I want to open a discussion on this topic, I’m sure many of you fine freeswitchers have encountered the pain of exceeding the MTU and things not handling it properly. I’ve also see this mindset that blocking all ICMP will somehow make your network more secure, In doing this you’re actually breaking PMTU and the internet in general. So check your firewalls, if you’re blocking repent now and fix it… Input and discussions would be welcome on this topic. I think this issue is more of an issue facing residential installs vs commercial installs… What have you seen? -- Brian West brian@freeswitch.org FreeSWITCH Solutions, LLC PO BOX 2531 Brookfield, WI 53008-2531 Twitter: @FreeSWITCH , @briankwest http://www.freeswitchbook.com http://www.freeswitchcookbook.com T: +1.918.420.9001 | F: +1.918.420.9002 | M: +1.918.424.WEST iNUM: +883 5100 1420 9001 ISN: 410*543 Skype:briankwest PGP Key: http://www.bkw.org/key.txt (AB93356707C76CED)
Hey Brian, Here in france, it is a common topic for ADSL links, not so much for SDSL ( only ATM impacted, EFM is fine ) and not at all on Optical Fiber. Now that we are our own ISP and don't sell ADSL, everything's fine :) There are no distinction on residential/commercial offers for that subject. The popular belief that 'badguycantpingmeimsafe' is still very strong ( though who would seriously loose time scanning a range with ICMP when tcp/udp does it well, and that after scanning with ICMP, you would anyway engage a port/app scan ? ). Each time I have to explain customers whom I don't manage the firewall why it is not good ( we have a perfect example with an administration's website, which needs MTU 1460 max, so that's quite easy to demo to the customer: you can upload, you can't ). We even distribute a "Best practice" manual for our customers which cover this. Le 18/02/2014 21:25, Brian West a écrit :
I want to open a discussion on this topic, I’m sure many of you fine freeswitchers have encountered the pain of exceeding the MTU and things not handling it properly. I’ve also see this mindset that blocking all ICMP will somehow make your network more secure, In doing this you’re actually breaking PMTU and the internet in general. So check your firewalls, if you’re blocking repent now and fix it… Input and discussions would be welcome on this topic.
I think this issue is more of an issue facing residential installs vs commercial installs… What have you seen?
-- Brian West brian@freeswitch.org FreeSWITCH Solutions, LLC PO BOX 2531 Brookfield, WI 53008-2531 Twitter: @FreeSWITCH , @briankwest http://www.freeswitchbook.com http://www.freeswitchcookbook.com
T: +1.918.420.9001 | F: +1.918.420.9002 | M: +1.918.424.WEST iNUM: +883 5100 1420 9001 ISN: 410*543 Skype:briankwest PGP Key: http://www.bkw.org/key.txt (AB93356707C76CED)
_________________________________________________________________________ Professional FreeSWITCH Consulting Services: consulting@freeswitch.org http://www.freeswitchsolutions.com
FreeSWITCH-powered IP PBX: The CudaTel Communication Server http://www.cudatel.com
Official FreeSWITCH Sites http://www.freeswitch.org http://wiki.freeswitch.org http://www.cluecon.com
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Hi Brian, folks, Understood, agreed, and sympathise. Problem (at least over this side of the pond) is customers using the cheapo routers provided by their ISP. These are often pre-configured in strange and stupid ways, or have ISPs who use TR-069 remote "configuration, for your comfort and enjoyment" that achieves the same purpose. However, at least there's a chance these can be fixed. Educating the customers is hard, but if you care, typically you CAN configure your own box to not zap PMTUD. It should be little surprise that the same firmware/UI that has such broken SIP ALG "support" also doesn't make it easy to block selected ICMP types. It sure isn't a surprise to me that these "free" routers also don't handle fragments and so get confused with some DNS traffic. Tried DNSSEC, anyone? However, the biggest problem in my experience is trying to explain to corporate IT folk why they should not do this. Yesterday I spent nearly an hour trying to explain to a corporate IT "network security specialist" why blocking NTP was not a good idea, and that he had just b*gg*r*d up a couple of hosted servers by doing that, and no, reflection attacks using NTP being in the news is not a good enough excuse. They have kit with very flexible interfaces, but IMHO have equally inflexible ideas. Finally, corporate kit is not always immune to its own stupidities. Whacky NAT support that didn't interwork with the original STUN specs was mostly found in corporate kit, not residential stuff. In an entirely unrelated note, the main movers to update the STUN spec to its current unusable bulk came from CISCO folk, as they claimed that STUN didn't work "for a significant percentage of existing equipment". I will also forgive them in another life for their early interpretation of the SIP specs; hands up all those who had to work around the 'who needs quotes in a SIP message?' or 'LWS means exactly one space character, mostly, except when it means none' funnies. One advantage of corporate IT departments is that you can apply a (Taser/cattle prod/clue stick) to a small number of people to achieve results for a lot of users; for residential customers/remote teleworkers it tends to be one by one. Ah, I feel much better for that. all the best, Lawrence On 18 Feb 2014, at 20:25, Brian West wrote:
I want to open a discussion on this topic, I’m sure many of you fine freeswitchers have encountered the pain of exceeding the MTU and things not handling it properly. I’ve also see this mindset that blocking all ICMP will somehow make your network more secure, In doing this you’re actually breaking PMTU and the internet in general. So check your firewalls, if you’re blocking repent now and fix it… Input and discussions would be welcome on this topic.
I think this issue is more of an issue facing residential installs vs commercial installs… What have you seen?
Just went thru this AT&T on my screw-verse connection the NvG510 is evil, the are coming by Friday to give me a Motorola 2210-02 that I hope fixes the stupidness. Sent from my iPhone
On Feb 18, 2014, at 4:48 PM, Lawrence Conroy <lconroy@insensate.co.uk> wrote:
Hi Brian, folks, Understood, agreed, and sympathise.
Problem (at least over this side of the pond) is customers using the cheapo routers provided by their ISP. These are often pre-configured in strange and stupid ways, or have ISPs who use TR-069 remote "configuration, for your comfort and enjoyment" that achieves the same purpose. However, at least there's a chance these can be fixed. Educating the customers is hard, but if you care, typically you CAN configure your own box to not zap PMTUD. It should be little surprise that the same firmware/UI that has such broken SIP ALG "support" also doesn't make it easy to block selected ICMP types. It sure isn't a surprise to me that these "free" routers also don't handle fragments and so get confused with some DNS traffic. Tried DNSSEC, anyone?
However, the biggest problem in my experience is trying to explain to corporate IT folk why they should not do this. Yesterday I spent nearly an hour trying to explain to a corporate IT "network security specialist" why blocking NTP was not a good idea, and that he had just b*gg*r*d up a couple of hosted servers by doing that, and no, reflection attacks using NTP being in the news is not a good enough excuse. They have kit with very flexible interfaces, but IMHO have equally inflexible ideas.
Finally, corporate kit is not always immune to its own stupidities. Whacky NAT support that didn't interwork with the original STUN specs was mostly found in corporate kit, not residential stuff. In an entirely unrelated note, the main movers to update the STUN spec to its current unusable bulk came from CISCO folk, as they claimed that STUN didn't work "for a significant percentage of existing equipment". I will also forgive them in another life for their early interpretation of the SIP specs; hands up all those who had to work around the 'who needs quotes in a SIP message?' or 'LWS means exactly one space character, mostly, except when it means none' funnies.
One advantage of corporate IT departments is that you can apply a (Taser/cattle prod/clue stick) to a small number of people to achieve results for a lot of users; for residential customers/remote teleworkers it tends to be one by one.
Ah, I feel much better for that.
all the best, Lawrence
On 18 Feb 2014, at 20:25, Brian West wrote: I want to open a discussion on this topic, I’m sure many of you fine freeswitchers have encountered the pain of exceeding the MTU and things not handling it properly. I’ve also see this mindset that blocking all ICMP will somehow make your network more secure, In doing this you’re actually breaking PMTU and the internet in general. So check your firewalls, if you’re blocking repent now and fix it… Input and discussions would be welcome on this topic.
I think this issue is more of an issue facing residential installs vs commercial installs… What have you seen?
_________________________________________________________________________ Professional FreeSWITCH Consulting Services: consulting@freeswitch.org http://www.freeswitchsolutions.com
FreeSWITCH-powered IP PBX: The CudaTel Communication Server http://www.cudatel.com
Official FreeSWITCH Sites http://www.freeswitch.org http://wiki.freeswitch.org http://www.cluecon.com
FreeSWITCH-users mailing list FreeSWITCH-users@lists.freeswitch.org http://lists.freeswitch.org/mailman/listinfo/freeswitch-users UNSUBSCRIBE:http://lists.freeswitch.org/mailman/options/freeswitch-users http://www.freeswitch.org
On Tue, 18 Feb 2014, Lawrence Conroy wrote:
Problem (at least over this side of the pond) is customers using the cheapo routers provided by their ISP. These are often pre-configured in strange and stupid ways, or have ISPs who use TR-069 remote "configuration, for your comfort and enjoyment" that achieves the same purpose. However, at least there's a chance these can be fixed. Educating the customers is hard, but if you care, typically you CAN configure your own box to not zap PMTUD. It should be little surprise that the same firmware/UI that has such broken SIP ALG "support" also doesn't make it easy to block selected ICMP types. It sure isn't a surprise to me that these "free" routers also don't handle fragments and so get confused with some DNS traffic. Tried DNSSEC, anyone?
Each market has its own idiosyncrasies. Being on the same side of the pond but with subtle little addition: All ADSL lines are terminated at the CPE. This means that you are not allowed to supply you own DSL modem but have to suffer whatever (still chepo) router du jour the ISP in their infinate wisdom have choosen. If you are lucky you can get them to (for a fee) enable bridge mode where they in most(!) cases stop touching the traffic. To add additional pain to the suffering most of them are using "customized" firmwares which are often not kept timely up-to-date or they simply stopped caring. That is just the usual residential and small office pains... And then we have the "enterprise" (and wannabes). They have the proper equipment but the IT departments are often - shall we say - lacking. Lawrences observations are spot on. So to get back to Brians original question: Where do you see the issues? I see them widely in both places and it comes down to the same basic issue: Nobody really cares! Getting things to really work *properly* is only a concern of a very very select few people. And most of the problems comes down to $$$ Residentials: The ISP only needs to push a simple product which is good enough for surfing. The quality of the firmswares being used on their CPE clearly demonstrates this. If you are into conspiracies you may not that many big ISPs are also telco's - but I honestly think it is more a question of $$$. Why supply a good CPE if most people accept the cheaper alternative. Sometimes you are able to configure them properly - other times that "feature" has been removed for simplicity Commercial: Most firewall admins I have been in touch with have often not had a full understanding of their field. And those who had where often impaired with a "security" deparment/commitee/person/etc. Large organisations have the muscle to hire real networking people - but unfortunately they hire "security" personel at the same time. The mainstream only learns from large mainstream problems. They have heard of "ping of death" which translates into ICMP=BAD! Whenever you come and try to educate people on the subject the typical reaction is not to readily embrace the more informed approach. Their stance is then that everything else is working and that you have a problem with your technology - because we know ICMP=BAD! And along the same lines: Try arguing that NAT is bad and that IP was invented as a point to point protocol. Mainstream interpretation: NAT=firewall - "You said that we do not need firewalls!". Sorry - this was not meant as flamebait. Luckily I do rarely deal with residential installs in my professional life. But on the commercial side we very very often end up spending more money on equipment rather than doing things "correctly". In the enterprise it is often easier to setup a seperate firewall/router for interconnect rather than getting the already existing infrastructure to play ball. And even to do that it ends up being easier to use seperate lines to avoid a lot of read tape! Truly a sad state of affairs... I took the bait and ended up ranting. My apologies! Kind Regards, Claus Andersen
Generally speaking various PMTU, ICMP, and MTU issues are a significant problem. My experience has been it's much worse with UDP than TCP as broken and/or misconfigured devices seem to cause more problems with UDP fragments than TCP fragments (which do generally work). I talk about this quite a bit here: http://blog.krisk.org/2013/09/apples-new-facetime-sip-perspective.html On Tue, Feb 18, 2014 at 3:25 PM, Brian West <brian@freeswitch.org> wrote:
I want to open a discussion on this topic, I'm sure many of you fine freeswitchers have encountered the pain of exceeding the MTU and things not handling it properly. I've also see this mindset that blocking all ICMP will somehow make your network more secure, In doing this you're actually breaking PMTU and the internet in general. So check your firewalls, if you're blocking repent now and fix it... Input and discussions would be welcome on this topic.
I think this issue is more of an issue facing residential installs vs commercial installs... What have you seen?
-- Brian West brian@freeswitch.org FreeSWITCH Solutions, LLC PO BOX 2531 Brookfield, WI 53008-2531 Twitter: @FreeSWITCH , @briankwest http://www.freeswitchbook.com http://www.freeswitchcookbook.com
T: +1.918.420.9001 | F: +1.918.420.9002 | M: +1.918.424.WEST iNUM: +883 5100 1420 9001 ISN: 410*543 Skype:briankwest PGP Key: http://www.bkw.org/key.txt (AB93356707C76CED)
_________________________________________________________________________ Professional FreeSWITCH Consulting Services: consulting@freeswitch.org http://www.freeswitchsolutions.com
FreeSWITCH-powered IP PBX: The CudaTel Communication Server http://www.cudatel.com
Official FreeSWITCH Sites http://www.freeswitch.org http://wiki.freeswitch.org http://www.cluecon.com
FreeSWITCH-users mailing list FreeSWITCH-users@lists.freeswitch.org http://lists.freeswitch.org/mailman/listinfo/freeswitch-users UNSUBSCRIBE:http://lists.freeswitch.org/mailman/options/freeswitch-users http://www.freeswitch.org
-- Kristian Kielhofner
participants (5)
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Brian West
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Claus Andersen
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Kristian Kielhofner
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Lawrence Conroy
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Tristan Mahé