-----Original Message----- From: nanog-request@nanog.org Date: Sat, 14 Jun 2008 21:54:35 To: <nanog@nanog.org> Subject: NANOG Digest, Vol 5, Issue 33 Send NANOG mailing list submissions to nanog@nanog.org To subscribe or unsubscribe via the World Wide Web, visit http://mailman.nanog.org/mailman/listinfo/nanog or, via email, send a message with subject or body 'help' to nanog-request@nanog.org You can reach the person managing the list at nanog-owner@nanog.org When replying, please edit your Subject line so it is more specific than "Re: Contents of NANOG digest..." Today's Topics: 1. RE: [NANOG] Introducing latency for testing? (Frank Bulk - iNAME) 2. Re: .255 addresses still not usable after all these years? (Greg VILLAIN) 3. Re: DNS problems to RoadRunner - tcp vs udp (Scott McGrath) 4. Re: DNS problems to RoadRunner - tcp vs udp (Jeroen Massar) 5. Re: [NANOG] Introducing latency for testing? (Chris Marlatt) 6. Re: [NANOG] Introducing latency for testing? (Joel Jaeggli) 7. Re: DNS problems to RoadRunner - tcp vs udp (Scott McGrath) 8. Re: DNS problems to RoadRunner - tcp vs udp (Simon Leinen) 9. Re: DNS problems to RoadRunner - tcp vs udp (Jeroen Massar) ---------------------------------------------------------------------- Message: 1 Date: Sat, 14 Jun 2008 13:34:53 -0500 From: "Frank Bulk - iNAME" <frnkblk@iname.com> Subject: RE: [NANOG] Introducing latency for testing? To: "'Mike Lyon'" <mike.lyon@gmail.com>, "NANOG" <nanog@merit.edu> Message-ID: <!&!AAAAAAAAAAAuAAAAAAAAAKTyXRN5/+lGvU59a+P7CFMBAN6gY+ZG84BMpVQcAbDh1IQAAAATbSgAABAAAACMh0iCc5e/TLORNwsUDcWNAQAAAAA=@iname.com> Content-Type: text/plain; charset="us-ascii" It's not free, but at a recent trade show I did see what appeared to be an affordable unit from Apposite Technologies (apposite-tech.com). And there's always PacketStorm. Frank -----Original Message----- From: Mike Lyon [mailto:mike.lyon@gmail.com] Sent: Friday, May 02, 2008 3:13 PM To: NANOG Subject: [NANOG] Introducing latency for testing? So I want to mimic some latency in a test network for DB replication. I am wondering what other's have used for this? Obviously, the best way to would be to actually have one box across the US or across the globe to actually test against but what if you don't have that? Are there any GPL software router solutions that would allow you to tweak the latency in between the two test boxes? Thanks in advance. -Mike _______________________________________________ NANOG mailing list NANOG@nanog.org http://mailman.nanog.org/mailman/listinfo/nanog ------------------------------ Message: 2 Date: Sat, 14 Jun 2008 20:33:21 +0200 From: Greg VILLAIN <nanog@grrrrreg.net> Subject: Re: .255 addresses still not usable after all these years? To: nanog@nanog.org Message-ID: <A2776BAD-491D-4F3D-9645-02EC7492E1FB@grrrrreg.net> Content-Type: text/plain; charset=US-ASCII; format=flowed; delsp=yes On Jun 14, 2008, at 12:26 AM, Mike Lewinski wrote:

David Hubbard wrote:

...

I remember back in the day of old hardware and operating systems we'd intentionally avoid using .255 IP addresses for anything even when the netmask on our side would have made it fine, so I just thought I'd try it out for kicks today. From two of four ISP's it worked fine, from Verizon FIOS and Road Runner commercial, it didn't. So I guess that old problem still lingers?

The TCP/IP stack in Windows XP is broken in this regard, possibly in Vista as well, though I've yet to have the displeasure of finding out. I have a router with a .255 loopback IP on it. My Windows XP hosts cannot SSH to it. The specific error that Putty throws is "Network error: Cannot assign requested address".

At least if I ever need to completely protect a device from access by Windows users, I have a good option :)

Mike

From what I recall, Microsoft's stack was based on the only free one they could afford back in the Trumpet/Winsock days, namely BSD's. It is either dependent on how the stack is integrated, or it simply implies that BSD's stack is(was) also broken (I'd tend to doubt that). Also, Vista's stack was supposed to have been re-developed from scratch, never checked it. Greg VILLAIN ------------------------------ Message: 3 Date: Sat, 14 Jun 2008 16:40:10 -0400 From: Scott McGrath <mcgrath@fas.harvard.edu> Subject: Re: DNS problems to RoadRunner - tcp vs udp To: Randy Bush <randy@psg.com> Cc: nanog@merit.edu Message-ID: <48542CAA.5010503@fas.harvard.edu> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Not to toss flammables onto the pyre. BUT there is a large difference from what the RFC's allow and common practice. In our shop TCP is blocked to all but authoratative secondaries as TCP is sinply too easy to DoS a DNS server with. We simply don't need a few thousand drones clogging the TCP connection table all trying to do zone transfers ( yes it happened and logs show drones are still trying ) For a long time there has been a effective practice of UDP == resolution requests TCP == zone transfers It would have been better if a separate port had been defined for zone transfers as that would obviate the need for a application layer gateway to allow TCP transfers so that zone transfers can be blocked and resolution requests allowed for now all TCP is blocked. Now just because someone has a bright idea they drag out a 20 y/o RFC and say SEE, SEE you must allow this because the RFC says so all the while ignoring the 20 years of operational discipline that RFC was written when the internet was like the quad at college everyone knew one and other and we were all working towards a common goal of interoperability and open systems , These days the net is more like a seedy waterfront after midnight where criminal gangs are waiting to ambush the unwary and consequently networks need to be operated from that standpoint. At the University networking level it is extremely difficult as we need to maintain a open network as much as possible but protect our infrastructure services so that they have 5 nines of availability back in the day a few small hosts would serve DNS nicely and we did not have people trying to take them down and/or infecting local hosts and attempting DHCP starvation attacks. And no we are not at the 5 nines level but we are working on it. - Scott Randy Bush wrote:

...

If my server responded to TCP queries from anyone other than a secondary server, I would be VERY concerned.

you may want to read the specs

randy

------------------------------ Message: 4 Date: Sat, 14 Jun 2008 22:47:47 +0200 From: Jeroen Massar <jeroen@unfix.org> Subject: Re: DNS problems to RoadRunner - tcp vs udp To: Scott McGrath <mcgrath@fas.harvard.edu> Cc: nanog@merit.edu Message-ID: <48542E73.9070109@spaghetti.zurich.ibm.com> Content-Type: text/plain; charset="iso-8859-1" Scott McGrath wrote: [..]

For a long time there has been a effective practice of

UDP == resolution requests TCP == zone transfers

WRONG. TCP is there as a fallback when the answer of the question is too large. Zone transfer you can limit in your software. If you can't configure your dns servers properly then don't run DNS. Also note that botnets have much more effective ways of taking you out. And sometimes domains actually require TCP because there are too many records for a label eg http://stupid.domain.name/node/651 If you are thus blocking TCP for DNS resolution you suddenly where blocking google and thus for some people "The Internet". Also see: http://homepages.tesco.net/J.deBoynePollard/FGA/dns-edns0-and-firewalls.html (Which was the second hit for google(EDNS0) after a link to RFC2671) Greets, Jeroen -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 187 bytes Desc: OpenPGP digital signature Url : http://mailman.nanog.org/pipermail/nanog/attachments/20080614/8dc85bfe/attac... ------------------------------ Message: 5 Date: Sat, 14 Jun 2008 16:47:32 -0400 From: Chris Marlatt <cmarlatt@rxsec.com> Subject: Re: [NANOG] Introducing latency for testing? To: frnkblk@iname.com Cc: NANOG <nanog@merit.edu> Message-ID: <48542E64.3000704@rxsec.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Frank Bulk - iNAME wrote:

It's not free, but at a recent trade show I did see what appeared to be an affordable unit from Apposite Technologies (apposite-tech.com). And there's always PacketStorm.

Frank

-----Original Message----- From: Mike Lyon [mailto:mike.lyon@gmail.com] Sent: Friday, May 02, 2008 3:13 PM To: NANOG Subject: [NANOG] Introducing latency for testing?

So I want to mimic some latency in a test network for DB replication. I am wondering what other's have used for this? Obviously, the best way to would be to actually have one box across the US or across the globe to actually test against but what if you don't have that? Are there any GPL software router solutions that would allow you to tweak the latency in between the two test boxes?

Thanks in advance.

-Mike

_______________________________________________ NANOG mailing list NANOG@nanog.org http://mailman.nanog.org/mailman/listinfo/nanog

IIRC ipfw can do this using dummynet and the delay directive. Regards, Chris ------------------------------ Message: 6 Date: Sat, 14 Jun 2008 14:08:25 -0700 From: Joel Jaeggli <joelja@bogus.com> Subject: Re: [NANOG] Introducing latency for testing? To: Chris Marlatt <cmarlatt@rxsec.com> Cc: NANOG <nanog@merit.edu> Message-ID: <48543349.7060400@bogus.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Chris Marlatt wrote:

Frank Bulk - iNAME wrote:

...

It's not free, but at a recent trade show I did see what appeared to be an affordable unit from Apposite Technologies (apposite-tech.com). And there's always PacketStorm.

Frank

-----Original Message----- From: Mike Lyon [mailto:mike.lyon@gmail.com] Sent: Friday, May 02, 2008 3:13 PM To: NANOG Subject: [NANOG] Introducing latency for testing?

So I want to mimic some latency in a test network for DB replication. I am wondering what other's have used for this? Obviously, the best way to would be to actually have one box across the US or across the globe to actually test against but what if you don't have that?

boxes across the globe have the property of being somewhat less deterministic than you'd like if you need repeatability.

IIRC ipfw can do this using dummynet and the delay directive.

it will also do jitter and drop rate... to wit, it's exactly what is need here. there are analogous tools for iptables based platforms. ------------------------------ Message: 7 Date: Sat, 14 Jun 2008 17:18:38 -0400 From: Scott McGrath <mcgrath@fas.harvard.edu> Subject: Re: DNS problems to RoadRunner - tcp vs udp To: Jeroen Massar <jeroen@unfix.org> Cc: nanog@merit.edu Message-ID: <485435AE.8060609@fas.harvard.edu> Content-Type: text/plain; charset=ISO-8859-1; format=flowed There is no call for insults on this list - Rather thought this list was about techincal discussions affecting all of us and keeping DNS alive for the majority of our customers certainly qualifies. We/I am more than aware of the DNS mechanisms and WHY there are there trouble is NO DNS server can handle directed TCP attacks even the root servers crumbled under directed botnet activity and we have taken the decision to accept some collateral damage in order to keep services available. We are a well connected university network with multi-gigabit ingress and egress with 10G on Abilene so we try to protect the internet from attacks originating within our borders AND we really feel the full wrath of botnets as we do not have a relatively slow WAN link to buffer the effects. Yes - we are blocking TCP too many problems with drone armies and we started about a year ago when our DNS servers became unresponsive for no apparent reason. Investigation showed TCP flows of hundreds of megabits/sec and connection table overflows from tens of thousands of bots all trying to simultaneously do zone transfers and failing tried active denial systems and shunning with limited effectiveness. We are well aware of the host based mechanisms to control zone information, Trouble is with TCP if you can open the connection you can DoS so we don't allow the connection to be opened and this is enforced at the network level where we can drop at wire speed. Open to better ideas but if you look at the domain in my email address you will see we are a target for hostile activity just so someone can 'make their bones'. Also recall we have a comittment to openess so we would like to make TCP services available but until we have effective DNS DoS mitigation which can work with 10Gb links It's not going to happen. - Scott Jeroen Massar wrote:

Scott McGrath wrote: [..]

...

For a long time there has been a effective practice of

UDP == resolution requests TCP == zone transfers

WRONG. TCP is there as a fallback when the answer of the question is too large. Zone transfer you can limit in your software. If you can't configure your dns servers properly then don't run DNS. Also note that botnets have much more effective ways of taking you out.

And sometimes domains actually require TCP because there are too many records for a label eg http://stupid.domain.name/node/651 If you are thus blocking TCP for DNS resolution you suddenly where blocking google and thus for some people "The Internet".

Also see: http://homepages.tesco.net/J.deBoynePollard/FGA/dns-edns0-and-firewalls.html

(Which was the second hit for google(EDNS0) after a link to RFC2671)

Greets, Jeroen

------------------------------ Message: 8 Date: Sat, 14 Jun 2008 23:23:44 +0200 From: Simon Leinen <simon.leinen@switch.ch> Subject: Re: DNS problems to RoadRunner - tcp vs udp To: Jon.Kibler@aset.com Cc: nanog@merit.edu Message-ID: <aaod63g17j.fsf@switch.ch> Content-Type: text/plain; charset=us-ascii Jon Kibler writes:

Also, other than "That's what the RFCs call for," why use TCP for data exchange instead of larger UDP packets?

TCP is more robust for large (>Path MTU) data transfers, and less prone to spoofing. A few months ago I sent a message to SwiNOG (like NANOG only less North American and more Swiss) about this topic, trying to explain some of the tradeoffs: http://www.mail-archive.com/swinog@lists.swinog.ch/msg02612.html Mostly I think that people "approaching this from a security perspective only" often forget that by fencing in the(ir idea of the) current status quo, they often prevent beneficial evolution of protocols as well, contributing to the Internet's "ossification". -- Simon. ------------------------------ Message: 9 Date: Sat, 14 Jun 2008 23:54:49 +0200 From: Jeroen Massar <jeroen@unfix.org> Subject: Re: DNS problems to RoadRunner - tcp vs udp To: Scott McGrath <mcgrath@fas.harvard.edu> Cc: nanog@merit.edu Message-ID: <48543E29.70809@spaghetti.zurich.ibm.com> Content-Type: text/plain; charset="iso-8859-1" Scott McGrath wrote:

There is no call for insults on this list

Insults? Where? If you feel insulted by any of the comments made on this list by people, then you probably are indeed on the wrong list. But that is just me.

- Rather thought this list was about techincal discussions affecting all of us and keeping DNS alive for the majority of our customers certainly qualifies.

[..blabber about DNS attacks over TCP..] If I where a botnet herder and I had to take out your site and I was going to pick TCP for some magical reason then I would not care about your DNS servers, I would just hit your webservers, hard. I mean just the 'index.html' (http://www.harvard.edu/) is 24Kb, that is excluding pictures and there is bound to be larger data there which you are going to send and the bots only have to say "ACK" to once in a while. Multiply that by say a small botnet of 1M hosts, each just requests that 24Kb file. You will have a million flows and won't have any way to rate limit that or control it. Your link was already full trying to send it back to the clients and next to that your server was probably not able to process it in the first place. Simple, effective, nothing you can do about it, except get way and way more hardware. If somebody wants to take you out, they will take you out. Just get one other box with 10GE (not too hard to do) or just get a million of them with a little bit of connectivity (which is quite easy apparently)...

We/I am more than aware of the DNS mechanisms and WHY there are there trouble is NO DNS server can handle directed TCP attacks even the root servers crumbled under directed botnet activity and we have taken the decision to accept some collateral damage in order to keep services available.

"The root servers crumbled" wow, I must have missed somebody taking out all the 13 separate and then individually anycasted root servers. Which btw only do UDP as currently '.' is still small enough. $ dig @a.root-servers.net. . NS +tcp [..] ;; Query time: 95 msec ;; SERVER: 2001:503:ba3e::2:30#53(2001:503:ba3e::2:30) ;; WHEN: Sat Jun 14 23:45:52 2008 ;; MSG SIZE rcvd: 604 That is only 1 packet to 1 packet, still only 500 bytes. While your little webserver would generate 24kb for that same sequence.

We are a well connected university network with multi-gigabit ingress and egress with 10G on Abilene so we try to protect the internet from attacks originating within our borders AND we really feel the full wrath of botnets as we do not have a relatively slow WAN link to buffer the effects.

The whole point generally of botnets is just the Denial of Service (DoS), if that is because your link is full or the upstreams link is full or because the service can't service clients anymore. But clearly, as you are blocking TCP-DNS you are DoSing yourself already, so the botherders win. Also note that Abilene internally might be 10G and in quite some places even 40G, but you still have to hand it off to the rest of the world and those will count as those 'slow WAN' links that you think everybody else on this planet is behind. (Hint: 10GE is kinda the minimum for most reasonably sized ISP's)

Yes - we are blocking TCP too many problems with drone armies and we started about a year ago when our DNS servers became unresponsive for no apparent reason. Investigation showed TCP flows of hundreds of megabits/sec and connection table overflows from tens of thousands of bots all trying to simultaneously do zone transfers and failing tried active denial systems and shunning with limited effectiveness.

How is a failed AXFR going to generate a lot of traffic, unless they are repeating themselves over and over and over again? Thus effectively just packeting you? Also, are you talking about Recursive or Authoritive DNS servers here? Where those bots on your network, or where they remote?

We are well aware of the host based mechanisms to control zone information, Trouble is with TCP if you can open the connection you can DoS so we don't allow the connection to be opened and this is enforced at the network level where we can drop at wire speed.

Do you mean that the hosts which do TCP are allowed to do transfers or not? As in the latter case they can't generate big answers, they just get 1 packet back and then end then FIN. Note also, that if they are simply trying to overload your hosts, UDP is much more effective in doing that already and you have that hole wide open apparently otherwise you wouldn't have DNS.

Open to better ideas but if you look at the domain in my email address you will see we are a target for hostile activity just so someone can 'make their bones'.

It probably has nothing to do with the domain name, it more likely has something to do with certain services that are available or provided on your network.

Also recall we have a comittment to openess so we would like to make TCP services available but until we have effective DNS DoS mitigation which can work with 10Gb links It's not going to happen.

You think that 10Gb is a 'fat link', amusing ;) There are various vendors, most likely also reading on this list, who can be more than helpful in providing you with all kinds of bad, but also a couple of good solutions to most networking issues that you are apparently having. But the biggest issue you seem to have is not knowing what the DoS kiddies want to take out and why they want to take it out. Greets, Jeroen PS: You do know that an "NS" record is not allowed to point to a CNAME I hope? (NS3.harvard.edu CNAME ns3.br.harvard.edu. RFC1912 2.4 ;) -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 187 bytes Desc: OpenPGP digital signature Url : http://mailman.nanog.org/pipermail/nanog/attachments/20080614/29473ad3/attac... ------------------------------ _______________________________________________ NANOG mailing list NANOG@nanog.org http://mailman.nanog.org/mailman/listinfo/nanog End of NANOG Digest, Vol 5, Issue 33 ************************************