Re: What's the point of prepend communities?

2017-11-01 Thread Michael Hallgren
Yes, sometimes very much so, and often nice to combine with local-pref settings based on upstream's "geo-community-values" when available. Cheers, mh Le 1 nov. 2017 à 18:59, à 18:59, Leo Bicknell a écrit: >In a message written on Mon, Oct 30, 2017 at 07:56:43PM +0100,

Re: What's the point of prepend communities?

2017-11-01 Thread Leo Bicknell
In a message written on Mon, Oct 30, 2017 at 07:56:43PM +0100, Michael Hallgren wrote: > But keep in mind that 'prepend communities' are fragile: I decide by local > preference whereto I send my traffic. Absolutely, but they are still very useful in many situations. -- Leo Bicknell -

Re: What's the point of prepend communities?

2017-10-30 Thread Michael Hallgren
Hi guys, But keep in mind that 'prepend communities' are fragile: I decide by local preference whereto I send my traffic. Cheers, mh Le 30 oct. 2017 à 18:25, à 18:25, Leo Bicknell a écrit: >In a message written on Thu, Oct 26, 2017 at 01:54:17PM -0600, Clinton >Work wrote:

Re: What's the point of prepend communities?

2017-10-30 Thread Leo Bicknell
In a message written on Thu, Oct 26, 2017 at 01:54:17PM -0600, Clinton Work wrote: > I believe that Jason is asking about an ISP BGP community to prepend > their AS when the BGP routes are received from the customer (not when Yeah, I typoed my example, should have been: There are paths: 1 2 3

Re: What's the point of prepend communities?

2017-10-29 Thread Brett Frankenberger
On Sun, Oct 29, 2017 at 07:01:13AM -0500, Mike Hammett wrote: > If I understand the OP correctly, I will use this real world example: > > https://onestep.net/communities/as174/ > > 174:3001 through 174:3003 as compared to doing the prepending > yourself. What is the functional difference? >

Re: What's the point of prepend communities?

2017-10-29 Thread Mike Hammett
<jason+na...@lixfeld.ca> To: "William Herrin" <b...@herrin.us> Cc: "NANOG" <nanog@nanog.org> Sent: Thursday, October 26, 2017 1:47:44 PM Subject: Re: What's the point of prepend communities? Hi Bill, > On Oct 26, 2017, at 2:37 PM, William Herrin <b...@her

Re: What's the point of prepend communities?

2017-10-28 Thread Rob Foehl
On Thu, 26 Oct 2017, Jason Lixfeld wrote: Absolutely. I understand the "Prepend to Network blah” use case. The case I don’t get is where the ISP makes no distinction in their policy document about how the prepending of their own AS is applied to their upstream announcements, implying that

Re: What's the point of prepend communities?

2017-10-28 Thread Steve Dodd
Keep in mind also that when you allow a customer to deprioritize a particular peer you can really blow up your COGS model (assuming you buy transit). Cheers, Steve On Thu, Oct 26, 2017 at 1:05 PM, William Herrin wrote: > On Thu, Oct 26, 2017 at 2:47 PM, Jason Lixfeld

Re: What's the point of prepend communities?

2017-10-26 Thread joel jaeggli
On 10/26/17 10:58, Jason Lixfeld wrote: > Hi, > > Of all the ISPs that I am familiar with that have a BGP community structure > usable by their peering partners and/or downstream customers, among other > things, they allow the customer to signal the ISP to prepend their own AS to > the as-path

RE: What's the point of prepend communities?

2017-10-26 Thread Naslund, Steve
Sent: Thursday, October 26, 2017 2:54 PM To: nanog@nanog.org Subject: Re: What's the point of prepend communities? I believe that Jason is asking about an ISP BGP community to prepend their AS when the BGP routes are received from the customer (not when advertising to a peer). I don't see

Re: What's the point of prepend communities?

2017-10-26 Thread Clinton Work
I believe that Jason is asking about an ISP BGP community to prepend their AS when the BGP routes are received from the customer (not when advertising to a peer). I don't see a functional difference between the two and I suspect that ISPs added support for convenience. If you already send BGP

Re: What's the point of prepend communities?

2017-10-26 Thread Brett Frankenberger
On Thu, Oct 26, 2017 at 03:05:25PM -0400, William Herrin wrote: > > You'd only use communities like that if you want to signal the ISP to > deprioritize your advertisement on a particular peer or set of peers but > not others. That's when you're getting fancy. It's not the norm. The norm > is you

RE: What's the point of prepend communities?

2017-10-26 Thread Naslund, Steve
- From: NANOG [mailto:nanog-boun...@nanog.org] On Behalf Of William Herrin Sent: Thursday, October 26, 2017 2:15 PM To: Jason Lixfeld Cc: NANOG Subject: Re: What's the point of prepend communities? On Thu, Oct 26, 2017 at 3:05 PM, William Herrin <b...@herrin.us> wrote: > On Thu, Oct

Re: What's the point of prepend communities?

2017-10-26 Thread Leo Bicknell
In a message written on Thu, Oct 26, 2017 at 02:47:44PM -0400, Jason Lixfeld wrote: > I understand how prepends fit in the context of best path selection, but my > question was more the difference between a customer signalling the ISP to > prepend their AS using a BGP community stamped to a

Re: What's the point of prepend communities?

2017-10-26 Thread William Herrin
On Thu, Oct 26, 2017 at 3:05 PM, William Herrin wrote: > On Thu, Oct 26, 2017 at 2:47 PM, Jason Lixfeld > wrote: > You'd only use communities like that if you want to signal the ISP to > deprioritize your advertisement on a particular peer or set of peers

Re: What's the point of prepend communities?

2017-10-26 Thread Jason Lixfeld
> On Oct 26, 2017, at 2:55 PM, Job Snijders wrote: > > If Network B offers some kind of “Prepend to Network C” BGP community, > network A will be able to utilize all of network B except the pieces that > perform less well. (This is ofcourse assuming that Network C picks some >

Re: What's the point of prepend communities?

2017-10-26 Thread William Herrin
On Thu, Oct 26, 2017 at 2:47 PM, Jason Lixfeld wrote: > Hi Bill, > > > On Oct 26, 2017, at 2:37 PM, William Herrin wrote: > > > > BGP routing is based on "distance". Distance in BGP is primarily > calculated as the number of ASNs in the AS Path. Prepends

Re: What's the point of prepend communities?

2017-10-26 Thread Job Snijders
Hi, In context of traffic engineering it may be that Network A (customer of Network B) observes that performance is suboptimal between Network B and Network C. If Network B offers some kind of “Prepend to Network C” BGP community, network A will be able to utilize all of network B except the

Re: What's the point of prepend communities?

2017-10-26 Thread Christopher Morrow
On Thu, Oct 26, 2017 at 2:47 PM, Jason Lixfeld wrote: > Hi Bill, > > > On Oct 26, 2017, at 2:37 PM, William Herrin wrote: > > > > BGP routing is based on "distance". Distance in BGP is primarily > calculated as the number of ASNs in the AS Path. Prepends

Re: What's the point of prepend communities?

2017-10-26 Thread Jason Lixfeld
Hi Bill, > On Oct 26, 2017, at 2:37 PM, William Herrin wrote: > > BGP routing is based on "distance". Distance in BGP is primarily calculated > as the number of ASNs in the AS Path. Prepends make a path more distance, > encouraging routers to choose a different path if one is

Re: What's the point of prepend communities?

2017-10-26 Thread William Herrin
On Thu, Oct 26, 2017 at 1:58 PM, Jason Lixfeld wrote: > Of all the ISPs that I am familiar with that have a BGP community > structure usable by their peering partners and/or downstream customers, > among other things, they allow the customer to signal the ISP to prepend >

What's the point of prepend communities?

2017-10-26 Thread Jason Lixfeld
Hi, Of all the ISPs that I am familiar with that have a BGP community structure usable by their peering partners and/or downstream customers, among other things, they allow the customer to signal the ISP to prepend their own AS to the as-path of a particular prefix announcement. What