Subject: Relative performance of IPv6 and IPv4 for current users

From: Bill Owens <[email-masked]>
Date: Tue, 1 Jul 2003 15:55:04 -0400

There's a small debate going on within the Apple IPv6 mailing list 
over whether it is wise to have an application prefer v6 
connectivity, when it is available, over v4. The argument against 
preferring to use v6 runs along the lines of "most people have only 
v4 connectivity, and for those few that have v6, the performance of 
v4 is usually better".

Although it is hardly a scientific way to conduct a survey, I'm 
curious what the members of this group think of that assertion. 
Personally, I find that my v6 connectivity is either just about as 
good as v4, or very much worse, and the difference is whether the 
other end is connected natively or through some variety of tunnel. 
But I don't have a good feel for what percentage of v6-accessible 
sites fall into each category.

There is also a sub-argument about 6to4, and whether it is sensible 
to enable 6to4 with anycast relay support given the dearth of relay 
routers. There seems to be some agreement that in the abscence of a 
local v6 router, allowing the machine to configure itself as a 6to4 
router without a relay is a reasonable compromise. I think that I can 
agree with that, if those v6 connection attempts which fail without 
the default route, do so rapidly enough to avoid delaying the 
eventual v4 connection. Would anyone with more 6to4 experience care 
to comment on that idea?

Bill.

---

From: Robert Elz <[email-masked]>
Date: Wed, 02 Jul 2003 04:54:42 +0700

Date:        Tue, 1 Jul 2003 15:55:04 -0400
    From:        Bill Owens <[email-masked]>
    Message-ID:  <a05200f6ebb2793f5b7a0@[199.109.32.35]>

  | Personally, I find that my v6 connectivity is either just about as 
  | good as v4, or very much worse, and the difference is whether the 
  | other end is connected natively or through some variety of tunnel. 

I don't see that distinction, perhaps because tunnels count for almost
all of the IPv6 I do.

It depends which performance is counted - I find that IPv6 connectivity
tends to work more reliably than IPv4 most of the time (but that may just
be that most people advertising IPv6 make sure it works most of the time,
whereas IPv4 is just everybody, some conscientious, others not.

On straight bandwidth type of performance (byte per second) it varies
day to day - my IPv6 and IPv4 travel over different paths, sometimes one
is more congested, other times the other is.

But, the real issue, for most people, is that IPv6 by-passes NAT, and
IPv4 doesn't.   That's the one that matters, and for that reason alone
I'd always take IPv6 in preference to IPv4 any day, regardless of how
much slower it seemed.

kre

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From: David Malone <[email-masked]>
Date: Tue, 1 Jul 2003 22:04:28 +0100

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> curious what the members of this group think of that assertion. 

If you're interested in another random data point, my IPv6 connectivity
is about the same as IPv4 at home and at work, as the ISPs provide
either native connectivity or connectivity via tunnels, and both
ISPs peer at the local IXP. During the SQL-slammer my IPv6 connectivity
was significantly better than IPv4 ;-)

> routers.

I really wonder if there is a dearth of 6to4 relay routers. My work
and home ISPs both have relay routers. When I use 6to4 with other
Irish ISPs I see the traffic going to several different relays (I
think I've seen two distinct ones on Germany and Switch in Switzerland).

	David.

---

From: "EricLKlein" <[email-masked]>
Date: Wed, 2 Jul 2003 10:56:09 +0300

Just out of curiosity, have the fixed that little problem in the MAC OS
where opening the printer selection window results in a ping every 30
seconds to all possible printers out there?

It was a problem in the old Mac OS, and if it is still there then you could
be sending out trillions of IMP pings every 30 seconds, this is almost as
good as Quake for killing a network.

---

From: Carlos Friacas <[email-masked]>
Date: Wed, 2 Jul 2003 09:47:15 +0100 (WEST)

> think I've seen two distinct ones on Germany and Switch in Switzerland).

Try: whois -h whois.ripe.net 192.88.99.0 | grep origin

:-)

> 	David.

Regards,

./Carlos                                                "Networking is fun!"
--------------         [http://www.ip6.fccn.pt]           http://www.fccn.pt
<[email-masked]>, CMF8-RIPE, CF596-ARIN, Wide Area Network Workgroup
F.C.C.N. - Fundacao para a Computacao Cientifica Nacional fax:+351 218472167
                [ See me @ h323:videoconf05.fccn.pt]
  "Internet is just routes (125953/461), naming (millions) and... people!"

---

From: Tim Chown <[email-masked]>
Date: Wed, 2 Jul 2003 10:23:20 +0100

> think I've seen two distinct ones on Germany and Switch in Switzerland).

Many networks have 6to4 relays that they do not advertise outside their
own network... so "dearth" is a visibility issue also...

Tim

---

From: "Craig A. Huegen" <[email-masked]>
Date: Wed, 2 Jul 2003 09:37:04 -0500 (Central Daylight Time)

> connectivity, when it is available, over v4. The argument against

Anecdotal case:  about a year ago I was downloading BIND 9 from
ftp.isc.org.  I typed "ftp ftp.isc.org"; it wasn't obvious, but my machine
used the IPv6 address.  I couldn't understand why the transfer was only
getting roughly 1 KB/sec.  I used "ping" and "traceroute" and things
looked just fine.  It wasn't until I scrolled up and saw "entering
extended passive mode" that I finally realized the performance problem --
I was using IPv6.  A resulting traceroute6 showed my routing from my home
to Cisco to Japan back to ISC.

Being the enterprise network control freak that I am, I would really like
a standardized ability to prefer IPv4 over IPv6 until we feel comfortable
that IPv6 reachability and performance of the topology is up to par with
the IPv4 network.  I'm sure we'll do fine, but I imagine we'll have a
number of cases where we're asked to figure out performance problems and
will end up realizing it's because IPv6 was used over IPv4.

/cah

-- 
Craig A. Huegen, Chief Network Architect      C i s c o  S y s t e m s
IT Transport, Network Technology & Design           ||        ||
Cisco Systems, Inc., 400 East Tasman Drive          ||        ||
San Jose, CA  95134, (408) 526-8104                ||||      ||||
email: [email-masked]       CCIE #2100      ..:||||||:..:||||||:..

---

From: David Malone <[email-masked]>
Date: Wed, 2 Jul 2003 17:39:11 +0100

> own network... so "dearth" is a visibility issue also...

If anyone is interested, I had a go at counting 6to4 relay routers
from the IPv6 side. I did this by tracerout6ing with a 6to4 source
address and then using tcpdump to catch the IPv4 addresses of
relay-routers that was used to encapsulate the replies. To decide
where to traceroute to, I used the ::1 addresses of each prefix in
the IPv6 BGP table (as seen from HEAnet this morning).

After doing this, I got replies encapsulated 26 different source
IPv4 addresses. One was the anycast address and I had a go at
guessing the countries of the remainder (AU:1 CZ:1 DE:1 FI:1 IE:1
JP:1 KR:3 LT:2 NL:3 NO:1 PT:1 SE:2 TH:1 TW:1 UK:2 US:3).

About 1/4 of the response packets came from the 6to4 anycast address,
so it seems to be worth trying to figure out how many relays it
represents. Looking at the histogram of TTLs in the IPv4 header,
it looks like there are at least 3 or 4.

To try to get a better idea, I tracerout6ed to a 6to4 address using
a routing header to get the packet to first go to nodes that had
had replies encapsulated with the anycast address. The second last
hop of these traceroutes should help identify the 6to4 relay.

This produced 27 IPv6 addresses, but sevral of them looked like
they were assigned to the same machine. Looking at the /32s that
these IPv6 addresses are in suggests that there are actually about
12 distinct relays in this group. Looking them up in whois shows
that two of the /32s are in switch, so we're probably looking at
11 (CH:1 DE:3 EE:1 FI:1 IE:1 JP:1 NL:1 UK:1 US:1).

In total, that's about 33, if you take into account a possible
overlap of 2 or 3.

[Naturally, I may have missed lots of relays that aren't visable
from the route to the ::1 address within a prefix...]

        David.

---

From: Sebastien Roy <[email-masked]>
Date: Wed, 02 Jul 2003 13:05:12 -0400

[email-masked] said:
> Being the enterprise network control freak that I am, I would really
> like a standardized ability to prefer IPv4 over IPv6 until we feel
> comfortable that IPv6 reachability and performance of the topology
> is up to par with the IPv4 network.

There is a way to do this if the OS implements rfc3484's policy table.
You can change the precedence of IPv4 addresses in this table to
accomplish this.  It's is described in section 10.3 of rfc3484.

> I'm sure we'll do fine, but I
> imagine we'll have a number of cases where we're asked to figure out
> performance problems and will end up realizing it's because IPv6 was
> used over IPv4.

Interestingly, my colleagues and I published a draft on "Dual Stack
IPv6 on by Default" (draft-roy-v6ops-v6onbydefault-00.txt) that
touches upon this briefly.  Version 01 of this draft was submitted
last weekend, so it should show up in the directory any day now.

-Seb