July 1996 - Test - lists.nanog.org

Re: Why aren't ISPs providing stratum 1 NTP service?
by avg＠ncube.com 17 Jul '96

17 Jul '96

>From customer's point of view, getting stratum 1 service is not a good idea. The stratum 2 clocks tend to be more stable. I think it would be a good idea to stop providing startum 1 service to anybody but ISPs who would then provide s2 clocks straight out of their ciscos to customers thus avoiding the symmetry issues. Reducing load on s1 clocks is also a good thing, as it could improve accuracy. --vadim >I just crossed the 200th machine syncing of one of my stratum 1 servers. I >like providing the service and it doesn't cost very much for me to offer the >service. the problem I have with this is that NTP hates asymmetric routing, >so the likelyhood is that for most people outside the provider that serves >this machine, NTP time is suspect. > >It seems to me that the days when running a GPS refclock into an NTP server >was exotic are long past. Why don't providers give NTP stratum 1 service to >their customers? Then I can at least shed some of the most suspect clients >(it's the routing path not the user that is suspect.) >In search of good time for all, >Jerry

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FYI: Internet gridlock article
by Hank Nussbacher 16 Jul '96

16 Jul '96

"Internet gridlock escalates, ISPs predict autumn Web brownouts" By Stephen Lawson InfoWorld Electric http://www.infoworld.com/cgi-bin/displayStory.pl?960715.gridlockisp.htm ---------------------------------------------------------------------- Hank Nussbacher Manager, Internet Technology Programs Telephone: +972 3 6978852 Vnet: HANK at TELVM1 Fax: +972 3 6978115 Internet: hank(a)ibm.net.il WWW: http://www.ibm.net.il/~hank ---------------------------------------------------------------------- IBM Israel 2, Weizmann St. Tel Aviv 61336 ====== ======= === === http://www.ibm.net.il/ ====== ======== ==== ==== Dialup registration: 177-022-3993 == == == ==== ==== Company services: 03-6978663 == ====== == === == Internet sales fax: 03-6978115 == == === == = == Enquiries: info(a)ibm.net.il ====== ======== === === Technical support: noc(a)ibm.net.il ====== ======= === === ----------------------------------------------------------------------

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re: problem at mae-west tonight?
by Rob Liebschutz 15 Jul '96

15 Jul '96

> The problem I have with the route server this evening is that I announce > my routes to the route server, and my policy configuration in the route server > reflects that I peer with Netcom, and so the route server tells Netcom how > to reach me. Unfortunately, packets leaving Netcom headed to me at layer 2 > are going into a black hole. To fix this, I've had to dump my peering with > the route server entirely, so that Netcom is only seeing my routes from AGIS > (our transit provider) and not from the route server. Ugh. My fears about > the route server not knowing the status of the layer 2 topology have come true, > and there's no way to fix this that doesn't involve manual intervention. > > -matthew kaufman > matthew(a)scruz.net > > Well, I run gated on a BSDI box for the Hooked MAE West router. I'm thinking about implementing a "pingnouse INTERVAL" option on the peer/group commands in gated, so it will periodically ping next hops received from the route servers and set the nouse bit if the nexthop is unreachable. Any better ideas? It would be nice to come up with a good mechanism for doing 3rd party keepalives that cisco and other router vendors would be willing to implement. Rob

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Re: problem at mae-west tonight?
by Rob Liebschutz 14 Jul '96

14 Jul '96

Actually I've seen the arp problem as well. What arp entry do you have for them? We have: mae-west.netcom.net (198.32.136.15) at 0:0:c:61:b:0 If yours is different, you could try deleting it and if it still comes back wrong, you could try temporarily adding a static entry. Are either you or netcom connected through a netedge? > ps. At this point, we still can't see Netcom... problem has lasted for 1 day, > 8 hours. From my interface (198.32.136.18) I cannot ping Netcom at > 198.32.136.15, but I can ping Alternet at 198.32.136.42. That points to > a layer 2 discontinuity. > >

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Re: problem at mae-west tonight?
by Rob Liebschutz 14 Jul '96

14 Jul '96

Yes, this type of topology failure is possible too. I can recall times when there were problems on the links between Ames and MFS. Yes, the link is 2 OC3s. > > Robert, > > It's my understanding that MAE-W is composed of two facilities, > one at MFS, and the second at NASA-AMES. > > It's my understanding that while a virtual medium is created, they > actually reside on two separate gigaswitches. I seem to recall 1 > or 2 OC3s connecting the two..... > > Given this, it is, then, possible that the route server is located > on segment A, while customers x,y, and z are located on segment B. > > If you are on segment A, and try to follow the RSes advice to talk > to x, y, and z, you are depending on the links connecting the two > segments. > > However, I may be incorrect. > > -alan

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Re: problem at mae-west tonight?
by matthew＠scruz.net 14 Jul '96

14 Jul '96

Original message <199607150340.UAA00784(a)elite.exodus.net> From: Robert Bowman <rob(a)elite.exodus.net> Date: Jul 14, 20:40 Subject: Re: problem at mae-west tonight? > > We experienced the same thing with Netcom. Currently we are peered with over > 40 netwroks through the RS, but I have only had this problem with Netcom. > > Is it really a next-hop problem or a Netcom internal problem? Last time > this happened, about 2 weeks ago, they cleared their RA session and did > some other things and everything came up fine. I did not get details from > the routing folks over there. > > I don't quite see how and where the layer 2 topology comes into play here. > Netcom should simply be seeing routes (through the RS) that state your MW > IP address and the routes advertised from it. Is there some reason that your MW > IP would be unreachable by Netcom? I am confused as to why this would ever > happen in the MW scenario. Now the PB-NAP is a different story with the > non-fully meshed scenario. > > Please explain what you mean Matt. Sure. Netcom changed out an FDDI card. There is a bad ARP entry or bridge table entry somewhere, which causes packets transmitted by Netcom towards me to be black-holed. MFS is, as far as I know, _still_ investigating this. However we can see the route server as can Netcom. The route server states our MW IP address, and so they transmit packets towards us using that, and yet the underlying layer 2 fabric is discarding those before they get to us. Yes, IF EVERYTHING WAS WORKING PROPERLY it is fully meshed... but things don't always work properly. What I know is that when I stopped believing the route server's routes to Netcom, there was still a discontinuity, but when I stopped telling the route server my routes (and it then stopped telling Netcom), Netcom switched to sending my packets to our transit provider, and my Netcom connectivity came back. That required both manual intervention AND tearing down the whole session with the route server (I can't easily get the route server to stop telling Netcom about me while still telling everyone else about me without editing my policy and waiting for it to appear on the RS) -matthew kaufman matthew(a)scruz.net ps. At this point, we still can't see Netcom... problem has lasted for 1 day, 8 hours. From my interface (198.32.136.18) I cannot ping Netcom at 198.32.136.15, but I can ping Alternet at 198.32.136.42. That points to a layer 2 discontinuity.

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Re: problem at mae-west tonight?
by Rob Liebschutz 14 Jul '96

14 Jul '96

On a regular basis, MAE West has failures that cause only some of the other routers to become unreachable. I believe all of the instances that I have heard of are related to problems with the Netedges which show up mostly under high load. I've heard various people call it the "Sleeping Interface" problem. It usually goes away when you reset the netedges, but under heavy load it can come back quickly. We have seen it extensively, when our 10mb connection became heavily loaded. Just yesterday, we upgraded to a DS3, so were hoping not to see it for a while. I know AGIS has also had this problem and I believe Best has seen it as well. Maybe you haven't seen it because you have a colocated router at MAE-WEST. Rob > We experienced the same thing with Netcom. Currently we are peered with over > 40 netwroks through the RS, but I have only had this problem with Netcom. > > Is it really a next-hop problem or a Netcom internal problem? Last time > this happened, about 2 weeks ago, they cleared their RA session and did > some other things and everything came up fine. I did not get details from > the routing folks over there. > > I don't quite see how and where the layer 2 topology comes into play here. > Netcom should simply be seeing routes (through the RS) that state your MW > IP address and the routes advertised from it. Is there some reason that your MW > IP would be unreachable by Netcom? I am confused as to why this would ever > happen in the MW scenario. Now the PB-NAP is a different story with the > non-fully meshed scenario. > > Please explain what you mean Matt. > > Rob > Exodus Communications Inc. > > > > > The problem I have with the route server this evening is that I announce > > > my routes to the route server, and my policy configuration in the route server > > > reflects that I peer with Netcom, and so the route server tells Netcom how > > > to reach me. Unfortunately, packets leaving Netcom headed to me at layer 2 > > > are going into a black hole. To fix this, I've had to dump my peering with > > > the route server entirely, so that Netcom is only seeing my routes from AGIS > > > (our transit provider) and not from the route server. Ugh. My fears about > > > the route server not knowing the status of the layer 2 topology have come true, > > > and there's no way to fix this that doesn't involve manual intervention. > > > > > > -matthew kaufman > > > matthew(a)scruz.net > > > > > > > > > > Well, I run gated on a BSDI box for the Hooked MAE West router. I'm > > thinking about implementing a "pingnouse INTERVAL" option on the > > peer/group commands in gated, so it will periodically ping next hops > > received from the route servers and set the nouse bit if the nexthop > > is unreachable. Any better ideas? > > > > It would be nice to come up with a good mechanism for doing 3rd party > > keepalives that cisco and other router vendors would be willing to > > implement. > > > > Rob > > > >

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Re: Re: problem at mae-west tonight?
by eautheme＠BayNetworks.com 14 Jul '96

14 Jul '96

Rob, In the OSPF community,we faced this same issue a few years back -- the issue being that all members of a single subnet were not reachable either by design or by error and fooling the listeners of the Designated Router (like the route server) into thinking that the nexthops were really reachable. We felt the pains of this especially over virtual circuit networks (Frame Relay, SMDS, and ATM). Temporary workarounds were created. The two better solutions were: 1) Using recommendations in RFC1586,"Guidelines for Running OSPF Over Frame Relay Networks". 2) Using Point-MultiPoint (P-MP) OSPF which is in the latest Internet-Draft of the revision to the RFC1583 (V2 OSPF Spec.). I prefer the P-MP solution because it is an automatic mechanism requiring very little configuration on a network administrators part and keeps the number of routing hops to a minimum. I vote for P-MP as a "Standard" solution for BGP-4 over discontiguous networks. I believe this concept was proposed on this mailing list a few months back. Now that ATM VCs are being used at NAPs with route servers, you'll see more and more of these problems arising...especially at NAPs where there isn't much coordination and cooperation in building and maintaining these high speed, virtual connections. Eural Authement Bay Networks Professional Services ******** > The problem I have with the route server this evening is that I announce > my routes to the route server, and my policy configuration in the route server > reflects that I peer with Netcom, and so the route server tells Netcom how > to reach me. Unfortunately, packets leaving Netcom headed to me at layer 2 > are going into a black hole. To fix this, I've had to dump my peering with > the route server entirely, so that Netcom is only seeing my routes from AGIS > (our transit provider) and not from the route server. Ugh. My fears about > the route server not knowing the status of the layer 2 topology have come true, > and there's no way to fix this that doesn't involve manual intervention. > > -matthew kaufman > matthew(a)scruz.net > > Well, I run gated on a BSDI box for the Hooked MAE West router. I'm thinking about implementing a "pingnouse INTERVAL" option on the peer/group commands in gated, so it will periodically ping next hops received from the route servers and set the nouse bit if the nexthop is unreachable. Any better ideas? It would be nice to come up with a good mechanism for doing 3rd party keepalives that cisco and other router vendors would be willing to implement. Rob

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Re: Routing flaps, was Re: Ping flooding
by Paul Ferguson 12 Jul '96

12 Jul '96

At 07:40 AM 7/12/96 -0600, Forrest W. Christian wrote: > >However, the world never needs to see this - it's an internal routing >issue and when the internal route flaps it shouldn't affect the external >routes. > >So in summary: > >1) Never flap your routes in public. What you do in your own home is >your own business. > I'm sorry, but I'm afraid that you're missing the point here. In most larger ISP backbones, the behavior of their IGP is indeed visible to the public, since in most instances, most of the Internet traffic relies on the stability of these interior (an esoteric term) networks. Therefore, whether interior or exterior flap is really of no relevance in this context. In smaller ISPs, where not a great deal of public traffic is transiting their (interior) backbone, granted, it is of lesser importance and visibility. - paul

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Re: Routing flaps, was Re: Ping flooding
by Justin W. Newton 12 Jul '96

12 Jul '96

At 10:37 AM 7/12/96 -0400, Paul Ferguson wrote: >At 07:40 AM 7/12/96 -0600, Forrest W. Christian wrote: > >> >>However, the world never needs to see this - it's an internal routing >>issue and when the internal route flaps it shouldn't affect the external >>routes. >> >>So in summary: >> >>1) Never flap your routes in public. What you do in your own home is >>your own business. >> > >I'm sorry, but I'm afraid that you're missing the point here. > >In most larger ISP backbones, the behavior of their IGP is indeed >visible to the public, since in most instances, most of the Internet >traffic relies on the stability of these interior (an esoteric term) >networks. Therefore, whether interior or exterior flap is really of >no relevance in this context. I think the real difference is this. If my routes are only seen at one place then it makes sense for me to announce them whether or not I can actually get to them. If, however, it is possible to get to parts of my network from one exchange, but not another then the routes should only be announced where they can actually be gotten to from (obviously). I.e. if I am a small to mid-sized provider who has multiple t-1's to the net to different providers, and then those t's come into the same physical network (either the same router or one's that are topologically adjacent to one another) chances are good that if one of those routers can't get to part of my network the other probably can't either. In this instance it makes sense for me to null0 the routes and do my part to not affect instability (only routes which originate in my AS though, if I have any multihomed downstreams then they would not want me announcing their routes when I can't get to them). If, however, I have a network which has multiple egresses to the internet at large it is very possible for one part of my network not to be able to reach certain sites while other parts can. I would then want to "announce my instability" so that I am only announcing networks where they can actually be reached from. Justin "Long babbling posts R us" Newton Justin Newton Internet Architect Erol's Internet Services

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