Netscope Traffic Engineering for IP Networks A Feldmann

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Netscope: Traffic Engineering for IP Networks A. Feldmann, A. Greenberg, C. Lund, N. Reingold

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 2/24/2021 Netscope 1

Organization • • • Motivation Netscope tool overview Building blocks Netscope Internet structure and

Organization • • • Motivation Netscope tool overview Building blocks Netscope Internet structure and building blocks Unleashing the power of Netscope – performing “what-if” experiments • Conclusion 2/24/2021 Netscope 2

Motivation • Today's IP networks are extremely large • Understanding them requires one to

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 2/24/2021 Netscope 3

Why do we need such tools • Service Quality – ISP’s provide performance guarantees

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 2/24/2021 Netscope 4

What is Netscope • Netscope is a unified set of software tools for managing

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 – performance debugging 2/24/2021 Netscope 5

Building Blocks of such a tool • Topology deduction. • Traffic measurements. • Combine

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. 2/24/2021 Netscope 6

Components of Netscope toolkit Visualization Netscope Routing Model Data Model Configuration 2/24/2021 Measurements Netscope

Components of Netscope toolkit Visualization Netscope Routing Model Data Model Configuration 2/24/2021 Measurements Netscope 7

A Note on implementation • Architectural/Technological changes can occur • Higher level modules must

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 2/24/2021 Netscope 8

Structure of Today’s Internet Devices & Links • Access Routers/Links • Peering Links •

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 2/24/2021 Netscope 9

Links Vs Trunks Link RS L 2 R L 21 2/24/2021 Trunk Devices Netscope

Links Vs Trunks Link RS L 2 R L 21 2/24/2021 Trunk Devices Netscope RD L 22 10

Topology Model • Unidirectional Link Attributes – Router originating link, name of the router

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 2/24/2021 Netscope 11

Topology Model (Contd. . ) • Device Attributes – name, location, trunks which originate

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 2/24/2021 Netscope 12

Traffic and what we are interested in • Some Observations – Customers connect to

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. 2/24/2021 Netscope 13

Traffic (contd. . . ) 2/24/2021 Netscope 14

Traffic (contd. . . ) 2/24/2021 Netscope 14

Determining Traffic Demands • Determining Access links associated with a customer – Based on

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 2/24/2021 Netscope 15

Traffic Measurement • Flow level measurement done at the edge of the network •

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. 2/24/2021 Netscope 16

Routing Model • Netscope’s routing module determines path(s) chosen by OSPF for each traffic

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 2/24/2021 Netscope 17

OSPF Tie-Breaking • There exists multiple shortest paths between a pair of routers. Example

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. 2/24/2021 Netscope 18

OSPF Tie-Breaking 2/24/2021 Netscope 19

OSPF Tie-Breaking 2/24/2021 Netscope 19

Visualization • Visualization environment provides a way to examine various network parameters and objects

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. 2/24/2021 Netscope 20

Visualization (contd. . . ) • Netscope allows to monitor/visualize a large number of

Visualization (contd. . . ) • Netscope allows to monitor/visualize a large number of statistics 2/24/2021 Netscope 21

Features of Netscope • With Netscope one can limit the display to a few

Features of Netscope • With Netscope one can limit the display to a few chosen demands. 2/24/2021 Netscope 22

Unleashing the power of Netscope Low utilization (<= 30%) Medium utilization ( 30%< u

Unleashing the power of Netscope Low utilization (<= 30%) Medium utilization ( 30%< u <= 60%) High utilization (> 60%) 2/24/2021 Netscope 23

Decreasing OSPF weights • Experimentation can be done in a similar way to divert

Decreasing OSPF weights • Experimentation can be done in a similar way to divert some of the traffic on the link between Cambridge and Chicago 2/24/2021 Netscope 24

Conclusions and Future work • Netscope is a powerful tool for network visualization •

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? ? 2/24/2021 Netscope 25

Thank you!!!!! 2/24/2021 Netscope 26

Thank you!!!!! 2/24/2021 Netscope 26