3. Internet Traffic Measurement 3 Why Measure ? Although
Internet works, it is far from being ideal Measurements of various
aspects of it will: Help us to better understand why it works the
way it does Help us to diagnose known problems and lead us one step
closer to their solutions Help us to design new features that the
Internet should provide to enable next-generation application
requirements Simply put, Internet Measurements is key to the design
of the next-generation Internet
4. Internet Traffic Measurement 4 What to Measure ? Physical
Properties Devices (routers, NAT boxes, firewalls, switches), Links
(wired, wireless) Topology Properties Various levels Autonomous
Systems (AS), Points of Presence (PoP), Routers, Interfaces Traffic
Properties Delays (Transmission, Propagation, Queuing, Processing
etc.), Losses, Throughput, Jitter
6. Internet Traffic Measurement 6 Measurement Tools Active
Measurement Passive Measurement Fused/Combined Measurement
Inference Measurement Others
7. Internet Traffic Measurement 7 Active Measurement Tools
Methods that involve adding traffic to the network for the purposes
of measurement Ping: Sends ICMP ECHO_REQUEST and captures
ECHO_REPLY Useful for measuring RTTs Only sender needs to be under
experiment control Traceroute: Ping nodes with incremental TTL from
one Find Hops between source and destination node Only sender needs
to be under experiment control There is some care about the
result
8. Internet Traffic Measurement 8 Active Measurement Load
Active Measurement inserts considerable load on network links if
attempting a large-scale topology discovery Optimizations reduce
this load considerably If single source is used, instead of going
from source to destination, a better approach is to retrace from
destination to source If multiple sources and multiple destinations
are used, sharing information among these would bring download
considerably
9. Internet Traffic Measurement 9 Passive Measurement Capture
traffic generated by other users and applications Routeview
collects BGP views (routing tables) from a large set of ASes OSPF
LSAs can processed to generate router graphs within an AS
10. Internet Traffic Measurement 10 Fused Measurement Active
Measurement + Passive Measurement + Fused Measurement mixed method
to use benefits of each method. Less Traffic Load Less Required
Storage More information for decision
11. Internet Traffic Measurement 11 Inference Measurment
Measurement Limitations Direct access impossible Topology and link
out of reach How to solve ? End-to-End Measurement Tomography:
process of inferring network topology, delays, packet losses etc.
using only end-to-end measurements
13. Internet Traffic Measurement 13 Measurement Level Bit &
Bytes (useless) Packets (High volume) High volume but valuable data
for offline & generate traffic Flow (limited to flows)
Protocols (Specific Protocol) TCP, UDP, IP, RTP, .. Application
(Known applications) HTTP, DNS, MAIL, VOIP, ... SNMP
14. Internet Traffic Measurement 14 Hidden Pieces - Middleboxes
Firewalls provide security Traffic Shapers assist in traffic
management Proxies improve performance NAT boxes utilize IP address
space efficiently Each of these impedes visibility of network
components. Example: firewalls may block active probing requests
NATs hide away the no. of hosts and the structure of the network on
the other side
17. Internet Traffic Measurement 17 Bandwidth Measurment
Bandwidth Measurement Amount of data the network can transmit per
unit time Three kinds of bandwidth capacity: max throughput a link
can sustain, available bandwidth: capacity used bandwidth bulk
transfer capacity: rate that a new single long-lived TCP connection
would obtain over a path
18. Internet Traffic Measurement 18 Path Provisioning by
Traceroute Suppose the path between A and D is to be determined
using traceroute A X Y D B C
19. Internet Traffic Measurement 19 Traceroute Process A X Y D
B C Dest = D TTL = 1 B: time exceeded
20. Internet Traffic Measurement 20 Traceroute Process A X Y D
B C Dest = D TTL = 2 C: time exceeded
21. Internet Traffic Measurement 21 Traceroute Process A X Y D
B C Dest = D TTL = 3 D: echo reply
22. Internet Traffic Measurement 22 Traceroute issues Path
Asymmetry (Destination -> Source need not retrace Source ->
Destination) Unstable Paths and False Edges Aliases Measurement
Load
23. Internet Traffic Measurement 23 Unstable Paths and False
Edges Inferred path: A -> B -> Y A X Y D B C Dest = D TTL = 1
B: time exceeded Dest = D TTL = 2 Y: time exceeded
24. Internet Traffic Measurement 24 Aliases IP addresses are
for interfaces and not routers Routers typically have many
interfaces, each with its own IP address IP addresses of all the
router interfaces are aliases Traceroute results require resolution
of aliases if they are to be used for topology building
25. Internet Traffic Measurement 25 Video Quality Measurment
Subjective Evaluation Variety cause of user experience Need many
user to vote Objective Evaluation Data Metrics (PSNR) Picture
Metrics (MPQM ,SSIM) Packet/Bit stream Metrics (Loss)
Full/Reduced/Non Reference Visible/Invisible distortion
26. Internet Traffic Measurement 26 Video Quality Measurment
GOP Frames (P, I, B) Slices
27. Internet Traffic Measurement 27 Video Quality Measurment
Stream should be packetized TS(DVB) vs RTP(IPTV) Passive
Measurement Deep Packet Inspection Resilience and Error correction
Quality Estimation (Fuzzy, NN, ...)