1. Netscope: Traffic Engineering for IP Networks
A.Feldmann, A.Greenberg, C.Lund, N.Reingold & J.Rexford
AT&T Labs
presented by
Rajendraprasad B.Hosamani
ECE Dept, Umass, Amherst
11/29/2018
Netscope

2. Organization Motivation Netscope tool overview
Building blocks Netscope
Internet structure and building blocks
Unleashing the power of Netscope
performing “what-if” experiments
Conclusion
11/29/2018
Netscope

3. Motivation Today's IP networks are extremely large
Understanding them requires one to understand
Routing policies
Current traffic flows
Network configuration
Managing such an IP network requires one to perform traffic measurement and network modeling
State-of-the-art methods rely on combination of intuition, experimentation, trial and error
Netscope attempts to provide s/w systems to do the same
11/29/2018
Netscope

4. Why do we need such tools
Service Quality
ISP’s provide performance guarantees in the form of SLA’s
Customers monitor the compliance.
Interdependent tunable parameters
Network growth
Traffic variability
Study the fluctuations in the distributions of IP traffic
11/29/2018
Netscope

5. What is Netscope
Netscope is a unified set of software tools for managing the performance of IP backbone networks.
With Netscope one can
generate global views of the network
Visualize network-wide implications of local changes
Experiment with changes in network configuration in a simulated environment
perform performance debugging
11/29/2018
Netscope

6. Building Blocks of such a tool
Topology deduction.
Traffic measurements.
Combine diverse network configuration and traffic measurements into a joint model.
Some way to capture the routing behavior in the network.
Visualization of all the above data in a way that it makes easy sense.
11/29/2018
Netscope

7. Components of Netscope toolkit
Visualization
Netscope
Routing Model
Data Model
Configuration
Measurements
11/29/2018
Netscope

8. A Note on implementation
Architectural/Technological changes can occur
Higher level modules must be flexible to handle this
Topology and traffic data can be derived from variety of sources
Lower level mainly consists of raw parsers
Should be designed for simplicity and extensibility
11/29/2018
Netscope

9. Structure of Today’s Internet
Devices & Links
Access Routers/Links
Peering Links
Backbone Routers/Links
Gateway Routers
Trunks/Devices
Policies & Logical Structure
AS and Areas
Internal/External policies(BGP)
OSPF/IS-IS/RIP
11/29/2018
Netscope

10. Links Vs Trunks RS RD L21 L2R L22 Link 11/29/2018 Netscope Trunk
Devices
Trunk
L21
L2R
L22
11/29/2018
Netscope

11. Topology Model Unidirectional Link Attributes
Router originating link,name of the router card,IP address of the interface, description of the purpose, capacity, OSPF weight
Bi-directional Link Attributes
Same as above, with some attributes common for both directions. For example: OSPF area
Router Attributes
name, loopback IP address, type of router (AR, BR, IGR), location
The links which the router originates
11/29/2018
Netscope

12. Topology Model (Contd.. ..)
Device Attributes
name, location, trunks which originate at the device
Trunk Attributes
Links traversing a given trunk.
Link Attributes
name,Source/Destination routers, Trunks making the link
11/29/2018
Netscope

13. Traffic and what we are interested in
Some Observations
Customers connect to backbone via multiple access links
Hence traffic introduced by a customer should be modeled as a demand from an access link to a set of peering links
Many external addresses are reachable via multiple peering links
Hence traffic from external internet to a customer should be modeled as a demand from a peering link to a set of access links.
11/29/2018
Netscope

14. Traffic (contd.....)
11/29/2018
Netscope

15. Determining Traffic Demands
Determining Access links associated with a customer
Based on forwarding table at each access router
Each table entry consists of customer prefix,card name of outgoing link
Router configuration files associates prefixes to links
Determining Peer links associated with a customer
Make use of the BGP routing tables which consists of next-hop AS path and IGR
Each external prefix is associated with a set of peering links
IGR and next hop gives us information about the peering links
11/29/2018
Netscope

16. Traffic Measurement
Flow level measurement done at the edge of the network
Measurement done by dumping the main IP, TCP/UDP header fields ,number of packets transmitted, bytes transferred, start and finish time of the flow.
The source and destination IP addresses of the flow can be associated with the appropriate prefix, and matched to the corresponding access/peering links.
With this aggregate traffic due to a customer (entering/leaving the network) can be calculated.
11/29/2018
Netscope

17. Routing Model
Netscope’s routing module determines path(s) chosen by OSPF for each traffic demand.
Netscope considers a single instance of the network topology and OSPF configuration
Netscope does not implement route summarization
11/29/2018
Netscope

18. OSPF Tie-Breaking
There exists multiple shortest paths between a pair of routers. Example :
Due to parallel links for additional capacity,similar OSPF weights.
Traditionally hashing is used to break ties
Hashing is vendor specific
Hence Netscope implements a hashing function which splits the traffic evenly.
11/29/2018
Netscope

19. OSPF Tie-Breaking
11/29/2018
Netscope

20. Visualization Visualization environment provides
a way to examine various network
parameters and objects
Figure displays attributes of a router
object which starts at a router in Dallas
and terminates at a router in LA.
11/29/2018
Netscope

21. Visualization (contd.....)
Netscope allows to monitor/visualize a large number of statistics
11/29/2018
Netscope

22. Features of Netscope
With Netscope one can limit the display to a few chosen demands.
11/29/2018
Netscope

23. Unleashing the power of Netscope
Low utilization (<= 30%)
Medium utilization ( 30%< u <= 60%)
High utilization (> 60%)
11/29/2018
Netscope

24. Decreasing OSPF weights
Experimentation can be done
in a similar way to divert some
of the traffic on the link
between Cambridge and Chicago
11/29/2018
Netscope

25. Conclusions and Future work
Netscope is a powerful tool for network visualization
Aids in performance debugging.
Netscope works on a static feed of topology
Future work may enhance it to continuous feed of topology
Support for wireless Ad-hoc networks??
11/29/2018
Netscope

26. Thank you!!!!!
11/29/2018
Netscope