Network Working Group                                             C. Xie
Internet-Draft                                                    Q. Sun
Intended status: Informational                             China Telecom
Expires: August 29, 2013                                        S. Jiang
                                            Huawei Technologies Co., Ltd
                                                       February 25, 2013


            Use case of IPv6 prefix semantics for operators
                     draft-sun-semantic-usecase-02

Abstract

   Embedding certain semantics into IPv6 addresses will bring a lot of
   benifits for operators to simplify network management and apply
   operations accordingly[I-D.jiang-semantic-prefix].  This memo
   illustrates the use case of semantic bits from operator's point of
   view, and provides considerations on how to design the semantic bits
   in IPv6 address.

Requirements Language

   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].

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on August 29, 2013.

Copyright Notice

   Copyright (c) 2013 IETF Trust and the persons identified as the
   document authors.  All rights reserved.




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   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
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   described in the Simplified BSD License.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  How to design the semantic bits  . . . . . . . . . . . . . . .  4
   3.  A use case for Semantic Prefix . . . . . . . . . . . . . . . .  6
     3.1.  Level-1 semantics  . . . . . . . . . . . . . . . . . . . .  6
     3.2.  Level-2 semantics  . . . . . . . . . . . . . . . . . . . .  7
   4.  Benifits of Semantic Use Case  . . . . . . . . . . . . . . . . 10
   5.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 11
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . . 11
   7.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 11
   8.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
     8.1.  Normative References . . . . . . . . . . . . . . . . . . . 11
     8.2.  Informative References . . . . . . . . . . . . . . . . . . 11
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12

























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1.  Introduction

   [I-D.jiang-semantic-prefix] introduces embedded semantics prefix
   solution in IPv6 context.  With more and more differentiated
   requirements raising in the current Internet, service operators may
   want to apply more complicated policies for different kinds of
   customers and services.  Policy control servers are introduced
   gradually in fixed network operator and mobile network operator.
   However, all of these policies can only take action based on
   efficient packet identification of different sematics.

   The semantics are mainly used in a local region within an operator.
   Carrying semantic bits directly in IPv6 prefix is not only efficient
   for routers to do packet identification, but also suitable for
   operators.  It provides an easy access and trustable fundamental for
   packet differentiated treatment.

   For operators, several motivations to use semantic prefixes are as
   follows:

   1.  Network Device management

   In order to achieve easy management for network devices, operators
   will usually apply a simple and specific numbering policy for network
   devices.  Besides, special-purpose security policies may be enforced
   for network devices other than for customers and service platforms.
   For example, when encountering a simple threat model from some
   subscribers' address block, operators may only filter the specific
   subscribers' address block other than the whole addresses network
   devices and service platforms.  As a result, separated and
   specialized address space for network device will help to identify
   the network device among numerous addresses and apply policy
   accordingly.

   2.  Differentiated user management

   In operator's network, different kinds of customers may have
   different requirements for service provisioning.  For example,
   broadband access subscribers usually have lower priority than
   enterprise customers.  And even for broadband access subscribers,
   different priorities can also be further divided to apply
   differentiated policy, e.g. bandwidth limit, etc.  In particular,
   semantic prefix would be quite useful for identifying subscriber's
   priority in downstream traffic across large-scale regions where
   subscriber's profile is difficult to syncronize.

   3.  High-priority service guarantee




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   Operators may provide their own ISP brokered services, .e.g. video
   streaming, IPTV, VOIP, etc, which usually have higher priority
   guarantee rent their IDC to third-party service platform, offering
   high priority services, .e.g. video streaming, VOIP, etc.

   4.  Service-based Routing

   Service-based routing usually has close relationship with operator's
   network architecture.  For example, some operators have distinct core
   networks for different kinds of services.  As a result, operators may
   offer different routing policy for specific service platforms
   .e.g.video streaming, VOIP, etc.  Different routing policies may also
   apply to high priority services.  In this case, semantic embedded in
   the IPv6 address will be very helpful to implement service-based
   routing.

   5.  Security Control

   For security requirement, operators need to take control and identify
   of certain devices/customers in a quick manner.

   6.  Easy measurement and statistic

   The semantic prefix provides explicit identifiers for measurement and
   statistic.  They are as simple as checking certain bits of address in
   each packets.

   The semantic bits should be defined after an operator have got its
   IPv6 address pool.  The embedded semantic bits should be carefully
   designed.  Firstly, the number of bits which can be used to carry
   semantic information.  Secondly, some sementics may easily raise the
   implementation complexity on host and network devices.  So careful
   considerations and tradeoff should be taken in semantic design.

   [I-D.jiang-semantic-prefix] has listed some semantics which may be
   useful to network operators.  In this document, we provide a use case
   to use some selected semantics, achieving enhanced network management
   and service provisioning ability with limited impact on existing
   network infrustructure.

   [Note: Further use cases could be added to reflect other requirements
   and implementation possibility.]


2.  How to design the semantic bits

   Depending on the IPv6 address space that network operators received
   from IANA or upstream network service providers, the number of



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   arbitrary bits in prefix is different.  For now, this document only
   discusses unicast address within IP Version 6 Addressing Architecture
   [RFC4291].

   The following are some guidelines for operators to design the
   semantic bits:

   o  Determine the number of semantic bits.  Typically, ISPs with
      millions subscribers would have /16 ~ /24 address space.  It
      allows 40~48 arbitrary bits in prefix to be set by network
      operators (assuming the network is not strictly managed by
      DHCPv6).  However, many ISPs plan to assign /56 or even /48 for
      subscribers, the arbitrary bits are reduced to 22~40.
      Furthermore, within the arbitrary bits, the locator function of IP
      address should be ensured first.  Enough consideration should be
      given for future expanding.  Some address space may be wasted in
      aggregation.  For a Semantic Prefix Domain that organizes several
      millions subscribers with a continuous IPv6 address block, 24 bits
      for locator function is a minimum safe allocation.  Hence, it is
      recommended to use 4~12 bits in prefix for embedded semantics.

   o  The number of semantics should be limited.  According to the above
      analysis, the number of semantic bits left for operators is quite
      limited.  Therefore, network operator should only use necessary
      semantics when they can bring benefits, especially IP-layer
      policy, e.g. policy routing, access control and filtering, QoS,
      network measurement, etc.  Network operators should be very
      careful to plan and manage the semantic field, and should self-
      restrict NOT to put too many semantic into prefix.  So that they
      may avoid trap themselves into very complicated management issues.

   o  Semantic overlap should be largely avoided .  Any potential
      scenarios that a given address may be mapped two or more semantic
      prefixes might be harmful.  Otherwise, if one subscriber is
      allocated with multiple semantics, context-based semantic
      selection mechanism must been introduced which might increase the
      complexity in device/hosts.  In our use case, either the source
      address or the destination address only belongs to one semantic so
      as to simplify address selection process.

   o  The design of semantic bits should be scalable and stable from the
      long-term.  It should reflect the general potential network
      strategy and policies in the future and should be defined in
      highly abstracted way since there might be quite a lot of unknown
      emerging services.

   o  Different size of addressing space should be planned carefully for
      different semantics.  Since different semantics usually consumes



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      different size of address space, operators should plan the size of
      address space according to the service model for different
      semantics.


3.  A use case for Semantic Prefix

   As mentioned in section one, operators may have multiple requirements
   to use semantics.  These requirements are largely falling into two
   categories: the first one is related to the network device features,
   while the second one is related to services provision and subscriber
   identification.

   The functional usage of the semantics for the two categories are
   quite different.  For example, the semantics for the first category
   does not need to carry QoS related information, but may need to
   reflect network architecture of the operator; while the semantics in
   the second category should reflect the QoS requirements of the given
   subscriber/service.

   With this in mind, in our use case, the semantics are defined
   hierarchically, in which the first level is to define the function
   types of the prefixes, and the second level is to define the further
   usage within that specific prefix type.

3.1.  Level-1 semantics

   Level-1 semantics can be used to define the function types of the
   prefixes.

      Function type (FT): the value of this field is to indicate the
      functional usage of this prefix.  The typical types for operators
      include network device, subscriber and service.

   The following is the example of FT value.
















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                                  IPv6 Prefix
   +--------+--------+------------------------------------------------+
   |        | FT     |                                                |
   +--------+--------+------------------------------------------------+
           /          \
          /            \
         +--------------+-------+
         |000:  network device  |
         |001:  service platform|
         |010:  service platform|
         |011:  subscriber      |
         |100:  subscriber      |
         |101:  subscriber      |
         |110:  reserved        |
         +----------------------+

                        Figure 1: FT Value Example

   In this example, one prefix type may have multiple FT values.  For
   example, FT value of the subscriber prefix can be
   010,011,100,101,110,111, The portion of each type should be estimated
   according to the actual requirements for operators.

   With the above FT defintion, the whole IPv6 addressing space is
   firstly divided into three parts(as in the following figure).

   +----------------------------------------------------------------+
   |                   IPv6 Addressing Space                        |
   +------------------------+--------------------+------------------+
   |      Subscriber        |   Service Platform |  Network Device  |
   |      Addressing        |     Addressing     |    Addressing    |
   |       Space            |      Space         |      Space       |
   +--------+--------+----------------------------------------------+

                    Figure 2: Addressing Space Division

3.2.   Level-2 semantics

   Level-2 semantics is to define more detailed usage in different
   Function Types (addressing space).

   1.  Network Device Type (NDT)

   Network Device Type (NDT) is to indicate different types of network
   devices.  Normally, one operator may have multiple networks,
   e.g.backbone network, mobile network, ISP brokered service network,
   etc.  Using NDT field to indicate specific network within an operator
   may help to apply some routing policies.  Besied, implementing the



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   NDT field in the left-most bits means that a single, simple access-
   control list implemented across all networking devices would be
   enough to enforce effective traffic segregation.  The Locator field
   is put behind NDT to indicate the region of a certain device.

   One example is shown in the following figure:

                                  IPv6 Prefix
   +--------+--------+------+-----------------------------------------+
   |        | FT(000)|  NDT |   Locator    |   Network Device bits    |
   +--------+--------+------+-----------------------------------------+
                    /        \
                   /          \
                  +------------+----+
                  |000:  Network 1  |
                  |001:  Network 1  |
                  |010:  Network 2  |
                  |011:  Network 2  |
                  |100:  Network 2  |
                  |101:  Network 2  |
                  |110:  Network 2  |
                  +-----------------+

                        Figure 3: NDT Value Example

   2.  Subscriber type (ST)

   Subscriber type is to indicate different types of subscribers, e.g.
   wireline broadband subscriber, mobile subscriber, enterprise, WiFi,
   etc.  This type of prefix is allocated to end users.  In particular,
   further divisions can be taken on subscriber's priorities within one
   type, e.g. golden broadband subscriber, silver broadband subscriber
   and bronze broadband subscriber.  This definition is based on
   operator's local service model.

   Here, the Locator will reflect the different regions of a subscriber,
   and is put before ST for better routing aggregation.

   One example is shown in the following figure:












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                               IPv6 Prefix
+--------+--------+---------------+------+-------------------------+
|        | FT(011)|  Locator      |  ST  |   Subscriber bits       |
+--------+--------+---------------+------+-------------------------+
                                 /        \
                                /          \
                    +----------+------------+--------------------------+
                    |0000: broadband access subscriber (high priority) |
                    |0001: broadband access subscriber(medium priority)|
                    |0010: broadband access subscriber (low priority)  |
                    |0011: broadband access subscriber (low priority)  |
                    |0100: mobile subscriber(high priority)            |
                    |0101: mobile subscriber (medium priority)         |
                    |0110: mobile subscriber (low priority)            |
                    |0111: mobile subscriber (low priority)            |
                    |1001: enterprise                                  |
                    |1000: enterprise                                  |
                    |1010: WiFi subscriber                             |
                    |1011: WiFi subscriber                             |
                    |110-111: Reserved                                 |
                    +--------------------------------------------------+

                        Figure 4: ST Value Example

   3.  Platform Type(PT)

   Platform type is to indicate typical service platforms offered by
   operators.  This field may have scalability problem since there are
   numerous types of services in the further .  It is recommended that
   only aggregated service platform types (e.g. according to service
   priority) should be defined in this field.  This type of prefix is
   usually allocated to service platforms in operator's data center.

   One example is shown in the following figure:

















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                                  IPv6 Prefix
   +--------+--------+---------------+------+-------------------------+
   |        | FT(001)|  Locator      |  PT  |   Platform bits         |
   +--------+--------+---------------+------+-------------------------+
                                    /        \
                                   /          \
                       +----------+------------+---------------+
                       |000:  high priority service platform   |
                       |001:  high priority service platform   |
                       |001:  medium priority service platform |
                       |010:  medium priority service platform |
                       |011:  medium priority service platform |
                       |100:  low priority service platform    |
                       |101:  low priority service platform    |
                       |110~111:  reserved                     |
                       +---------------------------------------+

                        Figure 5: PT Value Example


4.  Benifits of Semantic Use Case

   The following describes a few benifits (and non-exhaustive) of above
   semantic use case for an operator:

   1.  Easy network device management.  With the combinition of FT, NDT
       and Locator, network devices from different regions can be easily
       identified.  Besides, network-based routing policies can also be
       enforced with NDT.

   2.  Bi-directional subscriber quality of service guarantee.  Since ST
       is consistent with the overall communication process for a
       subscriber, bi-directional quality of service guarantee can be
       easily achieved for cross-region communication.

   3.  Fine-Grained user and service control.  Normally, ST is located
       in the source address of a subscriber, and PT is located in the
       destination address for upstream traffic.  Therefore, with a
       simple combination of ST and PT, fine-Grained service control can
       be applied to subscribers (e.g. high priority broadband access
       subscriber with high priority service platform).

   4.  Service-based Routing.  With the definition of ST, different
       routing policies can be applied according to ST field.

   Other requirements listed in section one can also be achieved in this
   use case.




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5.  IANA Considerations

   This document has no actions for IANA.


6.  Security Considerations

   Embedding semantics in prefix is actually exposing more information
   of packets explicit.  These informations may also provide convenient
   for malicious attackers to track or attack certain type of packets.
   When networks announce their local prefix semantics to their peer
   networks, it may increase the vulnerable risk.


7.  Acknowledgements

   Authors would like to show sincere appreciation to Erik Nygren, Joel
   Jaeggli, Owen DeLong for their comments and suggestions.


8.  References

8.1.  Normative References

   [I-D.jiang-semantic-prefix]
              Jiang, S., Sun, Q., and I. Farrer, "A Framework for
              Semantic IPv6 Prefix and Gap Analysis",
              draft-jiang-semantic-prefix-04 (work in progress),
              January 2013.

   [RFC0768]  Postel, J., "User Datagram Protocol", STD 6, RFC 768,
              August 1980.

   [RFC1918]  Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and
              E. Lear, "Address Allocation for Private Internets",
              BCP 5, RFC 1918, February 1996.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2460]  Deering, S. and R. Hinden, "Internet Protocol, Version 6
              (IPv6) Specification", RFC 2460, December 1998.

8.2.  Informative References

   [RFC2132]  Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor
              Extensions", RFC 2132, March 1997.




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   [RFC2661]  Townsley, W., Valencia, A., Rubens, A., Pall, G., Zorn,
              G., and B. Palter, "Layer Two Tunneling Protocol "L2TP"",
              RFC 2661, August 1999.

   [RFC2865]  Rigney, C., Willens, S., Rubens, A., and W. Simpson,
              "Remote Authentication Dial In User Service (RADIUS)",
              RFC 2865, June 2000.

   [RFC3315]  Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C.,
              and M. Carney, "Dynamic Host Configuration Protocol for
              IPv6 (DHCPv6)", RFC 3315, July 2003.


Authors' Addresses

   Chongfeng Xie
   China Telecom
   Room 708, No.118, Xizhimennei Street
   Beijing  100084
   P.R. China

   Email: sunqiong@ctbri.com.cn


   Qiong Sun
   China Telecom
   Room 708, No.118, Xizhimennei Street
   Beijing  100084
   P.R. China

   Email: bingxuere@gmail.com


   Sheng Jiang
   Huawei Technologies Co., Ltd
   No.156 Beiqing Road
   Beijing  100095
   P.R. China

   Email: jiangsheng@huawei.com











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