"How Will the Migration from IPv4 to
IPv6 Impact Voice and Visual
Communication?"
October 2011
A POLYCOM WHITEPAPER
Introduction
On World IPv6 Day1 (June 8, 2011), major
service providers--
including Google, Yahoo!, and Facebook--
will turn on Internet
Protocol version 6 (IPv6) and for 24 hours
they will offer their
content over IPv6. While IPv6
implementations started in the 1990s,
"World IPv6 Day" is the first global test
that is intended to help
service providers and vendors prepare for
the inevitable migration
to IPv6. Why is IPv6 so important to the
Internet? And how will the
migration to IPv6 affect voice and visual
communication?
This paper discusses the shortcomings of
the currently used IPv4
protocol and provides the rationale for
migration to IPv6. The new
protocol is not only a new way to package
and transport information
over the IP network, it also requires
changes in the architecture of
the Internet and enterprise intranets.
Since real-time applications
are very sensitive to changes in the transport
mechanism, this paper
will focus on the impact of IPv6 on voice
and visual communications.
The Business Case for IPv6
IPv6 is a very small portion of the
Internet traffic today and,
while everyone agrees that more IP
addressing space is needed,
businesses and service providers have
struggled to agree on the
business case for IPv6. Businesses are
trying to stall by buying
address space from other users, and, when
Microsoft purchased
IPv4 addresses from Nortel2, they set the
price for IPv4 address at
$11.25. Governments, including the U.S.
Government, have been
encouraging IPv6 by making it a mandatory
requirement for all
new products purchased by government
agencies. Since vendors
usually do not create separate product
lines for government, IPv6
has been implemented in everything from
telephones to video
endpoints to soft clients. For example,
Polycom's video solutions
support IPv6, including Polycom® HDX® endpoints
and the Polycom
RealPresence™ Platform: Polycom RMX® platforms
and Polycom
CMA® and DMA™ solutions.
It is also extremely urgent for
residential and mobile service
providers since they are even bigger IP
address space users than
businesses. The consumer market drives
content providers to
enable IPv6 in their services (hence World
IPv6 Day), which then
will drive even more IPv6 adoption in the
business community. IPv6
is gradually starting to make business
sense.
Living in the IPv4 World
All information on the Internet and on
private intranets is carried
in IP packets. The packet format was
defined in the 1980s and
described in the Internet Protocol
specification (also referred to as
IPv43). When IPv4 was designed, no one
really expected that the
Internet would become so pervasive and it
seemed reasonable to
use 32 bits (4 bytes) to address network
elements; this resulted in
approximately 4.3 billion addresses.
Figure 1 depicts the structure
of an IPv4 packet.
Figure 1: IPv4
Packet
The IP packet consists of a header and
data. The header includes
the addresses of the sender (source) and
the receiver (destination)
plus additional information necessary to
route the packet over the
IP network. The maximum size of the IP
packet was set to 65535
bytes which was more than enough for any
application at the time.
Since the organizations initially using
the Internet trusted each
other, security was not an important
requirement for IPv4, and the
protocol itself did not provide any
security mechanisms.
In the 1990s, the rapid growth of the
Internet led to the first
discussions about the design limitations
of the IPv4 protocol. The
industry was mostly concerned about the
small address space and
the discussion led to the definition of a
new packet protocol (IPv64)
that used 128-bit addresses. However,
changing the underlying
networking protocol requires service
providers to upgrade software
and hardware, then to reconfigure their
networks. No wonder
service providers did not rush into
implementing IPv6. Instead,
service providers used Network Address
Translation (NAT) and
later double-NAT as work-arounds to
overcome the address space
shortage. NATs are usually implemented as
part of firewalls, and
directly impact voice and video
communication because they hide
the real IP address of the destination.
This means that a voice/
video device on the Internet cannot just
call a device behind a
corporate NAT. In addition,
business-to-business calls must go
through multiple NATs, and this frequently
leads to call failures.
Even if the call goes through the NAT,
real-time application
performance takes a hit because NATs makes
computationally
intensive manipulations on both incoming
and outgoing packets,
which leads to additional delay.
Another fundamental problem with NATs is
that they change the IP
address field in the IP packet and this
leads to incorrect checksums
and encryption failures. In other words,
NATs break end-to-end
security in IP networks.
Mapping private and public IP addresses
(NAT) is one of the
three main functions in IPv4 firewalls
today. Another function
"How Will the Migration from IPv4 to IPv6
Impact Voice and Visual Communication?"
2
1
http://isoc.org/wp/worldipv6day/
2
http://www.computerworld.com/s/article/9215055/Microsoft_offers_7.5M_for_666_624_IPv4_addresses
3
IETF RFC 791,
http://www.ietf.org/rfc/rfc0791.txt?number=791
4
IETF RFC 1883
http://datatracker.ietf.org/doc/rfc1883/ and later RFC 2460,
http://www.ietf.org/rfc/rfc2460.txt?number=2460
A POLYCOM WHITEPAPER
is called "stateful firewall function."
When packets arrive from
the public network, the stateful firewall
function determines if
there is any outgoing traffic (that is,
from the private network to
the public network) belonging to the same
connection. If there
is, it lets inbound traffic into the
private network. If not, inbound
traffic is blocked and packets are
dropped. The third main firewall
function (Port Address Translation, or
PAT) maps private to public
port numbers. This is because IPv4
addresses are scarce and
applications often use many different
ports in association with
a single IP address. The next section
describes how the firewall
functionality changes with the arrival of
IPv6.
The Arrival of IPv6
The pool of available IPv4 addresses has
been depleted, yet service
providers need unique IP addresses for the
home routers, laptops,
and other mobile devices their customers
are using. The address
shortage is bad in Europe and even worse
in Asia where China is
adding something like 80 million Internet
users a year.
IPv6 can immediately alleviate the address
shortage. It allocates
128 bits for IPv6 addresses, which results
in approximately 340
undecillion (a number with 36 zeros5) IP
addresses. Figure 2
depicts the structure of an IPv6 packet
header with the much larger
address fields.
Figure2: IPv6
Packet
Breaking Barriers to Communication
Although the migration to IPv6 is driven
by the address shortage,
IPv6 brings many new functions that will
have impact on real-time
applications such as voice and video over
IP. Since there will be
enough IPv6 addresses for everyone and
everything, NATs can be
completely removed, and real-time
applications would work much
better on the Internet.
Some organizations believe that NATs'
ability to hide IP addresses
of internal IP servers and devices provide
security, and these
organizations push for retaining NATs in
IPv6 networks. However,
this argument is flawed since security
experts have repeatedly stated
that NATs today do not improve security
because a hacker can scan
the small IPv4 subnets--they usually have
just 255 IP addresses
each--within seconds, even if they are
behind a NAT. Scanning IPv6
subnets in comparison is futile because
these subnets are so large
that it would take years to find something
in the subnet.
Does IPv6 make firewalls obsolete? IPv6
firewalls will be required
in the future to perform the stateful
firewall function. However,
IPv6 firewalls will not need to perform
NAT and PAT. PAT is not
necessary since the IPv6 address space is
big enough to allow
applications to keep the original port
numbers. NAT is not defined
for IPv6, in order to simplify end-to-end
communication without
interruptions. Note that if a firewall
does not support IPv6, it will
not recognize an incoming IPv6 Ethernet
frame and will not let it
through. Several newer firewalls such as
Juniper NetScreen and
SRX and the Cisco ASA support IPv6, but
the vast installed base of
firewalls is still lagging behind.
Security
Removing the NAT enhances security by
allowing end-to-end
security protocols such as IPSEC6 to
efficiently secure the
communication in IP networks. IPSEC
encrypts the data in the IP
packet but allows routers to read and
modify IP, TCP, and UDP
headers. The IPSEC implementation requires
scalable identity
management infrastructure that must be
deployed in parallel to
IPv6/IPSEC, and as result the IPSEC
specification will continue
to be updated as better identity
management infrastructure and
encryption key mechanisms are developed.
Many security problems in IPv4 are related
to packet fragmentation,
which happens when a packet has to be sent
through a slower link.
The router splits the packet in multiple
fragments and sends them as
separate IP packets. The receiver must
recognize the fragmentation,
collect all pieces, and put the original
packet together; this process
can be susceptible to penetration. IPv6
does not allow packet
fragmentation by intermediaries/routers
because it requires that
oversize packets must be dropped, and an
ICMPv6 "Packet Too Big"
message be sent to the sender. The sender
then reduces the packet
size so that it can go across the network
in one piece.
Voice and Video Quality
Quality of Service (QoS) mechanisms
developed for IPv4 can
still be used with IPv6. Although it might
seem that real-time
applications could face potential
increased latencies as a result
of the larger address, the new header
structure in IPv6 allows
faster header parsing which leads to
faster packet forwarding in
routers. In particular, all optional
information is taken out of the
base header and transported via header
extensions. The impact on
real-time communication is positive: voice
and video packets will
move faster through the IPv6 network. It
is only in mixed IPv4-
IPv6 environments that latency increase
can be expected, due to
tunneling and translation delays.
3
5
http://en.wikipedia.org/wiki/Undecillion
6
IETF RFC 4301,
http://tools.ietf.org/html/rfc4301
A POLYCOM WHITEPAPER "How Will the Migration
from IPv4 to IPv6 Impact Voice and Visual Communication?"
The new packet structure in IPv6 allows
for larger packets with
jumbo payload of up to 4 billion bytes7.
This allows for sending more
video information in a single packet,
instead of splitting it in multiple
packets, which should benefit visual
communications, especially as
video quality increases and video packets
get larger.
However, larger packets lead to higher
end-to-end latency, so these
large packets are still not suited to live
voice and video applications.
Larger packets that exceed the so called Maximum
Transmission
Unit (MTU) on any of the links between
sender and receiver must
be fragmented, that is, split in smaller
packets. As mentioned above,
IPv6 does not allow routers to fragment
large packets and instead
requires them to drop the packet and send
an error message back
to the sender. Since there is no mechanism
to assure the IPv6
packet will go through end-to-end,
multiple routers on the path may
drop packets and several retransmissions
can follow before the
IPv6 packet goes through. This, of course,
leads to high latency that
negatively impacts the user experience on
voice and video calls.
On the positive side, IPv6 mandates that
all links must handle a
datagram size of at least 1280 bytes8;
this is called the "minimum
MTU". (In comparison, IPv4 has minimum MTU
of only 576 bytes).
If the sender keeps the IPv6 packets below
1280 Bytes, they will
always go through the IP network.
Migration to IPv6 - Starting from the
Backbone
There are fundamentally three ways to
manage the transition from
one version of a protocol to another, and
this is no different with the
migration from IPv4 to IPv6: dual-stack,
tunneling, and proxy with
translation.
In dual-stack implementations,
devices/terminals/endpoints on one
side and routers/switches on the other
support both IPv4 and IPv6
simultaneously.
With tunneling, if the backbone network
already supports IPv6
while attached regional/local networks
only support IPv4, tunnels
can be built either on the fly or
statically (per configuration); these
allow IPv4 packets to get encapsulated and
transported over
the IPv6 backbone, then converted back to
IPv4 packets at the
destination network.
The third approach of proxying with
translation can be deployed
when an IPv4-only network wants to
communicate to an IPv6-only
network. The translation mechanism
manipulates the smaller IPv4
addresses to create a corresponding IPv6
address, and a border
element performs the mapping between the
two formats. In effect,
this is a kind of IPv4-to-IPv6 NAT.
Note that just supporting the new IPv6
headers in networking
equipment is only a part of supporting
IPv6. Several other protocols
have been enhanced to support IPv6: the
Internet Control Message
Protocol (ICMP) v69, the SEcure Neighbor
Discovery (SEND)10,
the Dynamic Host Configuration Protocol
(DHCP) for IPv611, the
Domain Name System (DNS) for IPv612, Open
Shortest Path First
(OSPF) routing protocol for IPv613, and
Mobility Support in IPv614.
The migration to IPv6 started with network
backbones. Due to
Polycom's involvement in Internet2, we
know that this network
already provides IPv6 services to the US
Research and Education
community through two IPv4-to-IPv6 relay
routers. IPv6 support
is easy to do for backbones that do not
have any end users, and
where issues are mostly around
carrier-grade NATs and web filters
that look into packets and cannot
understand IPv6.
While some backbone networks such as
CERNET215 in China are
running only IPv6, many other backbone
networks are running
dual-stack. From a technology perspective,
supporting IPv6 on
the backbone is not a problem anymore but
work continues on
optimizing IPv4-IPv6 translation and
tunneling techniques.
The Network Today
Commercial service providers are in
different stages of deploying
IPv6. Global Crossing, for example, has
made a lot of progress,
while Level 3 has so far been less
aggressive in this area. It is
expected that after the acquisition16 is
completed, Level 3's network
will be up and running with IPv6.
National/regional/local networks are
mostly not running IPv6 yet.
However, National Research and Education
Networks (NRENs)17,
for example, that connect to Internet2
backbone in the USA and to
the GEANT backbone in Europe have time
until 2012 to convert to
IPv6.
IPv6 Support in the Polycom Solution
The Polycom visual communications solution
already supports IPv6.
HDX 6000, 7000, and 8000 endpoints have
been supporting IPv6
since version 2.5. Since HDX technology is
used in all of Polycom's
telepresence systems, IPv6 is supported in
OTX, RPX, and ATX
telepresence solutions.
4
7
IETF RFC 2675,
http://www.ietf.org/rfc/rfc2675.txt
8
The value of 1280
was selected to be below the Ethernet max frame size of 1500 Bytes, so that the
IPv6 packet can be efficiently transported in a single Ethernet frame. There
are also some other considerations around
the value of 1280
related to IPv4 -IPv6 tunneling.
9
RFC 4443,
http://www.ietf.org/rfc/rfc4443.txt?number=4443
10
RFC 3971,
http://www.ietf.org/rfc/rfc3971.txt?number=3971
11
RFC 3315,
http://www.ietf.org/rfc/rfc3315.txt?number=3315
12
RFC 4472,
http://www.ietf.org/rfc/rfc4472.txt
13
RFC 5340,
http://www.ietf.org/rfc/rfc5340.txt?number=5340
14
RFC 3775,
http://www.ietf.org/rfc/rfc3775.txt?number=3775
15
http://www.cernet2.edu.cn/index_en.htm
16
http://www.level3.com/en/About-Us/Newsroom/Press-Release-Archive/2011/2011-04-11-globalcrossing.aspx
17
http://en.wikipedia.org/wiki/National_research_and_education_network
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from IPv4 to IPv6 Impact Voice and Visual Communication?"
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3847_1011
In the Polycom RealPresence™ Platform,
RMX1500, 2000, and
4000 media platforms support IPv6 and can
be configured for
IPv6-only, IPv4-only, or for dual stack
IPv6-IPv4, which means that
both IP protocol versions run
simultaneously. IPv6 addresses can
be used to address external entities such
as H.323 gatekeepers,
SIP proxies, DNS Servers, and Default
Routers, as well as defined
participants. Less visibly to the end
user, IPv6 can be used to
address internal RMX components within the
RMX chassis, for
example, the control unit, the signaling
host, the shelf management,
and the media cards18.
The DMA 7000 solution supports IPv6 on all
key interfaces--to
the RMX solution, to the gatekeeper (the
CMA solution), on
the management interface, as well as for
connections to DNS,
Microsoft Active Directory, and other
servers in the network. Finally,
CMA 4000 and 5000 solutions supports IPv6
in "maximum security
mode" that is required for JITC
compliance.
Conclusion
The migration to IPv6 is inevitable but it
will not happen fast.
Network backbones will support IPv6 first,
followed by mobile and
residential service providers that are
running out of IPv4 addresses.
From the private networks, government and
education will lead the
way with businesses following them.
June 8, 2011 is the next in a series of
practical steps to take the
Internet and other IP networks to a future
unbounded by space
limitations, a future where everything can
have its own unique IP
address.
Acknowledgements
I would like to thank my colleagues Jeff
Rodman, Alex McCarthy,
Jeff Adams, Assaf Weissblat, and Andre
Reid for their contributions
to this work.
About the Author
Stefan Karapetkov is Emerging Technologies
Director at Polycom,
Inc. where he focuses on the visual
communications market
and technology. He has MBA from Santa
Clara University
(USA) and an MS degree in Engineering from
the University of
Chemnitz (Germany). He has spent more than
15 years in product
management, new technology development,
and product definition.
His blog is
http://videonetworker.blogspot.com/.
18
IPv6 is supported
with MPM+ and MPMx media cards
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from IPv4 to IPv6 Impact Voice and Visual Communication?"
About Polycom
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