GMPLS and MPLS Examined

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Large Scale IP Networks

• GMPLS and MPLS Examined
• Vijay Gill
• ltvgill_at_mfnx.netgt

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Agenda

• Background
• What is the problem
• Solutions - (G)MPLS
• Issues with the solutions above
• An alternative proposal
• Questions

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Acronyms

• PPS Packets Per Second
• ER/TE Explicit Routing/Traffic Engineering
• FEC Forwarding Equivalence Class
• CSPF Constrained Shortest Path First
• GMPLS Generalized Multi-Protocol Label Switching
  
• IGP Interior Gateway Protocol (OSPF/IS-IS/RIP)
• LDP Label Distribution Protocol
• SPF Shortest Path First

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Guide For Talk

• Optimize On
• Getting 95 of the problem with 15 effort
• Flexibility
• Operations And Engineering Guy
• Expertise in building systems, networks, and
  organizations that run IP networks
• Seen the results of the meeting between Networks
  Powered by PowerPoint and the Real World
• Hint The Real World wins every time

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• I dislike rigidity. Rigidity means a dead
  hand and flexibility means a living hand. One
  must understand this fully.
• -
  Miyamoto Musashi

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Ordinal Vs. Cardinal Optimization

• More important to quickly narrow the search for
  an optimal solution to a good enough subset
  than to calculate the perfect solution
• Ordinal (which is better) before Cardinal (value
  of optimum)
• Ballpark estimate
• Historical Internet Vs the Telco approach

we don't need to boil the ocean - all we want is
a poached fish
Based on work done by Yu-Chi Ho
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Soften Requirements

• Softening strict requirement of optimality can
  make problems tractable

Getting the best decision for certain
Cost 1m
Getting a decision within the top 5 With
probability 0.99
Cost 1m/x
In real life, we often settle for such a tradeoff
with x100 to 10,000
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MPLS

• M is for Multiprotocol (inside and out)
• But despite being able to carry anything
  inside, IP is the single most common payload
• IP routers are the most common outside
• Nameable aggregates of traffic have value
• Explicit Routing
• Comes with a price
• Hype! QoS! Sings, dances, julienne fries!
• One potato, to go.

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What Is The Problem

• Dense Network
• Protect Paths
• Routers out of PPS
• Solved by
• Constrained Meshed Routing
• Mindset Changed

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Problems Solved

• MPLS solved ER/TE problems
• RSVP-TE is extensible to ask for particular
  qualities of service etc. rather than just raw BW
• Got perverted by the vendor marketing folks
• Try to do everything under the sun
• QoS!

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The Myth of QoS

• FECs can be described which ask for particular
  queuing disciplines inside switches and routers
  (via the RSVP-TE mechanism) is very popular with
  some people
• Fancy queuing and careful resource management can
  in theory approach the lack of jitter that TDM
  provides
• Never overbook the jitter-free traffic
• Jitter-free traffic squeezes out the more elastic
  traffic
• Belief is that the combination of the control
  plane and the label-packet format can fully
  replace traditional TDM
• At the cost of some complexity and deploying "new
  stuff"

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QoS

• Tough thing to define
• Tougher to sell
• Better make sure Best Effort Internet services
  work
• All Gold, All the Time.
• Differentiation must be palpable to the end user
• Cost must not be prohibitive
• Should not be hard to manage
• Integrated with the best effort network
• Also keep up with best effort deployment
• QoS Quantity of Service
• What Are We Optimizing For?

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These exhibits were originally published in Peter
Ewens, Simon Landless, and Stagg Newman, "Showing
some backbone," The McKinsey Quarterly, 2001
Number 1, and can be found on the publication's
Web site, www.mckinseyquarterly.com. Used by
permission.
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Best Effort Is Good Enough

• Statistical multiplexing saves money
• Mixing various queuing disciplines into a
  statistically multiplexed network is
• Complicated
• Costly
• Full of side effects
• Overprovision for now
• Less "full" at peak traffic point less efficient
  
• But, no queue means no need for queuing
  disciplines
• Small risk of jitter/delay for the sake of less
  complexity vs. much more complexity

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Cheaper Faster Better

• Internet enabled applications will squeeze out
  (eventually) applications that arent.
• The number of mobile phone subscribers worldwide
  is expected to reach 560 million by year-end and
  to exceed the number of households with
  televisions by 2003.
• -Will Daugherty (McKinsey Company)

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GMPLS

• The RSVP-TE label mechanism is generalized in
  GMPLS to request resources of any nature, notably
  lambdas, SDH MUXes and "patch-panel" mappings
• GMPLS is a CONTROL PLANE not a packet system
  there is no requirement that MPLS "frames" be
  used in an GMPLS network

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GMPLS

• No centralized provisioning database
• Available resources are consumed where the CSPF
  reservation is allowed
• IGP does topology discovery (OSPF) detects faults
  and allows restart of reservations
• OSPF LSP database is also consulted to find the
  the CSPF, which will be requested (by RSVP or LDP
  to all the elements along the path) first.

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Unified Control

• The GMPLS argument is that one control and packet
  system can be used to knit together tremendously
  different network components
• IP Routers
• Switching gear
• Including ATM, SDH and WDM "switches"

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GMPLS Flexibility Points
Control
Control
Control
Control
DWDM
DWDM
DWDM Signalling
MPlS Control Plane

• UNI
• RSVP-TE or LDP based
• Routers request concatenation of resources
  through the network

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Benefits Of GMPLS

• Meshy Restoral
• Clients of all kinds (routers, TDM boxes)
• Saves on router ports
• Routers make expensive OEO
• Mitigation cost is amortized over lifetime of
  box
• Flattened topology

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Benefits of GMPLS

• Signaling between routers and optical switches
• Self provisioning
• Faster Provisioning

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Issues

• Best Abstraction Of A Topology Is The Topology
• Spend money on packet-handling rather than
  managing lots of meshed mid-sized boxes
• We have too many boxes now. Were not going to
  have a million more boxes in the network. That
  scenario is utterly unthinkable
• -Mike ODell

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Reexamining Optical Network Assumptions

• Replacing patch cords with OXCs doesnt affect
  the network much
• OXCs et al. allow you to redeploy the topology
• Real world topology doesnt change very fast
• Extend planning horizon
• City-pair macroflows are long lived and tractable
• Cost and complexity of running an IGP over the
  optical boxes to gain speed of restoral over a
  centralized system needs to be examined carefully

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Thoughts

• Our Control Theory-Fu is weak
• Get provisioning from 18 months to a day or two
• We don't know anything we could do with 50ms
  provisioning without making a disaster
• Centralize view of topology and lay out paths
  using expert systems vs. SPF in the network

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Self Provisioning Issues

• Internet is an intentionally overdamped system
• The consequences of being underdamped are
  catastrophic
• Got the T-shirt
• Frame Relay wars
• Improving the frequency response of the
  implementation implies lots more T-shirts

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Optimize For The Biggest Consumer

• Design Goals Are To Replace
• Back-to-back OEO in middle of nowhere
• Unnecessary OEO for passthrough
• Slow Humans

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Typically
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Typical Hut
ODF
ADM
Flexibility Points Add or drop traffic to the
network
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How To

• Use strong enough lasers
• Avoid turning pass-through frequencies into
  electrons
• Attenuation hit (thats what OEO is for)
• Divert frequency bands onto dark or transponders
  which do frequency conversion

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How To

• Integrate the MUX within the control plane of a
  large router
• Tell router not to use a certain frequency band
  for p2p traffic with its neighbor any more
  because it has to be dropped out an optical port.
  
• That port is dark fiber terminating
• A small WDM MUX (8 colors)
• End piece of equipment _at_ 2.5GHz, 10GHz, etc.

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Proposal
OEOOADM
ADM

• Optical ADM emits light as necessary by
  intercepting one frequency converting it
  electrically
• The ADM becomes the source of the bits

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How To

• The router doesn't look at the signal
• Doesnt do
• Regeneration
• Look for SONET/SDH signaling
• Passes through the frequency
• Unfortunate attenuation hit, but that's what OEO
  deals with).

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How To

• Any space not "reserved" is used in whatever way
  seems optimal for big-router-to-big-router
  connectivity, for moving packets.
• Use some of the spectrum to build a sub-ring or
  smaller p2p circuits for talking to smaller
  routers in flexibility points along the way, if
  any
• Or use separate fiber, if fiber-rich or for
  retaining a historical system in parallel
• Building a virtual dark fiber across this is
  possible, but you need to do your own regen
  (OEO), cross-connection, etc.

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This Solves For

• Optimizing the transmission resources for the
  largest consumer of optical bitstream IP
• Saves money on 1310/1550 lasers
• Power
• SGA

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Save The Hype

• You cannot combat glossy magazines with logic
• -Jeff Aitken
• Somehow best effort has become a pejorative.
• -Mike ODell

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Conclusions

• Even the very wise cannot see all ends
• Lets not paint ourselves into corners
• Stupid is flexible
• Modularity
• Theory of Real Options
• End2end arguments in system design
• Trade upfront CAPEX for long term OPEX
• Rise of the Stupid Network
• Assumptions still undergoing work

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References

• GMPLS http//search.ietf.org/internet-drafts/draf
  t-ietf-ccamp-gmpls-architecture-00.txt
• MPLS http//www.rfc-editor.org/rfc/rfc3031.txt

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Questions

• Thanks to
• Mike ODell, Sean Doran, and
• Bill Barns