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Composite Transport Group (CTG)
Framework and Requirements
draft-so-yong-mpls-ctg-framework-requirement-00.txt
Ning So
Andrew Malis
Dave McDysan
Lucy Yong
[email protected]
[email protected]
[email protected]
[email protected]
MPLS - 73nd IETF Minneaplis
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Motivation
Issues when deploying multiple parallel links in MPLS
backbone
Aggregated link utilization is not efficient
• Some links many be congested while others stay near empty
Operators do not have enough ability to control the traffic flows
under this network environment
Inefficiency/Inflexibility of Logical Interface Bandwidth
Allocation
Ship-in-the-night mode when using multiple logically-separated
routing instances in single physical router
Draft provides:
Problem statement in today’s IP/MPLS network
Composite Transport Group Framework
Composite Transport Group Requirments
Objective:
Develop an aggregated traffic transport method over multilink
trunk to resolve the problems today’s MPLS enabled network
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Issue when using multi parallel links
Hashing
Assume network transporting large amount of micro flows with
similar bandwidth requirements
It does not work under the following operating conditions
• Large portion of the customer traffic are encrypted so the in coming
flows cannot be broken down into micro flows
• Some machine-to-machine traffic flows are at ultra-high rate
• Multiple parallel trunks have different bandwidth, interface types,
and/or latencies
Assigning individual LSPs to links using planning tool
Bypass tunnel bandwidth for LSPs are often set to near 0 to free up
backbone bandwidth for other traffic
During the network failure congestion may happen on some of the
parallel trunks while others are almost empty
Facility Protection
Require a dedicated link for protection. No protection sharing when
using multiple links and unwanted link performance degradation
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Issue when using multi parallel links (2)
Existing technology leads to poor link utilization or poor
performance.
Without per-flow TE information, LDP network has even more
problem utilizing multiple parallel backbone trunk efficiently
Carriers forced to deploy single higher capacity link, which is more
expensive, and often not widely available.
Multiple logically-separate routing instances in a single
physical router
Sharing common parallel backbone when aggregated traffic
exceeds a single link becomes impossible due to the ship-in-thenight operating condition
Delicate physical link for each routing instance is not efficient
Delicate link capacity for each routing instance limits carrying a
high rate of flows
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Composite Transport Group (CTG)
CTG is the method to transport aggregated traffic
over a composite link
Composite Link is defined in ITU-T Q12 G.800
Contain multiple component links supported by separate
server layer trails
Transport over a composite link may not preserve the
symbol sequence
CTG is a local traffic engineering and transport
selection technology
Give traffic engineering among component links
Provide component link recovery
Auto flow measurement
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CTG Framework
CTG creates CTG connections on the composite link
CTG connection must have assigned BW and is eligible to transport
on any component link
LSP, LDP or IP traffic is mapped to CTG connections
CTG connection TE can be derived from LSP TE or from auto BW
measurement
CTG selects one component link to transport an CTG connection
based on TE of CTG connections and component link condition
The selection may change due to component failure or CTG
connection condition changes
Component Links
LSP, LDP, IP
5 CTG connections
C
T
G
3 CTG connections
9 CTG connections
R1
C
T
G
R2
Composite Link
Note: To reduce auto BW measurement burden, it is expected that LDP and IP traffic is in small amount.
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Requirements for CTG
CTG Appearance as a Routable Virtual Interface
Multiple routing instances see a separate "virtual interface" to a shared composite
transport group composed of parallel physical links between a pair of routers.
The CTG would communicate parameters (e.g., admin cost, available bandwidth,
maximum bandwidth, allowable bandwidth) for the "virtual interface" associated
with each routing instance.
CTG mapping of traffic to Component Links for all connections with and/or
without TE information
Using TE information from the control planes of the routing instances attached to
the virtual interface when available, or
Using traffic measurements when it is not.
Bandwidth Control for Connections with and without TE information
The CTG SHALL support a policy based preemption capability such as the signaled
or configured preemption and holding parameters
• For RSVP-TE LSP(s), signal the router that the TE-LSP has been preempted.
• For LDP(s), where the CTG is aware of the LDP signaling involved to the preempted label
stack depth, signal release of the label to the router
• For IP traffic without MPLS labels, indicate congestion to the router or block IP traffic.
CTG Transport Resilience
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Next Steps
Seeking input/comments from other carriers on the
problem statement, framework and requirements
Determine what aspects are relevant to IETF standards
Determine what aspects are relevant to an informational
IETF RFC
Seeking carriers and vendors to work on a CTG solution
draft in parallel with refinement of requirements.
What is the best IETF working group(s) to discuss this
draft in the next meeting(s)?
Is there a re-chartering necessary in these group(s)?
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Acknowledgement
Many Thanks to:
Frederic Jounay from France Telecom
Adrian Farrel from Olddog
Ron Bonica from Juniper
For the reviews and great suggestions.
Feedbacks and comments are welcome
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