Traffic Engineering. Traffic Engineering

Transcription

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

2 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 2

3 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 3

4 Reasons for Traffic Engineering Economics more packets, fewer $$$ Address deficiencies of IP routing Tactical tool for network operations Class-of-service routing 4

5 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%. 5

6 The Fish Problem a deficiency in IP routing R8 R2 R3 R4 R5 R1 R6 R7 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 6

7 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 7

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,

9 The Overlay Solution L2 L2 L2 L2 L2 L2 Physical Logical Layer 2 network used to manage the bandwidth Layer 3 sees a complete mesh 10

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 11

11 Traffic Engineering & MPLS + = or Router ATM Switch 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 ATM MPLS Router 12

12 An LSP Tunnel R8 R2 R3 R4 R5 R1 R6 R7 Labels, like VCIs can be used to establish virtual circuits Normal Route R1->R2->R3->R4->R5 Tunnel: R1->R2->R6->R7->R4 13

13 LSP Tunnel Setup R8 R2 R3 R4 Pop R9 R R6 R7 32 R5 22 Setup: Path (R1->R2->R6->R7->R4->R9) Tunnel ID 5, Path ID 1 Reply: Communicates Labels and Label Operations Reserves bandwidth on each link 21

14 Multiple Parallel Tunnels Automatically load shared Weighted by bandwidth to nearest part in 16 Traffic assigned by either Source-Destination hash Round robin 22

15 Automatic Load Balancing New York #1 LSP Tunnel #1 Link #1 London #1 Stockholm New York #2 LSP Tunnel #2 Link #2 London #2 Frankfurt Amsterdam Brussels Washington LSP Tunnel #3 Link #3 Paris Munich 23

16 Additional Features Adjusting to failures Requires rapid notification Adjusting to improvements Need to account for Global optimality Network stability 24

17 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) 25

18 Local Protection via a Bypass Tunnel R2 R4 R8 R9 R3 R1 R5 R10 R6 R7 Bypass Tunnel Primary Paths Backup Paths 26

19 Path Protection R2 R4 R8 R9 R3 R1 R5 R10 R6 R7 Primary Path Backup Path 27

20 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 28