TEAS Working Group                                             A.Wang
Internet Draft                                           China Telecom

Intended status: Standard Track                            June 30,2016
Expires: December 30, 2016


                         PCE in Native IP Network
                   draft-wang-teas-pce-native-ip-00.txt


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Copyright Notice

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Abstract

   This document defines the PCE use case and solution that can be
   deployed within the native IP network, using Multi-BGP session
   strategy and PCE-based central control to assure the end2end traffic
   performance, and proposes the corresponding extension to PCEP
   protocol to transfer the key parameters between PCE and the
   underlying network device (PCC).

Table of Contents


   1. Introduction ................................................ 2
   2. Conventions used in this document ........................... 3
   3. Dual-BGP solution for simple topology........................ 3
   4. Dual-BGP in large Scale Topology ............................ 5
   5. Multi-BGP for Extended Traffic Differentiation .............. 5
   6. PCE based solution for Multi-BGP strategy deployment..........6
   7. PCEP extension for key parameter transformation. ............ 8
   8. Security Considerations ..................................... 8
   9. IANA Considerations ......................................... 8
   10. Conclusions ................................................ 8
   11. References ................................................. 8
      11.1. Normative References .................................. 8
      11.2. Informative References................................. 9
   12. Acknowledgments ............................................ 9

1. Introduction

Currently, PCE based traffic assurance requires the underlying network
devices support MPLS and the network must deploy multiple LSPs to
assure the end-to-end traffic performance. LDP/RSVP-TE or Segment
Routing should be enabled within the network to establish various MPLS
paths. Such solution will certainly work but the main drawback of it is
that all the LSP paths are divided logically, that is to say, all the
LSP paths that go through one physical link will share and compete the


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same resource and MPLS technology has no better solution to meet the
requirements for determined QoS effect.
On the other hand, there are some legacy networks that does not deploy
the MPLS control and forward plane technology, but also need to assure
the QoS of application traffic. Deploy some dedicated links statically
to meet such requirements is one option but it is not feasible in the
service provider network, because the volume and path of application
traffic will be vary from time to time.
In summary, there are scenarios that the current PCE-based MPLS
solution can't be deployed within the network, because the following
user requirements:
1)        End to End traffic assurance.
2)        Determined Qos Effect.
3)        No complex MPLS signaling procedure, support Native IP environment.
4)        Flexible deployment
5)        Central control.

This document defines the PCE use case and solution that can be
deployed within the native IP network, using PCE-based central control
and  Multi  BGP  sessions  strategy  to  assure  the  end2end  traffic
performance, meet the above requirements in dynamical and central
control mode, proposes the corresponding extension to PCEP protocol to
transfer the key parameters between PCE and the underlying network
device(PCC).


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. Dual-BGP solution for simple topology.

This section introduces first the dual-BGP solution for simple topology
that 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 are normal traffic, traffic between IP12 and IP22 are
priority traffic that should be treated differently.
There is only Native IP protocol being deployed between R1 and R2. The
traffic between each address pair will be changed timely and the
corresponding source/destination addresses of the traffic may also be
changed dynamically.
The key idea of the Dual-BGP solution for this simple topology is the


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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 static 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 IP12, and the traffic between IP21
and IP22 will go through different physical links between R1 and R2,
each type of traffic occupied the different dedicated physical links
and will not influence with each other.

If there is more traffic between IP12 and IP13 need to be assured, one
can reassign more physical links on R1 and R2 to reach the loopback
address lo1(also the next hop for BGP Peer pair2), the prefixed that
advertised by two BGP peer need not be changed.

If, for example, there are traffic from another address pair need 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.

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


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                   Fig.1 Design Philosophy for Dual-BGP Solution


4. 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
neighbor by neighbor 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, that is to say, select one router which
performs the role of RR (for example R3 in Fig.2 - Dual-BGP Solution
using Route Reflector for large scale network), every other router will
establish two BGP 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 static routes on theses router
respectively, point 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--------------+
                     |                            |
          SW1-------R1-------R5---------R6-------R7--------SW2
                     |        |          |        |
                     +-------R2---------R4--------+
   Fig.2 Dual-BGP solution using route reflector for large scale network



5. Multi-BGP for Extended Traffic Differentiation

Discussed in the document so far, is the requirement for traffic
differentiation to classify traffic into two classes: Assured traffic
or best effort (normal) traffic. Dual-BGP solution(simple topology or
large  scale  topology)  can  meet  above  requirements.  In  general
situations, several additional traffic differentiation criteria exist,
including:
?  Traffic requires low latency links and not sensitive to packet loss
?  Traffic requires low packet loss but can endure higher latency
?  Traffic requires lowest jitter path



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?  Traffic requires high bandwidth links
These varying traffic requirements may 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 composition requirements in
large scale network via the traditional distributed routing protocol,
but these requirements can be solved using the PCE-based architecture
since 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 the various network
performance requirements of different traffic type.


6. PCE based solution for Multi-BGP strategy deployment.

With the advent of SDN concepts within IP network, it is possible to
deploy the PCE related technology into the underlying native IP network,
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 underlying topology information via the BGP-LS protocol via
   one router, such as the route reflector R3 in Fig.3
2)        It collects also the link utilization information via the SNMP
   protocol.


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3)        Upon the application's requirement, for example, the bi-direction
   traffic assurance between SW1/SW2, the PCE will calculate the
   appropriate link path, which can be assigned to such traffic in
   dedicated mode, other normal traffic will not pass through such
   physical links.
4)        PCE will then send the key parameters to R1 and R7 respectively, to
   let R1 and R7 build another i/eBGP neighbor with R3, advertise the
   prefixes that owned by SW1/SW2.
5)        If the calculated dedicated path is via some physical links that
   belong to R1-R2-R4-R7, then PCE need also build the connection with
   these on-path routers, send some key parameters to them to build the
   path to the BGP next-hop via the address of physical links between
   R1/R2,R2/R4,R4/R7.
6)        If the assured traffic prefixes are changed and the total volume of
   assured traffic is not exceed the physical capacity of the previous
   end-to-end path, then the PCE need only change the related
   information on R1 and R7.
7)        If the volume of the assured traffic exceeds the capacity of previous
   calculated path, then PCE must recalculate the appropriate path to
   accommodate the exceeding traffic in some new end-to-end physical
   link. It then need to send some relevant key parameters to the on-
   path routers to build such path hop by hop.

                               +----+
                     ***********+PCE +*************
                     *         +--*-+            *
                     *           / * \            *
                     *             *              *
                 PCEP*             *BGP-LS/SNMP   *PCEP
                     *             *              *
                     *             *           \  * /
                   \ * /           *            \ */
                    \*/-----------R3--------------*
                     |                            |
                     |                            |
          SW1-------R1-------R5---------R6-------R7--------SW2
                     |        |          |        |
                     |        |          |        |
                     +-------R2---------R4--------+
            Fig.3 PCE based solution for Multi-BGP deployment





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7. PCEP extension for key parameter transformation.

In order to pass the key parameters to the underlying routers and keep
the overall implementation as simple as possible, it is appropriate to
extend the PCEP protocol to transfer the key parameters.
Based on the design philosophy of afore mentioned Multi-BGP deployment
scenario, the key parameters should include the following information:
1)        BGP peer address and assured prefixes that will be advertised via
   this BGP session
2)        Static route information/Destination(BGP next hop) and Next Physical
   Link Address.

Once the router receive such information, it should establish the BGP
session with the peer appointed in the PCEP message, advertises the
prefixes that contained in the corresponding PCEP message, and build
the end to end dedicated path hop by hop.

The detail format and the processing procedure of the above two
extensions will be provided in another draft.

8. Security Considerations

   TBD

9. IANA Considerations

   TBD

10. Conclusions

   TBD

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



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             Computation Element (PCE) Communication Protocol

             (PCEP)", RFC 5440, March 2009,

                     <http://www.rfc-editor.org/info/rfc5440>.

11.2. Informative References

   TBD

12. Acknowledgments

   TBD



Authors' Addresses

   Aijun Wang
   China Telecom
   Beiqijia Town, Changping District
   Beijing,China

   Email: wangaj@ctbri.com.cn


























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