Cisco Cisco IOS Software Release 12.2(18)S
MPLS Traffic Engineering – DiffServ Aware (DS-TE)
Feature Overview
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Cisco IOS Release 12.2(18)S
Feature Overview
MPLS traffic engineering allows constraint-based routing of IP traffic. One of the constraints satisfied by
CBR is the availability of required bandwidth over a selected path. DiffServ-aware Traffic Engineering
extends MPLS traffic engineering to enable you to perform constraint-based routing of “guaranteed” traffic,
which satisfies a more restrictive bandwidth constraint than that satisfied by CBR for regular traffic. The
more restrictive bandwidth is termed a sub-pool, while the regular TE tunnel bandwidth is called the global
pool. (The sub-pool is a portion of the global pool.) This ability to satisfy a more restrictive bandwidth
constraint translates into an ability to achieve higher QoS performance (in terms of delay, jitter, or loss) for
the guaranteed traffic.
CBR is the availability of required bandwidth over a selected path. DiffServ-aware Traffic Engineering
extends MPLS traffic engineering to enable you to perform constraint-based routing of “guaranteed” traffic,
which satisfies a more restrictive bandwidth constraint than that satisfied by CBR for regular traffic. The
more restrictive bandwidth is termed a sub-pool, while the regular TE tunnel bandwidth is called the global
pool. (The sub-pool is a portion of the global pool.) This ability to satisfy a more restrictive bandwidth
constraint translates into an ability to achieve higher QoS performance (in terms of delay, jitter, or loss) for
the guaranteed traffic.
For example, DS-TE can be used to ensure that traffic is routed over the network so that, on every link, there
is never more than 40 percent (or any assigned percentage) of the link capacity of guaranteed traffic (for
example, voice), while there can be up to 100 percent of the link capacity of regular traffic. Assuming QoS
mechanisms are also used on every link to queue guaranteed traffic separately from regular traffic, it then
becomes possible to enforce separate “overbooking” ratios for guaranteed and regular traffic. (In fact, for
the guaranteed traffic it becomes possible to enforce no overbooking at all—or even an underbooking—so
that very high QoS can be achieved end-to-end for that traffic, even while for the regular traffic a significant
overbooking continues to be enforced.)
is never more than 40 percent (or any assigned percentage) of the link capacity of guaranteed traffic (for
example, voice), while there can be up to 100 percent of the link capacity of regular traffic. Assuming QoS
mechanisms are also used on every link to queue guaranteed traffic separately from regular traffic, it then
becomes possible to enforce separate “overbooking” ratios for guaranteed and regular traffic. (In fact, for
the guaranteed traffic it becomes possible to enforce no overbooking at all—or even an underbooking—so
that very high QoS can be achieved end-to-end for that traffic, even while for the regular traffic a significant
overbooking continues to be enforced.)
Also, through the ability to enforce a maximum percentage of guaranteed traffic on any link, the network
administrator can directly control the end-to-end QoS performance parameters without having to rely on
over-engineering or on expected shortest path routing behavior. This is essential for transport of applications
that have very high QoS requirements (such as real-time voice, virtual IP leased line, and bandwidth
trading), where over-engineering cannot be assumed everywhere in the network.
administrator can directly control the end-to-end QoS performance parameters without having to rely on
over-engineering or on expected shortest path routing behavior. This is essential for transport of applications
that have very high QoS requirements (such as real-time voice, virtual IP leased line, and bandwidth
trading), where over-engineering cannot be assumed everywhere in the network.
DS-TE involves extending OSPF (Open Shortest Path First) routing protocol, so that the available sub-pool
bandwidth at each preemption level is advertised in addition to the available global pool bandwidth at each
preemption level. And DS-TE modifies constraint-based routing to take this more complex advertised
information into account during path computation.
bandwidth at each preemption level is advertised in addition to the available global pool bandwidth at each
preemption level. And DS-TE modifies constraint-based routing to take this more complex advertised
information into account during path computation.
Benefits
DiffServ-aware Traffic Engineering enables service providers to perform separate admission control and
separate route computation for discrete subsets of traffic (for example, voice and data traffic).
separate route computation for discrete subsets of traffic (for example, voice and data traffic).
Therefore, by combining DS-TE with other Cisco IOS features such as QoS, the service provider can:
•
Develop QoS services for end customers based on signaled rather than provisioned QoS
•
Build the higher-revenue generating “strict-commitment” QoS services, without overprovisioning
•
Offer virtual IP leased-line, Layer 2 service emulation, and point-to-point guaranteed bandwidth
services including voice-trunking
services including voice-trunking
•
Enjoy the scalability properties offered by MPLS
Related Features and Technologies
The DS-TE feature is related to OSPF, IS-IS, RSVP (Resource Reservation Protocol), QoS, and MPLS
traffic engineering. Cisco documentation for all of these features is listed in the next section.
traffic engineering. Cisco documentation for all of these features is listed in the next section.