Network Monitoring for Internet Traffic Engineering

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Network Monitoring for Internet Traffic
Engineering

• Jennifer Rexford
• ATT Labs Research
• Florham Park, NJ 07932
• http//www.research.att.com/jrex

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(No Transcript)
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Tracking the ATT IP Backbone

• Traffic
• Modem records for each WorldNet dial connection
• SNMP link and loss statistics for every link
• Flow-level measurement on selective peering links
• Packet-level measurement on two edge links
• Performance
• Active probes of performance for each pair of
  cities
• Network state
• Configuration file from each router
• Fault data from each router (alarms and polling)
• BGP routing tables for routers connecting to
  peers
• BGP update messages from two core routers

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Outline

• ISP backbone networks
• Service provider backbone
• Routing protocols
• Network model for traffic engineering
• Topology, capacity, and routing configuration
• Destinations reachable via neighboring domains
• Populating the model
• Static snapshot (config files, forwarding tables)
• Real-time view (OSPF monitor, iBGP monitor)
• Integration in traffic engineering tool

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Internet Service Provider Backbone
modem banks, business customers, web/e-mail
servers
neighboring providers
Backbone routers
Gateway routers
Access routers
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Border Gateway Protocol (BGP)

• ASes exchange info about who they can reach
• Update messages exchanged over a TCP connection
• Local policies for path selection (which to use?)
  
• Local policies for route propagation (who to
  tell?)
• Policies configured by the ASs network operator

I can reach 12.34.158.0/23 via AS 1
I can reach 12.34.158.0/23
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2
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flow of traffic
12.34.158.5
AS Autonomous System
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Interior Gateway Protocol (Within an AS)

• Routers flood information to learn the topology
• Routers determine next hop to reach other
  routers
• Path selection based on link weights (shortest
  path)
• Link weights configured by the network operator

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1
3
1
3
2
5
1
3
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Path cost 8
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Traffic Engineering in an ISP Backbone

• Network topology
• Connectivity and capacity of routers and links
• Configurable policies for resource allocation
• Path selection, buffer management, and link
  scheduling
• Traffic demands
• Expected/offered load between points in the
  network
• Performance objective
• Balanced load, low latency, service level
  agreements
• Question Given the topology and traffic demands,
  which configuration parameters should be used?

This talk focuses on the topology and
configuration part.
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Our Approach Measure, Model, and Control

• Monitor the network to collect the various inputs
• Model the network-wide path-selection process
• Build tools on top of the data and the model

Routing configuration
Topology
Distributed routing protocols
Offered traffic
BGP updates
Flow of traffic through the network
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Network Topology

• Router
• Loopback IP address (e.g., 12.123.37.250)
• IP addresses of interfaces
• Link
• Network address (e.g., 12.125.133.88/30)
• Capacity (e.g., 10 Mbps, 622 Mbps)

12.125.133.88/30
12.123.37.250
12.7.108.3
12.125.133.89
12.125.133.90
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Core and Edge Links

• Core link
• OSPF weight per interface
• OSPF area

area 9
1024
512

• Edge link
• Set of destination prefixes

12.34.158.0/23, 192.0.2.0/24
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Populating the Model Daily Snapshot

• Router configuration files
• Router name, OS version, IP address, running
  processes
• Individual interfaces and their location in the
  router
• Set of commands applied against the router
• Processing the configuration data
• Parsing the commands applied to each router
• Identifying all of the outgoing interfaces at the
  router
• Finding each pair of interfaces that forms a core
  link
• Populates part of the model
• Router, links, and link capacities
• Identification of edge and core links
• OSPF weights and areas for core links

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Example Router Configuration File

• Language with hundreds of different commands
• Cisco IOS is a de facto standard config language
• Sections for interfaces, routing protocols,
  filters, etc.

version 12.0 hostname MyRouter ! interface
Loopback0 ip address 12.123.37.250
255.255.255.255 ! interface Serial9/1/0/40
description MyT1Customer bandwidth 1536 ip
address 12.125.133.89 255.255.255.252 ip
access-group 10 in !
interface POS6/0 description MyBackboneLink
ip address 12.123.36.73 255.255.255.252 ip ospf
cost 1024 ! router ospf network 12.123.36.72
0.0.0.3 area 9 network 12.123.37.250 0.0.0.0
area 9 ! access-list 10 permit 12.125.133.88
0.0.0.3 access-list 10 permit 135.205.0.0
0.0.255.255 ip route 135.205.0.0 255.255.0.0
Serial9/1/0/40
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Daily Snaphot Continued

• Router forwarding tables
• Next-hop interface(s) for each destination prefix
• Processing the forwarding tables
• Identify next hops associated with edge
  interfaces
• Ignore entries where next hop is a core interface
• Extract the associated destination prefixes
• Populates part of the model
• Set of prefixes reachable via each edge link
• Or, set of edge links associated with each prefix

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Example Forwarding Table (show ip cef)
Prefix Next Hop
Interface 4.20.90.120/29 12.123.28.134
POS7/0
12.123.28.130 POS6/0 4.20.90.128/29
12.123.28.130 POS6/0 4.24.7.104/30
12.123.28.134 POS7/0 4.36.100.0/23
192.205.32.126 ATM5/0.1 6.0.0.0/8
12.123.28.134 POS7/0
12.123.28.130
POS6/0 9.2.0.0/16 192.205.32.126
ATM5/0.1 9.3.4.0/24 12.123.28.130
POS6/0 9.3.5.0/24
12.123.28.130 POS6/0 9.20.0.0/17
192.205.32.178 POS0/3
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Locating the Set of Egress Links for Prefix d
Prefix d exit links i, k
i
Table entry (d, i)
k
d
Table entry (d, k)
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Populating the Model Real-Time View

• OSPF monitor
• Up/down status of routers and their interfaces
• OSPF weight and area for each interface
• Acquiring the real-time view
• Software router (GateD) that implements OSPF
  routing
• Physical adjacency with an operational router
• Copy of all flooded link-state advertisements

Route monitor
Router
OSPF messages
Router
Router
Work by A. Shaikh and A. Greenberg
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Real-Time View (Continued)

• iBGP monitor
• Destination prefixes associated with each edge
  link
• Frequency of changes, attributes of routes, etc.
• Acquiring the real-time view
• Software router (Zebra) that implements BGP
  routing
• Logical adjacency (TCP) with operational routers
• Best route for each prefix from each vantage
  point

Route monitor
Router
BGP messages
BGP messages
Router
Router
Work with T. Griffin and D. Caldwell
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Toolkit for Traffic Engineerng

• Other components of traffic engineering
• Traffic measurements at destination prefix level
• Path computation based on OSPF weights/areas
• Network visualization to display flow of traffic
• Optimization algorithm for selecting good weights

Visualization
Optimization
Routing model
Traffic model
Network model
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Combining With Traffic Measurements
Peering point
Color/size of node proportional to traffic to
this router (high to low) Color/size of link
proportional to traffic carried (high to low)
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Conclusions

• Summary
• Network model for traffic engineering (TE)
• Populating the model from existing data sets
• Real-time monitoring of OSPF and BGP messages
• Integration of the network model in a TE tool
• Ongoing work
• Extensions to support changes to BGP policies
• Analysis of the real-time OSPF and BGP data
• Improved support for measurement on routers
• Driving goal
• Accurate, timely, network-wide view of topology,
  routing, and traffic data

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To Learn More...

• Network overview and routing model
• Traffic engineering for IP networks
  (http//www.research.att.com/jrex/papers/ieeenet0
  0.ps)
• Measurement infrastructure
• "Measurement and analysis of IP network usage and
  behavior(http//www.research.att.com/jrex/paper
  s/ieeecomm00.ps)
• Topology and configuration
• IP network configuration for intradomain traffic
  engineering (http//www.research.att.com/jrex/pa
  pers/ieeenet01.ps)
• Traffic demands
• Deriving traffic demands for operational IP
  networks Methodology and experiences
  (http//www.research.att.com/jrex/papers/sigcomm
  00.ps)
• OSPF monitor
• An OSPF topology server Design and evaluation