1. draft-jounay-pwe3-dynamic-pw-update-00.txt IETF 70 PWE3 Working Group
Vancouver, December 2007
F. Jounay, P. Niger, France Telecom
Y. Stein, RAD Data Communications
H. Shah, Ciena Corp

2. Problem Statement Use Case identified : Mobile Backhauling
IETF70, December 2007
Problem Statement
Use Case identified : Mobile Backhauling
CESoPSN PW used to carry the 2G traffic (mainly voice traffic)
CESoPSN specifications
Inherent trade-off between bandwidth consumption and latency
=> The Operator must setup CESoPSN PW so as to carefully match the PW capacity to the actual payload.
Problem Statement
when upgrading the network (e.g.: introduction of new cells, new services…) the capacity of particular PWs needs to grow without interrupting ongoing voice services used by numerous customers.
Although interface parameter update will generally be a rare event for most applications, it is still highly recommended not to negatively impact customer services.
Solutions so far proposed to increase a CESoPSN PW capacity
Teardown the existing PW, and setup a new one with the new appropriate parameters
Cons: service disruption
Setup an additional PW for the specific additional bandwidth
Cons: as many pw as updates required
IETF70, December 2007

3. Possible solutions Scenario1 "New PW"
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Possible solutions
Scenario1 "New PW"
Setting up a new PW in parallel with the updated interface parameters
New FEC => new PW label
Static switching from the old to the new PW
Scenario2 "PW Update"
Remaining the existing FEC
New Label Mapping message including the new interface parameters
 Dynamic PW Update
IETF70, December 2007

4. PW Update Overview 2 options for the solution description
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PW Update Overview
2 options for the solution description
Definition of a specific mechanism to allow on-the-fly updating of CESoPSN PW capacity, i.e. while avoiding service interruption
Definition of a generic mechanism for PW parameters Update
The draft defines the generic solution and addresses the CESoPSN use case
Potential other use cases
PW interface parameters of other PW Type
PW Label Update (may be required for OAM purpose, Step from static to dynamic PW (Status negotiation…) setup)… …
IETF70, December 2007

5. CESoPSN Update Solution Overview
IETF70, December 2007
CESoPSN Update Solution Overview
Need a way to update the PW interface parameters without service disruption
Requirement
Signaling the update in the control plane
Synchronizing the update in the data plane (The Length field of CESoPSN PW packet is not sufficient to correctly restitute the traffic over the AC, see next slides)
Proposal
Control plane: new LDP mapping message with a PW Update sub-TLV
To be included to the LDP Label Mapping initiated to update the PW
To indicate the update behavior of the new LDP mapping
Backward compatibility: otherwise the new LDP message is usually dropped since an existing label has already been assigned to this FEC
Data plane: in-band detection based on the new label assignment
Required to allow the egress PE to forward over the AC the received traffic with the new format
IETF70, December 2007

6. CESoPSN Interface Parameters Extracted from [PW TDM CTRL]
Configured by the operator
N: Number of DS0 channels in the corresponding attachment circuit that must be retrieved from the E1 frames and must be transported over the CESoPSN PW.
D: Packetization latency in millisecond (application-related)
Derived/calculated
B: Number of frames to be encapsulated per PW packet derived from the Latency
B = 8*D (8 E1 frames per second)
P: Total Payload (Bytes) per PW packet
P: B*N
Signaled (PW setup)
N: The interface parameter CEP/TDM Bit-Rate (0x07) is defined for all kinds of structure-aware emulation
P: The interface parameter CEP/TDM Payload Bytes (0x04) is defined for a set of TDM PW types including SAToP, CESoPSN PWs
'update' operation encompass change in configuration ensued by update signaling.
IETF70, December 2007

7. CESoPSN Interface Parameters
IETF70, December 2007
CESoPSN Interface Parameters
P = B*N
 N is known as it has been advertised
 B = P / N
LDP Label Mapping [FEC129, Label, int.par.(N, P)]
PE1
PW1
AI1
AI2
PE2
ce1
ce2 N
?...
PW1 P =
B (3) x N
E1 frame
Payload
N bytes
E1 frame
Payload
N bytes
IETF70, December 2007

8. The PW Update sub-TLV Definition of a new LDP TLV TYPE (e.g. 0x096D)
| |
Generalized ID FEC
| PW Update TLV |
| Interface Parameters |
| " |
|0|0| Generic Label (0x0200) | Length |
| Label |
|1|0| PW Status (0x096A) | Length |
| Status Code |
|1|0| PW Update Type (0x096D)| Length |
| Update Code |
Update code
e.g.,
Interface Parameters
PW label
Keeping the existing
LDP TLV TYPE (0x096B)
For the int. parameters values
IETF70, December 2007

9. Procedure (e.g. cesopsn PW update)
IETF70, December 2007
Procedure (e.g. cesopsn PW update)
Increase the PW capacity
Step 1: update the PW capacity following the proposal
Step 2 : update the CE to allow it to transport more payload per E1 frames
Decrease the PW capacity
Step 1 : update the CE to allow it to transport less payload per E1 frames
Step 2: update the PW capacity following the proposal
Remark: e.g. the cesopsn PW encapsulates non used-timeslots between the step 1 and step 2.
IETF70, December 2007

10. PW Update Illustration for cesopsn PW
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PW Update Illustration for cesopsn PW
Initial config (N=15, P = D(1ms)*8*15= 120)
PE1
PW1
AI1
AI2
PE2
ce1
ce2
LDP Label Mapping ([SAI1, SAI2], L1, (P=120, N=15)]
LDP Label Mapping ([SAI2, SAI1], L2, (P=120, N=15)] L2
8 X L1
IETF70, December 2007

11. PW Update Illustration for cesopsn PW
IETF70, December 2007
PW Update Illustration for cesopsn PW
Update config (N=20, P = D(1ms)*8*20= 160)
PE1
PW1
AI1
AI2
PE2
ce1
ce2
LDP Label Mapping ([SAI1, SAI2], L10, PW Update (L, iP), (N=20, P=160)]
LDP Label Mapping ([SAI2, SAI1], L20, PW Update (L, iP), (N=20, P=160)] L2
L20 L1
L10
Non Used-timeslots to be encapsulated during the transition step
IETF70, December 2007

12. Next Steps Add a section describing the PW Label removal from the LFIB
IETF70, December 2007
Next Steps
Add a section describing the PW Label removal from the LFIB
Describe the MS-PW approach
Soliciting comments
IETF70, December 2007