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Summary of Ivip for the RRG final discussion and selection process
http://www.firstpr.com.au/ip/ivip/Ivip-RRG.html Robin Whittle 2009-12-17 (Typos and expression fixed 2009-12-18)
Ivip (pr. eye-vip, est. 2007-06-15) is a core-edge separation scheme
applicable to IPv4 and IPv6. It provides multihoming, portability of
address space and inbound traffic engineering for end-user networks of
all types: those with current PI space, those which need their own
address space but which can't afford PI space and networks or devices
(mobile devices) which need just a single IPv4 address or /64 of IPv6
Ivip's mapping system is based on fast-push of all mapping changes to
local (within the ISP or end-user network) full database query servers.
Consequently, ITRs reliably and quickly gain the mapping information they
need, and all traffic packets are tunneled to the correct ETR without
loss or significant delay.
In contrast to other core-edge separation schemes, Ivip's ITRs are given
a single ETR address for each range of mapped address space (which need
not be a binary-boundary subnet). Ivip ITRs do not need to test reachability
to ETRs because the mapping for a given range of address space is updated
for each ITR which needs it, in real-time - within a few seconds at most.
End-user networks are responsible for mapping changes and would typically
contract this function to specialized companies which monitor the
reachability of their ETRs and change the mapping to achieve multihoming
failure recovery and/or TE. So the mechanisms which choose the mapping
are directly controlled by the end-user networks, and are completely
separate from the core-edge separation scheme itself.
Ivip meets all the constraints imposed by the need for widespread
voluntary adoption .
ITRs can be dedicated devices, including servers or hardware-based
routers. The ITR function can be integrated into the sending host. 
Ivip-mapped end-user address space ("EID" in LISP terminology) can be
divided into separately mapped ranges, on IP address boundaries (IPv4)
or /64 boundaries (IPv6).
The global fast-push mapping distribution network has a structure like a
cross-linked multicast tree (although other methods could be used).
All mapping changes are sent to the full database Query Servers (QSDs) in
each ISP or end-user network which has ITRs. (Each such network would
typically have two or more QSDs, each with a different pair of mapping
feeds from different parts of the fast-push system.) Each mapping change
typically incurs a small fee, such as a few cents or tens of cents, which
will deter frivolous changes and help pay for much of the mapping
Compared to conventional unscalable BGP techniques, and to the use of
core-edge separation architectures with non-real-time mapping systems,
end-user networks will be able to achieve more flexible and responsive
inbound TE. If inbound traffic is split into several streams, each to
addresses in different mapped ranges, then real-time mapping changes can
be used to steer the streams between multiple ETRs at multiple ISPs - to
any ETR in the world.
Open ITRs in the DFZ (OITRDs, similar to LISP's PTRs) tunnel packets sent
by hosts in networks which lack ITRs. So multihoming, portability and
TE benefits apply to all traffic. Ivip-mapped space covering the address
needs of up to hundreds of thousands of end-user networks are contained
within a single BGP-advertised prefix. OITRDs around the Net advertise
such prefixes, gathering packets from non-upgraded networks to the
closest (in DFZ terms) OITRD. OITRDs are financed by traffic-based fees
payable by the end-user networks whose address is mapped. OITRDs are
operated directly or indirectly by the individual mapping distribution
organizations which collectively operate the global fast-push mapping
ITRs request mapping either directly from a local QSD or via one or more
layers of caching query servers (QSCs) which in turn request it from a
local QSD. (QSCs are not required, but will reduce the number of queries
made to each QSD.) QSDs remember which ITR or QSC requested mapping of a
range of end-user space. If, during the caching time of the mapping
reply, the QSD receives from the fast-push system a changed mapping for
this range of addresses, the QSD sends a mapping update to the one or
more ITRs or QSCs which requested this mapping. The QSCs likewise send
this update to whichever ITRs or QSCs requested this mapping. These
updates are secured by nonce sent in map request and will reach the ITRs
which need them a few tens of milliseconds after the QSD receives
the mapping change.
ETRs may be in ISP or end-user networks. IP-in-IP encapsulation is used,
so there is no UDP or any other header. PMTUD (Path MTU Discovery)
management with minimal complexity and overhead will handle the problems
caused by encapsulation, and adapt smoothly to jumboframe paths becoming
available in the DFZ. The outer header's source address is that of the
sending host - which enables existing ISP BR filtering of source
addresses to be extended to Ivip-encapsulated packets by the simple
mechanism of the ETR dropping packets whose inner and outer source
address do not match.
An end-user network would typically pay rent for their mapped address
space, which they could split dynamically into any number of individually
mapped ranges. They would also pay a fee per mapping update and fees for
the traffic their network brings through OITRDs. These services may be
provided by a single company. End-user networks would typically
subcontract control of the mapping of their address space to a specialized
company, perhaps the same as the one they rent their space from.
In addition, end-user networks pay one or more ISPs for Internet access.
They could use an ETR at the ISP, which could be shared by other end-user
networks. Alternatively, they could run their own one or more ETRs and
connect each one to the Net via a small amount of PA space provided by
their ISP - perhaps a single IPv4 address.
Ivip would be a good basis for the TTR approach to mobility . This
is a scalable approach to IPv4 and IPv6 mobility in which the MN keeps
its own Ivip-mapped IP address(es) no matter how or where it is
physically connected, including: on conventional PA or PI space, on an
address which is implemented via conventional Mobile IP techniques or
on the Ivip-mapped address space of an end-user network - in all cases
including behind one or more layers of NAT.
Path-lengths are typically optimal or close to optimal and the MN
communicates normally with all other non-mobile hosts (no stack or
app changes), and of course other MNs.
ETR and ITR functions are combined in a Translating Tunnel Router
which is located close to, or perhaps within, access networks. MNs
establish two-way tunnels to one or more nearby TTRs, but can still
use TTRs which were formerly close, but are now distant. A new TTR
would typically only be desirable if the MN moves more than 1000km.
Mapping only needs to change when the MN wants to receive incoming
packets from a new TTR. No mapping changes are required when the MN
changes one or more of its physical addresses, since it establishes
a new tunnel to its one or more current TTRs from each new address.
Modified Header Forwarding
Separate schemes for IPv4 and IPv6 enable tunneling from ITR to ETR
without encapsulation. This will remove the encapsulation overhead
and PMTUD problems. Both approaches involve modifying all routers
between the ITR and ETR to accept a modified form of the IP header.
These schemes require new FIB/RIB functionality in DFZ and some other
routers but do not alter the BGP functions of DFZ routers.
Amenable to widespread voluntary adoption due to no need for host changes,
complete support for packets sent from non-upgraded networks and no
significant degradation in performance. Only core-edge separation schemes
with local full-database query servers can ensure that ITRs tunnel the
initial packets in a new communication flow without dropping them and with
delays of no more than a few tens of milliseconds.
Minimal encapsulation overhead. In the long term it will be possible to
migrate Modified Header Forwarding to eliminate encapsulation overhead and
the need for PMTUD management. Depending on the time-scale, it may be
possible to upgrade the routers before introducing Ivip - and so to
introduce it on IPv4 and/or IPv6 with Modified Header Forwarding. This
would make ITRs and ETRs simpler since there would be need for PMTUD
Complete, modular, separation of the control of ITR tunneling behavior from
and the core-edge separation scheme itself: end-user networks control
mapping in any way they like, in real-time. Therefore, ITRs and ETRs can
be relatively simple. The mapping data itself is much simpler than for
other core-edge separation schemes: just the start and end address of the
range to be mapped, and a single ETR address. There is no need for
multiple ETR addresses, priorities or weightings - and no need for ITR-ETR
communication except occasionally for longer packets for the purpose of
While the TTR Mobility approach can be used with any core-edge separation
scheme, Ivip's real-time mapping system enables all ITRs to tunnel packets
to a newly selected TTR in a few seconds. So the MN could drop the tunnel
to the old TTR within a few seconds. An architecture with a non-real-time
mapping system would need to wait minutes or tens of minutes for cached
mapping in ITRs to expire before the MN could stop tunneling to the old
A small fee per mapping change deters frivolous changes and helps pay for
pushing the mapping data to all QSDs. End-user networks who make frequent
mapping changes for inbound TE, should find these fees attractive
considering how it improves their ability to utilize the bandwidth of
multiple ISP links.
Fees for OITRD usage provides a business model for OITRD deployment and
avoids unfair distribution of the costs of handling packets from non-
Existing source address filtering arrangements at BRs of ISPs and end-user
networks are prohibitively expensive to implement directly in ETRs, since
for larger numbers of addresses, they can only be implemented with
expensive hardware (power-hungry TCAM). Ivip's outer header's source
address is the same as the sending host's address, and simple ETR logic,
without any need for configuration or knowledge of the BR filtering
arrangements, enforces the filtering on all decapsulated traffic packets.
QSDs receive all mapping changes and store a complete copy of the mapping
database. Some fancy protocols and a global network of servers will be
required to push this information robustly, securely and rapidly to the
QSDs. Also, the QSDs need to access centralized servers to initially load
their database and recover from lost update packets. However this approach
eliminates the cost of developing and running an architecture with more
complex mapping in which ITRs have to choose which ETR to use.
There is inefficiency in each QSD receiving and storing all mapping, most
of which will never be needed by any one QSD. However, this avoids the
major problem faced by architectures with a global distributed query server
mapping system: dropping or significantly delaying initial packets while
the ITR awaits its map reply.
While mapping data is compact, scaling the system to 10^9 or 10^10
separately mapped ranges of addresses looks daunting now, but will not be
such a challenge by the time these numbers arise. The worst case is 10^10
IPv6 mappings of about 32 bytes each (start /64, end /64 and ETR address).
This totals 320GB and fits in a consumer hard drive today. It will
probably not be a problem for ordinary server or PC RAM by the time such
adoption (almost all of it for mobile devices) is achieved.
It is possible that in some DFZ failure modes, where ETR-A is reachable
from some parts of the Net and ETR-B is reachable from other parts, that a
system such as LISP or APT will achieve better multihoming connectivity,
due to each ITR individually deciding which ETR to use. During such a
state, Ivip can't achieve full connectivity, since all ITRs are tunneling
either to ETR-A or to ETR-B. However, such conditions are likely to be
transitory and the LISP/APT ITRs may take some time to make their
 At present, not behind NAT, but if the host creates a two-way tunnel to
one or more QSCs/QSDs, it can contain an ITR function even when behind
one or more layers or NAT. It would be possible to put an ITR function
in a mobile or poorly connected sending host, but it would be better
to use an external, well-connected, ITR in these cases.