*35C3 preroll music*
Herald Angel: Welcome everybody to this
talk, "How does the Internet work?" And our speaker is Peter Stuge and I'm very
happy that he is here to explain to all of us how the infrastructure of the Internet
really works. I am pretty sure we will all learn a lot today. Please give a big and
warm round of applause for Peter Stuge. *applause*
Stuge: Thank you. Thank you very much. Thank you for being here. This is amazing.
Translation into French, wow. So I want to talk about how the Internet works. And I
try to, try to... yeah, try to shine some light on all the technologies that are
involved when we use the Internet every day. So, why this talk? Some motivation
first, then a little bit of brief background just how the Internet got
started. And then we get into the details. So what actually happens between the web
browser and the website, that's the starting point. So in the description I
listed things from bottom up, so from the very low level packet stuff and through
the various layers of the network stack up into the applications. And that's the
building blocks part, but I inserted this overview first, what is actually going on
between the browser and the website because that's what most people already
know and use a lot. Some parts, well, some details about the different protocols and
in the end some recommendations for further talks, if you find these topics
interesting. So the reason I want to give this talk is to talk about how does the
Internet work, right? The mechanisms that we use all the time... but aren't
mentioned very much. So they are sort of obscured or... well I don't know if hidden
is the right word but we wouldn't.. we don't experience the network itself very
much, right? We experience the various services that we use and they, the
services, they try their hardest to keep us interested, to tickle our imagination
and... I think it's dangerous to not talk a little bit about the network every now
and then. And to think about the network, and to actually fight for a public network
that is available to all and equal. Also neutral. If we focus on the service
providers alone then they're going to be deciding what we can do with the network.
But the point of, or the great thing about, how the Internet is neutral today
is that we're all connected or we could all connect to each other. We don't
really have to use these service providers. We tend to. This is somehow a
human nature to sort of go towards centralization and monopolization. But the
Internet is a tool that would allow us to try more variants or other kinds of
structures. And we need to be aware of that and the importance of net neutrality.
If we don't talk a bit about the network we might lose it. So. How did it all get
started? In 1970, then ARPA, they started the ARPANET. So ARPA back then is this is
now DARPA. That's the Defense Advanced Research Projects Agency. They develop
technology for the U.S. military. And they did back then as well. So the ARPANET was,
as the quote says, from this very very old document, that the objective is to get all
their suppliers connected into a network together, and being able to exchange
information so that they can, I guess, make progress more quickly, more
efficiently. Right? Now it's something else. I think that's good. So let's let's
look at what happens between the browser and the web site. So we have a person
using a laptop and they have a browser and they type in a web address.
"events.ccc.de", for example. To read the blog posts, the latest blog posts about
the Congress. So then the browser really does two different things first of all. To
get, to show this page. So first of all it has to ask for the the way to reach this
website that we want to reach. Computers, they don't deal very well with names or
text. At least not the network part of computers or systems. So there is this
translation somehow like a phonebook, I'll get back to that in a bit, called DNS,
which is used primarily... it has a few other uses as well, but it's used
primarily to get from this name that we entered, "events.ccc.de", that we can also
somehow easily remember, to the network address. The IP address of this web site.
So that's part one. And it says System DNS because the browser doesn't do all of
this phone book lookup itself. It can rely on the operating system to take care of
this. Unfortunately. So that's the parentheses that's what the operating
system is doing its using a few protocols UDP, IP and that becomes a network packet.
We'll get back to those in just a little bit. So once the browser has the the
network address the IP address of this website it creates a connection. So it
contacts the web server and it uses this set of protocols. So it first uses IP to
reach the IP address of the server and in particular it uses TCP for this connection
type, we'll get back to those in a little bit, as well what what their properties
are. And on top of that the browser then uses the HTTP protocol. We'll see an
example of that in the very end. How or to get to request the the web page that we
wanted to see. And that's all happening on the laptop in the browser and part in
the operating system that we're using whatever that might be. Then there's of
course this long chain, or sometimes not so long, but usually several several
machines along the way, routers, we might have a wireless router at home or in a
coffee shop or here at Congress, and beyond that there is certainly there are
certainly some more routers along the way from or between our laptop, my laptop, and
the destination that I want to contact. So all of these routers they receive some
packets, they look at the addresses, where it's going, in particular, and then sends
it along its way. So they're they're just forwarding packets all all day long.
Finally at the destination on the web server there are also two parts. So first
of all the request that was sent by the browser is received. It goes through these
these different layers, different protocols, and the website server
software, it looks at the request and it says OK somebody wanted the first blog
post, then I'll send that right back the same way that I received the request, and
that's part two. So returning the response to this request, and it goes all the way
through the routers the same path but in the reverse direction to the laptop. So
let's let's look at all these different building blocks. All right. So let's start
with the small smallest one in the network packet. I talked about packets going back
and forth, so the packets, or a packet, is sort of the atom on the network--it's the
smallest useful unit that is sent or processed by the network. I think a good
way to explain packets is with regular postcards that you can send with mail,
because their size, their maximum allowed size, is pretty much standardised. You
can't send a postcard which is one meter, right? And that's the same with the
network packets, you can't send arbitrarily large network packets. One
pretty common maximum size is 1500 bytes or roughly characters. So just to give an
idea of of how fairly small the packets are actually and even that might, I don't
know do, 1500 characters fit on a postcard? No I guess not, I think that's
too much. So maybe the packets are a little bit larger than postcards, but
still the analogy is pretty good because you send them out and and there's very
little, there's a little bit of structure, like there's a stamp perhaps, and a
recipient address but that's pretty much it. So what you what you write on the
postcard on the on the other side is really up to you and it's the same with
the packets, they can contain anything, but if you write in the language that the
receiver doesn't know, then they're going to receive the packet and then actually
just drop it because they don't know what you're trying to tell them. So packets,
they are sent and received through network interfaces. This is an Ethernet cable LAN
port, or a Wi-Fi antenna, or maybe a 3G modem if you're on the go out and about
and your cell phone does this of course as well right. The cell phone has Wi-F if
you're in a coffee shop maybe, or it has 3G if you're in the subway or on the tram.
And one interesting thing, or where the comparison to the postcards doesn't really
fit anymore, is that network interfaces, they can easily pass millions of packets
in a single second. So it can be can be quite a lot of information going through
especially if you have a good internet connection like here at Congress. So then
the next step or sort of if you start looking at OK what can we put on the
information side of the postcard, right, where where we can put any message we
want. For this talk I'm only going to focus on IP version 4. I know it's it's
old and legacy and we really shouldn't be using it still but it is, it's dominant so
far, it won't be forever, but so far it's quite common. And I think it's something
that most of us have at least seen when setting up the Wi-Fi or the new Internet
connection, right? This IP address that I put up on the slide is maybe the most
common IP address there is, right, for the for the new wireless router. These IP
addresses they consist of the four numbers and they are the four numbers. They range
from 0 to 255 and then there's now four of them and with dots in between is just how
we write them. This is an efficient way for machines to identify themselves. But,
the reason IP version 4 isn't so great anymore is that it's quite a small number
of addresses. So it turns out that the Internet is pretty popular and worldwide
the addresses have run out or are running out. There aren't enough addresses for all
the devices that are actually participating or somehow connected to the
Internet. IPv6 will solve this. Let's see. Maybe maybe we'll live to experience that.
So what is what is a network then? There are different kinds of networks. I've
written physical networks and logical or abstract networks. Physical network is
cabling, right? If you have some kind of connection from your Internet service
provider that goes to your wireless router or if you have a LAN setup like in the
hack center with a switch and lots of cables to each, one cable to each
computer, that's a physical network and that's a tangible thing right. That's
something we can we can touch and we can modify it with our hands and so on. But
then there are also and that's that's certainly one network type and another
equally valid network type is the logical network, or as I also call it the abstract
network, which is defined only by the addresses used by some set of computers
that are communicating together. So here's an example of an IP network that might be
used with the wireless router and that has the IP address up on top right. And the
there's sort of a pattern right. The first three digits are the same. And that's the
network address. And the very last part is zero with this slash 24. Meaning that 24
first bits of the 32. So now it's technical maths and binary and sorry, but
essentially the 24 means the first three numbers are always the same. And within
this logical network, so within this group of computers or systems that can
communicate with each other, only the very last digit will change. And as long as
this is the case we don't need a router, yet. We can--all these computers or all
these systems--they can communicate directly with each other on the local
network or on a Wi-Fi or or whatever. And the slash 24 (/24) and with the
255.255.255.0 that's just two different ways to express exactly the same thing. So
where do these IP addresses come from and how, who has them, and so on? So if we get
a wireless router then we have some IP addresses. But me and my friend we both
have the same perhaps IP addresses because we have a wireless router from the same
supplier. Right. And this is a little bit of a special case. Those aren't Internet
IP addresses. They're used only very locally. So only in one home network, only
in one company network, perhaps. The public IP addresses are the ones that are
on the outside of this wireless router that I got, and the wireless router
typically only has one. Some Internet providers give you a few but it's very
easy to have a lot more devices in your home or in your office than public IP
addresses that you get from your Internet provider. So the IP addresses, they are
assigned to the Internet providers, or the other way around, Internet providers they
apply for some range of some number of IP addresses. And here in Europe there is an
organisation called RIPE in charge of allocating a block of IP addresses to the
Internet companies that are actively connecting to other Internet companies and
maybe are also your Internet providers and mine. So and RIPE they have, they of
course have colleagues in different parts of the world. So I think there are four or
five, maybe even six of the RIR organizations, the regional network
centers. They assign IP address blocks to the Internet companies, and by Internet
company I don't only mean Internet providers that we use at home and at work,
but also really any larger company that has a service available on the Internet.
So all the streaming sites that you can imagine, all the, most, well several large
just websites that are used every day will also have their own IP address range and
will be active in finding different ways to connect to the Internet providers so
that the end users can have as good an experience as possible when they're
visiting there or using their services. So I talked about the Internet companies,
they are trying to find good ways to connect to each other or to make it
possible for users with one Internet company to reach either users at another
Internet company or some service provided by some Internet company. And that's,
that's the routing that's going on, both in the wireless wireless router at home
but just as well and and even more so in all of these routers on the Internet that
are handing packets back and forth. So starting with the wireless home router, it
typically has one local network. At least. It might have more. So I had a home router
that had both the regular Wi-Fi network and I was also able to configure a guest
network or guest password. So that's actually two. It's Wi-Fi, so it's not
really so intuitive, but those are two separate physical networks, because if
you're connected to one you can't communicate directly with the other
network without a router. Now there's some chance that the wireless router will do
this, will enable this communication, but it's not for sure and it's not it's not
certain. And in fact it's more likely that it won't work because this guest access,
you're supposed to be able to give that to somebody who's just visiting and maybe you
don't want them to access your printer or your storage cabinet or whatever. Right?
So it's quite likely that this guest network doesn't get access to the main
network. So two different networks, even though it's the same the same radio waves
or the same air that's carrying the radio waves but the key property by the, or with
a wireless or a home router, is that it almost always only has a single Internet
connection, so it has a single connection to some Internet provider or in in the
direction of the Internet. Typically that's that's the telco. But in some cases
there's even, especially in the US, there's the situation where the telco or
the Internet provider is also a content service provider. And that's a pretty bad
situation. In particular if you have no options, no choice. So we have the home
router with a single connection towards the Internet to the Internet provider.
Let's compare that with the Internet routers that are further out on the
Internet and operated by the many different Internet companies. They will
similarly have one or more local networks that belong to them the same way that the
wireless network belongs to the home router or wireless company, or sorry an
Internet company or an internet organization, let's say like the CCC as
well, it has some some equipment and servers with the events.ccc.de server for
example, is part of the CCC slice of the Internet, and the router that's
responsible for all of CCC's networks is responsible for. Also this IP segment
where the web servers. Now the big difference here is that those Internet
routers, or the routers that are further out on the Internet than our home routers,
they typically connect to at least two but usually many more other Internet routers.
Exactly how is it different in every location. There are some norms and some
common topology is but this is... so the connections that exist are determined by
by peering agreements between the Internet companies and their Internet organizations
there. They can of course have agreements with whoever. So it's not so easy to tell
them beforehand what a particular organization, how a particular
organization, will do peering. This is an interesting topic. There are some more
talks on this as well that I'm referring to later. One, at least one model, is to
have a site. Some data center somewhere where an Internet exchange is running. So
this is an organization whose sole purpose is to enable many different Internet
companies or Internet organisations to somehow make their way there, put some
cables to this data center, and all connect together and be able to exchange
traffic between each other efficiently and maybe even at no cost. That's an
interesting topic because there are so many different business models for the
peering agreements. So the Internet exchanges is one model. There's a handful
of them in Germany and that's about the scale of it. Private peering is of course
possible to where organisations just have a direct connection between each other.
And OK. So these connections they are then established somehow and how do the routers
know where to send what? And that's a good question. This is managed by routing
protocols, BGP is one. One such application or some, BIRD, is one
application and then BGP is the protocol. So there are some rules, you can configure
what to prefer, what route to prefer, but you can also just say I don't really care
so much and just use whatever is available. And of course this depends on
how much you have to pay for traffic that you send which way. If you have a really
good peering agreement with another Internet organization and you're able to
send a lot of traffic their way then without having to pay very much extra or
maybe anything at all then of course you're going to try to send as much
traffic as possible that way. All right, so now we're getting, we've looked at IP
addresses and IP addresses... we know some systems on the Internet or connected to
the Internet... all systems connected to the Internet, they have some IP address.
And if we know the IP address we can try to reach that system.Yeah, yeah. That's a
bit unfortunate. So. The first um the first bullet point is UDP. It's... now
we're talking about, okay, so on the on the postcard when we're writing stuff
there we we put the IP address because we know what system we want to reach. But we
want to send it some kind of message as well. There are a few different ways to
structure messages. And these are the most common ones, or the ones that make up
almost all of the traffic on the Internet. So the first one is UDP. It's quite like
postcards. So it's just a single message. There's no context, there's no connection
between two different messages, and there's also no guarantees about how this
message will, or this packet will, perform on the network. So if you send out a UDP
packet it might arrive or it might not and you'll never know. And that can seem a bit
useless but actually it's quite good in many cases. For example if you're doing
real time audio or video streaming UDP, is a good choice because it's real time
information, so if something is missing maybe there will be a glitch in the audio
or there will be some glitch in the video, but it's not so important to wait and
delay the image to fix that glitch. It's better to get the next image and just
replace the image. So just keep on going. And for that UDP is a really good fit.
Just send it send it along and if it arrives it arrives, most of the time it
does arrive. Most of the time it works fine. So sometimes a good choice. The next
point there is TCP. So maybe you've heard the term TCP/IP and TCP/IP is exactly
the... so specifically it's the combination of this, this TCP then, I'll
get into it in a second, with the IP address in both TCP and UDP. They have the
concept of a port. So that's a second address. You could compare that with,
let's say, the IP address is the street name and the port is the house number on
that particular street. So it's a bit more precise. You know it's that system but
that system might offer many services and you want one specific one. So for each of
the common services that we use, email and web and Jabber and whatever, there are
typical port numbers that are allocated and always the same. So that I don't have
to guess or or look up what it is. So with TCP, what are the properties of that?
That's more like a stream of letters that you have to go to the post office and
acknowledge that you've received. So the recipient of a TCP packet or a network
packet with IP and TCP inside of it will always confirm reception to the sender. So
this allows this concept of a connection that I mentioned, where both sides talking
to each other are synchronized and know where the other party is in this
communication or in this connection. What data has been received and what has not
yet been received. So the packets, TCP packets can of course also get lost,
right? There's no guarantee with any network that it will always function
correctly. You can just pull the cable and it will not be possible to send any
packets.So TCP will recognize that. Oh, so I sent some packets out, but they haven't
been confirmed, they haven't been acknowledged. OK. I'll try again. I'll
send again a few times and it's usually adjustable how long TCP will be retrying
to communicate. And finally it will give up and say yeah, sorry, it seems that this
connection is broken. It's not possible to communicate anymore over this path. But if
you're quick and you plug the cable back in then maybe everything will heal or the
connection will just continue functioning just as if there was never an
interruption, because the network software is just keeping track of what has been
sent, what has been received, and can recover from this loss of communication.
And the third one on the bottom is this SCTP. This is not quite so widespread but
it's still a very powerful mix. It's a lot younger than the other two. So UDP and TCP
they are... I'd like to say 70s and 80s. Yeah. So quite old. whereas SCTP I think
the standard was final, or the first version of the standard came in 2000, so
it's quite a lot younger, tis is protocol. But it's a powerful combination of
properties from both the older ones so you can have... whereas TCP you just have a
constant stream of text, essentially, or image or whatever content you are
transferring... with UDP you had this message that's on the postcard, like
that's one postcard that you're sending, that's the fixed fixed message. TCP
doesn't have that concept, it's just information all the time until the
connection closes. SCTP you can have a connection concept where both sides are
aware of the communication status or the position and the communication, but you
will be able to use it. You will still be able to send messages like on the
postcards. So you have a fixed size piece of information that you want to transfer
and you can send that as a unit, whereas if you're only using TCP, like we do on
the web all the time, you have to build a lot of stuff around or on top of TCP in
order to achieve the same thing. So if I want to transfer an image or when my
browser wants to download an image, there's quite a lot of extra work that has
to go into making that possible with the regular TCP protocol that is being used
for now, so it would advantage SCTP certainly. It also has the retry, the
reliable delivery, if you want to, and you can also use multi-homing. So that's not
so common yet. As I said typically in the wireless home routers they only have the
single Internet connection but that might change, we might in the future see several
different kinds of Internet connections that we're using, and SCTP would be able
to take advantage of that quite easily whereas the other ones cannot. So SCTP
can send the same information over several different connections and whatever comes
first arrives first at the destination and is accepted. This is of course a bit
wasteful but in some cases maybe it's not a problem. So that's an exciting... I
think exciting new feature. Let's see what the future brings. It seems that TCP is
going away slowly but surely. Let's see what happens. But then some companies,
they're providing systems where they want, they want to control much more of how the
software is using the network, how the software is communicating on the network,
and the way that these systems are built. Cell phones typically are smartphones.
It's not so easy to do that with either TCP or SCTP, but it's quite easy to do it
if they're using UDP, so I think that's a big motivator for them to try to move away
from TCP and use UDP even more. Let's see. Sorry. So then we'll get in to some
applications. Now we've written on the postcard, we've written addresses, IP
addresses, the system that we want to communicate with, and we've chosen either
UDP or TCP depending on what what is most suitable. Actually it depends typically on
the application. So some applications require one or the other and a few
applications can do either or. The first thing I'd like to mention here is DNS. I
call it the phone book, the Internet phone book. But there is one big difference. A
phone book is something we get from from one publisher, right? The phone company
typically. And they, or the POC here at Congress, and they've just collected or
they know all the phone numbers and they send us the list, right, with the names.
DNS is different in that everybody who has who has a name in the DNS, in the domain
name system, so anybody can register a domain name. And anybody who does that can
can publish some information there. You can decide what you publish. Actually you
can decide if you publish. So let's say you have a thousand IP addresses you can
decide if you want to publish names for all of those thousand or if you just maybe
publish a few of them that are going to be interesting for other people to use. And
90 percent of them are just internal internal systems. So everybody gets to
choose what they what they publish and everybody can publish. Also can run the
infrastructure, storing this information on their own. So it's not that you have to
send this in somewhere necessarily and they publish it for you. You can actually
do that on your own. So it's decentralized. Very good. still it's super
super old protocol, from from those days of from those early days of the internet.
Nobody was thinking about security and nobody had done a lot of attacks on these
protocols, Whether it it be reliability attacks or or just forgery attacks and so
on. That wasn't a concerned because this was designed for companies working for
the government. Right. So everybody was interested in collaborating and there were
no bad actors. The Internet now is, again, quite different. So most of these these
old protocols actually aren't so great anymore. The basic functionality of DNS or
the phonebook is to publish IP addresses but you can publish other things as well.
If you're interested in DNS there's a good talk about that later on. I mentioned it a
bit. So the next application I want to talk about is SMTP or simple
mail transfer protocol. This is what is used to deliver every single email in the
world. All the time. All day long. Now one thing that's a bit interesting or quite
interesting but also problematic, I'd say, about email and not SMTP per se but the
scope of SMTP is, that SMTP is used only to send email. So SMTP doesn't have
anything to do with receiving email. This means that there's a separate mechanism
for receiving email. And the way these two these two different protocols or
mechanisms work end up putting the cost of email with the person receiving mail. So I
have to pay in order to be there with information or with money to get an email
address where I have some some gigabytes of storage. Whereas people sending email
they don't have to pay anything. They just need an internet access and then they can
send all the emails they want, all day long, to every single possible address
email address in the world. And that's why we have a spam problem on the Internet.
Yeah that's a bug. Let's see if this can get fixed. Email is so tightly integrated
into our everyday lives that ... I'm not sure. But let's see. That would be great.
So the last application protocol I want to mention is the HTTP hypertext transfer
protocol that's used for web. You recognize it from the web browser URLs.
Webpage used to be just hypertext so text with some links. That's all they could do
in the very beginning. I'd like to show an example of SMTP. Actually I have to do
something about this, because it's not so not so easy to read. Let's see... I
should've done that already. Sorry about that. Um so this is an example of an email
delivery. This is all it takes to send an email on the Internet. The arrow pointing
left is received from the email server, from the SMTP server. And the arrow
pointing this way [right] is what we send to the email server when we want to send
an email. So if we connect to an email server, for example mine, it will send us
some text. We are using TCP and we're using port 25 for SMTP. So we get a stream
of text going back and forth. The the server tells us 220 and its name, that's
some kind of welcome code. We say HELO my name is laptop. Because I'm doing this
from my laptop. The the mail server says OK, good to meet you. And then we say I
want to send an email where the sender address is test@stuge.se. And if you're
paying attention here the sender of the e-mail gets to say what the sender address
is. So this is why it's super easy for anyone to forge email from any sender
address. It's just part of the message. The server accepts the sender, even though
the sender might not even exist. I tell it the recipient (RCPT). This is for me,
meant for me. The server says OK. Then I say here's the DATA for this email and the
server says: go on, start sending me the contents. And then I send send an email
where the the sender is Trollolol and just some fake sender address, whatever subject
and some text. And in the end I finish with a dot to say ok, end of message. The
server says OK. And then I say to the server I want to QUIT not, I don't want to
talk to you anymore. The server says "closing" goodbye. And this is e-mail on
the network. Last example: a web page, access over HTTP. So this is even even
simpler. I've simplified this even a little bit more. If you want to try this
yourself, please do. So HTTP is also TCP and port 80. I tried talking to the
events.ccc.de web server. Same thing here: Arrows pointing this way [right] is what
we send when we contact the server. So. Connection opens. I send "GET / HTTP1.0"
because I want to get the main page and I'm saying I'm speaking HTTP version 1.0.
And then I tell it OK I want to access this start page on the hostname
events.ccc.de. Then I send it an empty line. That's to say OK this is my request.
And then there comes the response (arrows going in the other direction [left]) where
the web server says what you're asking for is not available here where you're asking
for it. You have to go somewhere else. It's a redirect. The 301 is the HTTP code
for redirect. And this content that you're asking for, this page, it's been
moved permanently. The new location is https://events.ccc.de. So I was using an
IP and TCP connection with no encryption. And that's why I can just type in the GET
and the "Host:" line. But the web server tells me I'm sorry I don't want to talk to
you without encryption. So you have to go to this HTTPS address instead. Thank you
events.ccc.de! I like encryption. That's good. And thank you also to all the
angels that make Congress possible because without them and without you, who are
here, who are angels, there wouldn't be any Congress. And also I want to say a
huge "thank you" to you in the audience, for being curious and wanting to learn
something new.
applause
Herold Angel: Thank you very much Peter. Now we have some time
left for Q and A so if you have questions please do line up at the microphones that
you find here. If you want to ask anything. Do we have a question from the
Internet. No. The Internet is out of questions. Do I see anybody standing at
any microphone? Please make yourself known if I overlook you. Any questions? Oh, at
microphone five. Please do ask your question.
Question: You mentioned that you think SMTP has a kind of bug, in the sense that,
you can just send an e-mail and the responsibility is on the side of the
receiver. So if you call it a bug it seems you have an easy solution.
Answer: I'm sorry, but, no, I don't. I mean I wish! That that would be great!
It's not so easy to fix because it is a property of SMTP, right, and of the e-mail
system that we're using. So there was a proposal a long long time ago, by somebody
much smarter than me, called "Internet Mail 2000" where actually the whole thing
is switched around, so that the sender has to store the message, and the receiver can
go and pick it up. So there, the cost is is is placed on the sender. And I think
that would go a long way to solving the spam problem. But it's not compatible with
the e-mail software that we have today. So it's not clear to me, how we would be able
to migrate in a good way, unfortunately.
Harald Angel: Thank You. Do we have any other questions? That does not seem to be the
case, so please give another warm round of applause to Peter Stuge. Thank you very
much for the talk. Peter: Thank you.
*applause*
*postroll music*
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