1Traffic Engineering © 1999, Cisco Systems, Inc. MPLS Traffic Engineering George Swallow George Swallow

2Traffic Eng. © 1999, Cisco Systems, Inc. Cisco Systems What is Traffic Engineering Taking control of how traffic flows in your network in order to -  Improve overall network performance  Offer premium services  As a tactical tool to deal with network design issues when the longer range solution are not deployed

3Traffic Eng. © 1999, Cisco Systems, Inc. Cisco Systems Voice Traffic Engineering Telco’s noticed that demands vary widely by time of day Began “engineering the traffic” long ago Evolved over time Now fully automated

4Traffic Eng. © 1999, Cisco Systems, Inc. Cisco Systems Reasons for Traffic Engineering Economics – more packets, fewer $$$ Address deficiencies of IP routing Tactical tool for network operations Class-of-service routing

5Traffic Eng. © 1999, Cisco Systems, Inc. Cisco Systems Mike O’Dell, UUnet Economics of Traffic Engineering “The efficacy with which one uses the available bandwidth in the transmission fabric directly drives the fundamental ‘manufacturing efficiency’ of the business and its cost structure.” Savings can be dramatic. Studies have shown that transmission costs can be reduced by 40%.

6Traffic Eng. © 1999, Cisco Systems, Inc. Cisco Systems The “Fish” Problem a deficiency in IP routing IP uses shortest path destination based routing Shortest path may not be the only path Alternate paths may be under-utilized while the shortest path is over-utilized R8 R2 R6 R3 R4 R7 R5 R1

7Traffic Eng. © 1999, Cisco Systems, Inc. Cisco Systems Deficiencies in IP Routing Chronic local congestion Load balancing Across long haul links Size of links Difficult to get IP to make good use unequal size links without overloading the lower speed link

8Traffic Eng. © 1999, Cisco Systems, Inc. Cisco Systems Load Balancing Making good use of expensive links simply by adjusting IGP metrics can be a frustrating exercise!

9Traffic Eng. © 1999, Cisco Systems, Inc. Cisco Systems Overlay Motivation Separate Layer 2 Network (Frame Relay or ATM) Mike O’Dell UUnet, November 17, 1996 “The use of the explicit Layer 2 transit layer gives us very exacting control of how traffic uses the available bandwidth in ways not currently possible by tinkering with Layer 3-only metrics.”

10Traffic Eng. © 1999, Cisco Systems, Inc. Cisco Systems The Overlay Solution Layer 2 network used to manage the bandwidth Layer 3 sees a complete mesh L3 L3 L3 L3 L3 L3 L3 L2 L2 L2 L2 L2 L2 L3 L3 L3 L3L3 PhysicalLogical

11Traffic Eng. © 1999, Cisco Systems, Inc. Cisco Systems Overlay Drawbacks Extra network devices (cost) More complex network management Two-level network without integrated NM Additional training, technical support, field engineering IGP routing doesn’t scale for meshes Number of LSPs generated for a failed router is O(n 3 ); n = number of routers

12Traffic Eng. © 1999, Cisco Systems, Inc. Cisco Systems Traffic Engineering & MPLS MPLS fuses Layer 2 and Layer 3 Layer 2 capabilities of MPLS can be exploited for IP traffic engineering Single box / network solution + or = RouterATM Switch MPLS Router ATM MPLS Router

13Traffic Eng. © 1999, Cisco Systems, Inc. Cisco Systems An LSP Tunnel R8 R2 R6 R3 R4 R7 R5 R1 Normal Route R1->R2->R3->R4->R5 Tunnel: R1->R2->R6->R7->R4 Labels, like VCIs can be used to establish virtual circuits

14Traffic Eng. © 1999, Cisco Systems, Inc. Cisco Systems Comprehensive Traffic Engineering Network design Engineer the topology to fit the traffic Traffic engineering Engineer the traffic to fit the topology fixedtraffic matrix, Given a fixed topology and a traffic matrix, what set of explicit routes offers the best overall network performance?

15Traffic Eng. © 1999, Cisco Systems, Inc. Cisco Systems The Traffic Engineering System TE Tunnel CLI Router NetworkTraffic Engineering Tools Configuration Collection Traffic Analysis Traffic Engineering Design and Modeling StatisticsStatistics

16Traffic Eng. © 1999, Cisco Systems, Inc. Cisco Systems Approaches to Traffic Engineering Topology Type of Traffic Comprehensive TE Comprehensive for Premium Flows Tactical for Premium Flows Tactical TE

17Traffic Eng. © 1999, Cisco Systems, Inc. Cisco Systems Tactical Traffic Engineering Links not available Infrastructure doesn’t exist Lead times too long Failure scenarios Unanticipated growth and shifts in traffic

18Traffic Eng. © 1999, Cisco Systems, Inc. Cisco Systems Tactical TE An Example Major US ISP  New web site appears Within weeks becomes the largest traffic source on their network One of their PoPs becomes completely congested  Once the problem was identified TE tunnels were established to route away any traffic passing through that PoP, but not destined or sourced there Congestion was completely resolved in 5 minutes

19Traffic Eng. © 1999, Cisco Systems, Inc. Cisco Systems System Block Diagram Traffic Engineering Control Path Selection TE Topology Database RSVP Flooding Routing IS-IS/OSPF TE Link Adm Ctl Forwarding Engine

20Traffic Eng. © 1999, Cisco Systems, Inc. Cisco Systems TE Tunnel Attributes Bandwidth Setup & Holding priorities Used for Admission Control Resource class affinity Simple policy routing Path Options Input to route selection

21Traffic Eng. © 1999, Cisco Systems, Inc. Cisco Systems LSP Tunnel Setup Setup: Path (R1->R2->R6->R7->R4->R9) Tunnel ID 5, Path ID R8 R2 R6 R3 R4 R7 R1 R5 R9 Reply: Communicates Labels and Label Operations Reserves bandwidth on each link Pop 32

22Traffic Eng. © 1999, Cisco Systems, Inc. Cisco Systems Multiple Parallel Tunnels Automatically load shared Weighted by bandwidth to nearest part in 16 Traffic assigned by either Source-Destination hash Round robin

23Traffic Eng. © 1999, Cisco Systems, Inc. Cisco Systems Automatic Load Balancing New York #1 New York #2 Washington London #1 London #2 Paris Stockholm Munich Brussels Frankfurt Amsterdam Link #1 Link #2 Link #3 LSP Tunnel #1 LSP Tunnel #2 LSP Tunnel #3

24Traffic Eng. © 1999, Cisco Systems, Inc. Cisco Systems Additional Features Adjusting to failures Requires rapid notification Adjusting to improvements Need to account for Global optimality Network stability

25Traffic Eng. © 1999, Cisco Systems, Inc. Cisco Systems Protection Strategy Two pronged approach: Local protection Repair made at the point of failure us to keep critical applications going Fast - O(milliseconds) Sub-optimal Path protection An optimized long term repair Slower - O(seconds)

26Traffic Eng. © 1999, Cisco Systems, Inc. Cisco Systems Local Protection via a Bypass Tunnel R2 R3 R6 R4 R8 R7 R1 R10 R9 R5 Primary Paths Bypass Tunnel Backup Paths

27Traffic Eng. © 1999, Cisco Systems, Inc. Cisco Systems Path Protection R2 R3 R6 R4 R8 R7 R1 R10 R9 R5 Primary Path Backup Path

28Traffic Eng. © 1999, Cisco Systems, Inc. Cisco Systems Summary Traffic engineering provides the means to  Save transmission costs  Address routing deficiencies  Attack tactical network engineering problems  Provide better QoS Making sure resource are available Minimizing disruption

29Traffic Engineering © 1999, Cisco Systems, Inc. Thank You