Slashdot is powered by your submissions, so send in your scoop

 



Forgot your password?
typodupeerror
×
Networking The Internet

The Night the IETF Shut Off IPv4 208

IP Freely writes "At this year's Internet Engineering Task Force meeting in Philadelphia, conference organizers shut off IPv4 for an hour. Surprisingly, chaos did not ensue. 'After everyone got his or her system up and running, many people started looking for IPv6-reachable web sites, reporting those over Jabber instant messaging — which posed its own challenges in the IPv6 department. I was surprised at the number of sites and wide range of content available over IPv6. Apart from — obviously — IPv6-related sites; they ranged from "the largest Gregorian music collection in Internet" to "hardcore torrents." Virtually none of the better known web destinations were reachable over IPv6. That changed when ipv6.google.com popped into existence.'"
This discussion has been archived. No new comments can be posted.

The Night the IETF Shut Off IPv4

Comments Filter:
  • by rrkap ( 634128 ) on Friday March 14, 2008 @03:27PM (#22753946) Homepage
    I'm glad to know that the internet will still be able to fulfill its primary purpose as a porn distribution channel when we switch over to ipv6.
  • by Reality Master 201 ( 578873 ) on Friday March 14, 2008 @03:28PM (#22753958) Journal
    More about the hardcore torrents, please.
  • Okay... (Score:5, Interesting)

    by TFer_Atvar ( 857303 ) on Friday March 14, 2008 @03:28PM (#22753966) Homepage
    Who else put ipv6.google.com in their address bar just to see what would happen?
    • Re:Okay... (Score:5, Funny)

      by webword ( 82711 ) on Friday March 14, 2008 @03:32PM (#22753998) Homepage
      ** damn your eyes! **

      Yes, I tried. And yes, I just lost geek points. (-1)

      "Natalie Portman + Linux" (+1)

      We'll call it even, OK?
    • Re:Okay... (Score:5, Informative)

      by DeadBeef ( 15 ) on Friday March 14, 2008 @03:34PM (#22754020) Homepage
      I did, the google logo does a little dance, other than that it just looks like google.

      I guess I was expecting too much, but the sites that are indexed appear to be just the regular ipv4 sites, so they have ipv6 enabled the web frontend to the search engine but not the back end that goes and crawls the web.
      • Re:Okay... (Score:5, Informative)

        by stsp ( 979375 ) on Friday March 14, 2008 @04:11PM (#22754436) Homepage

        I did, the google logo does a little dance, other than that it just looks like google.
        The logo can also be seen with IPv4: http://www.google.com/images/ipv6_logo.gif [google.com]
      • I did, the google logo does a little dance, other than that it just looks like google.

        Just remember kame.net got there first with their turtle ;)
      • Re:Okay... (Score:5, Informative)

        by Sesse ( 5616 ) <sgunderson@big[ ]t.com ['foo' in gap]> on Friday March 14, 2008 @04:54PM (#22754808) Homepage

        Hi. I work (among other things) with IPv6 in Google, although I was only distantly released to this launch (some of my code was used in the monitoring components). It's nice to see we're getting attention :-)

        You're entirely right that at the moment, only web search has an AAAA record. (However, with some trickery, you can get several other Google services running too -- just add /etc/hosts lines to the same IP, and you'll probably be able to run Maps, GMail and several others over IPv6.) We don't yet crawl, send or receive e-mail, or support GTalk over IPv6, and we definitely cannot guarantee anything about the uptime of the IPv6 versions of our services. (We've had a few years to make a production-grade IPv4 network, give us some time to make it IPv6-ready too!) Think of it as the first baby step; although we don't have a roadmap published (we almost never talk about future products in Google) I think it's pretty safe to say that there will be more.

        Whether there should be services that are not available over IPv4, though, is an entirely different discussion. If you had a cool service and could offer it to the world, would you keep it away from 99.9% of the Internet just because you could?

        /* Steinar */
        - Software engineer, Google Norway

    • Re: (Score:2, Informative)

      by corsec67 ( 627446 )

      #dig ipv6.google.com

      ; <<>> DiG 9.3.4 <<>> ipv6.google.com
      ;; global options: printcmd
      ;; Got answer:
      ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 40073
      ;; flags: qr rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 0, ADDITIONAL: 0

      ;; QUESTION SECTION:
      ;ipv6.google.com. IN A

      ;; ANSWER SECTION:
      ipv6.google.com. 10166 IN CNAME ipv6.l.google.com.
      ipv6.l.google.com. 0 IN A 208.69.32.130

      ;; Query time: 206 msec
      ;; SERVER: 10.0.0.1#53(10.0

      • Re: (Score:3, Funny)

        by hansamurai ( 907719 )

        Not having an A record would make it quite hard to view, so I didn't even try.
        So instead of just pasting the site in your address bar to see what was there, you did a dig query on it?

        Sorry, I don't really mean to sound sarcastic... Friday afternoon...
      • Re:Okay... (Score:4, Informative)

        by DavidTC ( 10147 ) <slas45dxsvadiv.v ... m ['box' in gap]> on Friday March 14, 2008 @03:51PM (#22754180) Homepage
        That's the point. It's IPv6 only:
        $ dig ipv6.google.com aaaa

        ;; QUESTION SECTION:
        ;ipv6.google.com.               IN      AAAA

        ;; ANSWER SECTION:
        ipv6.google.com.        10792   IN      CNAME   ipv6.l.google.com.
        ipv6.l.google.com.      5       IN      AAAA    2001:4860:0:2001::68
        ipv6.l.google.com.      5       IN      AAAA    2001:4860:0:1001::68
      • what are you talking about? The log you posted specifically showed an A record!
        By default, dig asks for an A record. try 'dig ipv6.google.com AAAA'. I got the following:

        ;; QUESTION SECTION:
        ;ipv6.google.com. IN AAAA

        ;; ANSWER SECTION:
        ipv6.google.com. 10642 IN CNAME ipv6.l.google.com.
        ipv6.l.google.com. 5 IN AAAA 2001:4860:0:1001::68
        ipv6.l.google.com. 5 IN AAAA 2001:4860:0:2001::68

        I could connect to ipv6.google.com, but I run IPv6 along IPv6, and I didn't bother checking w

        • Re: (Score:3, Funny)

          by AceJohnny ( 253840 )

          I could connect to ipv6.google.com, but I run IPv6 along IPv6, and I didn't bother checking whether the connection was through IPv5 or IPv6, since, as we have shown, ipv6.google.com has both an A (for IPv) and AAAA (for IPv6) records.

          Damn, I managed to mistype every "IPv4" reference. There must be a meaning for this...
          I meant "IPv4 along IP6" and "through IPv4 or IPv6" and "(for IPv4)"
        • Re:Okay... (Score:5, Funny)

          by bcmm ( 768152 ) on Friday March 14, 2008 @03:58PM (#22754252)
          You use IPv5?

          Wow, that's obscure.
          • IPv5 (Score:5, Interesting)

            by jd ( 1658 ) <imipak@ y a hoo.com> on Friday March 14, 2008 @05:19PM (#22754986) Homepage Journal
            I believe IPv5 is formally defined as TUBA, although another poster mentions realtime connections (which wouldn't seem to be an IP version, per se, but the layer running over IP) and POTS (which I'm damn sure is a layer 1 to layer 2 concept). There's also an IPv7. As far as I know, no TUBA drivers exist for Linux (damn shame) and I'm very certain no services (eg: DNS) exist for it.

            (When it comes to Linux support for protocols, it's a popular platform for early developers, but maintenance can be an issue. enSKIP and SGI's STP code are abandonware, the real-time network driver for RTAI is infrequently updated, and the GAMMA Active Messages driver is seriously stalled in a number of areas. Many updates to Web100 have just been kernel increment updates, not bugfixes or added features. I don't recall seeing any support for VIA - which is fair enough, given it's dead - or iWarp. Linux' QoS supports RED, but neglected BLUE, GREEN, BLACK, WHITE and PURPLE the last time I looked.)

            • Re: (Score:3, Informative)

              I believe IPv5 is formally defined as TUBA

              No, IPv5 is ST-II, the Internet Stream protocol, defined in RFC 1190. TUBA is one of the experimental proposals that led to IPv6, and has never been assigned an IP version number.

      • by daveb ( 4522 )
        JEESE!!

        you didn't REALLY expect to get useful technical information information from DIG [dig.com] did you?

        oh

        wait ...

    • Re: (Score:2, Interesting)

      Ok, I got a server not found from work and from home so I can only assume I'm not set up right in either place. So, who can point me to what's probably wrong (for home, not work)? I'm running a NetGear router (don't remember what model) but I presume it doesn't support IPV6. Does that mean I have to replace my router in order to be able to view IPV6-only sites? How do I know if I buy a new router that it will support them?
      • Re: (Score:3, Informative)

        by jd ( 1658 )
        If you want to do things the hard way, you could try: OpenWRT [openwrt.org]. If you prefer the easy way, use a tunnel broker. Then only your machine needs to support IPv6, your router doesn't.
      • Re:Okay... (Score:5, Informative)

        by Tony Hoyle ( 11698 ) <tmh@nodomain.org> on Friday March 14, 2008 @05:28PM (#22755056) Homepage
        Pretty much no home routers support ipv6.

        Basically you can either buy a cisco and upgrade to an ISP that'll route ipv6 (that's the neatest way of doing it, but is expensive and limits your ISP choice), or if you can get hold of an old WRT54G you can install a custom firmware that supports ipv6 and create a tunnel to a tunnel broker somewhere - it'll be much slower (tunnel latency is typically 300ms+ for the first hop because there are so few of them) but you'll be 'on' the ipv6 internet.
        • Re:Okay... (Score:5, Informative)

          by fyonn ( 115426 ) <dave@fyonn.net> on Friday March 14, 2008 @06:54PM (#22755648) Homepage
          or you can use an apple airport extreme router which supports ipv6 out of the box, though you might need to turn the "firewall" off to get the full functionality.
          • Re: (Score:3, Informative)

            by laffer1 ( 701823 )
            Airport Express base stations also support IPv6. I have two and it even encourages use of IPv6 in the manual.

            I've been tempted to play with it, but I don't believe my Wii can handle it. It's not just routers that need some work.
    • by Cadre ( 11051 )
      I did, though I expected it to work since I have had IPv6 access for awhile now. I just didn't know that Google had an IPv6 site. Google's homage to the dancing Kame is pretty nice.
    • Re:Okay... (Score:5, Informative)

      by mobilesteve ( 899951 ) on Friday March 14, 2008 @04:17PM (#22754488)
      If you really want to see what Google's IPv6 page looks like, you can use SixXs's IPv6 to IPv4 looking glass: http://ipv6.google.com.ipv4.sixxs.org/ [sixxs.org]
    • by The Mgt ( 221650 )
      Me. It's now my homepage.
    • me. ipv6.google.com looks pretty much as I expected, but there is a difference: the letters jump on load, but only on the first load.
  • by MichaelCrawford ( 610140 ) on Friday March 14, 2008 @03:34PM (#22754018) Homepage Journal
    My Googling hasn't yielded any insight. I should be listing them from my article Links to Tens of Thousands of Legal Music Downloads [goingware.com].

  • I was there (Score:5, Informative)

    by Zarhan ( 415465 ) on Friday March 14, 2008 @03:35PM (#22754030)
    And really, only problems I saw were the fact that it's pain in the ass to get automatic DHCPv6 working. The idea is that IPv6 stateless autoconfig (router advertisement) has a bit that tells the client if they should get ALL config via DHCP or just additional (like DNS addresses). However, no easy way to make Linux kernel execute DHCPv6 client based on the received stateless autoconfig bit.

    Anyway, after statically configuring DNS servers, things were very smooth. Google et al worked, I could access entire IPv4 web via sixxs.org (just go http://slashdot.org.sixxs.org/ [sixxs.org] to access Slashdot via IPv6), I could SSH to my home servers...only things that seemed a bit odd were failing reverse DNSes on some hops when running traceroute. Jabber worked, IRC worked.

    Great experience and experiment.
    • DHCPv6 (Score:4, Interesting)

      by tlambert ( 566799 ) on Friday March 14, 2008 @03:59PM (#22754276)
      I _really_ fail to understand the rationale for DHCPv6.

      IPv6 was designed o that stateless autoconfig resulted in routable addresses.

      Combine that with ZEROCONF, and you can discover everything that a DCHP server is going to be able to tell you, and more.

      The only technical rationale I've ever heard is for reverse DNS, to prevent someone getting on the local net without authorization and relaying through your SMTP server, but that requires that you configure your DHCP server to only serve to "trusted" MAC addresses. It's also totally useless with DNSUPDAT, since anyone who gets an address can update the reverse in their home domain, and relay out that instead (which is more secure anyway).

      So the only rationale I see is controlling access to network dialtone (a business rationale, based on the business model of selling packets rather than selling pipes - a model I happen to disagree with allowing to continue to exist).

      So whose idea was it to turn on DHCPv6?

      -- Terry
      • by Zarhan ( 415465 )
        Clicked on wrong link and replied at wrong place in thread - reply at http://slashdot.org/comments.pl?sid=488070&cid=22754460 [slashdot.org]
      • Re:DHCPv6 (Score:5, Informative)

        by gclef ( 96311 ) on Friday March 14, 2008 @04:40PM (#22754690)
        One of the things the zeroconf and autoconf folks keep missing is that large organizations (like where I am) need to know which host had a given IP at a given time in the past. We need records and accounting, basically. While DHCP isn't perfect, by any stretch, a fully-autoconf (or zeroconf) network doesn't fill that need, and would be an absolute nightmare for the security folks.

        For example, if I get a complaint about a laptop a few days after the event, how am I supposed to find that host once it's moved onto another network? Are people seriously saying I should have to walk every single router neighbor table (or arp table, if we're talking v4) looking for a specific 64-bit number? The network I work on has literally thousands of routers & switches. That's simply a non-starter. With DHCP, I at least have a > 50% chance of finding the MAC of a host (and where it is now) with a simple query.

        In short, business needs are driving it. Almost every discussion I've seen of IPv6 for large enterprises (not ISPs) has assumed that DHCPv6 will be used, and that autoconf + zeroconf will not.
      • Re:DHCPv6 (Score:4, Informative)

        by Tony Hoyle ( 11698 ) <tmh@nodomain.org> on Friday March 14, 2008 @05:37PM (#22755112) Homepage
        Stateless autoconfig will only tell you the ipv6 address and router. It's not good enough for full config.

        You need to distribute the addresses of DNS, NTP, WINS, etc. etc. - for that you need DHCPv6.

        Zeroconf will not cut it. That's for discovering services on the local subnet only... not broadcasting DNS addresses etc. On top of that it won't cross routers (by design), making it unsuitable for any reasonable size network (It has exactly the same issues as Netbios broadcast in fact, which hardly ever works.. hence the WINS hack which also hardly ever works).

        Reverse DNS you mentioned - this not solvable without DHCPv6 at present (and is a critical issue for a well functioning network).

        The other issue with stateless autoconfig is you can't fix the addresses centrally. In theory they should stay the same but in practice network cards die.. and the address is just the MAC address of the network card. If that happens to your main webserver you're screwed.
        • Re: (Score:3, Informative)

          by profplump ( 309017 )
          You do *not* needs DHCP to get DNS addresses under IPv6. See http://tools.ietf.org/html/draft-ietf-dnsop-ipv6-dns-configuration-06 [ietf.org] -- the RA method is site-local not link-local, so it works across routers if they are configured correctly. And once you have DNS you can configure everything else via SRV records.

          On the "MAC addresses change" note, an ease solution is to simply change the MAC address of the replacement card to match the old one. Since the old one is no longer in use there's no conflict, and the
      • Re: (Score:3, Interesting)

        by Junta ( 36770 )
        Others have mentioned the accounting thing, I think that's a very good example, it's much easier to track what is going on when a definitive DHCPDISCOVER transaction appears. One could make the argument for DNS update requests to be a good indicator, but that's not nearly as to the point and not required to occur.

        On a more purely technical note, how do I tell server176 boot firmware that it should be loading file 'deployimg.176', while telling server12 to be loading 'recordimg.5', or whatever? How do I te
    • Re:I was there (Score:5, Interesting)

      by Zarhan ( 415465 ) on Friday March 14, 2008 @04:13PM (#22754460)
      I _really_ fail to understand the rationale for DHCPv6.

      IPv6 was designed o that stateless autoconfig resulted in routable addresses.


      Informing client about DNS, NTP etc servers is just icing on cake.

      The primary purpose is accounting (And insert whatever Orwellianisms you want here). Especially in enterprise networks. ISPs also are interested, to provide equivalent functionality to DHCPv4 "option 82" or similar ones that tie specific IP to specific user or at least DSL connection. So basically the driver is requirement to have managed IPv6 addressing without random hosts just deciding whatever they want to use (EUI-64, CGAs, whatever). In fact, the recent trend seems to be that when deploying network, DHCPv6 is not only preferred option, it seems to become the *only* allowed option. (Basically: Filter traffic so that only the DHCPv6-allocated address is allowed to communicate.)

  • 'Apart from -- obviously -- IPv6-related sites; they ranged from "the largest Gregorian music collection in Internet" to "hardcore torrents."'

    Once you can get porn on the medium, you know it is a winner.
  • yo (Score:3, Insightful)

    by rice_burners_suck ( 243660 ) on Friday March 14, 2008 @03:54PM (#22754212)
    The trouble with ipv6 is that ipv4 works so well for 90% of the population (in the same manner that 76% of statistics are made up on the spot) that nobody who doesn't really care about this won't put in an effort to make the switch. It looks like going 100% ipv6 is quite a few years off, foo.
    • by jandrese ( 485 )
      Well, that and my ISP doesn't route IPv6 traffic, so if I wanted to use it I'd have to tunnel over IPv4, and that's just pointless complexity I don't really need in my network. If my ISP supported IPv6 I'd turn it on even though, as mentioned in the article, trying to use IPv6 on the current internet tends to break stuff and add delays to other things.
    • Re: (Score:3, Interesting)

      The trouble with ipv6 is that ipv4 works so well for 90% of the population (in the same manner that 76% of statistics are made up on the spot) that nobody who doesn't really care about this won't put in an effort to make the switch. It looks like going 100% ipv6 is quite a few years off, foo.

      To you average user there should be no effort, since it should just work. The problem is that there are still gaping holes that need to be resolved. For example no DHCPv6 client provided standard with MacOS X. Sure you
    • Re:yo (Score:4, Insightful)

      by Loke the Dog ( 1054294 ) on Friday March 14, 2008 @04:51PM (#22754772)
      Well, IPv4 is ultimately the reason why people have NATs, and from my experience, most people with a NAT do occtionally run into problems. But these people could never guess that their problems are caused by the NAT and could be solved by simply getting more IPs.

      For this reason, you rarely see people picking ISPs that offer more IPs and that means IPv6 comes along slowly. From the ISPs point of veiw, supply of IPs is greater than demand.

      Its like people who use a terrible OS (and I'm not even talking Vista here, but more like win 98 or something) and get viruses and all sorts of malware. They don't seem to understand that all those issues they're having with their computer is not something you have to put up with, that there is a solution. This makes demand for really good OSes relatively low.
    • Well... IPv4 works well because IPv6 doesn't. My ISP doen't offer IPv6, so their customers don't use it, so there's no demand so they don't offer it.

      After some complaint, they did apparently offer it for a shot time last summer but today the only mention of it on their website is in their Wikipedia mirror.
    • in the same manner that 76% of statistics are made up on the spot

      I always thought it was higher, around 80%.

      But seriously, my favorite statistic from Slashdot today is this:

      According to the study, redoing the P2P into what they call P4P can reduce the number of 'hops' by an average of 400%.
      I suppose it's probably not made up, but it is meaningless.
  • More IPv6 sites here (Score:5, Informative)

    by Midnight Thunder ( 17205 ) on Friday March 14, 2008 @04:10PM (#22754418) Homepage Journal
    Sixxs.net lists some IPv6 web sites in its Wiki:

    http://www.sixxs.net/wiki/Category:IPv6-specific_content [sixxs.net]

    and there is also some other 'Cool IPv6 stuff' listed on the Sixxs web site:

    http://www.sixxs.net/misc/coolstuff/ [sixxs.net]
  • by Gud ( 78635 ) on Friday March 14, 2008 @04:25PM (#22754534)
    Someone should fix that and the traffic would have gone back up to normal load :-)

    Here is my list of sites that I was able to reach using native IPv6
    using IE worked:
                    ipv6.google.com
            www.ripe.net
            www.apnic.net
            www.stupi.net
            www.arin.net
            www.icann.org
            www.nlnetlabs.nl

    Failed foillowing sites did not work
            www.cisco.net/com
                    www.microsoft.com
            www.speakeasy.net
            slashdot.org
            news.bbc.co.uk
            www.mbl.is
            www.cnn.com
            www.comcast.com/net
            news.com.com
            www.ibm.com
           
    • Re: (Score:3, Informative)

      by Sesse ( 5616 )
      There's a www.ipv6.cisco.com, but it has MTU issues, at least from here. /* Steinar */
  • by daniel23 ( 605413 ) on Friday March 14, 2008 @04:26PM (#22754540)
    slashdot was missing,too, and unlike google it still is.

    dp@phoenix:~/Desktop$ ping6 ipv6.google.com
    PING ipv6.google.com(2001:4860:0:1001::68) 56 data bytes
    64 bytes from 2001:4860:0:1001::68: icmp_seq=1 ttl=53 time=221 ms
    64 bytes from 2001:4860:0:1001::68: icmp_seq=2 ttl=53 time=214 ms
    64 bytes from 2001:4860:0:1001::68: icmp_seq=3 ttl=53 time=221 ms

    --- ipv6.google.com ping statistics ---
    3 packets transmitted, 3 received, 0% packet loss, time 2026ms
    rtt min/avg/max/mdev = 214.969/219.185/221.367/3.006 ms

    dp@phoenix:~/Desktop$ ping6 ipv6.slashdot,org
    unknown host

    dig ipv6.google.com AAAA

    ;; flags: qr rd ra; QUERY: 1, ANSWER: 3, AUTHORITY: 7, ADDITIONAL: 0

    ;; QUESTION SECTION:
    ;ipv6.google.com.               IN      AAAA

    ;; ANSWER SECTION:
    ipv6.google.com.        10455   IN      CNAME   ipv6.l.google.com.
    ipv6.l.google.com.      5       IN      AAAA    2001:4860:0:1001::68
    ipv6.l.google.com.      5       IN      AAAA    2001:4860:0:2001::68

    dig slashdot.org AAAA

    ;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 0

    • slashdot was missing,too, and unlike google it still is.

      Does this mean with we will have to remove Slashdot's Nerd approval rating?
    • Re: (Score:2, Insightful)

      did you think of trying ipv6.slashdot.org instead of ipv6.slashdot,org?

      • you do have a point there, or rather a comma, but it's a wrong error:

        ping6 ipv6.slashdot.org gives unknown host and the typo was introduced only when I did it all once again to copy paste from it to the post.
  • Presumably, IPv6 will itself eventually be replaced by something better.
  • Ok,so IPv6 works and is usable. Now what? None of the major web properties are yet on IPv6, nor are any of the major carrier networks that the users are connected to. The problem is that there is not yet any business case for anyone to be the first to migrate. It generates no revenue. Until there is an actual motive to move to IPv6, it's only interesting to geeks.

    Hopefully, when the supply of IPv4 addresses runs out (in a little over two years), there will be a Chinese fire drill for everyone to migra
    • Re: (Score:3, Insightful)

      Or you can just bite the bullet and put in the hours, acknowledging that it won't lead to extra revenue but is necessary for the internet to continue.
  • by MK_CSGuy ( 953563 ) on Friday March 14, 2008 @04:34PM (#22754636)
    With blackjack, and hookers!
  • What I really want to know is, how many of the people who had computers at that conference were users who had no clue what IPv6 even was, much less how to configure their computer to use it.

    It's one thing to say IPv6 is ready because a conference filled with engineers could download their pron with IPv4 turned off. It's entirely another thing to say that IPv6 is ready because it works without my mother even knowing the difference.
  • Is there a list somewhere with sites that were and were not available using IPv6?
    • You want a list of 99.99% of the sites on the entire internet???? :p

      Better to start with a list of what *is* available.
  • Get IPv6 (Score:4, Informative)

    by klapaucjusz ( 1167407 ) on Friday March 14, 2008 @11:24PM (#22757392) Homepage

    A lot of people think they need their ISP's help to get IPv6 connectivity. That's not the case. If you're running Windows Vista, or if you use an Apple Airport router, you should get connectivity to the IPv6 Internet out of the box. If you're running Linux, I've writtent a short HOWTO about IPv6 under Linux [jussieu.fr].

E = MC ** 2 +- 3db

Working...