Download MPLS with TE Lab

Lab
MPLS with Traffic Engineering
Last Update 2011.06.01
1.0.0
Copyright 2011 Kenneth M. Chipps Ph.D.
www.chipps.com
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Source
• This lab was developed by ibarrere
• That is the only name listed on the site
• It is found in a blog post from May 2009 on
the http://www.networking-forum.com web
site at
– http://www.networkingforum.com/blog/?p=145
• This looks like a very useful site
Copyright 2011 Kenneth M. Chipps Ph.D. www.chipps.com
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What is MPLS
• MPLS is the next development in privately
managed shared networks
• Large networks have migrated from
dedicated T carrier circuits directly
connecting sites to each other, to the first
shared service provider network based on
Frame Relay, to now MPLS
• MPLS uses tunnels between sites to carry
traffic needing different types of QoS
Copyright 2011 Kenneth M. Chipps Ph.D. www.chipps.com
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What is MPLS
• The source work on MPLS is defined in
RFC 3031
• MPLS flows are connection-oriented and
packets are routed along paths preconfigured by service providers called LSP
- Label Switched Paths
Copyright 2011 Kenneth M. Chipps Ph.D. www.chipps.com
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What is MPLS
• Basic MPLS has been extended with a set
of Generalized MPLS extensions that
allow it to handle different types of traffic
between the same general end points
Copyright 2011 Kenneth M. Chipps Ph.D. www.chipps.com
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Operation of MPLS
• Metaswitch provides an excellent
discussion and graphic to show how
MPLS works
• They say
– MPLS works by tagging the traffic, in this
example packets, with an identifier, a label, to
distinguish the LSPs
Copyright 2011 Kenneth M. Chipps Ph.D. www.chipps.com
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Operation of MPLS
– When a packet is received, the router uses
this label and sometimes also the link over
which it was received to identify the LSP
– It then looks up the LSP in its own forwarding
table to determine the best link over which to
forward the packet, and the label to use on
this next hop
– A different label is used for each hop, and it is
chosen by the router or switch performing the
forwarding operation
Copyright 2011 Kenneth M. Chipps Ph.D. www.chipps.com
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Operation of MPLS
– This allows the use of very fast and simple
forwarding engines, which are often
implemented in hardware
– Ingress routers at the edge of the MPLS
network classify each packet potentially using
a range of attributes, not just the packet's
destination address, to determine which LSP
to use
Copyright 2011 Kenneth M. Chipps Ph.D. www.chipps.com
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Operation of MPLS
– Inside the network, the MPLS routers use only
the LSP labels to forward the packet to the
egress router
– Here is their graphic on this
Copyright 2011 Kenneth M. Chipps Ph.D. www.chipps.com
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Operation of MPLS
Copyright 2011 Kenneth M. Chipps Ph.D. www.chipps.com
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Operation of MPLS
• The MPLS label is a four-byte, fixedlength, locally-significant identifier
• According to Cisco it looks like this
Copyright 2011 Kenneth M. Chipps Ph.D. www.chipps.com
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Operation of MPLS
Copyright 2011 Kenneth M. Chipps Ph.D. www.chipps.com
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Operation of MPLS
• Cisco also says
• This label is placed between the data link
layer header and network layer
• The top of the label stack appears first in the
packet, and the bottom appears last
• The network layer packet immediately follows
the last label in the label stack
Copyright 2011 Kenneth M. Chipps Ph.D. www.chipps.com
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Operation of MPLS
Copyright 2011 Kenneth M. Chipps Ph.D. www.chipps.com
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LDP Traffic Capture File
• Let’s look at some of these frames
• Download
– LDP and RSVP.cap
• Start Wireshark by double-clicking on the
file
• Expand all of frame 1
Copyright 2011 Kenneth M. Chipps Ph.D. www.chipps.com
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LDP Traffic Capture File
Copyright 2011 Kenneth M. Chipps Ph.D. www.chipps.com
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LDP Traffic Capture File
• This is a LDP Hello frame
• Notice the destination is the 224.0.002
multicast address
• This is the all routers address
• In other words, who’s out there
• In frame 6 we see a LDP Hello from the
other end of the link at 172.16.1.2
Copyright 2011 Kenneth M. Chipps Ph.D. www.chipps.com
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LDP Traffic Capture File
Copyright 2011 Kenneth M. Chipps Ph.D. www.chipps.com
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LDP Traffic Capture File
• In frame 72 we see both ends are talking
to each other
• They are poking each other with a stick
• In other words, are you still awake
Copyright 2011 Kenneth M. Chipps Ph.D. www.chipps.com
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LDP Traffic Capture File
Copyright 2011 Kenneth M. Chipps Ph.D. www.chipps.com
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LDP Traffic Capture File
• We see a number of both these types of
LDP traffic as the connection does its work
Copyright 2011 Kenneth M. Chipps Ph.D. www.chipps.com
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Types of MPLS Links
• There are many types of MPLS
connections to a service provider’s MPLS
network
• For example, ATT supports MPLS
connections through what they call IP
VPNs
• As they say
Copyright 2011 Kenneth M. Chipps Ph.D. www.chipps.com
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Types of MPLS Links
– Network-based VPN
• Deployed on the AT&T global network, which uses
multiprotocol level switching (MPLS) to provide
high-performance, any-to-any communication
around the globe
Copyright 2011 Kenneth M. Chipps Ph.D. www.chipps.com
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What is Traffic Engineering
• Metaswitch says this about traffic
engineering in MPLS networks
– Traffic Engineering is the process where data
is routed through the network according to a
management view of the availability of
resources and the current and expected traffic
– The class of service and quality of service
required for the data can also be factored into
this process
Copyright 2011 Kenneth M. Chipps Ph.D. www.chipps.com
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What is Traffic Engineering
– Traffic Engineering may be under the control
of manual operators
– They monitor the state of the network and
route the traffic or provision additional
resources to compensate for problems as
they arise
– Alternatively, Traffic Engineering may be
driven by automated processes reacting to
information fed back through routing protocols
or other means
Copyright 2011 Kenneth M. Chipps Ph.D. www.chipps.com
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What is Traffic Engineering
– Traffic Engineering helps the network provider
make the best use of available resources,
spreading the load over the layer 2 links, and
allowing some links to be reserved for certain
classes of traffic or for particular customers
Copyright 2011 Kenneth M. Chipps Ph.D. www.chipps.com
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What is Traffic Engineering
– There are currently two label distribution
protocols that provide support for Traffic
Engineering
• RSVP - Resource ReSerVation Protocol
• CR-LDP - Constraint-based Routed Label
Distribution Protocol
Copyright 2011 Kenneth M. Chipps Ph.D. www.chipps.com
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MPLS and Traffic Engineering
• MPLS and Traffic Engineering work
together to provide tunnels that carry a
certain class of service from one point to
another
Copyright 2011 Kenneth M. Chipps Ph.D. www.chipps.com
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MPLS in a Lab Environment
• As it is difficult to create a real MPLS
network in a lab environment and since
simulation programs do not offer a MPLS
cloud as they do for Frame Relay, this lab
will use an emulation program
• In this case GNS3 running Dynagen which
is controlling the Dynamips emulator
• How to use GNS3 is covered in detail in
another presentation on this web site
Copyright 2011 Kenneth M. Chipps Ph.D. www.chipps.com
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Lab Network
• Here is the lab network as setup in GNS3
• To create the topology either
– Download and open this file in GNS3
• MPLS With Traffic Engineering Lab.net
– or
– Lay the routers out as the diagram that
follows shows
Copyright 2011 Kenneth M. Chipps Ph.D. www.chipps.com
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Lab Network
• When the routers are placed be sure the
labels match as well
• Next the modules to be added to the
routers, which are all 7200 models
• Then the connections between the routers
are made
• To simplify the setup the modules are all
the same even though some of them are
not actually needed in all the routers
Copyright 2011 Kenneth M. Chipps Ph.D. www.chipps.com
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Lab Network
Copyright 2011 Kenneth M. Chipps Ph.D. www.chipps.com
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Modules Required
Copyright 2011 Kenneth M. Chipps Ph.D. www.chipps.com
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Modules Required
• The modules are
– Slot 0
• C7200-IO-FE
– Slot 1
• PA-GE
– Slot 2
• PA-2FE-TX
– Slot 3
• PA-GE
Copyright 2011 Kenneth M. Chipps Ph.D. www.chipps.com
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Connections
Copyright 2011 Kenneth M. Chipps Ph.D. www.chipps.com
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Connections
Copyright 2011 Kenneth M. Chipps Ph.D. www.chipps.com
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Lab Network
• The routers are all running this IOS
– c7200-advipservicesk9-mz.150-1.M5.bin
Copyright 2011 Kenneth M. Chipps Ph.D. www.chipps.com
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Configuration
• As the configurations are lengthy for this
many routers they are provided as
separate links to copy and paste txt files
listed just below this lab’s link
• Download each one of these, then copy
and paste the contents to each router
based on the name of the file and the
corresponding router
Copyright 2011 Kenneth M. Chipps Ph.D. www.chipps.com
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Verify Connectivity
• Let’s see if it worked
• Enter
– show mpls traffic-eng tunnels
• This shows
Copyright 2011 Kenneth M. Chipps Ph.D. www.chipps.com
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Verify Connectivity
Copyright 2011 Kenneth M. Chipps Ph.D. www.chipps.com
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Verify Connectivity
• Ping all of the interfaces
• For example from R4 to R5
– ping 10.10.1.2
• These should all work
Copyright 2011 Kenneth M. Chipps Ph.D. www.chipps.com
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Verify Connectivity
• Examine the routing table
• Here from R0
Copyright 2011 Kenneth M. Chipps Ph.D. www.chipps.com
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Verify Connectivity
Copyright 2011 Kenneth M. Chipps Ph.D. www.chipps.com
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RSVP Capture File
•
•
•
•
•
Let’s open the same capture file
We will see how RSVP did its work for us
Go to frame 24
Expand all of the RSVP level
Here the two ends are talking to each
other in a path message over tunnel 2
• As we can see there is a lot to say
Copyright 2011 Kenneth M. Chipps Ph.D. www.chipps.com
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RSVP Capture File
Copyright 2011 Kenneth M. Chipps Ph.D. www.chipps.com
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RSVP Capture File
Copyright 2011 Kenneth M. Chipps Ph.D. www.chipps.com
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RSVP Capture File
Copyright 2011 Kenneth M. Chipps Ph.D. www.chipps.com
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RSVP Capture File
Copyright 2011 Kenneth M. Chipps Ph.D. www.chipps.com
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RSVP Capture File
Copyright 2011 Kenneth M. Chipps Ph.D. www.chipps.com
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What Do The Commands Do
• Let’s look at some of the commands used
to see what they do
– ip cef
• To turn on CEF – Cisco Express Forwarding
• This is required by Cisco routers doing tag
switching of which label switching is a form
• As Cisco says
– CEF switching is a proprietary form of scalable switching
intended to tackle the problems associated with demand
caching
Copyright 2011 Kenneth M. Chipps Ph.D. www.chipps.com
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What Do The Commands Do
– With CEF switching, the information which is
conventionally stored in a route cache is split up over
several data structures
– The CEF code is able to maintain these data structures
in the Gigabit Route Processor
– The data structures that provide optimized lookup for
efficient packet forwarding include
• It is on by default in some devices
– mpls traffic-eng tunnels
• Enables traffic engineering on the router
Copyright 2011 Kenneth M. Chipps Ph.D. www.chipps.com
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What Do The Commands Do
– tunnel destination 172.16.255.13
• The IP address of the end of the tunnel
• Where the traffic is going
– tunnel mode mpls traffic-eng
• Specifies the encapsulation method for the tunnel
• In this case mpls
Copyright 2011 Kenneth M. Chipps Ph.D. www.chipps.com
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What Do The Commands Do
– tunnel mpls traffic-eng autoroute announce
• This tells the routing protocol to consider the
existences of the tunnel in its route calculations
• Otherwise the routing protocol will not send traffic
through the tunnel
• If not this, then a static route will have to be used
Copyright 2011 Kenneth M. Chipps Ph.D. www.chipps.com
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What Do The Commands Do
– tunnel mpls traffic-eng priority 2 2
• This configures the setup and reservation priority
for the tunnel
• The first number is the priority
• The second is the hold
• The numbers are the same
– tunnel mpls traffic-eng bandwidth 158
• This is the bandwidth of the tunnel in kibps
• The range is 1 to 4294967295
Copyright 2011 Kenneth M. Chipps Ph.D. www.chipps.com
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What Do The Commands Do
– tunnel mpls traffic-eng path-option 1 explicit
name BOTTOM
• This sets up a path option for the tunnel
• In this case the path is an IP explicit path related
back to the tunnel destination
• The path is also in this case given a name
– no routing dynamic
• To prevent routing updates being sent through the
tunnel
• They still go out, just not through the tunnel
Copyright 2011 Kenneth M. Chipps Ph.D. www.chipps.com
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What Do The Commands Do
– mpls ip
• Enables the router to perform forwarding of MPLS
labels in IPv4 packets along normally routed paths
– mpls traffic-eng tunnels
• Sets up MPLS traffic engineering for an interface
Copyright 2011 Kenneth M. Chipps Ph.D. www.chipps.com
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What Do The Commands Do
– ip rsvp bandwidth 750000
• Specifies how much bandwidth can be used by
traffic engineering
– ip rsvp resource-provider none
• To enable or in this case disable any resourceprovider, in other words a quality of service setting,
for aggregate flow
• Aggregate flow refers to the traffic and its
corresponding QoS requirements
Copyright 2011 Kenneth M. Chipps Ph.D. www.chipps.com
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What Do The Commands Do
– mpls ldp autoconfig area 0
• This command is to ease the configuration of LDP
for the routing protocol
• Without it all of the interfaces would have to be
setup one by one for LDP
• LDP is the Label Distribution Protocol
– mpls traffic-eng router-id Loopback0
– This tells us the router identifier for the node is the
IP address of that interface
Copyright 2011 Kenneth M. Chipps Ph.D. www.chipps.com
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What Do The Commands Do
– mpls traffic-eng area 0
– When OSPF is the routing protocol this configures
the router to flood traffic engineering for the
specified OSPF area
Copyright 2011 Kenneth M. Chipps Ph.D. www.chipps.com
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What Do The Commands Do
– ip explicit-path name BOTTOM enable
–
–
–
–
Specifies an explicit path name or number
Enables that path
The commands that follow detail the path or paths
Such as
– next-address 172.16.1.2
– next-address 172.16.3.2
– Bottom or top forces traffic though a specific path
Copyright 2011 Kenneth M. Chipps Ph.D. www.chipps.com
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MPLS with Traffic Engineering
• As we can see when compared to the
basic MPLS configuration this one is much
more complex
• But MPLS with traffic engineering is the
main point to MPLS, therefore a
configuration along these lines is called for
Copyright 2011 Kenneth M. Chipps Ph.D. www.chipps.com
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