TEAS Working Group A.Wang
Internet Draft China Telecom
Quintin Zhao
Boris Khasanov
HuaiMo Chen
Huawei Technologies
Penghui Mi
Tencent Company
Intended status: Experimental Track January 25, 2018
Expires: July 24, 2018
PCE in Native IP Network
draft-wang-teas-pce-native-ip-07.txt
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Abstract
This document defines the framework for CCDR traffic engineering
within Native IP network, using Dual/Multi-BGP session strategy and
PCE-based central control architecture.
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The proposed central mode control framework conforms to the concept
that defined in RFC " An Architecture for Use of PCE and the PCE
Communication Protocol (PCEP) in a Network with Central Control".
The scenario and simulation results of CCDR traffic engineering is
described in draft "CCDR Scenario, Simulation and Suggestion".
Table of Contents
1. Introduction ................................................. 2
2. Dual-BGP framework for simple topology. ...................... 3
3. Dual-BGP in large Scale Topology ............................. 4
4. Multi-BGP for Extended Traffic Differentiation ............... 5
5. CCDR based framework for Multi-BGP strategy deployment........ 6
6. PCEP extension for key parameters delivery. .................. 7
7. CCDR Deployment Consideration ................................ 7
8. Security Considerations....................................... 8
9. IANA Considerations .......................................... 8
10. Conclusions ................................................. 8
11. References .................................................. 9
11.1. Normative References.................................... 9
11.2. Informative References.................................. 9
12. Acknowledgments ............................................ 10
1. Introduction
Draft [I-D.draft-wang-teas-ccdr] describes the scenario and simulation
results for the CCDR traffic engineering. In summary, the requirements for
CCDR traffic engineering in Native IP network are the following:
1) No complex MPLS signaling procedure.
2) End to End traffic assurance, determined QoS behavior.
3) Identical deployment method for intra- and inter- domain.
4) No influence to existing router forward behavior.
5) Can utilize the power of centrally control(PCE) and
flexibility/robustness of distributed control protocol.
6) Coping with the differentiation requirements for large amount
traffic and prefixes.
7) Flexible deployment and automation control.
This document defines the framework for CCDR traffic engineering
within Native IP network, using Dual/Multi-BGP session strategy and
CCDR architecture, to meet the above requirements in dynamical and
central control mode. Future PCEP protocol extensions to transfer the
key parameters between PCE and the underlying network devices(PCC)
are provided in draft [draft-wang-pcep-extension-native-IP]
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2. Dual-BGP framework for simple topology.
Dual-BGP framework for simple topology is illustrated in Fig.1, which
is comprised by SW1, SW2, R1, R2. There are multiple physical links
between R1 and R2. Traffic between IP11 and IP21 is normal traffic,
traffic between IP12 and IP22 is priority traffic that should be
treated differently.
Only Native IGP/BGP protocol is deployed between R1 and R2. The traffic
between each address pair may change timely and the corresponding
source/destination addresses of the traffic may also change dynamically.
The key idea of the Dual-BGP framework for this simple topology is
the following:
1) Build two BGP sessions between R1 and R2, via the different loopback
address lo0, lo1 on these routers.
2) Send different prefixes via the two BGP sessions. (For example,
IP11/IP21 via the BGP pair 1 and IP12/IP22 via the BGP pair 2).
3) Set the explicit peer route on R1 and R2 respectively for BGP next
hop of lo0, lo1 to different physical link address between R1 and
R2.
So, the traffic between the IP11 and IP21, and the traffic between
IP12 and IP22 will go through different physical links between R1 and
R2, each type of traffic occupy the different dedicated physical
links.
If there is more traffic between IP12 and IP22 that needs to be
assured , one can add more physical links on R1 and R2 to reach the
loopback address lo1(also the next hop for BGP Peer pair2). In this
cases the prefixes that advertised by two BGP peer need not be
changed.
If, for example, there is traffic from another address pair that
needs to be assured (for example IP13/IP23), but the total volume of
assured traffic does not exceed the capacity of the previous
appointed physical links, then one need only to advertise the newly
added source/destination prefixes via the BGP peer pair2, then the
traffic between IP13/IP23 will go through the assigned dedicated
physical links as the traffic between IP12/IP22.
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Such decouple philosophy gives the network operator more flexible
control ability on the network traffic, get the determined QoS
assurance effect to meet the application's requirement. No complex
MPLS signal procedures is introduced, the router need only support
native IP protocol.
| BGP Peer Pair2 |
+------------------+
|lo1 lo1 |
| |
| BGP Peer Pair1 |
+------------------+
IP12 |lo0 lo0 | IP22
IP11 | | IP21
SW1-------R1-----------------R2-------SW2
Links Group
Fig.1 Design Philosophy for Dual-BGP Framework
3. Dual-BGP in large Scale Topology
When the assured traffic spans across one large scale network, as
that illustrated in Fig.2, the dual BGP sessions cannot be
established hop by hop especially for the iBGP within one AS. For
such scenario, we should consider to use the Route Reflector (RR) to
achieve the similar Dual-BGP effect, select one router which performs
the role of RR (for example R3 in Fig.2), every other edge router
will establish two BGP peer sessions with the RR, using their
different loopback addresses respectively. The other two steps for
traffic differentiation are same as one described in the Dual-BGP
simple topology usage case.
For the example shown in Fig.2, if we select the R1-R2-R4-R7 as the
dedicated path, then we should set the explicit peer routes on these
routers respectively, pointing to the BGP next hop (loopback
addresses of R1 and R7, which are used to send the prefix of the
assured traffic) to the actual address of the physical link
+------------R3--------------+
| |
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SW1-------R1-------R5---------R6-------R7--------SW2
| | | |
+-------R2---------R4--------+
Fig.2 Dual-BGP Framework for large scale network
4. Multi-BGP for Extended Traffic Differentiation
In general situation, several additional traffic differentiation
criteria exist, including:
o Traffic that requires low latency links and is not sensitive to
packet loss
o Traffic that requires low packet loss but can endure higher latency
o Traffic that requires lowest jitter path
o Traffic that requires high bandwidth links
These different traffic requirements can be summarized in the
following table:
+----------+-------------+---------------+-----------------+
| Flow No. | Latency | Packet Loss | Jitter |
+----------+-------------+---------------+-----------------+
| 1 | Low | Normal | Don't care |
+----------+-------------+---------------+-----------------+
| 2 | Normal | Low | Dont't care |
+----------+-------------+---------------+-----------------+
| 3 | Normal | Normal | Low |
+----------+-------------+---------------+-----------------+
Table 1. Traffic Requirement Criteria
For Flow No.1, we can select the shortest distance path to carry the
traffic; for Flow No.2, we can select the idle links to form its end
to end path; for Flow No.3, we can let all the traffic pass one
single path, no ECMP distribution on the parallel links is required.
It is difficult and almost impossible to provide an end-to-end (E2E)
path with latency, latency variation, packet loss, and bandwidth
utilization constraints to meet the above requirements in large scale
IP-based network via the traditional distributed routing protocol,
but these requirements can be solved using the CCDR architecture
since the PCE has the overall network view, can collect real network
topology and network performance information about the underlying
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network, select the appropriate path to meet the various network
performance requirements of different traffic type.
5. CCDR based framework for Multi-BGP strategy deployment.
With the advent of SDN concepts towards pure IP networks, it is
possible now to accomplish the central and dynamic control of network
traffic according to the application's various requirements.
The procedure to implement the dynamic deployment of Multi-BGP
strategy is the following:
1) PCE gets topology and link utilization information from the
underlying network, calculate the appropriate link path upon
application's requirements.
2) PCE sends the key parameters to edge/RR routers(R1, R7 and R3 in
Fig.3) to build multi-BGP peer relations and advertise different
prefixes via them.
3) PCE sends the route information to the routers (R1,R2,R4,R7 in
Fig.3) on forwarding path via PCEP, to build the path to the BGP
next-hop of the advertised prefixes.
4) If the assured traffic prefixes were changed but the total volume
of assured traffic does not exceed the physical capacity of the
previous end-to-end path, then PCE needs only change the related
information on edge routers (R1,R7 in Fig.3).
5) If volume of the assured traffic exceeds the capacity of previous
calculated path, PCE must recalculate the appropriate path to
accommodate the exceeding traffic via some new end-to-end physical
link. After that PCE needs to update on-path routers to build such
path hop by hop.
+----+
***********+PCE +*************
* +--*-+ *
* / * \ *
* * *
PCEP* *BGP-LS/SNMP *PCEP
* * *
* * \ * /
\ * / * \ */
\*/-----------R3--------------*
| |
| |
SW1-------R1-------R5---------R6-------R7--------SW2
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| | | |
| | | |
+-------R2---------R4--------+
Fig.3 PCE based framework for Multi-BGP deployment
6. PCEP extension for key parameters delivery.
The PCEP protocol needs to be extended to transfer the following key
parameters:
1) BGP peer address and advertised prefixes.
2) Explicit route information to BGP next hop of advertised prefixes.
Once the router receives such information, it should establish the
BGP session with the peer appointed in the PCEP message, advertise
the prefixes that contained in the corresponding PCEP message, and
build the end to end dedicated path hop by hop. Details of
communications between PCEP and BGP subsystems in router's control
plane are out of scope of this draft and will be described in
separate draft.[draft-wang-pce-extension for native IP]
The reason why we selected PCEP as the southbound protocol instead of
OpenFlow, is that PCEP is suitable for the changes in control plane
of the network devices, there OpenFlow dramatically changes the
forwarding plane. We also think that the level of centralization that
requires by OpenFlow is hardly achievable in many today's SP networks
so hybrid BGP+PCEP approach looks much more interesting.
7. CCDR Deployment Consideration
CCDR framework requires the parallel work of 2 subsystems in router's
control plane: PCE (PCEP) and BGP as well as coordination between
them, so it might require additional planning work before deployment.
8.1 Scalability
In CCDR framework, PCE needs only to influence the edge routers for
the prefixes differentiation via the multi-BGP deployment. The route
information for these prefixes within the on-path routers were
distributed via the traditional BGP protocol. Unlike the solution
from BGP Flowspec, the on-path router need only keep the specific
policy routes to the BGP next-hop of the differentiate prefixes, not
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the specific routes to the prefixes themselves. This can lessen the
burden from the table size of policy based routes for the on-path
routers, and has more scalability when comparing with the solution
from BGP flowspec or Openflow.
8.2 High Availability
CCDR framework is based on the traditional distributed IP protocol.
If the PCE failed, the forwarding plane will not be impacted, as the
BGP session between all devices will not flap, and the forwarding
table will remain the same. If one node on the optimal path is failed,
the assurance traffic will fall over to the best-effort forwarding
path. One can even design several assurance paths to load balance/hot
standby the assurance traffic to meet the path failure situation, as
done in MPLS FRR.
From PCE/SDN-controller HA side we will rely on existing HA solutions
of SDN controllers such as clustering.
8.3 Incremental deployment
Not every router within the network support will support the PCEP
extension that defined in [draft-wang-pce-extension-native-IP]
simultaneously. For such situations, router on the edge of sub domain
can be upgraded first, and then the traffic can be assured between
different sub domains. Within each sub domain, the traffic will be
forwarded along the best-effort path. Service provider can
selectively upgrade the routers on each sub-domain in sequence.
8. Security Considerations
TBD
9. IANA Considerations
TBD
10. Conclusions
TBD
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11. References
11.1. Normative References
[RFC4655] Farrel, A., Vasseur, J.-P., and J. Ash, "A Path
Computation Element (PCE)-Based Architecture", RFC
4655, August 2006,<http://www.rfc-editor.org/info/rfc4655>.
[RFC5440]Vasseur, JP., Ed., and JL. Le Roux, Ed., "Path
Computation Element (PCE) Communication Protocol
(PCEP)", RFC 5440, March 2009,
<http://www.rfc-editor.org/info/rfc5440>.
[RFC8283] A.Farrel, Q.Zhao et al.," An Architecture for Use of PCE
and the PCE Communication Protocol (PCEP) in a Network with Central
Control", [RFC8283], December 2017
11.2. Informative References
[I-D.draft-wang-teas-ccdr]
A.Wang, X.Huang et al. "CCDR Scenario, Simulation and Suggestion"
https://datatracker.ietf.org/doc/draft-wang-teas-ccdr/
[I-D. draft-ietf-teas-pcecc-use-cases]
Quintin Zhao, Robin Li, Boris Khasanov et al. "The Use Cases for
Using PCE as the Central Controller(PCECC) of LSPs
https://tools.ietf.org/html/draft-ietf-teas-pcecc-use-cases-00
March,2017
[draft-wang-pcep-extension for native IP]
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Aijun Wang, Boris Khasanov et al. "PCEP Extension for Native IP
Network" https://datatracker.ietf.org/doc/draft-wang-pce-extension-
native-ip/
12. Acknowledgments
The authors would like to thank George Swallow, Xia Chen, Jeff
Tantsura,Scharf Michael,Daniele Ceccarelli and Dhruv Dhody for their
valuable comments and suggestions.
The authors would also like to thank Lou Berger, Adrian Farrel,
Vishnu Pavan Beeram, Deborah Brungard and King Daniel for their
suggestions to put forward this draft.
Authors' Addresses
Aijun Wang
China Telecom
Beiqijia Town, Changping District
Beijing,China
Email: wangaj.bri@chinatelecom.cn
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Quintin Zhao
Huawei Technologies
125 Nagog Technology Park
Acton, MA 01719
USA
EMail: quintin.zhao@huawei.com
Boris Khasanov
Huawei Technologies
Moskovskiy Prospekt 97A
St.Petersburg 196084
Russia
EMail: khasanov.boris@huawei.com
Huaimo Chen
Huawei Technologies
Boston, MA,
USA
EMail: huaimo.chen@huawei.com
Penghui Mi
Tencent
Tencent Building, Kejizhongyi Avenue,
Hi-techPark, Nanshan District,Shenzhen 518057, P.R.China
Email kevinmi@tencent.com
Raghavendra Mallya
Juniper Networks
1133 Innovation Way
Sunnyvale, California 94089 USA
Email: rmallya@juniper.net
Shaofu Peng
ZTE Corporation
No.68 Zijinghua Road,Yuhuatai District
Nanjing 210012
China
Email: peng.shaofu@zte.com.cn
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