TEAS Working Group A. Wang
Internet-Draft China Telecom
Intended status: Experimental Q. Zhao
Expires: February 27, 2020 B. Khasanov
Huawei Technologies
H. Chen
Futurewei
R. Mallya
Juniper Networks
August 26, 2019
PCE in Native IP Network
draft-ietf-teas-pce-native-ip-04
Abstract
This document defines the framework for traffic engineering within
native IP network, using Dual/Multi-Border Gateway Protocol (BGP)
sessions strategy and Path Computation Engine (PCE) -based central
control architecture. The proposed central mode control framework
conforms to the concept that defined in [RFC8283]. The scenario and
simulation results of traffic engineering in Native IP network is
described in draft [I-D.ietf-teas-native-ip-scenarios].
Status of This Memo
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This Internet-Draft will expire on February 27, 2020.
Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions used in this document . . . . . . . . . . . . . . 3
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. CCDR Framework in Simple Topology . . . . . . . . . . . . . . 3
5. CCDR Framework in Large Scale Topology . . . . . . . . . . . 5
6. CCDR Multi-BGP Strategy . . . . . . . . . . . . . . . . . . . 5
7. CCDR Framework for Multi-BGP Strategy . . . . . . . . . . . . 6
8. PCEP Extension for Key Parameters Delivery . . . . . . . . . 7
9. Deployment Consideration . . . . . . . . . . . . . . . . . . 8
9.1. Scalability . . . . . . . . . . . . . . . . . . . . . . . 8
9.2. High Availability . . . . . . . . . . . . . . . . . . . . 8
9.3. Incremental deployment . . . . . . . . . . . . . . . . . 9
10. Security Considerations . . . . . . . . . . . . . . . . . . . 9
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
12. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 9
13. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
13.1. Normative References . . . . . . . . . . . . . . . . . . 10
13.2. Informative References . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
1. Introduction
Draft [I-D.ietf-teas-native-ip-scenarios] describes the scenarios and
simulation results for traffic engineering in native IP network. To
meet the requirements of various scenarios, the solution for traffic
engineering in native IP network should have the followings criteria:
o No complex Multiprotocol Label Switching (MPLS) signaling
procedures.
o End to End traffic assurance, determined Quality of Service (QoS)
behavior.
o Same deployment method for intra-domain and inter-domain.
o No influence to forwarding behavior of the router.
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o Can exploit the power of centrally control and flexibility/
robustness of distributed control protocol.
o Coping with the differentiation requirements for large amount
traffic and prefixes.
o Flexible deployment and automation control.
This document defines the framework for traffic engineering within
native IP network, using Dual/Multi-BGP session strategy, to meet the
above requirements in dynamical and centrally control mode. It
defines the Centrally Control Dynamic Routing (CCDR) framework. The
related Path Computation Element Communications Protocol (PCEP)
extensions to transfer the key parameters between PCE and the
underlying network devices are provided in draft
[I-D.ietf-pce-pcep-extension-native-ip].
2. Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119] .
3. Terminology
This document uses the following terms defined in [RFC5440]: PCE,
PCEP
The following terms are defined in this document:
o CCDR: Central Control Dynamic Routing
o E2E: End to End
o ECMP: Equal Cost Multipath
o QoS: Quality of Service
o RR: Route Reflector
o SDN: Software Definition Network
4. CCDR Framework in Simple Topology
Figure 1 illustrates the CCDR framework for traffic engineering in
simple topology. The topology is comprised by four devices which are
SW1, SW2, R1, R2. There are multiple physical links between R1 and
R2. Traffic between IP11(on SW1) and IP21(on SW2) is normal traffic,
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traffic between IP12(on SW1) and IP22(on SW2) is priority traffic
that should be treated differently.
Only native Interior Gateway Protocol (IGP) /BGP protocol is deployed
between R1 and R2. The traffic between each address pair may change
in real time and the corresponding source/destination addresses of
the traffic may also change dynamically.
The key ideas of the CCDR framework for this simple topology are the
followings:
o Build two BGP sessions between R1 and R2, via the different
loopback address lo0, lo1 on these routers.
o Send different prefixes via the established BGP sessions. For
example, IP11/IP21 via the BGP pair 1 and IP12/IP22 via the BGP
pair 2.
o 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.
After the above actions, 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 set of traffic occupies different
dedicated physical links.
If there is more traffic between IP12 and IP22 that needs to be
assured , one can add more physical links between 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 the BGP peers need not be
changed.
If, for example, there is traffic from another address pair that
needs to be assured (for example IP13/IP23), and the total volume of
assured traffic does not exceed the capacity of the previous
appointed physical links, one need only to advertise the newly added
source/destination prefixes via the BGP peer pair2. The traffic
between IP13/IP23 will go through the assigned dedicated physical
links as the traffic between IP12/IP22.
Such decouple philosophy gives network operator flexible control
ability on the network traffic, achieve the determined QoS assurance
effect to meet the application's requirement. No complex MPLS signal
procedures is introduced, the router needs only support native IP
protocol.
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| BGP Peer Pair2 |
+------------------+
|lo1 lo1 |
| |
| BGP Peer Pair1 |
+------------------+
IP12 |lo0 lo0 | IP22
IP11 | | IP21
SW1-------R1-----------------R2-------SW2
Links Group
Figure 1: CCDR framework in simple topology
5. CCDR Framework in Large Scale Topology
When the assured traffic spans across the large scale network, as
that illustrated in Figure 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 effect. Every edge router will establish two
BGP peer sessions with the RR via different loopback addresses
respectively. The other steps for traffic differentiation are same
as that described in the CCDR framework for simple topology.
As shown in Figure 2, if we select R3 as the RR, every edge router(R1
and R7 in this example) will build two BGP session with the RR. If
the PCE calculates select the dedicated path as R1-R2-R4-R7, then the
operator 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 selected forwarding address.
+----------R3(RR)------------+
| |
SW1-------R1-------R5---------R6-------R7--------SW2
| | | |
+-------R2---------R4--------+
Figure 2: CCDR framework in large scale network
6. CCDR Multi-BGP Strategy
In general situation, different applications may require different
QoS criteria, which may include:
o Traffic that requires low latency and is not sensitive to packet
loss.
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o Traffic that requires low packet loss and can endure higher
latency.
o Traffic that requires low jitter.
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 path that is comprised by
under loading links from end to end; for Flow No.3, we can let all
assured traffic pass the determined single path, no Equal Cost
Multipath (ECMP) distribution on the parallel links is desired.
It is almost impossible to provide an End-to-End (E2E) path with
latency, jitter, packet loss constraints to meet the above
requirements in large scale IP-based network via the distributed
routing protocol, but these requirements can be solved with the
assistance of PCE, because the PCE has the overall network view, can
collect real network topology and network performance information
about the underlying network, select the appropriate path to meet
various network performance requirements of different traffics.
7. CCDR Framework for Multi-BGP Strategy
The framework to implement the CCDR Multi-BGP strategy are the
followings. Here PCE is the main component of the Software
Definition Network (SDN) controller and is responsible for optimal
path computation for privileged traffic.
o SDN controller gets topology and link utilization information from
the underlying network.
o PCE calculates the appropriate path upon application's
requirements, sends the key parameters to edge/RR routers(R1, R7
and R3 in Fig.3) to establish multi-BGP peer sessions and
advertises different prefixes via them.
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o 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.
o If the assured traffic prefixes were changed but the total volume
of assured traffic does not exceed the physical capacity of the
previous E2E path, PCE needs only change the prefixed advertised
via the edge routers (R1,R7 in Fig.3).
o If the volume of assured traffic exceeds the capacity of previous
calculated path, PCE can recalculate the appropriate paths to
accommodate the exceeding traffic. After that, PCE needs to
update on-path routers to build the forwarding path hop by hop.
+-------+
***********+SDN/PCE+**********
* +---*---+ *
* / * \ *
* * *
PCEP* BGP-LS/SNMP *PCEP
* * *
* * \ * /
\ * / * \ */
\*/-----------R3--------------*
| |
| |
SW1-------R1-------R5---------R6-------R7--------SW2
| | | |
| | | |
+-------R2---------R4--------+
Figure 3: CCDR framework for Multi-BGP deployment
8. PCEP Extension for Key Parameters Delivery
The PCEP protocol needs to be extended to transfer the following key
parameters:
o Peer addresses pair that is used to build the BGP session
o Advertised prefixes and their associated BGP session.
o 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.
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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 [I-D.ietf-pce-pcep-extension-native-ip] .
The reason that 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, while OpenFlow dramatically changes the
forwarding plane. We also think that the level of centralization
that requires by OpenFlow is hardly achievable in SP networks so
hybrid BGP+PCEP approach looks much more interesting.
9. Deployment Consideration
9.1. Scalability
In CCDR framework, PCE needs only influence the edge routers for the
prefixes advertisement via the multi-BGP deployment. The route
information for these prefixes within the on-path routers were
distributed via the 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 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 expandability when
comparing with the solution from BGP flowspec or Openflow.
9.2. High Availability
The CCDR framework is based on the 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 unchanged.
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 Fast
Reroute (FRR).
For high availability of PCE/SDN-controller, operator should rely on
existing HA solutions for SDN controller, such as clustering
technology and deployment.
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9.3. Incremental deployment
Not every router within the network will support the PCEP extension
that defined in [I-D.ietf-pce-pcep-extension-native-ip]
simultaneously.
For such situations, router on the edge of domain can be upgraded
first, and then the traffic can be assured between different domains.
Within each domain, the traffic will be forwarded along the best-
effort path. Service provider can selectively upgrade the routers on
each domain in sequence.
10. Security Considerations
The PCE should have the capability to calculate the loop-free E2E
path upon the status of network condition and the service
requirements in real time.
The PCE need consider the explicit route deployment order (for
example, from tail router to head router) to eliminate the possible
transient traffic loop.
CCDR framework described in this draft puts more requirements on the
function of PCE and its communication with the underlay devices.
Service provider should consider more on the protection of PCE and
their communication with the underlay devices, which is described in
document [RFC5440]
CCDR framework does not require the change of forward behavior on the
underlay devices, then there will no additional security impact on
the devices.
11. IANA Considerations
This document does not require any IANA actions.
12. Acknowledgement
The author would like to thank Deborah Brungard, Adrian Farrel,
Huaimo Chen, Vishnu Beeram, Lou Berger, Dhruv Dhody, Haomian Zheng,
Penghui Mi, Shaofu Peng and Jessica Chen for their supports and
comments on this draft.
13. References
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13.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation
Element (PCE) Communication Protocol (PCEP)", RFC 5440,
DOI 10.17487/RFC5440, March 2009,
<https://www.rfc-editor.org/info/rfc5440>.
[RFC8253] Lopez, D., Gonzalez de Dios, O., Wu, Q., and D. Dhody,
"PCEPS: Usage of TLS to Provide a Secure Transport for the
Path Computation Element Communication Protocol (PCEP)",
RFC 8253, DOI 10.17487/RFC8253, October 2017,
<https://www.rfc-editor.org/info/rfc8253>.
[RFC8283] Farrel, A., Ed., Zhao, Q., Ed., Li, Z., and C. Zhou, "An
Architecture for Use of PCE and the PCE Communication
Protocol (PCEP) in a Network with Central Control",
RFC 8283, DOI 10.17487/RFC8283, December 2017,
<https://www.rfc-editor.org/info/rfc8283>.
13.2. Informative References
[I-D.ietf-pce-pcep-extension-native-ip]
Wang, A., Khasanov, B., Cheruathur, S., Zhu, C., and S.
Fang, "PCEP Extension for Native IP Network", draft-ietf-
pce-pcep-extension-native-ip-03 (work in progress), March
2019.
[I-D.ietf-teas-native-ip-scenarios]
Wang, A., Huang, X., Qou, C., Li, Z., and P. Mi,
"Scenarios and Simulation Results of PCE in Native IP
Network", draft-ietf-teas-native-ip-scenarios-06 (work in
progress), June 2019.
[I-D.ietf-teas-pcecc-use-cases]
Zhao, Q., Li, Z., Khasanov, B., Dhody, D., Ke, Z., Fang,
L., Zhou, C., Communications, T., Rachitskiy, A., and A.
Gulida, "The Use Cases for Path Computation Element (PCE)
as a Central Controller (PCECC).", draft-ietf-teas-pcecc-
use-cases-04 (work in progress), July 2019.
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Authors' Addresses
Aijun Wang
China Telecom
Beiqijia Town, Changping District
Beijing 102209
China
Email: wangaj3@chinatelecom.cn
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
Futurewei
Boston, MA
USA
Email: huaimo.chen@futurewei.com
Raghavendra Mallya
Juniper Networks
1133 Innovation Way
Sunnyvale, California 94089
USA
Email: rmallya@juniper.net
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