IPD TTL=64
IPD
Vantage Point
A DB C
Vantage Point
IPB
IPD TTL=2IPD TTL=1
IPC
11Internet Topology Discovery
Probe packets are carefully constructed to elicit intended response from a probe destination
traceroute probes all nodes on a path towards a given destination• TTL-scoped probes obtain ICMP error messages from routers on the path• ICMP messages includes the IP address of intermediate routers as its source
Merging end-to-end path traces yields the network map
S DA B C
Destination
Internet Topology MeasurementTopology Collection (traceroute)
TTL=1
IPA
TTL=2
IPB
TTL=3
IPC
TTL=4
IPD
Vantage Point
12Internet Topology Discovery
Internet Topology Measurement:Background
Internet Topology Mapping 13
S
L
U
H
C
N
W
A
s.2
l.1
s.3
u.1
l.3
u.3
h.1
k.3
h.2
h.3
a.3
u.2k.1 c.4
a.1 a.2
w.3c.3w.1
c.2
n.1 n.3
w.2
l.2
K
c.1
k.2
dh.4
Trace to Seattle
h.4
l.3
s.2
Trace to NY
h.4
a.3
w.3
n.3
Internet2 backbone
Internet Topology Measurement:Background
Internet Topology Mapping 14
S
L
UC
N
A
s.2
l.1
s.3
u.1
l.3
h.1
k.3
h.2
a.3
u.2k.1 c.4
a.1 a.2
w.3c.3w.1
c.2
n.1 n.3
w.2
l.2
K
c.1
k.2
h.3
dh.4
s.1e f
n.2
H
W
u.3
Internet Topology MeasurementTopology Collection
Internet2 backbone
Traces• d - H - L - S - e• d - H - A - W - N - f• e - S - L - H - d• e - S - U - K - C - N - f• f - N - C - K- H - d• f - N - C - K - U - S - e
S
L
U
K
C
H
A
W
Ne
d
f
15Internet Topology Discovery
Outline Introduction Internet Topology Collection
• Basic Techniques
• Some measurement projects & platforms• Issues in Topology Collection
Issues in Topology Construction• Resolving Anonymous Routers • Resolving Alias IP Addresses• Resolving Genuine Subnets
Summary
16Internet Topology Discovery
17
PlanetLab• Currently consists of 1020 nodes at 483 sites• Since the beginning of 2003, 1000+ researchers develop new
technologies for • distributed storage• network mapping• peer-to-peer systems• distributed hash tables• query processing
CAIDA (Cooperative Association for Internet Data Analysis)• Provides tools and analyses promoting the engineering and
maintenance of a robust, scalable global Internet infrastructure.• San Diego Supercomputer Center @ UCSD
Topology Data Collecting Platforms - I
Internet Topology Discovery
18
Macroscopic Topology Measurements (Skitter project) by CAIDA• characterize macroscopic connectivity and performance of the
Internet• allow various topological and geographical representations at
multiple levels of aggregation granularity• provide a valuable input for empirically-based modeling of the
Internet behavior and properties
Skitter, developed by CAIDA• skitter measurement tool reads a file of destinations and writes
a file of traceroute paths• ...
Topology Data Collecting Platforms - II
Internet Topology Discovery
19
• ...• ICMP traceroutes are used• RTTs are also stored• 24 monitors around the world• 970K common destination, IPv4 addresses• Scamper does the similar thing for IPv6
Archipelago (Ark) is the evolution of the skitter infrastructure, by CAIDA• skitter monitors• skitter measurement tool• an internal web server for distributing destination lists• a file storage server for collecting traces from monitors
Topology Data Collecting Platforms - III
Internet Topology Discovery
20
The Distributed Internet Measurements and Simulations (DIMES)• Model of SETI@home• Counts more than 20,343 agents scattered over five continents• “What we ask is not so much your CPU or bandwidth (which
we hardly consume), but rather, your location.” iPlane
• Measuring the Internet: performs traceroutes from various VPs -- PlanetLab nodes and traceroute servers -- to construct a router interface-level atlas of the Internet.
• Clustering interfaces into PoPs• Measuring link attributes• Opportunistic measurements• Route prediction
Topology Collecting Platforms - IV
Internet Topology Discovery
21
Rocketfuel tries to get the picture of the ISPs• Number of required probes is decreased
• directed probing• path reduction (ingress & egress)
• Alias resolution• Router identification and annotation (DNS and ISP naming)• Report on properties of maps from ten diverse ISPs :
• Size of POPs• Distribution of router outdegree• Inter-domain peering structure
Topology Collecting Platforms - V
Internet Topology Discovery
22
Scriptroute allows everyone to measure from several VPs• Proposes remote measurement execution on PlanetLab nodes• RPT tool avoids retracing paths
TTM, developed by RIPE NCC• Full mesh between roughly a hundred monitors • One-way delay, packet loss, and bandwidth are also stored
Atlas is based on “source-routed IPv6 traceroute”• probe engine, topology constructor, topology verifier, interactive
visualization program
Topology Collecting Platforms - VI
Internet Topology Discovery
23
TCP Sidecar• a technique and associated API for embedding measurement
probes into non-measurement TCP streams • avoids abuse reports and allows measurements to tunnel through
NATs and behind firewalls • Augment traceroute (TR) probes with IP Record Route option (RR)
DipZoom (Deep Internet Performance Zoom)• Focused, on-demand Internet measurements• Offers a matchmaking service which uses P2P concepts to bring
together experimenters in need of measurements with external measurement providers.
• DipZoom participants offer measurements for the benefit of being able to access measurements offered by other participants
Topology Collecting Platforms - VII
Internet Topology Discovery
Outline Introduction Internet Topology Collection
• Basic Techniques
• Some measurement projects & platforms
• Issues in Topology Collection
Issues in Topology Construction• Resolving Anonymous Routers • Resolving Alias IP Addresses• Resolving Genuine Subnets
Summary
24Internet Topology Discovery
25
Forward & primary paths • Asymmetric routing• miss out on backup paths
Unbiased Sampling
Traceroute & load balancer (Paris traceroute)
MPLS (TTL reduction)
Misconfigurated network elements
Issues in Topology CollectionIssues I
Internet Topology Discovery
26
Third-party address (multi homing)
Redundancy• intra-monitor redundancy• inter-monitor redundancy• DDoS
Responsiveness• ICMP echo request• TCP syn • UDP port unreachable
Issues in Topology Collection Issues II
Internet Topology Discovery
Outline Introduction Internet Topology Collection
• Basic Techniques
• Some measurement projects & platforms
• Issues in Topology Collection
Issues in Topology Construction• Resolving Alias IP Addresses• Resolving Anonymous Routers • Resolving Genuine Subnets
Summary
27Internet Topology Discovery
28
Alias Resolution• Iffinder• Ally• DNS based method• Graph based method• Analytical IP Alias Resolution (APAR)• Record route option
Issues in Topology Construction - I at Router Level
Internet Topology Discovery
Each interface of a router has an IP address.
A router may respond withdifferent IP addresses to different queries.
Alias Resolution is the process of grouping the interface IP addresses of each router into a single node.
Inaccuracies in alias resolution may result in a network map that• includes artificial links/nodes • misses existing links
Alias Resolution
.5.33
.18
.13.7
Denver
29Internet Topology Discovery
30
Anonymous Router Resolution• Basic heuristics [Bilir 05] & [Xin 06]• Graph minimization approach [Yao 03]• ISOMAP based dimensionality reduction approach [Xin 06]• Graph based induction
Issues in Topology Construction - II at Router Level
Internet Topology Discovery
Anonymous Router Resolution Problem
Anonymous routers do not respond to traceroute probes and appear as a in path traces• Same router may appear as a in multiple traces.• Anonymous nodes belonging to the same router should be resolved.
Anonymity Types1. Ignore all ICMP packets2. ICMP rate-limiting3. Ignore ICMP when congested4. Filter ICMP at border5. Private IP address
31Internet Topology Discovery
U K C N
L H A W
S
xy
z
Sampled network
x
y
zS U
L
C
A
W
Resulting network
32
Genuine Subnet Resolution• Inferring Subnets in Router-level Topology Collection Studies
[Gunes 07]
Issues in Topology Construction - III at Router Level
Internet Topology Discovery
33
Genuine Subnet ResolutionProblem
Subnet resolution• Identify IP addresses that are connected over the same medium
Improve the quality of resulting topology map
IP2 IP3
IP1
IP2 IP3
IP1
Internet Topology Discovery
(observed topology) (inferred topology) (underlying topology)C D
A B
C D
A B
C D
A B
C D
A B
Summary Introduction
• Internet as a Complex Network• Motivations on Internet Topology Measurement
Internet Topology Collection• Basic Techniques• Some Measurement Projects & Platforms• Issues in Topology Collection
Issues in Topology Construction• Resolving Anonymous Routers • Resolving Alias IP Addresses• Resolving Genuine Subnets
34Internet Topology Discovery
Questions ?
Internet Topology Discovery 35