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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
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on December 12, 2017.
Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved.
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
carefully, as they describe your rights and restrictions with respect
to this document.
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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
1. 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.
2. 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.
3. 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.
4. 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.
5. 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
6. 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.
7. 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.
8. 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.
9. IANA Consideration
This is a first level draft for proposed standard. Hence, IANA
actions should come into play at a later stage, if needed.
10. Security Consideration
This document does not include any security related issues.
11. Acknowledgments
The author would like to thank to Professor Amitava Datta of
University of Western Australia for his review and constructive
comments.
12. Normative References
[1] Nordmark, E. and R. Gilligan, "Basic Transition Mechanisms for
IPv6 Hosts and Routers", RFC 4213, October 2005.
[2] Fuller V., Li. T., "Classless Inter-Domain Routing (CIDR): The
Internet Address Assignment and Aggregation Plan", RFC 4632,
August 2006.
[3] Huston, G., "Commentary on Inter-Domain Routing in the
Internet", RFC 3221, December 2001.
[4] Q. Vohra, E. Chen., "BGP Support for Four-octet AS Number
Space", RFC 4893, May 2007.
[5] Srisuresh, P. and K. Egevang, "Traditional IP Network Address
Translator (Traditional NAT)", RFC 3022, January 2001.
[6] J. Moy., "OSPF Standardization Report", RFC 2329, April 1998
[7] P.V. Mockapetris., "Domain names - concepts and facilities",
RFC 1034, November 1987.
[8] S. Bandyopadhyay, "Solution for Site Multihoming in a Real IP
Environment", <draft-shyam-site-multi-41> work in progress.
[9] C. Perkins, Ed., D. Johnson, J. Arkko, "Mobility Support in
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IPv6" RFC 6275, July 2011.
[10] S. Thomson, T. Narten, T. Jinmei, "IPv6 Stateless Address
Autoconfiguration", RFC 4862, September 2007.
[11] P.V. Mockapetris, "Domain names - implementation and
specification", RFC 1035, November 1987.
[12] D. Eastlake 3rd, "Domain Name System (DNS) IANA
Considerations", RFC 5395, November 2008.
13. Informative References
[13] Postel, J., "Internet Protocol", STD 5, RFC 791,
September 1981.
[14] Rekhter, Y., and T., Li, "A Border Gateway Protocol 4 (BGP-
4)",RFC 1771, March 1995.
[15] Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6)
Specification, RFC 1883, December 1995.
[16] Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998.
[17] Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6)
Specification", RFC 2460, December 1998.
[18] Rosen, E., Viswanathan, A. and R. Callon, "Multiprotocol
Label Switching Architecture", RFC 3031, January 2001.
14. 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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