MPLS Swallow
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Transcript of MPLS Swallow
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MPLS additions to RSVP
Tunnel identification
Tunnel parameter negotiation
Routing policy distribution
Routing debugging information
Scalability improvements LSP merging
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Tunnel identification
New Session C-Type
, ,
Semantics are that the complete filter
specification is the Label
Extended Tunnel ID can be used to scope
session to a single source router (i.e. ensure
globally unique tunnel identification)
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Tunnel identification (2)
New Sender_Template
LSP_ID allows a source to share a session
with itself. Useful for reroute and
bandwidth change operations
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Tunnel parameter negotiation
LABEL_REQUEST object
Carries L3 protocol ID to describe contents of
the tunnel
Range of acceptable label values
LABEL object
Carries selected label value
Session Attribute/Policy ObjectSetup & hold priorities
Flags
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Routing policy distribution
EXPLICIT_ROUTE_OBJECT
List of IP addresses for loose or strict source
route
Carries path for session
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Routing debugging information
RECORD_ROUTE_OBJECT
List of systems in the path
Useful for
loop detection & avoidance
debugging policy configuration
Subsequently pinning a route
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TE Setup
Path : ERO (R1->R2->R6->R7->R4->R9) Tunnel ID 5, LSP_ID 1
Resv: Communicates labels and Establishes label OperationsReserves bandwidth on each link
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R8
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R6
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400401_10F8_c1
UUnet-9803
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TE Rerouting - Alternate Path
Setup: Path (R1->R2->R3->R4->R9) Tunnel ID 5, LSP_ID 2
Until R9 gets new Path Message, current Resv is refreshed
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R8
R2
R6
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UUnet-9803
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TE - Switching Paths
PopPop
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R8
R2
R6
R3
R4
R7
R1
R5
R9
440401_10F8_c1
UUnet-9803
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Resv: Allocates labels for both pathsReserves bandwidth once per link
PathTear Can then be sent to remove old path (and release
resources)
8926
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RSVP scaling issues
Refresh packets scale linearly with the
number of sessions
Sending lots of little packets has high
overhead
Sessions need not be refreshed
independently
Still need capacity to deal with peak
signaling events (e.g., link failure)
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Possible approaches
Aggregate refresh messages verbatim
Decreases packet processing overhead
Provides substantial improvement
Trivial modification
Requires a capability bit
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Possible approaches (2)
Transmit a refresh digest (IS-IS model)
Decreases packet processing overhead
Decreases signaling bandwidth
Increased protocol complexity
Need a capability bit
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Possible approaches (3)
Run RSVP on top of TCP (BGP model)
Significant departure from soft state model
Add router-to-router keepalives to provideliveness
Reliability provided hop-by-hop
No refreshes necessaryMust explicitly tear down sessions
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LSP merging
Merging: multi-point to point LSPs
Work in progress
Automatic merging of compatible LSPs
e.g. same ERO
Merging is voluntary - can disable
Sources initiate LSPs, control compatibility
Input welcome