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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

OSPF Tie-Breaking 11/29/2018 Netscope

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

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

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

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

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

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

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