draft-ietf-mpls-te-scaling-analysis-00.txt   draft-ietf-mpls-te-scaling-analysis-01.txt 
Network Working Group S. Yasukawa Network Working Group S. Yasukawa
Internet-Draft NTT Internet-Draft NTT
Intended Status: Informational A. Farrel Intended Status: Informational A. Farrel
Expires: April 2008 Old Dog Consulting Created: October 13, 2007 Old Dog Consulting
O. Komolafe Expires: April 13, 2008 O. Komolafe
Cisco Systems Cisco Systems
October 2007 An Analysis of Scaling Issues in MPLS-TE Backbone Networks
An analysis of scaling issues in MPLS-TE backbone networks
draft-ietf-mpls-te-scaling-analysis-00.txt draft-ietf-mpls-te-scaling-analysis-01.txt
Status of this Memo Status of this Memo
By submitting this Internet-Draft, each author represents that any By submitting this Internet-Draft, each author represents that any
applicable patent or other IPR claims of which he or she is aware applicable patent or other IPR claims of which he or she is aware
have been or will be disclosed, and any of which he or she becomes have been or will be disclosed, and any of which he or she becomes
aware will be disclosed, in accordance with Section 6 of BCP 79. aware will be disclosed, in accordance with Section 6 of BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that other Task Force (IETF), its areas, and its working groups. Note that other
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7.1 Two Layer Hierarchy .......................................... 24 7.1 Two Layer Hierarchy .......................................... 24
7.2 Three Layer Hierarchy ........................................ 25 7.2 Three Layer Hierarchy ........................................ 25
7.3 Issues with Hierarchical LSPs ................................ 26 7.3 Issues with Hierarchical LSPs ................................ 26
8. Scaling Improvements Through Multipoint-to-Point LSPs ......... 26 8. Scaling Improvements Through Multipoint-to-Point LSPs ......... 26
8.1 Overview of MP2P LSPs ........................................ 27 8.1 Overview of MP2P LSPs ........................................ 27
8.2 LSP State : A Better Measure of Scalability .................. 27 8.2 LSP State : A Better Measure of Scalability .................. 27
8.3 Scaling Improvements for Snowflake Networks .................. 28 8.3 Scaling Improvements for Snowflake Networks .................. 28
8.3.1 Comparison with Other Scenarios ............................ 30 8.3.1 Comparison with Other Scenarios ............................ 30
8.4 Scaling Improvements for Ladder Networks ..................... 31 8.4 Scaling Improvements for Ladder Networks ..................... 31
8.4.1 Comparison with Other Scenarios ............................ 32 8.4.1 Comparison with Other Scenarios ............................ 32
8.4.2 LSP State Compared with LSP Numbers ........................ 32 8.4.2 LSP State Compared with LSP Numbers ........................ 33
8.5 Issues with MP2P LSPs ........................................ 33 8.5 Issues with MP2P LSPs ........................................ 33
9. Combined Models ............................................... 34 9. Combined Models ............................................... 34
10. Management Considerations .................................... 34 10. Management Considerations .................................... 35
11. Security Considerations ...................................... 35 11. Security Considerations ...................................... 35
12. Recommendations .............................................. 35 12. Recommendations .............................................. 35
13. IANA Considerations .......................................... 35 13. IANA Considerations .......................................... 36
14. Acknowledgements ............................................. 35 14. Acknowledgements ............................................. 36
15. Intellectual Property Consideration .......................... 36 15. Intellectual Property Consideration .......................... 36
16. Normative References ......................................... 36 16. Normative References ......................................... 36
17. Informative References ....................................... 36 17. Informative References ....................................... 37
18. Authors' Addresses ........................................... 37 18. Authors' Addresses ........................................... 38
19. Disclaimer of Validity ....................................... 38 19. Disclaimer of Validity ....................................... 38
20. Full Copyright Statement ..................................... 38 20. Full Copyright Statement ..................................... 38
1. Introduction 1. Introduction
Network operators and service providers are examining scaling issues Network operators and service providers are examining scaling issues
as they look to deploy ever-larger traffic engineered Multiprotocol as they look to deploy ever-larger traffic engineered Multiprotocol
Label Switching (MPLS-TE) networks. Concerns have been raised about Label Switching (MPLS-TE) networks. Concerns have been raised about
the number of Label Switched Paths (LSPs) that need to be supported the number of Label Switched Paths (LSPs) that need to be supported
at the edge and at the core of the network. The impact on control at the edge and at the core of the network. The impact on control
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o E LSPs targeting local PEs o E LSPs targeting local PEs
o (S(1)-1)*E*M(1) LSPs targeting remote PEs o (S(1)-1)*E*M(1) LSPs targeting remote PEs
The remote segments may be counted as: The remote segments may be counted as:
o (S(1)-1)*E outgoing LSPs targeting remote PEs o (S(1)-1)*E outgoing LSPs targeting remote PEs
o <= 3*S(1)*E incoming LSPs targeting any PE (there are precisely o <= 3*S(1)*E incoming LSPs targeting any PE (there are precisely
P(1) nodes attached to any other P(1) node). P(1) nodes attached to any other P(1) node).
Hence, treating L(1) as a measure of LSP state rather than a count of Hence, using X(1) as a measure of LSP state rather than a count of
LSPs, we get: LSPs, we get:
L(1) <= E + (S(1)-1)*E*M(1) + (S(1)-1)*E + 3*S(1)*E X(1) <= E + (S(1)-1)*E*M(1) + (S(1)-1)*E + 3*S(1)*E
<= (4 + M(1))*S(1)*E - M(1)*E <= (4 + M(1))*S(1)*E - M(1)*E
The number of LSPs at the P(2) nodes is also improved. We may also The number of LSPs at the P(2) nodes is also improved. We may also
count the LSP state in the same way so that there are: count the LSP state in the same way so that there are:
o M(2) LSPs targeting local PEs o M(2) LSPs targeting local PEs
o M(2)*(S(1)*E) LSPs from local PEs to all other PEs o M(2)*(S(1)*E) LSPs from local PEs to all other PEs
o S(1)*E - M(2) LSPs to remote PEs. o S(1)*E - M(2) LSPs to remote PEs.
So treating L(2) as a measure of LSP state and not a count of LSPs, So using X(2) as a measure of LSP state and not a count of LSPs, we
we have: have:
L(2) = M(2) + M(2)*(S(1)*E) + S(1)*E - M(2) X(2) = M(2) + M(2)*(S(1)*E) + S(1)*E - M(2)
= (M(2) + 1)*S(1)*E = (M(2) + 1)*S(1)*E
Our examples from Section 5.2 give us the following numbers: Our examples from Section 5.2 give us the following numbers:
With S(1) = 6, M(1) = 10, and M(2) = 17, we see: With S(1) = 6, M(1) = 10, and M(2) = 17, we see:
E = 170 E = 170
S(PE) = 1020 S(PE) = 1020
L(PE) = 2038 X(PE) = 2038
L(2) = 18360 X(2) = 18360
L(1) <= 12580 X(1) <= 12580
Alternatively, with S(1) = 10, M(1) = 10, and M(2) = 20, we see: Alternatively, with S(1) = 10, M(1) = 10, and M(2) = 20, we see:
E = 200 E = 200
S(PE) = 2000 S(PE) = 2000
L(PE) = 3998 X(PE) = 3998
L(2) = 42000 X(2) = 42000
L(1) <= 26000 X(1) <= 26000
8.4.1 Comparison with Other Scenarios 8.4.1 Comparison with Other Scenarios
The use of MP2P compares very favourably with all scaling scenarios. The use of MP2P compares very favourably with all scaling scenarios.
It is the only technique able to reduce the value of L(2), and it It is the only technique able to reduce the value of X(2), and it
does this by a factor of almost two. The impact on L(1) is better does this by a factor of almost two. The impact on X(1) is better
than everything except the three level hierarcy. than everything except the three level hierarcy.
The following table provides a quick cross-reference for the figures The following table provides a quick cross-reference for the figures
for the example ladder networks. for the example ladder networks. Note that the previous figures are
modified to provide counts of LSP state rather than LSP numbers.
Again, each LSP contributes one state at its end points, and two
states at transit nodes.
Thus, for the all cases we have
X(PE) = 2*(S(PE) - 1) or
X(PE) = 4*(S(PE) - 1) if disambiguation is required.
In the unmodified (flat) case, we have:
X(2) = 2*(M(2)*(2*S(PE) - M(2) - 1))
X(1) = 2*(M(1)*M(2)*(2*S(PE) - M(2)*(M(1) + 1)))
In the 2-level hierarchy, we have:
X(2) = 2*(2*M(2)*(S(PE) - 1) - M(2)*(M(2) - 1))
X(1) = S(1)*S(1) + 2*S(1) + 4*E*E*(S(1) - 1) - 2*E*M(2) - 2
In the 3-level hierarchy, we have:
X(2) = 2*(2*M(2)*(S(PE) - 1) - M(2)*(M(2) - 1)) + 2*(S(1)*M(1) - 1)
X(1) = S(1)*S(1) + 2*S(1) + 4*M(1)*M(1)*S(1) - 2*M(1)(M(1) + 1) - 2
Example A: S(1) = 6, M(1) = 10, and M(2) = 17 Example A: S(1) = 6, M(1) = 10, and M(2) = 17
Example B: S(1) = 10, M(1) = 10, and M(2) = 20 Example B: S(1) = 10, M(1) = 10, and M(2) = 20
Example| Count | Unmodified | 1-Level | 2-Level | MP2P Example| Count | Unmodified | 2-Level | 3-Level | MP2P
| | | Hierarchy | Hierarchy | | | | Hierarchy | Hierarchy |
-------+-------+------------+------------+-------------+------- -------+-------+------------+------------+-------------+-------
A | L(2) | 34374 | 34374 | 34492 | 18360 A | X(2) | 68748 | 68748 | 68866 | 18360
| L(1) | 777410 | 286138 | 1118 | 12580 | X(1) | 1554820 | 572266 | 2226 | 12580
-------+-------+------------+------------+-------------+------- -------+-------+------------+------------+-------------+-------
B | L(2) | 79580 | 79580 | 79778 | 42000 B | X(2) | 159160 | 159160 | 159358 | 42000
| L(1) | 2516000 | 716060 | 1958 | 26000 | X(1) | 5032000 | 1433998 | 3898 | 26000
8.4.2 LSP State Compared with LSP Numbers 8.4.2 LSP State Compared with LSP Numbers
Recall that in Section 8.3, the true benefit of MP2P was analyzed Recall that in Section 8.3, the true benefit of MP2P was analyzed
with respect to the LSP segment state required, rather than the with respect to the LSP segment state required, rather than the
actual number of LSPs. This proved to be a more acurate comparison of actual number of LSPs. This proved to be a more acurate comparison of
the techniques because the MP2P LSPs require state on each branch of the techniques because the MP2P LSPs require state on each branch of
the LSP so the saving is not linear with the reduced number of LSPs. the LSP so the saving is not linear with the reduced number of LSPs.
A similar analysis could be performed here for the ladder network A similar analysis could be performed here for the ladder network
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