Transcript Migrating from Frame Relay to an IP Service

MPLS
Traffic Engineering
George Swallow
[email protected]
Traffic Engineering
© 1999, Cisco Systems, Inc.
1
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
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
R8
R3
R4
R2
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
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
L3
L3
L2
L3
L2
L2
L2
L3
L2
L3
L2
L3
L3
L3
L3
L3
L3
L3
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(n3); 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
R8
R3
R4
R2
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
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 Comprehensive
for
TE
Premium Flows
Tactical
for
Premium Flows
Tactical
TE
Type of Traffic
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
 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
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
R9
R8
R3
R4
R2
Pop
R5
R1
32
49
17
R6
R7
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
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
LSP Tunnel #1
Link #1
Stockholm
London
#1
Frankfurt
New York
#2
LSP Tunnel #2
Link #2
London
#2
Amsterdam
Brussels
Washington
Traffic Eng.
© 1999, Cisco Systems, Inc.
LSPTunnel #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
R9
R2
R4
R8
R3
R1
R5
R10
R7
R6
Bypass Tunnel
Primary Paths
Backup Paths
Traffic Eng.
© 1999, Cisco Systems, Inc.
Cisco Systems
26
Path Protection
R9
R2
R4
R8
R3
R1
R5
R10
R7
R6
Primary Path
Backup Path
Traffic Eng.
© 1999, Cisco Systems, Inc.
Cisco Systems
27
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
Traffic Eng.
© 1999, Cisco Systems, Inc.
Cisco Systems
28
Thank You
Traffic Engineering
© 1999, Cisco Systems, Inc.
29