The Rising Technical Challenges of Networking at Home, by Geoff HustonIPv6 News
For me, one of the more interesting sessions at the recent IETF
81 meeting in July was the first meeting of the recently
established Homenet Working Group.
Whats so interesting about networking the home?
Well, if you regard challenges as interesting, then just about
everything is interesting when you look at networking in the
home!
Its been a very long time since the state-of-the-art in home
Internet was plugging the serial port of the PC into the dialup
modem. Even the ADSL modem, even when combined with some for of
WiFi base station, is looking distinctly passé these days. Today
the home network is seeing the intersection of a whole set of
interests, including the phone service, the TV service, home
security services, energy management, utility service metering,
possibly other forms of home device monitoring, and, oh yes,
connecting the laptops and the mobile devices to the net. And of
course its not just a home LAN over a wired network. WiFi home
networks are commonplace, and of course there are various Bluetooth
devices. Maybe sometime soon it will be common for the home network
to also host some form of 3G femtocell as well. But these days even
that level of network complexity is not enough.
Increasingly, the home office is part of the work office, and if
there are a number of residents at home then the home network may
be an endpoint for a number of corporate and institutional Virtual
Private Networks (VPNs). Within all this mélange we want
sophisticated security. Its not just protecting the home network
from the neighbors, but the security requirements include the
ability that allows individuals to partition off their work-VPN
part of the home network from other home users. Oh, and for
resiliency we might want a second provider, such as a mobile
service to the home, so we might want to add site-based
multi-homing to the mix. And now we need to make all this fly in
both IPv6 and IPv4.
Thats a massive agenda of requirements. But to make this
situation truly challenging, we cant expect every home to come with
an IT Operational Service Manager to ensure that all the various
devices you bring into the home and connect to the network all
function as required for the homes particular requirements. Indeed,
we cant expect any home to be so lavishly supported, nor can we
afford to support home networking with a bevy of specialized call
centers with on-demand support specialists expert in the panoply of
consumer devices that are being sold today.
With home networks the bottom line is that the consumer is
effectively on their own, and all this equipment better just work
straight out of the box. No configuration, no buttons, it just has
to work!
Routing @ Home
The evolution of networking at home has progressed from a single
computer to a basic Local Area Network (LAN), and from there to an
ether-bridged network with a number of WiFi and wired LAN segments.
All these environments have a single common architecture of a
single boundary unit that acts as a point of demarcation between
the Internet Service Provider (ISP) and the home network. This unit
is generally called Customer Premises Equipment (CPE), and
typically encompasses the functions of a modem, IPv4 NAT, DHVPv4
server, DHCPv6 server, security firewall, bridge and rudimentary
router.
But its unrealistic to assume that home networks will continue
to use a centralized model that places the entire management
functionality of the home network in a single unit. So how should
we view home networks? Should home networks be a single bridged
LAN, or are we seeing the evolution of home networks into multiple
distinct domains with a routing fabric to glue them together? And
if this is the case what routing protocol should be used?
I have noticed in the low end of the CPE market its not uncommon
to see a rudimentary routing functionality supported by RIP. Now,
thankfully, its RIPv2, so the routing protocol can be configured
with variable length subnet masks, but even so, RIP is a very basic
and simple routing protocol. But perhaps in this environment that
might be a positive factor rather than a liability, in so far as
RIP is simple enough to be auto-configurable. On the other hand if
there is an emergent need for more complex functions then maybe we
need to look a little harder at what options are available.
One of these more complex functions is the issue of subnet
management. In IPv6 the CPE will collect an IPv6 address prefix.
This differs from the conventional IPv4 environment where the CPE
is typically assigned a single IPv4 address. So the ensuing
question is: Is it possible to automate the distribution of IPv6
subnets across the entire home network? What form of management
protocol is appropriate for this role.
And of course the world gets a whole lot more complicated if the
home network has two (or more) service providers. In the IPv6
environment this starts to become a challenging task, not only with
the distribution of multiple subnets across the home network, but
also in the issue of exit path selection. If the home network is
exercising due diligence to prevent source address spoofing it is
also necessary for the homes routing infrastructure to deliver an
outgoing packet to the right exit ISP, where the source address of
the outgoing packet needs to match the address prefix provided by
the corresponding ISPs service. In other words there is a
requirement for source address routing in the home. This is a
challenge that was not really addressed by the Site Multi-Homing
Working Group (SHIM6), despite the best of intentions, and it
represents an even greater challenge if the intent is to provide
mechanisms that can achieve this in an unmanaged home network
environment.
I must admit to some concern here. Weve managed to keep routing
work by using two principles. The first is to try and keep the
routing task as simple as possible. Routing propagates a single
best path to a destination. It does not necessarily do this
quickly, nor necessarily does it carry around with it a whole set
of alternatives. It does just one job. And with that weve been able
to keep routing working. The second principle is to admit the that
we have never really succeeded with the first principle of
functional simplicity and we have always had expertise at hand to
oversee the routing function and apply manual patches as required!
The specialized requirements for the home network appears to be
breaking both principles. The requirements are certainly not simple
and I see a mix of routing techniques, including various forms of
policy-based routing requirements entering the discussion.
Secondly, there is no assurance that if things fail there is
expertise at hand to mend the failure. Indeed the more complex the
routing environment the greater the potential for complex forms of
failure. Indeed as we contemplate ever more complex requirements in
the home network, the greater the risk of encountering failure by
design where it is just not possible to design products for this
environment that can just work.
Names @ Home
What should I call my printer? More to the point, how should I
identify my WiFi printer to all those devices at home that want to
use it to print. Im sure that I would not like to use a proprietary
naming scheme that requires me to add additional name resolution
software to every device at home that wants to print something, nor
do I want to transcribe IP addresses into everything. Id like my
printer to get dynamically assigned IPv4 and IPv6 addresses when
the device is plugged in and switched on, and have the printers
name published via a generic name resolution mechanism, namely the
DNS.
But most of the time the rest of the world has no need to know
the name of my printer at home, and Im not sure that its a good
move, security wise, to gratuitously publish information in the
public DNS. So what I would like for my printer is some form of
local or scoped DNS, where I can name my printers, my disk servers,
and other devices that I have at home in the context of my home and
not have this information leak further afield. Is this scoped form
of name resolution possible in the context of the DNS?
Multicast DNS (mDNS) is perhaps one of the strongest candidates
for this role. In essence mDNS replaces the explicit server /
client structure of the DNS with a scoped name subdomain of .local
that is inherently scoped to the scope of the associated multicast
domain. This allows a client to perform DNS-like name resolution
functions on a local network without the need to configure a
conventional DNS server environment, and without the need to obtain
global delegation of a site name in the global DNS.
An alternative approach is to use a conventional DNS delegation
and conventional unicast DNS queries and responses. Clients are
able to use DNS Dynamic Updates to update the local DNS server with
their details as they come online. The DNS server itself can be
advertised to all clients via the Simple Service Discovery Protocol
(SSDP), as part of the larger Universal Plug and Play (UPnP)
framework.
Sensing and Serving @ Home
Where too from here? Its certainly the case that electronics has
managed to pervade just about every device at home. Electricity
meters are morphing into household energy management systems, and
many other household appliances are now controlled by internal
processors. But individually configuring each of these devices is a
forbidding task. Even adding an interface to allow manual
configuration can often be a challenging objective.
So the objective here is to define a standard mechanism to allow
sensors to sense their local environment when powered up, obtain an
IP address, advertise their existence and capabilities to the
network, and, as appropriate, rendezvous with the sensors
controller or controllers across the home network.
This is another instance of a more generic class of automating
the installation and use of services in lightly managed or even
unmanaged networks, and intersects significantly with the
objectives encompassed with SSDP and uPNP. The potential volume of
such devices places this more squarely into a class of IPv6-only
services, I suspect, which is a significant extension to the
existing IPv4-centric uPnP frameworks.
What is needed here is a bootstrap protocol that can provide a
connecting device with:
- address configuration
- routing setup
- name management and name server discovery
- discovery of other services and controllers
- security capabilities
Securing @ Home
One of the most significant issues with home networks lies in
the area of security management. Host computers in a home network
often want to place a very high level of implicit trust in their
immediate network neighbours at the same home. Its not unusual for
hosts in a home network to share printers, file servers, data, and
even user profiles. Indeed, its probably commonplace. But beyond
this local security domain a host should become paranoid and treat
all connection attempts with suspicion. But where does the local
trust domain start and stop? What is the local security
boundary?
This is difficult to answer in an automated fashion. Its no
longer the local LAN, particularly as as home network transition
into routed networks. Its something to do with a local multicast
scope, but that assumes that its possible to define a multicast
scope that encompasses the local trust domain of the home network,
and to do that we are back at the same question.
And even if you thought you might have a clean answer to that
question, you need to remind yourself about telecommuting. With
telecommuting there is a requirement to partition out an entire
local network segment and lift it out of the home environment and
the home security domain and transplant it into the work security
domain.
Everything @ Home
Home is certainly the new field of engagement for networked good
and services. But its certainly the most challenging environment.
Its an environment where out-of-the-box interoperability is of
paramount importance, and therefore its an environment where
standards really matter. And, perhaps surprisingly, its one of the
networking environments that appear to raise the most challenges.
Its an unforgiving environment where there is no real substitute
for simplicity and reliability in a plug and play world. And for
the IETFs Homenet Working Group, there is really a lot of work to
do to take a diverse set of approaches used today, add a bucketful
of IPv6, and produce a coherent set of outcomes in the form of
standards that support robust capable home networks that work in an
unmanaged environment. By any metric thats a big ask.
Ahhh home! There really is no place quite like it!
Written by Geoff Huston, Author
& Chief Scientist at APNIC
2011-08-05 09:44:29, Source: http://www.fix6.net/archives/2011/08/03/the-rising-technical-challenges-of-networking-at-home-by-geoff-huston/http://www.ipv6news.info
Comparing IPv4 and IPv6 PerformanceIPv6 News
The active measurements the RIPE NCC carried out on World IPv6
Day on 8 June 2011 included ICMP (Internet Control Message
Protocol) and ICMP6 (ICMP for IPv6) measurements from our vantage
points to selected hostnames of World IPv6 Day participants and
other dual-stacked parties. We used these measurements to determine
the performance of IPv4 versus IPv6 connections.
The figure below shows a histogram of all relative IPv4 versus
IPv6 performance data points collected during World IPv6 Day. A
single data point consists of the ratio of IPv4 and IPv6
performance from a single vantage point to a single destination
during a 10-minute interval.

The image shows that while this distribution has a bell shape,
it is a little fatter on the IPv4 side. This means that IPv4 is
faster more often than IPv6. What this tells us is that you are
slightly better off in an IPv4-only environment than in an
IPv6-only environment. On a dual-stack client that unconditionally
prefers IPv6 to IPv4, IPv4 is more often the faster protocol, but
this is far from a universal truth. There is also a significant
chance that IPv6 is faster, since the IPv6-is-faster part of the
histogram also has a significant volume.
Note that we measured ICMP and ICMP6, and not HTTP performance.
Also, the IPv4 and IPv6 end points for a given hostname may be
topologically and/or geographically in (very) different places,
especially when proxies are used for IPv6 to IPv4 translation. In
cases where the IPv4 and IPv6 destination end points are not at the
same location, the distance between a vantage point and either the
IPv4 or IPv6 destination end point has a large influence on the
measured performance.
In conclusion, we can say that comparable IPv4 and IPv6
performance can be seen as an indication of a mature deployment of
both IPv4 and IPv6 in a network. In the data we analysed, we see
that IPv4 is still generally faster then IPv6, but for a
significant fraction of measurements IPv6 is the faster
protocol.
For more detailed information, please refer to the background
article on RIPE Labs:
Measuring World IPv6 Day Comparing IPv4 and IPv6
Performance.
Written by Mirjam Kuehne
2011-08-02 13:09:09, Source: http://www.fix6.net/archives/2011/08/01/comparing-ipv4-and-ipv6-performance/http://www.ipv6news.info
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