INTERNET DRAFT                                          S. Bandyopadhyay
draft-shyam-real-ip-framework-34.txt                       June 12, 2017
Intended status: Experimental
Expires: December 12, 2017


    An Architectural Framework of the Internet for the Real IP World
                  draft-shyam-real-ip-framework-34.txt

Abstract

   This document tries to propose an architectural framework of the
   internet in the real IP world. It describes how a three-tier mesh
   structured hierarchy can be established in a large address space
   based on fragmenting it into some regions and some sub regions inside
   each of them. It addresses issues which could be relevant to this
   architecture in the context of IPv6. It shows how to make a
   transition from private IP to real IP without making significant
   changes with the existing network.

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
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   This Internet-Draft will expire on December 12, 2017.

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Table of Contents
   1. Introduction.....................................................2
   2. Background.......................................................3
   3. A Three tier mesh structured hierarchical network................4
      3.1. Route propagation...........................................5
      3.2. Determination of prefix lengths.............................7
           3.2.1. A pseudo optimal distribution of prefixes in
                  a 64bit architecture.................................8
           3.2.2. Whether to go for a two tier or three tier hierarchy
                  .....................................................9
      3.3. Issues related to Satellite communications.................10
   4. Provider Independent addressing, name services and multihoming..11
      4.1. PI address Resolution......................................12
           4.1.1. Record Format.......................................16
           4.1.2. Messages............................................17
           4.1.3. Master file and data file...........................19
           4.1.4. Zone maintenance and transfers......................20
   5. Issues related to IP mobility...................................21
      5.1. Changes expected with the specifications related
           to IP mobility.............................................22
   6. Refinements over existing IPv6 specification....................23
   7. Distributed processing and Multicasting.........................25
   8. Transition to real IP from private IP...........................26
   9. IANA Consideration..............................................27
   10. Security Consideration.........................................27
   11. Acknowledgments................................................27
   12. Normative References...........................................27
   13. Informative References.........................................28
   14. Author's Address...............................................28

. Introduction

   Transition from IPv4 to IPv6 is in the process. Work has been done to
   upgrade individual nodes (workstations) from IPv4 to IPv6. Also,
   there are established documents to make routers/switches to work to
   support IPv4 as well as IPv6 packets simultaneously in order to make
   the transition possible [1].  CIDR[2] based hierarchical architecture
   in the existing 32-bit system is supposed to be continued in IPv6 too
   with a large address space. There are documents/concerns over BGP
   table entries to become too large in the existing system [3]. There
   are proposals to upgrade Autonomous System number to 32-bit from
   16-bit to support the demand at the same time [4]. The challenge
   relies on how to make the transition smooth from IPv4 to a real IP
   world with least changes possible.

   The term "real IP environment" is referred to an environment where
   hosts in a customer network will possess globally unique IP addresses
   and communicate with the rest of the world without the help of



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   NAT[5]. This document reflects changes required with the BSD 4.4
   source code where ever applicable.

. Background

   Existing system is in work with Autonomous System (AS) and inter-AS
   layer with the approach of CIDR. In order to meet the need within the
   32-bit address space, Autonomous Systems of various sizes maintain
   CIDR based hierarchical architecture. With the help of NAT [5], a
   stub network can maintain an user ID space as large as a class A
   network and can meet its useful need to communicate with the rest of
   the world with very few real IP addresses. With the combination of
   CIDR and NAT applied in the entire space, most of the part of 32-bit
   address space gets effectively used as network ID. If the same gets
   continued with a larger network ID, load in the switches will become
   too high.

   With traditional CIDR based hierarchy, a node of higher prefix can be
   divided into number of nodes with lower prefixes. Each divided node
   can further be subdivided with nodes of further lower prefixes. This
   process can be continued till no further division is possible. The
   point worth noting is at each point the designer of the network has
   to preconceive the future expansion of the network with the concept
   in the mind that the resource can not be exhausted at any point of
   time. This phenomenon leads the designer to allocate resources much
   higher than whatever is needed which leads to a space of unused
   address space and the concept of H-D (host-density) ratio comes into
   play. The problem gets aggravated once resource gets exhausted by any
   chance. e.g. a node of prefix /16 can be divided with a number of
   nodes of prefixes /24. If any one of the nodes /24 gets exhausted,
   resources of other nodes of prefixes /24 can not be used even if they
   are available.

   In IPv4 environment, there is a desperate attempt of the service
   providers to provide internet services with the help of NAT. e.g. a
   large educational institute meets its current requirement with 4 real
   IP addresses; one for its mail server, one for its web server, one
   for its ftp server and another one for its proxy server to provide
   web based services to all of its users. These four types of services
   are used by any organization of any size(it may be 400 or even
   40000). In the current provider network these organizations are
   supported their need with 4 IP addresses and the CIDR based tree has
   been built using these components together. When private IP will be
   replaced with real IP, each customer network will require IP
   addresses based on its size and requirement. Transitioning to real IP
   space with provider assigned addresses with CIDR based approach
   itself without reorganization of the existing provider network may
   not be a difficult task. This will continue with all the problems



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   associated with routing and problems related to distribution. Mesh
   structured hierarchy is convenient to reduce the routing overhead as
   well as for distribution of network resources in a suitable manner in
   the long run.

. A Three-tier mesh structured hierarchical network

   As Autonomous Systems of various sizes are supported, Autonomous
   Systems and the nodes inside the Autonomous Systems can be viewed as
   graphically lying on the same plane within the address apace. If
   network can be viewed as lying on different planes, routing issues
   can be made simpler. If network is designed with a fixed length of
   prefix for the Autonomous System everywhere, routing information for
   the rest will get confined with the other part of the network prefix.
   Which means the maximum size of AS gets assigned to all irrespective
   of their actual sizes. This can be made possible with the advantage
   of using a large address space and dividing it into number of regions
   of fixed sizes inside it. Thus entire network can be viewed as a
   network of inter-AS layer nodes. Each node in the inter-AS layer can
   act either only as a router in the inter-AS layer or as a router in
   the inter-AS layer with an Autonomous System attached to it with a
   single point of attachment or as an Autonomous System with multiple
   Autonomous System border routers (ASBR) appearing like a mesh. Thus
   two tier mesh structured hierarchy gets established between AS layer
   and inter-AS layer with each AS having a fixed length of prefix.

   Based on the definition of Autonomous System, it is a small area
   within the entire network that maintains its own independent identity
   that communicates with the rest of the world through some specific
   border routers. In the similar manner, if a larger area (say region
   or state) can be considered as network of Autonomous Systems, that
   can maintain its own identity by communicating with the rest of the
   world through some border routers (say, state border router), mesh
   structured hierarchy can be established within the inter-AS layer.
   The inter-AS layer will be split into inter-AS-top and inter-AS-
   bottom. To maintain this hierarchy, each node of inter-AS-top needs
   to have multiple regional or state border routers (say, SBR) through
   which each one will communicate with the rest of the world in the
   similar manner an Autonomous System maintains ASBR. Thus, entire
   network will appear as a network of nodes of inter-AS-top layer. To
   maintain hierarchy, each node of the inter-AS-top needs to have a
   fixed length of prefix. i.e. each node of the inter-AS top will be
   assigned a maximum (fixed) number of nodes of Autonomous Systems.

   Thus, with three-tier mesh structured hierarchy in the network layer,
   network ID can be viewed as A.B.C. If pA, pB and pC be the prefix
   lengths of inter-AS-top, inter-AS-bottom and AS layers respectively,
   there will be 2^pA nodes at the topmost layer, 2^pB at the inter-AS-



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   bottom layer and 2^pC nodes at the AS layer. Thus the entire space
   gets divided into a fixed number of regions and each region gets
   divided into fixed number of sub regions. This division is supposed
   to be made based on geography, population density and their demands
   and related factors.

   Let nMaxInterASTopNodes be the possible maximum number of nodes
   assigned at the top most layer and nMaxInterASBottomNodes be that at
   the inter-AS-bottom layer and nMaxASNodes at the AS layer. Where
   nMaxInterASTopNodes <= 2^pA and nMaxInterASBottomNodes <= 2^pB and
   nMaxASNodes <= 2^pC.

3.1. Route propagation

   With hierarchy established, routing information that gets established
   inside a node of inter-AS-top, does not need to be propagated to
   another node of inter-AS-top. Entire routing information of inter-AS-
   top layer needs to be propagated to inter-AS-bottom layer. So, each
   router of inter-AS layer will have two tables of information, one for
   the inter-AS-top and another for the inter-AS-bottom of the inter-AS-
   top node that it belongs to. BGP (with little modification) will work
   very well with a trick applied at the SBRs. Each SBR will not
   propagate the routing information of inter-AS-bottom layer of its
   domain to another SBR of neighboring domain. i.e. SBR of one top
   layer node will propagate routing information only of inter-AS-top
   layer to SBR of another top layer node. Inside a node of inter-AS-
   top, routing information of inter-AS-top and inter-AS-bottom need to
   be propagated from one ASBR to another neighboring ASBR. Inside a top
   layer node A, routing information of another top layer node B will
   have two parts; one for the list of SBRs through which a packet will
   traverse from top layer node A to B and another for the list of ASBRs
   through which the packet will traverse from one AS to another inside
   A. In terms of BGP, AS_PATH attribute will be split into two parts;
   one for the information of the top layer and another for the bottom
   layer. Within the same node A routing information of one AS to
   another AS will not have any top layer information. i.e. the top
   layer information will be set to as NULL.

   Similarly, each node of the AS layer will have three tables of
   routing entries. One for the inter-AS-top, one for the inter-AS-
   bottom and another for the routing information inside the Autonomous
   System itself.

   Introduction of hierarchy at the inter-AS layer reduces the size of
   the routing table substantially. With the availability of hardware
   resources if flat address space is maintained at each layer, problems
   related to CIDR can be avoided. With flat address space, no
   hierarchical relationship needs to be established between any two



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   nodes in the same layer. So, all the nodes inside each layer can be
   used till they get exhausted. With flat address space (i.e.  without
   prefix reduction), BGP tables will have maximum nMaxInterASTopNodes +
   nMaxInterASBottomNodes entries.

   IGP like OSPF has got provision to divide AS into smaller areas. OSPF
   hides the topology of an area from the rest of the Autonomous System.
   This information hiding enables a significant reduction in routing
   traffic. With the support of subnetting, OSPF attaches an IP address
   mask to indicate a range of IP addresses being described by that
   particular route. With this approach it reduces the size of the
   routing traffic instead of describing all the nodes inside it, but
   introduces another level of hierarchy. If subnetting concept can be
   avoided from the AS layer(with the additional overhead of computation
   inside the SPF tree), each area can be configured from a free pool of
   addresses based on its requirement dynamically. So, an AS can be
   divided into number of areas of heterogeneous sizes with the nodes
   from a free pool of address space.

   Similarly, the concept of area can be introduced in the inter-AS-
   bottom layer the way it works in OSPF. The area border routers in the
   inter-AS-bottom layer have to behave exactly in the similar manner
   the way an ABR behaves in OSPF.  i.e. an area border router will hide
   the topology inside an area to the rest of the world and will
   distribute the collected information inside the area to the rest. It
   will distribute the collected routing information from outside to the
   nodes inside as well. In order to implement this, protocol running in
   the inter-AS layer (say BGP) will have to introduce a 'cost' factor.
   This cost factor can be interpreted as the cost of propagation of a
   packet from one AS to another. The protocols running inside AS layer
   (RIP/OSPF, etc) will have to the supply the cost information for a
   packet to travel from one ASBR to another. All the protocols must
   behave in unison for supplying this information. The cost factor is
   needed for a remote node while sending a packet to a node inside an
   area while more than one area border routers are equidistant from
   that remote node. Thus inter-AS-bottom layer (i.e. one inter-AS-top
   level node) can be divided into number of areas of heterogeneous
   sizes with nodes of AS from a free pool of address space. BGP adopts
   a technique called route aggregation. Along with route aggregation it
   reduces routing information within a message. In the similar manner,
   introduction of area inside inter-AS-bottom layer will not only
   reduce the complexity of the protocol, but will reduce the size of a
   BGP packet substantially.

   With this architecture, each node(router) inside an AS is represented
   as A.B.C.  Each node may or may not be attached with a network which
   acts as a leaf node (i.e. a network will not act as a transit). In
   order to make use of user-id space properly and to support customer



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   networks of heterogeneous sizes, the user-ID space needs to be
   divided as subnet-ID and user-ID. Profoundly, a VLSM (variable length
   subnet mask) type of approach has to be adopted at each node of an
   AS. So, each node of the AS layer will act as the root of a tree
   whose leaves are independent small customer networks which will act
   as stub. As the routing information of inter-AS layer as well as AS
   layer need not be passed inside any node of the VLSM tree, each
   router inside the tree should maintain default route for any address
   outside of its network. With this approach, load on each router of
   the service providers will become negligible. Protocols that supports
   VLSM with MPLS/VPN has to be implemented inside the tree (inside the
   VLSM tree, all the physical ports of a switch have to be configured
   with the subnet mask. So, mere MPLS on top of static routing table
   should do the rest).

   The fundamental assumptions based on which this architecture lies can
   be summarized as follows:

   i) Entire network can be viewed as a network of regions or states
   where each region or state can have its own identity by communicating
   with the rest of the world through some state border routers. Each
   region or state is a network of Autonomous Systems. Each region as
   well as each Autonomous System inside them will have a fixed
   (maximum) length of prefix.

   ii) Availability of hardware resources is such that flat address
   space can be maintained at the inter-AS layer.

   Introduction of mesh-structured hierarchy will have several
   advantages:

      o  Load at each router will get reduced substantially.
      o  Concept of CIDR style approach and complexity related to
           prefix reduction can be easily avoided.
      o  Mesh structured hierarchy will make traffic evenly distributed.
      o  Physical cable connection can be optimized.
      o  Administrative issues will become easier.

3.2. Determination of prefix lengths

   With this architecture, IP address can be described as A.B.C.D where
   the D part represents the user id. Each router in the inter-AS layer
   will have two tables of information, one for the inter-AS-top and
   another for the inter-AS-bottom of the inter-AS-top node that it
   belongs to. Whereas, each node of the AS layer will have three tables
   of routing entries; one for the inter-AS-top, one for the inter-AS-
   bottom and another for the routing information inside the Autonomous
   System itself. In the worst case. a node inside an AS needs to



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   maintain nMaxInterASTopNodes + nMaxInterASBottomNodes + nMaxASNodes
   entries in its routing table.

   The dynamic nature of allocating an area from a free pool of address
   space is more frequent at the AS layer than at the inter-AS-bottom
   layer. As OSPF supports all the features needed, it can be considered
   as default choice in the AS layer.  Existing implementation of OSPF
   (Version 2) supports subnetting, by which an entire area can be
   represented as a combination of network address and subnet mask. With
   this approach, entire routing table gets reduced substantially.  With
   the removal of subnetting, all the nodes inside an area will have an
   entry inside the routing table (OSPF Version 1). So the deterministic
   factor is what is the maximum number of nodes inside an AS OSPF can
   support once subnetting support gets removed. So the prefix length of
   AS layer will be determined by this factor of OSPF.

   With the introduction of hierarchy in the inter-AS layer, number of
   entries in the BGP routing table will get reduced substantially. Even
   if pA and pB both are selected as 16, number of routing entries come
   within the admissible range of existing BGP protocol. But, it is the
   responsibility of IANA to come out with a scheme how
   nMaxInterASTopNodes and nMaxInterASBottomNodes are to be selected.
   Each top level node will have nMaxInterASBottomNodes nodes. It will
   be a waste of address space if each country gets assigned a top level
   nodes (e.g. china has got a population of 1,306,313,800 people where
   as Vatican City has got only 920 according to a census of 2006). So a
   moderate value of nMaxInterASBottomNodes is desirable, with which
   larger countries will have a number of top level nodes. e.g. each
   state of USA can be assigned a top level node. With the introduction
   of area in the inter-AS-bottom layer, each top level node can be
   divided into number of areas of heterogeneous sizes. So, a group of
   neighboring countries with less population can share the address
   space of a top level node. Similarly, user-id space has to be decided
   based on the largest area VLSM tree should be spanned through. All
   these issues are completely geo political and have to be decided by
   IANA.

3.2.1. A pseudo optimal distribution of prefixes in a 64bit architecture

   In order to have optimal use of cable connections, length of the VLSM
   tree is expected to be as short as possible. Also any single
   organization may prefer to have its user id space to be under the
   same network id. So, a 16bit user-id may become insufficient for
   places like large university campus, where as 32bit will become too
   large. Hence, 24bit user-id will be a moderate one which is the class
   A address space in IPv4 (also used as the space for private IP). As
   published in 1998 [6], OSPF can support an area with 1600 routers and
   30K external LSAs. So, 11 bits are needed to support this space. With



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   the assumption that OSPF can support much more address space with the
   advancement of hardware technology as well as to keep the space open
   for future expansions, 12 bits are assigned for the AS layer. 16 bits
   are assigned for the inter-AS-bottom layer. So, if on the average,
   16bit equivalent space gets used within the user-id space (i.e. one
   out of 256) and 8bit equivalent nodes gets used inside an AS (16% of
   1600), for a top level node (with 16bit equivalent AS nodes), it will
   generate 2^40 IP addresses, which will give 8629 IP addresses per
   person in Japan (with a population of 127417200; Japan is at the 10th
   position from the top in the population list of the world). So, even
   if all the countries with population less than or equal to Japan are
   assigned a top level node and all the provinces/states of countries
   with larger population are assigned a top level node each, total
   number of nodes will come well under 1024. If a number of neighboring
   countries with lesser population shares a top level node, total
   number of top level nodes will come down further.  This suggests that
   62 bit equivalent (10(pA)+16(pB)+12(pC)+24(user-id)) space will be
   good enough for unicast addresses. This distribution expects OSPF to
   support 65K (64K+1K) external LSAs.

   64bit address space may be divided into two 63bit blocks as follows:

   i. Global unicast addresses with the most significant bit set to 0.
   This space is equally divided into provider assigned (PA) address
   space with prefix 00 and provider independent (PI) address space with
   prefix 01. Provider independent address space will be used for the
   customers who would like to retain their number even after changing
   their providers. As routing will be based on PA addresses, each PI
   address will be associated to at least one PA address. Section 4
   describes issues related to PI addressing in detail.

   ii. Address space with the MSB set to 1 will be distributed within
   the rest. Each of them will have a fixed prefix which will be
   determined with the consultation with IANA.  This distribution will
   be based on the requirements and the work that have already been done
   in connection to IPv6 along with the following requirements:

   a) Router address space: Any node in the router address space will be
   designated with a prefix followed by A.B.C.router-id.

   b) Address space for multicasting:

   c) Address space for private IP: A 32 bit address space should be
   good enough for private IP.

3.2.2. Whether to go for a two-tier or three-tier hierarchy

   Establishment of hierarchy in the inter-AS layer reduces the size of



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   BGP entries to a great extent, but leads to an improper use of
   address space due to geo-political reason. If hierarchy in the inter-
   AS space gets removed, entire 26bit (10+16) space will be available
   for a single layer and use of inter-AS space will be true to its
   sense, but will increase external LSA (and/or number of entries in
   the BGP table) dramatically. So, it depends on to what extent OSPF
   can support external LSAs. BGP expects the packet length to be
   limited to 4096 bytes. BGP manages to make it work with this
   limitation with the concept of prefix reduction in the CIDR based
   environment.  As the number of inter-AS nodes increases, BGP has to
   change this limit in order to make it work in flat address space. The
   alternate will be to divide the inter-AS space into number of areas
   as defined in section 2.1. The area border routers will advertise the
   aggregated information to the rest of the world. BGP may have to
   incorporate both the options at the same time.  As the number of
   nodes in the inter-AS layer increases, in order to reduce the number
   of entries in the routing table, inter-AS space has to be split into
   two separate planes.  So, two-tier hierarchy can be considered as an
   interim state to go for three-tier hierarchy.  If it so happen that
   current available data is good enough to support the present need, it
   will be worth to look for to what extent it can support in the
   future. Assignment of inter-AS nodes in two-tier hierarchy should be
   based on the geographical distribution as if it is part of three-tier
   hierarchy.  Otherwise, introduction of three-tier hierarchy in the
   future will become another difficult task to go through. Based on the
   report of year 2011, BGP supports ~400,000 entries in the routing
   table. With this growing trend, BGP may have to change the limit of
   packet length even in a CIDR based environment. With the introduction
   of two-tier hierarchy, number of entries in the routing table will
   come down drastically and with the three-tier approach, it will come
   down further.

3.3. Issues related to Satellite communications

   Establishment of hierarchy in the inter-AS layer expects the only way
   any two autonomous systems in two different top level nodes
   communicate is through their SBRs. If two autonomous systems inside
   the same top level node communicate through satellite, it will be
   considered as a direct link between them. Whenever autonomous system
   'ASa' of top level node 'A' communicates with autonomous system 'ASb'
   of top level node 'B' through satellite, they have to go through
   their state border routers. i.e.  satellite port inside 'A' that
   communicates with a satellite port inside 'B' will be considered as
   state border router. If multiple such ports exists inside node 'A',
   all of them will be equidistant from any port inside 'B'.  Which
   expects any satellite port inside 'B' to have prior knowledge of list
   of autonomous systems that will be under the purview of any port
   inside 'A'. So, all the satellite ports of 'A' have to exchange such



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   group of information with all the satellite ports of 'B' and vice
   versa.  These group of autonomous systems can be considered as a
   cluster of autonomous systems inside an area of a top level node. If
   number of such ports is small, some heuristics can be applied while
   assigning AS numbers in order to reduce the processing time during
   the circuit establishment phase.  It will become difficult to
   maintain such heuristics once the number of such ports becomes large.
   So, in case of satellite communication, the advantage of establishing
   hierarchy inside inter-AS layer diminishes as the number of satellite
   ports increases. If any private corporate maintains its own satellite
   channel to communicate between its offices at distant locations, all
   of these offices are going to be considered as under the user-id
   space of its network. Service providers that provide satellite
   services to the end-site customers, can operate in the usual manner
   as they will provide connection to customer networks which will act
   as stub.

. Provider Independent addressing, name services and multihoming

   Provider independent addressing can be conceived as naming a host
   with a number. It can be used by customer networks who would like to
   retain their number even after changing their service provider; also
   it is useful to designate a host uniquely if the customer network is
   multihomed. Just like in name services, as address corresponding to a
   name needs to be resolved first to initiate communication, the same
   is required for PI addressing. Each globally unique PI address will
   be associated to at least one global unicast provider assigned
   address. For a host with single interface, this number will be same
   as the number of service providers the customer network is associated
   with.

   As either source or destination or both may be multihomed, there
   could be multiple paths to communicate between two hosts. This is
   required both for name services as well as for PI addressing.

   A system call needs to be introduced to get the source address based
   on the destination address. If application program needs to use the
   destination address directly, it needs to use this system call.

   int getcommaddr(int sockfd, struct in_addr *dst, struct addr_pair
   *endpts);

   'addr_pair' holds the addresses of communication end points as
   follows:

   struct addr_pair {
       struct in_addr src;
       struct in_addr dst;



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   };

   'getcommaddr'[8] returns the number of source-destination pairs for
   communication; the field 'endpt' will hold the array of these
   addresses. The array will be in sorted manner based on the best
   possible route.  'sockfd' is used to get the 'type of service'
   assigned. So, an application program needs to set its type of service
   before using this call.

   'getcommaddr needs to call a routine 'getmappedaddr' to resolve the
   mapped provider assigned addresses of a provider independent address.

   int getmappedaddr(struct in_addr *piaddr, struct in_addr *mpiaddr);

   'getmappedaddr' will return number of mapped addresses and 'mpiaddr'
   will hold their values.

   Users may use name instead of IP address to reach the destination.  A
   new system call needs to be introduced 'gethostbynamewithsrcaddr',
   which is an extension to 'gethostbyname' as follows:

   struct hostent *gethostbynamewithsrcaddr(int sockfd,const char *name,
                  int *nroutes, struct addr_pair *endpts);

   'gethostbynamewithsrcaddr'[8] takes 'name' and 'sockfd' as input
   parameters and finds out the best possible route to reach the
   destination. It returns the pointer to the 'hostent' structure as
   returned by 'gethostbyname' system call.  The parameter 'nroutes'
   gets the number of possible routes to be used and the corresponding
   source and destination addresses gets assigned to 'endpts' in sorted
   manner. 'sockfd' is used to get the 'type of service' assigned. So,
   an application program needs to set its type of service before using
   this call.

   An application program needs to use these source addresses from the
   top (i.e. the 0th) to establish connection with the destination. It
   needs to bind source address 'src' and then connect with the
   destination address 'dst'.

4.1. PI address Resolution

   This section tries to come up with a solution for PI address
   resolution with the approach of DNS[7] with necessary differences.
   Just like name space in DNS, entire address range with prefix 01 will
   be the address space used by PI addresses. Servers that will hold the
   information of mapping between PI addresses and corresponding PA
   addresses will be called as PIMapServers and the programs that will
   be used to resolve addresses will be called as PIMapResolvers.



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   In case of DNS where name is used in hierarchical format to resolve
   the addresses, PI address resolution will be based on the prefix of
   the PI address used for resolution.  The prefix is determined based
   on the architectural model used for the internet.  Based on the
   prefix information addresses of a list of servers can be found out
   that will act as regional servers which will be used to resolve
   mapped PA addresses corresponding to that PI address. A prefix will
   serve a fixed address space within entire PI address space. Address
   space belonging to a prefix will be distributed within customer
   networks of heterogeneous sizes. Address space allocation and the
   mapping of associated PA address(es) will be assigned by a regional
   authority. The regional authority will be fully responsible for the
   operation of regional servers in that region.

   Like DNS, there are some root servers which will have some fixed
   addresses, under which there are some prefixes which will act as top-
   level-domains. In case of CIDR based hierarchy, these prefixes may be
   of different prefix lengths which are selected based on the
   requirements. Each prefix in a top level domain can further be split
   into number of prefixes with the approach of CIDR. This tree
   structured hierarchy will be kept on growing till we get prefixes
   associated with regional servers. Each prefix associated with a
   regional server will be distributed amongst customer networks of
   various sizes as well as prefixes that will again be associated with
   some regional servers with the approach of CIDR. These regional
   servers can be considered as equivalent to  the authoritative name
   servers of DNS which are associated with zones. As stated earlier,
   prefixes starting with "00" will be assigned for provider assigned
   addresses and prefix starting with "01" will be assigned for provider
   independent addresses where as prefix starting with "1" will be
   assigned for addresses of all other types.

   As inherent hierarchy is involved in "Mesh Structured Hierarchy",
   this hierarchy goes up to two levels. As usual, there will be some
   root servers with fixed assigned addresses. Each root server will
   have prefixes with "01.A" that will act like top level domain. Under
   each top level domain, there will be entries with prefixes "01.A.B".
   Within a region "A.B", every global PA address is represented as
   "00.A.B.C.user-id". In order to support customer networks of
   heterogeneous sizes with the approach of VLSM, the "user-id" portion
   is further divided as "subnet-id.userid". So, the effective network
   prefix of a customer network in PA address space is "00.A.B.C.pa-
   subnet-id". Within an "A.B", entire PI address space with prefix
   "01.A.B" will be distributed within customer networks of
   heterogeneous sizes. So, effective network prefix of a customer
   network with PI address will be "01.A.B.pi-subnet-id". A particular
   prefix "01.A.B.pi-subnet-id" will be mapped to at least one provider
   assigned prefix of same prefix length.  For a multihomed customer



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   network within "A.B" that receives services from two service
   providers will have prefixes "00.A.B.C1.pa-subnet-id1" and
   "00.A.B.C2.pa-subnet-id2". A PI address prefix "01.A.B.pi-subnet-id"
   of same length will be mapped to both these prefixes of PA address
   space. Every region "A.B" will have regional server and backup
   server(s) with a maximum limit (say 4) with net addresses
   "00.A.B.server1", "00.A.B.server2", "00.A.B.server3" and
   "00.A.B.server4".

   Each PIMapServer will have a database of records that will have
   information to resolve PI addresses. In memory copy of a region will
   have an array of records where each record will have the following
   format.

   +------------+---------+------+-----+-------+-----------+
   | NetAddress | NetMask | Type | TTL | NAddr | Addr(1-4) |
   +------------+---------+------+-----+-------+-----------+

   First two fields "NetAddress/NetMask" represents the PI address range
   of a network. "Type" will be either Domain/Referral/Individual/
   SingleEntry/Default based on which a query and rest of the fields of
   a record have to be processed. A PI address can have maximum four
   mapped PA addresses. "Addr1", "Addr2", "Addr3", "Addr4" will hold the
   corresponding PA addresses and "NAddr" will hold the number of such
   addresses. The field "TTL" is a 32bit integer measured in seconds
   which will hold same meaning and approach as defined in the
   specification of DNS[7]. When a server receives a query for an
   address "X", it extracts the record of the network based on
   "NetAddress/NetMask" and "X" from its database. If no matching record
   is found, a negative response is sent. Based on the "Type" of the
   record, the query is processed in the following manner.

   Type=Domain:

   This is the most common type. If a customer network would not like to
   maintain a map server opts for this option. In this case there will
   be one to one mapping between a PI address and corresponding PA
   addresses. The fields "Addr1"/"Addr2"/"Addr3"/"Addr4" will hold the
   PA Net Addresses corresponding to the PI address of the network.
   Server will send the matching record to the resolver with
   Type=Domain. Resolver will extract the user-id portion of "X" and
   find the corresponding mapped PA addresses based on
   "Addr1"/"Addr2"/...etc.

   Theoretically, "A.B" portion of a PI address need not match with the
   "A.B" portion of the corresponding PA addresses. Consider a large
   corporate that has its corporate office and a branch office within
   the same region of a particular "A.B" and some other offices with



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   different values of "A.B". The corporate can maintain a contiguous
   range of PI addresses for the ease of its operation. It needs to
   split entire PI address range based on its offices and assign the
   corresponding PA addresses. In order to minimize the path of a query
   it is desirable that "A.B" of a PI address and its corresponding
   mapped PA addresses belong to the same region.

   Type=Referral:

   This is used when an address within the domain "NetAddress"/"NetMask"
   has to be processed by another map server. The map server may itself
   be another regional server or a server within a customer network.

   When a customer network would like to have a direct control for the
   mapping of its addresses it needs to opt for this option.
   "Addr1"/"Addr2"/"Addr3"/"Addr4" of the database entry will hold the
   pointer to the information associated to each map server. "NAddr"
   will hold the number of map servers that can be referred. Information
   of each server will hold the following values: PI address of the map
   server + Number of PA addresses to reach the map server + PA
   addresses of the map server. Any one of these map servers need to be
   queried for further processing. A server may act either in recursive
   mode or in iterative mode based on its implementation just like in
   DNS. A large corporate may have different offices and each (or some
   of them) may maintain a map server based on their policies.

   When a server needs to handle a particular address separately, it
   needs to set "NetAddress" with that particular address and all the
   bits of "NetMask" will be set to "1". The "Type" field has to be set
   as "SingleEntry"(which is similar to the Type Address(A) in terms of
   DNS). If some of its addresses need to be handled separately but for
   the rest common rule may apply (like Type=Domain), records of the
   individual entries should be processed first and then for the rest.
   In these cases "Type" has to be set as "Default". So, a server of a
   customer network may have database entries with Type=Domain/Referral
   /SingleEntry/Default.  It makes sense for a server (or a master file)
   to have entries with Type=Default, but from the point of a resolver,
   it does not make any sense. So a server needs to extract the PA
   addresses and form a record with Type=SingleEntry and send it back to
   the resolver.

   For a host having multiple interfaces, each interface may be assigned
   PA addresses supplied by all the service providers, but it is
   desirable that PI address gets mapped to only one of them (preferably
   for a CE router, the interface which will have the shortest path will
   be mapped PI address with the PA address associated with that CE
   router).




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   Type=Individual:

   This is meant for the individual users opting for services like
   telephonic services that need to maintain PI address. With this
   option a mobile user may maintain its PI address after changing its
   service provider. A map server needs to maintain some networks with a
   range of PI addresses in its database. When a query for an address
   "X" is received, server needs to get the corresponding record where
   "Addr1" will hold the pointer to a open file descriptor (or pointer
   to the in memory copy) of a separate data file where there will be
   one to one mapping between PI address and its corresponding PA
   address of all the assigned PI addresses. These networks and
   assignment of individual PI addresses have to be done by the regional
   authority.

   As with Type=Default, Type=Individual does not make any sense to a
   resolver. So, server needs to extract PA address and form a record
   with Type=SingleEntry and send it back to the resolver.

   As stated above, this solution is based on the approach of DNS. For
   the ease of implementation and to make use of the existing source
   code related to DNS (e.g. BIND) most of the features have been taken
   from DNS. Where ever differences arise, the approach followed by this
   document has to be accepted.

   IANA has to assign a port (e.g. 53 in case of DNS) for its UDP/TCP
   based implementation.

4.1.1. Record Format

   Each record (the way they will appear in a master file or will be
   used for communication) will have the following format:

   NetAddress/NetMask + Type + <TTL> + RDATA (Type specific information)

   Record types are primarily the types of records as described above
   along with two other types SOA (Start of a zone of authority) and MPS
   (host with Type=SingleEntry that acts as a Map server for this zone).
   Types are defined as follows:

   Types               values          comments
   -----------------------------------------------------------
   SEN (SingleEntry)      1    same as type A(address) in DNS
   MPS (MapServer)        2    Map server
   DMN (Domain)           3
   DEF (Default)          4
   REF (Referral)         5
   SOA (Start of a zone)  6



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   IND (Individual)       7
   DFL (Data File)        8
   -----------------------------------------------------------

   RDATA of different types will appear as follows:

   Type=SOA:
   PI address of server+SERIAL+REFRESH+RETRY+EXPIRE+MINIMUM (meaning and
   values of SERIAL/REFRESH/RETRY/EXPIRE/MINIMUM are same as they were
   defined in section 3.3.13 of RFC 1035[11])

   Type=(SEN/MPS):
   NAddr(Number of addresses) + corresponding PA addresses

   Type=(DMN/DEF):
   NAddr(Number of addresses) + corresponding Net addresses

   Type=REF:
   NAddr(Number of map server) + for each map server (PI address of map
   server + NAddr(Number of addresses of map server) + corresponding PA
   addresses))

   Type=IND:
   NAddr(=1) + full path name of the data file

   Type=DFL:
   Data file name + SERIAL + Number of records in the data file(unsigned
   long int)

   TTL value of a record has to be set to 0 if it is not relevant or to
   accept the value associated with the record of SOA.

4.1.2. Messages

   In order to support most of the features of DNS, message format has
   been retained almost same as that of DNS. So, all the relevant fields
   will be processed exactly in the same manner as that have been done
   in DNS and all the irrelevant issues have to be ignored. Rest of this
   section describes where and how changes have to be made.

   As defined in RFC 1035, the top level format of message is divided
   into 5 sections (some of which are empty in certain cases) shown
   below:

       +---------------------+
       |        Header       |
       +---------------------+
       |       Question      | the question for the name server



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       +---------------------+
       |        Answer       | answering part of the question
       +---------------------+
       |      Authority      | authoritative map server
       +---------------------+
       |      Additional     | additional information
       +---------------------+

   The header section has been retained as defined in RFC 5395[12] as
   follows:

        0  1  2  3  4  5  6  7  8  9  10 11 12 13 14 15
       +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
       |                      ID                       |
       +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
       |QR|   OpCode  |AA|TC|RD|RA| Z|AD|CD|   RCODE   |
       +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
       |                QDCOUNT/ZOCOUNT                |
       +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
       |                ANCOUNT/PRCOUNT                |
       +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
       |                NSCOUNT/UPCOUNT                |
       +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
       |                    ARCOUNT                    |
       +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+

   The question section will have two parts:
   QType(one octet unsigned int)+QData.

   Query types are defined as follows:

   QTypes       values          comments
   -----------------------------------------------------------
   SEN            1    query for mapped PA address
   SOA            6    query information related to SOA
   DF             7    query information related to data file
   DFXFER         249  data file transfer
   DFIXFR         250  incremental data file transfer
   IXFR           251  incremental authoritative data file xfr
   AXFR           252  authoritative data file transfer
   -----------------------------------------------------------

   QData will hold values based on QType.

   Following section describes issues related to QType=SEN.  Issues
   related to all other QTypes (i.e. related to file transfer) will be
   discussed afterwords.




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   For QType=SEN(1): QData=PI address that needs to be resolved.

   The answer section, authority section and additional section will
   have a number of resource records where the number will be specified
   in the header.

   On receiving a query, map server will return the matching record from
   its database.  If response is address, the answer section will hold
   the record of any one of these two types: SEN/DMN.

   If Type=DMN, resolver needs to extract the mapped addresses as
   described in section 4.1.

   If Type=DMN, entire address range will appear in the form of
   NetAddress/NetMask. This will have advantages while catching data for
   any particular address, but getting the information of the entire
   address range.

   If the response is referral, answer section will be empty and the
   authoritative section will hold the record with Type=REF.

   If server supports recursion, for each iterative process that it
   receives a record with Type=REF, it needs to push the record to the
   additional section of the message that needs to be sent to the
   resolver. So, additional section will hold the records of Type=REF of
   the chain of the tree through which PA addresses have been resolved.

4.1.3. Master file and data file

   Section 5 of RFC 1035 states:

   "Master files are text files that contain RRs in text form.  Since
   the contents of a zone can be expressed in the form of a list of RRs
   a master file is most often used to define a zone, though it can be
   used to list a cache's contents."

   Section 5.1 of RFC 1035 states:

   "The format of these files is a sequence of entries.  Entries are
   predominantly line-oriented, though parentheses can be used to
   continue a list of items across a line boundary, and text literals
   can contain CRLF within the text.  Any combination of tabs and spaces
   act as a delimiter between the separate items that make up an entry.
   The end of any line in the master file can end with a comment.  The
   comment starts with a ";" (semicolon)."

   Master files follow the same approach and format in the line of DNS
   as described in section 5 of RFC 1035 with necessary differences.



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   An example master file may look like as follows:

   @ "PI NetAddr"/"Net Mask"  SOA  "PI address of primary server" (
                                    20     ; SERIAL
                                    7200   ; REFRESH
                                    600    ; RETRY
                                    3600000; EXPIRE
                                    60)    ; MINIMUM
   "PI NetAddr"/"Net Mask"    MPS  0  NAddr "PA addresses"
   "PI NetAddr"/"Net Mask"    SEN  0  NAddr "PA addresses"
   "PI NetAddr"/"Net Mask"    DMN  0  NAddr "Net addresses"
   "PI NetAddr"/"Net Mask"    DEF  0  NAddr "Net addresses"
   "PI NetAddr"/"Net Mask"    IND  0  NAddr(=1) "Data file name"

   A data file contains a sequence of entries where each entry appears
   in a separate line. Each entry is a mapping between a PI address and
   its associated PA address separated by space(s). Entries are
   generally sorted with PI address.  As in case of master file comments
   can be inserted with the start of a ";" (semicolon) that will end at
   the end of the line.  Data files are commonly associated with the map
   servers maintained by regional authority, but they are not generally
   associated with the map servers maintained by individual customer
   networks.

   A map server may have a number of data files. These files have to be
   defined in another file (a supporting file, the way boot file
   "named.boot" is used in BIND) that will have information of each of
   them. An entry in that file will follow the same format of a record
   (Type=DFL) and will have the following fields:

   "PI NetAddr"/"NetMask" TTL(0) "Data File Name" SERIAL "Number of
   records".

   This file will be used to process message with QType=DF which will be
   used to support data file transfer/incremental data file transfer.

   For QType=DF(7):  QData="PI NetAddr"/"NetMask" of the desired network
   For QType=SOA(6): QData="PI NetAddr"/"NetMask" of the desired zone

   A map server will return a record of Type=DFL on receiving a query
   with QType=DF where as it will return a record of Type=SOA on
   receiving a query with QType=SOA.

4.1.4. Zone maintenance and transfers

   Section 4.3.5 of RFC 1034 states:

   "The general model of automatic zone transfer or refreshing is that



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   one of the name servers is the master or primary for the zone.
   Changes are coordinated at the primary, typically by editing a master
   file for the zone.  After editing, the administrator signals the
   master server to load the new zone.  The other non-master or
   secondary servers for the zone periodically check for changes (at a
   selectable interval) and obtain new zone copies when changes have
   been made.

   To detect changes, secondaries just check the SERIAL field of the SOA
   for the zone.  In addition to whatever other changes are made, the
   SERIAL field in the SOA of the zone is always advanced whenever any
   change is made to the zone."

   Zone maintenance and transfer will follow same approach as DNS.

   Processing of AXFR will have the same approach as DNS followed by
   DFXFER for all the data files. Frequency of update of data files will
   be high compared to the frequency of update of Master file. Changes
   in data files will follow NOTIFY followed by DFIXFR. Transfer of data
   files will follow the same approach followed for master file in DNS.

. Issues related to IP mobility

   An interface of a customer network may have several IP addresses
   (e.g. for a multihomed customer site, each interface will have
   multiple global unicast addresses also it may have private
   addresses). For a mobile node that has been moved to a customer
   network which gets service from a service provider and maintains
   private IP addresses, will have at least three IP addresses; provider
   assigned unicast address, private address and its permanent "Home
   Address". The "Home Address" will be aliased with the provider
   assigned address (i.e. the co-located care-of address). So the
   interface structure needs to have an additional field to hold the
   value of care-of address. The PCB structure will have an additional
   field 'inp_lcladdr'.  So 'inp_lcladdr' will have the current provider
   assigned address that a foreign node needs to use for communication.
   The field 'inp_laddr' that is used to hold the value of local address
   will hold the value of "Home Address" of a mobile node. Similarly,
   PCB needs to introduce another field 'inp_fcladdr' to support the
   destination address to be mobile.  The existing field 'inp_faddr'
   which is used to address a foreign address will hold the value of
   "Home Address" of the mobile node. Customers with PI address who
   would like to have mobility support, the mapped address will be
   considered as the "Home Address" of the mobile node.

   An outgoing packet from a mobile node in a foreign site needs to be
   stacked with the associated care-of address. While initiating
   communication, the 'bind' system call needs to go through the



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   interface list and fetch the associated structure to check whether
   the source address is aliased or not and needs to fill the value of
   'inp_lcladdr' of PCB accordingly.

   When TCP receives a SYN for connection establishment, it allocates a
   PCB and assigns the values for 'inp_laddr', and related fields.
   During this phase, TCP also needs to check whether the local address
   is aliased or not (based on the fields of interface structure; which
   is applicable for a mobile node at foreign site) and needs to fill
   the values of 'inp_lcladdr' accordingly. Similarly if destination
   address is found to be aliased, based on the stacking type, it needs
   to fill up the field 'inp_fcladdr'.

   IP address stacking can be performed with the approach introduced in
   section 6.4 of RFC6275[9]. RFC6275 talks about the stacking of IP
   addresses for a destination address (Let us call it as type 0
   stacking). Two more types of stacking need to be introduced; type 1
   stacking where only source address will appear in the stack and type
   2 stacking where both source address and destination address will
   appear in the stack with a particular type of ordering.

   Protocol output routine like 'tcp_output' or 'udp_output' needs to
   fill the IP packet in the following manner.

   If the socket contains a valid 'inp_lcladdr', use 'inp_lcladdr' as
   the source address and 'inp_laddr' will appear in the stack. If the
   socket contains a valid 'inp_fcladdr' use 'inp_fcladdr' as the
   destination address and 'inp_faddr' will appear in the stack. If only
   'inp_fcladdr' contains a valid address where as 'inp_lcladdr' is
   NULL, use type 0 stacking. If only 'inp_lcladdr' contains a valid
   address where as 'inp_fcladdr' is set as NULL, use type 1 stacking.
   If both 'inp_lcladdr' and 'inp_fcladdr' contains valid addresses, use
   type 2 stacking.

   Protocol input routine like 'tcp_input' or 'udp_input' needs to
   process the packet in the reverse order based on the type of
   stacking.  For type 0 stacking, use the address in the stack as the
   destination address; for type 1 stacking, use the address in the
   stack as the source address; for type 2 stacking use both source
   address and destination address from the stack.

5.1. Changes expected with the specifications related to IP mobility

   RFC6275 demands correspondent node binding from mobile nodes for
   route optimization. This binding is required when a connection gets
   established as well as when the mobile node changes it address space.
   There are application like HTTP which opens up multiple connections
   on the run time which are very short lived. If mobile nodes need to



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   send binding messages for all the connections, network will be
   unnecessarily congested. This congestion can be avoided with the
   establishment of binding at the time of connection establishment
   itself.  So, if TCP server happens to be mobile, it will set the
   value of 'inp_lcladdr' in the stack while sending SYN+ACK. TCP client
   which initiates communication through 'connect' needs to set
   'inp_fcladdr' field on receiving TCP+ACK. With this approach
   correspondent node binding messages need to be sent only when a
   mobile node changes its position from one address space to another.

   Route optimization is not applicable to applications which are of
   multicast type.  In these cases packets need to be forwarded with the
   mechanism of reverse tunneling with the approach of "IP Encapsulation
   within IP" as defined in RFC2003.  In order to support packet
   delivery with route optimization method as well as with
   "Encapsulating Delivery Style" based on the application type the
   protocol control block needs to introduce another field
   'inp_hagentaddr' to hold the address of the home agent of the mobile
   node. The interface structure also needs to have same field. The
   'bind' system call needs to go through the interface list to fetch
   'inp_hagentaddr' to the PCB along with 'inp_lcladdr' as described
   earlier. So, protocol output routines like 'tcp_output', 'udp_output'
   need to fill up the packets based on the application type. In
   "Encapsulating Delivery Style" packets need to be formed in the
   following manner.

   The inner IP header will contain
      Source Address: Home address of the mobile node
      (i.e. 'inp_laddr')
      Destination address: Address of the correspondent node
      (i.e. 'inp_faddr')
   The outer IP header will contain
      Source Address: co-located care of address of the mobile node
      (i.e. 'inp_lcladdr')
      Destination Address: Address of the home agent of the mobile node
      (i.e. 'inp_hagentaddr')
   Protocol field: IP in IP

. Refinements over existing IPv6 specification

   As IPv6 was envisioned long before some of the newer technologies
   e.g. MPLS came into picture, some refinements can be made over the
   existing specification. These considerations are related to bandwidth
   usages and performance inside switches. Experimental results show
   that smaller packet size gives better result for the processing of RT
   packets.  So, it is desirable to have IP packet header to be as small
   as possible.




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   As described earlier, evaluation of the parameters
   nMaxInterASTopNodes, nMaxInterASBottomNodes and nMaxASNodes is geo-
   political and have to be decided by IANA. Once these parameters are
   determined with mutual agreements, values of pA, pB, pC and prefix
   length of user id can be determined. With 64bit address space, IP
   header will be reduced by 16 bytes.

   The 'flow label' field of IPv6 packet header may not be of any use
   with MPLS is in use. ATM used to have 4 priority classes. The first
   specification of IPv6 RFC-1883 used a 4bit type of service field
   along with a 24bits flow label field. These two were modified to a
   8bit type of service field and a 20bit flow label field in the
   current spec RFC-2460.  Too many priority classes may increase
   complexities to process inside switches. If type of service field of
   IPv6 header may be reduced to be of 4bit length as it was stated in
   RFC-1883 and 'flow label' field gets removed, another three bytes may
   be reduced from the IPv6 header.

   The field 'Hop Limit' has got a 8bit value in the existing spec. The
   role of this field needs to be discussed properly with a large
   address space.

   RFC4862[10] introduces the concept of "Stateless auto configuration"
   with the goal in mind that no manual configuration is required by
   individual machines before connecting them to the network. It
   generates a link local address with a link-local prefix and the link
   address (e.g. Ethernet/E.164 for ISDN) first. This link local address
   is used to configure global unicast address and any other
   configurable parameters based on router advertisement.  Global
   unicast addresses are generated by the prefix supplied by the router
   advertisement and the link specific interface identifier. This
   identifier can be as large as 64 bit length. So irrespective of the
   size of the network (it may be 10000 or 100 or even less than that)
   every customer network will consume a 64bit equivalent addresses.
   This seems to be a huge blunder. What is expected is the length of
   the interface identifier is equivalent to support the number of nodes
   supported by that subnet. In order to achieve this the router itself
   or a server in that subnet needs to maintain a storage which will
   generate the interface identifier based on the request from
   individual hosts.  It may be desirable that interface identifiers are
   generated from DHCP servers. With the option of generating interface
   identifier through DHCP, changes in the auto configuration process
   can be looked at as follows:

   From the point of view of a host, it can be considered as a two step
   process. Host needs to send Router Solicitations message to find out
   the presence of a router. Router Advertisement message should include
   an option field which will inform whether prefix information should



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   be configured through Router Advertisement or through DHCP.  Host
   needs to send a request message to get the interface identifier.  If
   both the information needs to be obtained from a DHCP server they can
   be obtained through a single message.

   From the server's point of view, it needs to maintain a database for
   a mapping of the link-layer address and subnet specific interface
   identifier. Lifetime of an interface identifier has to be processed
   in the usual manner the way existing DHCP implementation treats IP
   addresses.

   There seem to be another possible danger to obtain prefix information
   through Router Advertisement. As the Router Advertisement comes in
   the form of ICMP messages, once it is received by the ICMP layer, it
   looses information from which interface the message has been received
   (This problem arises for hosts that are having multiple interfaces
   and not all of them are attached to the same subnet).  So, auto
   configuration of a host has to be performed one interface at a time
   by making all other interfaces disabled. Once configuration of all
   the interfaces are done, all of them have to be enabled.

   If it is expected that hosts should reconfigure their addresses
   dynamically based on Router Advertisement message, Router
   Advertisement needs to generate a special message for a certain
   amount of time that needs to include old prefix and the corresponding
   new prefix in the message.

   In order to support multihoming[8], prefix information needs to
   include the fields 'default router' and 'next hop address' to reach
   the default router for each of the prefixes.

   In a 64bit architecture, link-local address can be formed with a
   link-local prefix and link-layer address in a suitable manner; say it
   can be formed with a 16bit link-local prefix followed by a 48bit
   link-layer address. For hardware that supports more than 48bit
   addressing (say E.164), the least significant 48bits may be
   considered to generate link-local addresses.

. Distributed processing and Multicasting

   With the inherent hierarchy involved in this architecture,
   distributed applications can also be structured in a suitable manner.
   Say, for a commonly used web based application a master level server
   will be there at every top level node. Any change that might happen
   in the application, has to be synchronized within these master level
   servers first. There might be servers at the middle layer (inside
   each inter-AS-bottom) inside each top level node. Once the changes
   get reflected at the master node, all the servers at the middle layer



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   needs to update themselves with their master level node. This will
   reduce network traffic substantially. Inherent hierarchy in the
   architecture will also help establishing multicast tree in the
   similar manner. Work on these issues can be progressed only after
   this architecture gets approved.

. Transition to real IP from private IP

   Both CIDR based hierarchy and Mesh structured hierarchy expects a
   VLSM tree at the bottom. In VLSM, in real IP space with provider
   assigned (PA) addresses, assignment of network resources has to be
   associated with the address space to be used with the type of
   service. Within a typical switch supporting multiple types of ports,
   a line card of strength OC48 can be replaced with 4 line cards of
   strength OC12. An OC12 card may also be replaced with 4 OC3 cards. An
   OC12 card may be attached to another switch with DS3 ports and so on.
   When it reaches to the customer network port density of a switch has
   to be directly proportional to the address block that a customer
   network will be assigned to. i.e. each customer network has to be
   assigned a block of address space (say, 128, 256, 512, 1K, 2K etc).
   Within the switch these ports have to be assigned net address/net
   mask the way VLSM works.

   In IPv4 environment, providers have provided services in terms of
   bandwidth of the ports say, 2 Mbps/4 Mbps/1 Gbps line etc. If these
   ports were assigned addresses based on the number of users of the
   customer network, transition from private IP to real IP is simple.
   Consider a switch that has supplied 2 Mbps line to a set of customers
   with number of users within 1K to 2k, each of them will be assigned a
   block of 2K each. But if number of users are not proportional to the
   bandwidth used, say same 2 Mbps line were used to customers of sizes
   1K, 2K 10K and 16K respectively reorganization will be needed if
   possible. This rearrangement may be possible within the switch itself
   or by connecting ports of appropriate sizes from different switch,
   otherwise each of them has to be assigned an address block of 16K
   each or with the way VLSM works whatever is suitable. So, address
   block assignment in the VLSM tree has to grow in a bottom up
   approach.

   Thus, transition of existing provider network without (or very
   little) rearrangement to a real IP space with CIDR based approach is
   apparently not a difficult job. In a CIDR based approach, sizes of
   the VLSM trees are heterogeneous that leads to number of routing
   entries to be very high. Mesh structured hierarchy is convenient to
   reduce the routing overhead as well as for distribution of network
   resources in a suitable manner in the long run. To covert CIDR based
   approach to Mesh structured hierarchy requires reorganization mainly
   in the routing domain and by splitting trees of very large sizes (>24



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   bit address space) at the top.

   Section 3.2.1 reveals that in Mesh structured hierarchy a 64bit
   architecture will be good enough for our need in a provider assigned
   (PA) address space; the same is true for CIDR based approach as well.

. IANA Consideration

   This is a first level draft for proposed standard. Hence, IANA
   actions should come into play at a later stage, if needed.

. Security Consideration

   This document does not include any security related issues.

. Acknowledgments

   The author would like to thank to Professor Amitava Datta of
   University of Western Australia for his review and constructive
   comments.

. Normative References

   []  Nordmark, E. and R. Gilligan, "Basic Transition Mechanisms for
        IPv6 Hosts and Routers", RFC 4213, October 2005.

   []  Fuller V., Li. T., "Classless Inter-Domain Routing (CIDR): The
        Internet Address Assignment and Aggregation Plan", RFC 4632,
        August 2006.

   []  Huston, G., "Commentary on Inter-Domain Routing in the
        Internet", RFC 3221, December 2001.

   []  Q. Vohra, E. Chen., "BGP Support for Four-octet AS Number
        Space", RFC 4893, May 2007.

   []  Srisuresh, P. and K. Egevang, "Traditional IP Network Address
        Translator (Traditional NAT)", RFC 3022, January 2001.

   []  J. Moy., "OSPF Standardization Report", RFC 2329, April 1998

   []  P.V. Mockapetris., "Domain names - concepts and facilities",
        RFC 1034, November 1987.

   []  S. Bandyopadhyay, "Solution for Site Multihoming in a Real IP
        Environment", <draft-shyam-site-multi-41> work in progress.

   []  C. Perkins, Ed., D. Johnson, J. Arkko, "Mobility Support in



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        IPv6" RFC 6275, July 2011.

   [] S. Thomson, T. Narten, T. Jinmei, "IPv6 Stateless Address
        Autoconfiguration", RFC 4862, September 2007.

   [] P.V. Mockapetris, "Domain names - implementation and
        specification", RFC 1035, November 1987.

   [] D. Eastlake 3rd, "Domain Name System (DNS) IANA
        Considerations", RFC 5395, November 2008.

. Informative References

   [] Postel, J., "Internet Protocol", STD 5, RFC 791,
        September 1981.

   [] Rekhter, Y., and T., Li, "A Border Gateway Protocol 4 (BGP-
        4)",RFC 1771, March 1995.

   [] Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6)
        Specification, RFC 1883, December 1995.

   [] Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998.

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

   [] Rosen, E., Viswanathan, A. and R. Callon, "Multiprotocol
        Label Switching Architecture", RFC 3031, January 2001.

. Author's Address

   Shyamaprasad Bandyopadhyay
   HL No 205/157/7, Kharagpur 721305, India
   Phone: +91 3222 225137
   e-mail: shyamb66@gmail.com















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