Transcript No Slide Title

MPLS-TP OAM
OAM for an MPLS Transport Profile
Loa Andersson, Acreo AB
IAB, MPLS WG co-chair
February 2006
MPLS Interop 2008
#1
www.acreo.se
MPLS-TP Starting points
PHP is part of the MPLS architecture
– It is a powerful
– It solves more problems than it creates
– Removing it creates more problems
than it solves
– We should try ti see how we can use
the PHP, rather than to remove it
February 2006
MPLS Interop 2008
#2
www.acreo.se
MPLS-TP OAM Forwarding
MEP
A
B
MIP-1
TT
TL
TL
TL
TL
C
MIP-2
TT-1
TL’
TL
TL
TL
February 2006
PHP
TL
TL
TL
TL’
TL
TL
PHP
TL
TL
MPLS Interop 2008
D
MEP
TT-2
TL’
TL
TT-3
PHP
TL
TL’
#3
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Legend for the previous slide
The “cylinder” indicates links between LSRs.
At an ingress LSR one or more labels are
pushed onto a packet
At intermediate LSRs labels are swapped
At pen ultimate LSRs Labels are popped
At egress LSRs actions are taken on the top
label
The LSRs are in the gaps between the links.
LSRs that don’t have a MEP or MEP are called
A, B, C and D, if they have the are called MEP
or MIP
The thinner cylinder represents the OAM
channel
February 2006
MPLS Interop 2008
#4
www.acreo.se
Naming of tunnels
The outermost (top of label stack) tunnel is
called Transport Tunnel (TT)
Transport Tunnels that is carried in other
Transport Tunnels is called TT-n
In the figures we have TT, TT-1, TT-2 and TT-3
On every level below the TT it is possible to
multiple TTs, e.g. TT-1, TT-1’, TT-1’’ etc.
There is only a single tunnel for OAM between
a pair of MEP and MEP/MIP.
February 2006
MPLS Interop 2008
#5
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Forwarding
When a LSR sends a packet across the
transport LSP it pushes the entire Label
stack needed.
When a packet reaches the pen-ultimate
hop of the current of a transport LSP
level, the top label is popped and the
packet forwarded with the next label on
top
At the egress LSR the packet is
forwarded based on the label on the top
of the stack
February 2006
MPLS Interop 2008
#6
www.acreo.se
MPLS-TP OAM MEP to MEP
MEP
A
B
MIP-1
TT
TL
TL
TL
TL
LFU
C
TT-1
TL’
TL
TL
TL
LFU
February 2006
PHP
TL
TL
TL
LFU
TL’
TL
TL
FLU
PHP
TL
TL
LFU
MPLS Interop 2008
MIP-2
D
MIP-3 MEP
TT-2
TL’
TL
LFU
TT-3
PHP
TL
LFU
TL’
LFU
#7
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Communication MEP to MEP
When an MEP sends an OAM packet the LSR
pushes a label stack where the transport label
that is comes to the top of the stack at the PHP
before the MIP that the OAM packet is
addressed to is replaced by the LFU
When a packet with the LFU at the top of the
stack is received the LSR locates the ACH after
the label with the BoS bit set
Apart from information indicating what OAM
procedures that is required the ACH needs to
carry information on what LSP this is
requested for, this may require an aggreate
LSPid
February 2006
MPLS Interop 2008
#8
www.acreo.se
MPLS-TP OAM MEP to MIP-1
MEP
A
B
TL
LFU
TL’
LFU
PHP
LFU
February 2006
MIP-1
C
MPLS Interop 2008
MIP-2
D
MEP
#9
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MPLS-TP OAM MEP to MIP-2
MEP
A
B
TL
TL
LFU
TL’
TL
LFU
PHP
TL
LFU
February 2006
MIP-1
TL’
FLU
C
MIP-2
D
MEP
PHP
LFU
MPLS Interop 2008
# 10
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MEP to MIP communication
The only difference between MEP to MIP communication
and MEP to MEP communication is that the label stack
only needs to be populated to take the the packet to the
LSR with the MIP, the rest of the label stack may be
omitted.
If the redundant part of the label stack is present the LFU
will not have the BoS set
The MPLS architecture has been operating with unidirectional LSPs. This works for bi-directional LSPs as
well. It is not clear if the response OAM channel needs to
be bundled with the LSP in the reverse direction or if
direct communication between originating MEP and the
responder is allowed. Both schemes works with this
architeture.
February 2006
MPLS Interop 2008
# 11
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Questions
Is MIP to MIP communication needed?
Is MIP to MEP communication needed for other
purposes than responses on communications
that were initiated by the MEP?
If one set up LSPs from a NMS or manually this
is fiarly straightforward.
If one is using a control plane it might require
extensions to the signaling protocol, especially
the concept of an aggregate LSPid needs to be
investigated.
February 2006
MPLS Interop 2008
# 12
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