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RE: VoIP QOS best practices
by Ray Burkholder 10 Feb '03

10 Feb '03

QoS is important on T1 circuits and makes voice higher priority. Voice can even be done on sub T1 circuits with excellent results. In this regard, there are some additional packet sizing and fragementation issues to worry about in order to make voice packet timing constant, but nothing impossible to over-come. There are commonly accepted industry practices for this. Old hat for many practitioners in the Voip world. Ray Burkholder > -----Original Message----- > From: Charles Youse [mailto:cyouse@register.com] > Sent: February 10, 2003 14:09 > To: Bill Woodcock > Cc: nanog(a)nanog.org > Subject: RE: VoIP QOS best practices > > > > My main concern is that some of the sites that will be tied > with VoIP have only T-1 data connectivity, and I don't want a > surge in traffic to degrade the voice quality, or cause > disconnections or what-have-you. People are more accustomed > to data networks going down; voice networks going down will > make people shout. > > C. > > -----Original Message----- > From: Bill Woodcock [mailto:woody@pch.net] > Sent: Monday, February 10, 2003 1:05 PM > To: Charles Youse > Cc: nanog(a)nanog.org > Subject: RE: VoIP QOS best practices > > > > That doesn't seem to make a lot of sense - is it that > QoS doesn't work as advertised? > > That's generally true as well. But why would you need it? What's the > advantage to be gained in using QoS to throw away packets, when the > packets don't need to be thrown away? > > > As someone who is looking to deploy VoIP in the near > future this is of particular interest. > > Go ahead and deploy it. It's easy and works well. It > certainly doesn't > need anything like QoS to make it work. > > -Bill > > >

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RE: VoIP QOS best practices
by Charles Youse 10 Feb '03

10 Feb '03

That doesn't seem to make a lot of sense - is it that QoS doesn't work as advertised? As someone who is looking to deploy VoIP in the near future this is of particular interest. C. -----Original Message----- From: Bill Woodcock [mailto:woody@pch.net] Sent: Monday, February 10, 2003 12:48 PM To: nanog(a)nanog.org Subject: Re: VoIP QOS best practices > > Looking for some links to case studies or other documentation which > > describe implementing VoIP between sites which do not have point to > > point links. From what I understand, you can't enforce end-to-end QoS > > on a public network, nor over tunnels. I'm wondering if my basic > > understanding of this is flawed and in the case that it's not, how is > > this dealt with if the ISPs of said sites don't have any QoS policies? QoS is completely unnecessary for VoIP. Doesn't appear to make a bit of difference. Any relationship between the two is just FUD from people who've never used VoIP. -Bill

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Cisco 7507, erratic behaviour
by Drew Weaver 10 Feb '03

10 Feb '03

Howdy, Im having a little difficulty with a 7507, when I do sh run it just returns a newline and doesn't show me any the running-configuration. My privelege level is 15, and this worked yesterday. I also did wr term, same thing.. New line.. Nothing.. My start-config hasn't been modified, and show start works great. Everything is working Ok in the router, however I am concerned for obvious reasons. ;-) Thanks, -Drew

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E-bay problem.
by Shaun Bryant 10 Feb '03

10 Feb '03

Does anyone have a security contact at ebay that can be reached at this hour? Thanks Shaun

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Singing the Southwest Networking Blues
by Paul Caskey 10 Feb '03

10 Feb '03

Out in the badlands of New Mexido where the tumbleweeds blow, Tier 1 POPs are nowhere to be seen. I get long-hauled to a different state just for an Internet T1 from UUNET. Unfortunately, Albuquerque is an important business hub in my company, and we have several locations in NM & CO. But the rest are on the east coast and down south. A couple of pictures tell the story: http://www.swcp.com/pcaskey/tmp/NANOG.html I generally get good service with all my sites having UUNET connections, but it's kind of a bummer being routed through Los Angeles just to get to San Antonio. In fact, I'd be happy to buy a point-point line to the east, perhaps to my locations in D.C. or Research Triangle, if I could get any kind of decent latency guarantee. Then set up GRE tunnels to control traffic flow. Or maybe I could stay on the Internet, if a route could be found that would drift generally eastward, instead of going west and almost doubling the geographic distance. Offers and suggestions welcome. I'm at NANOG 27 in Phoenix right now. So far, the best theories involve some type of Sprint connection to Dallas / Fort Worth, because Sprint seems to have that path figured out better than UUNET. Then cross to UUNET on the private exchange in FtWorth. The latency through that exchange appears quite favorable. There'd be some addressing and routing issues to work out. My company does have an AS number, but we're not multi-homed, yet. I need to keep my UUNET line(s), so I'm looking for an addition, not a replacement. I would have to laugh if I could get to UUNET faster over Sprint than over UUNET. But that may be the way things are in the Wild West. TIA for any insights, and of course I'll summarize what I learn. -- Paul Caskey Albuquerque, NM, USA Information System Architect pcaskey(a)swcp.com -------------------------------------------------------------------- "You're basically killing each other to see who's got the better imaginary friend." --Rich Jeni, on war over religion

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Re: Cascading Failures Could Crash the Global Internet
by Michael Lamoureux 09 Feb '03

09 Feb '03

"sgorman1" == sgorman1 <sgorman1(a)gmu.edu> writes: sgorman1> Homogenous, in this context, does not mean similar platform sgorman1> connectivity, but nodes with same degree connecting to each sgorman1> other. Ah, that makes it more clear. So a full mesh would be better? ;-) sgorman1> Lots of problems in applying that to cascading failures in sgorman1> reality - making AS701 disappear, BGP allowing a cascading sgorman1> traffic failure from "having to redistribute" AS701's sgorman1> traffic etc etc. Hope that makes it more clear, but it is sgorman1> just my interpretation of someone elses work. Yeah, I have all sorts of problems with applying this model to reality. But then, we already determined that I was being stupid. ;-) thanks, Michael

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Re: Cascading Failures Could Crash the Global Internet
by Stewart, William C (Bill), SALES 09 Feb '03

09 Feb '03

I think the key is that the failures described in the paper are caused by overload rather than other things - too much demand for power blows out the generator, and without it, the grid tries to get the power from the next nearest generators, which overload and fail, and try to pull an even large amount from the _next_ nearest, etc. So the bit about heterogeneity is probably referring to the fact that some nodes are bigger or better-connected than others, and are more likely to blow out a bunch of their neighbors when they fail and shed a big load. That's not really how Internet systems usually fail. Overload can cause problems, and we've seen congestion collapse in the past, but TCP is usually tuned to discourage it; when a system is overloaded, well-behaved applications (which is most of them) back off, gradually or rapidly, but unless the load is weird enough to blow out router CPUs or crowd out BGP and OSPF packets, usually the network itself stays up and running. If what's failing is an overload of BGP routes or something, that's different - and sometimes the load on the system shrinks as components fail, but sometimes that just makes everything flap all at once, increasing load and delaying convergence.

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OT: 111 8th Ave. Parking
by Charles Sprickman 09 Feb '03

09 Feb '03

Hi, Any advice? Any secret spots? I've been there exactly once and I didn't see any good spots. Looking to go in this weekend, but would love hints for weekday travel as well. Thanks, Charles -- Charles Sprickman spork(a)inch.com

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Re: Cascading Failures Could Crash the Global Internet
by sgorman1＠gmu.edu 09 Feb '03

09 Feb '03

Ya - that pretty much sums it up - interesting model dubious application in reality. Homogenous, in this context, does not mean similar platform connectivity, but nodes with same degree connecting to each other. It is more likely for a node with ten connections to connect to other nodes with ten connections than one with one or two connections. The Internet is heterogenous. So, take UUnet as your nodes at the AS level and lets say it has 1700 or so connections to other AS's. Most of those other AS's would not not also have 1700 connections, thus it is heterogenous. Lots of problems in applying that to cascading failures in reality - making AS701 disappear, BGP allowing a cascading traffic failure from "having to redistribute" AS701's traffic etc etc. Hope that makes it more clear, but it is just my interpretation of someone elses work. ----- Original Message ----- From: Douglas Denault <doug(a)safeport.com> Date: Saturday, February 8, 2003 3:23 pm Subject: Re: Cascading Failures Could Crash the Global Internet > I believe the answer meant heterogenous has a meaning in a > statistical context. > As I was a Real Variables guy I, was weak on statistics (of my > day). Math guys > love to use perfectly good English words giving them different > meanings. > Assuming that the given definition is correct, the applicability > of the > assumption to the backbone is still not clear to me. While not > doubting the > mathematical model, it seems to me there is little empirical > evidence to support > it in this context. Or I am in the second half of your second point. > > On 8 Feb 2003, Michael Lamoureux wrote: > > > "sgorman1" == sgorman1 <sgorman1(a)gmu.edu> writes: > > > > sgorman1> I believe the comments about heterogenous networks has > to do > > sgorman1> with a measurement called assortivitiy that is used in > > sgorman1> statistical mechanics. A homogenous network is when nodes > > sgorman1> connect preferentially to nodes like them. In a > > sgorman1> heterogenous network they connect to nodes that are > not like > > sgorman1> them. For networks like the Intneret and the electric > grid> sgorman1> it is measured by the number of connections a node > has.> > > sgorman1> The kicker, that the author's are alluding to, is that the > > sgorman1> more heterogenous a network is the more vulnerable it > is to > > sgorman1> targeted attack. By taking out a highly connected > node - > > sgorman1> lots of poorly connected nodes that use it as a hub are > > sgorman1> lost. The AS network had the highest heterogenous > score of > > sgorman1> real-world tested networks, so lots of folks on that > > sgorman1> bandwagon. > > > > I don't see how the fact that a network is homogeneous or > > heterogeneous has anything to do with how well connected it is. The > > only possible sense to this I can see is that, statistically, > you are > > more likely to have a platform that the attacker has a viable attack > > for if you have lots of different platforms. But at the same > time, if > > the attacker only has one exploit (or whatever attack vector), then > > you are also in a MUCH better position than someone who's > network is > > made up 100% of that platform. I'm still not sure how having a > > homogeneous network helps. > > > > Either you aren't explaining it well, or I'm being stupid. I > consider> both possibilities to be equally likely at this point. > ;-) > > > > > > IMHO, > > Michael > > > > _____ > Douglas Denault > doug(a)safeport.com > Voice: 301-469-8766 > Fax: 301-469-0601 > > >

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Re: Cascading Failures Could Crash the Global Internet
by Michael Lamoureux 08 Feb '03

08 Feb '03

"sgorman1" == sgorman1 <sgorman1(a)gmu.edu> writes: sgorman1> I believe the comments about heterogenous networks has to do sgorman1> with a measurement called assortivitiy that is used in sgorman1> statistical mechanics. A homogenous network is when nodes sgorman1> connect preferentially to nodes like them. In a sgorman1> heterogenous network they connect to nodes that are not like sgorman1> them. For networks like the Intneret and the electric grid sgorman1> it is measured by the number of connections a node has. sgorman1> The kicker, that the author's are alluding to, is that the sgorman1> more heterogenous a network is the more vulnerable it is to sgorman1> targeted attack. By taking out a highly connected node - sgorman1> lots of poorly connected nodes that use it as a hub are sgorman1> lost. The AS network had the highest heterogenous score of sgorman1> real-world tested networks, so lots of folks on that sgorman1> bandwagon. I don't see how the fact that a network is homogeneous or heterogeneous has anything to do with how well connected it is. The only possible sense to this I can see is that, statistically, you are more likely to have a platform that the attacker has a viable attack for if you have lots of different platforms. But at the same time, if the attacker only has one exploit (or whatever attack vector), then you are also in a MUCH better position than someone who's network is made up 100% of that platform. I'm still not sure how having a homogeneous network helps. Either you aren't explaining it well, or I'm being stupid. I consider both possibilities to be equally likely at this point. ;-) IMHO, Michael

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