35C3 - How does the Internet work?

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 [e-mail]. 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

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