MPLS Traffic Engineering George Swallow swallow cisco com Traffic

MPLS Traffic Engineering George Swallow swallow@cisco. com Traffic Engineering © 1999, Cisco Systems, Inc. 1

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

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 Traffic Eng. © 1999, Cisco Systems, Inc. Cisco Systems 3

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

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. ” Mike O’Dell, UUnet Savings can be dramatic. Studies have shown that transmission costs can be reduced by 40%. Traffic Eng. © 1999, Cisco Systems, Inc. Cisco Systems 5

The “Fish” Problem a deficiency in IP routing R 8 R 3 R 4 R 2 R 5 R 1 R 6 R 7 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 Traffic Eng. © 1999, Cisco Systems, Inc. Cisco Systems 6

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 Traffic Eng. © 1999, Cisco Systems, Inc. Cisco Systems 7

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

Overlay Motivation Separate Layer 2 Network (Frame Relay or ATM) “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. ” Mike O’Dell UUnet, November 17, 1996 Traffic Eng. © 1999, Cisco Systems, Inc. Cisco Systems 9

The Overlay Solution L 3 L 2 L 2 L 3 L 3 L 3 L 3 Physical Logical • Layer 2 network used to manage the bandwidth • Layer 3 sees a complete mesh Traffic Eng. © 1999, Cisco Systems, Inc. Cisco Systems 10

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 Traffic Eng. © 1999, Cisco Systems, Inc. Cisco Systems 11

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

An LSP Tunnel R 8 R 3 R 4 R 2 R 5 R 1 R 6 R 7 Labels, like VCIs can be used to establish virtual circuits Normal Route R 1 ->R 2 ->R 3 ->R 4 ->R 5 Tunnel: R 1 ->R 2 ->R 6 ->R 7 ->R 4 Traffic Eng. © 1999, Cisco Systems, Inc. Cisco Systems 13

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

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

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

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

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

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

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

LSP Tunnel Setup R 9 R 8 R 3 R 4 R 2 Pop R 5 R 1 32 49 17 R 6 R 7 22 Setup: Path (R 1 ->R 2 ->R 6 ->R 7 ->R 4 ->R 9) Tunnel ID 5, Path ID 1 Reply: Communicates Labels and Label Operations Reserves bandwidth on each link Traffic Eng. © 1999, Cisco Systems, Inc. Cisco Systems 21

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

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

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

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) Traffic Eng. © 1999, Cisco Systems, Inc. Cisco Systems 25

Local Protection via a Bypass Tunnel R 2 R 9 R 4 R 8 R 3 R 1 R 5 R 10 R 7 R 6 Bypass Tunnel Primary Paths Backup Paths Traffic Eng. © 1999, Cisco Systems, Inc. Cisco Systems 26

Path Protection R 2 R 9 R 4 R 8 R 3 R 1 R 5 R 10 R 7 R 6 Primary Path Backup Path Traffic Eng. © 1999, Cisco Systems, Inc. Cisco Systems 27

Summary Traffic engineering provides the means to ØSave transmission costs ØAddress routing deficiencies ØAttack tactical network engineering problems ØProvide better Qo. S Making sure resource are available Minimizing disruption Traffic Eng. © 1999, Cisco Systems, Inc. Cisco Systems 28

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