Re: Internet vulnerabilities

["Stephen J. Wilcox" <steve () opaltelecom co uk>]

Hi Marshall

If a route isnt withdrawn when the end network/device fails then no system will
fix that.

Presumably anycast wouldnt enable load balancing anyway as BGP only installs a
single route?

Or are you thinking both of these would be solved with a BGP enhancement?


Dont understand the multiple anycast comment, do you mean as it stands now? If
so it works fine if you inject the same route into an IGP providing you ensure
theres no IGP load balancing if you intend on doing TCP (altho most applications
for this appear to be UDP single request-responses)

Steve

On Fri, 5 Jul 2002, Marshall Eubanks wrote:

> On Fri, 5 Jul 2002 13:36:49 +0100 (BST)
>  "Stephen J. Wilcox" <steve () opaltelecom co uk> wrote:
> > Doesnt announcing the same routing prefix into BGP from multiple locations do
> > the same thing without needing a new range or enhancement in IGMP etc ?
> >
> > We do this in IGP currently..
> >
> > Steve
>
> As I see it, the problems with doing this in BGP are
>
> - it's static - no failover. If AS 701 and AS 1239 are both
> announcing a route to foo, and your preferred route is "through" AS701,
> and the AS701 foo goes down, then you do not
> automatically switch over to the AS1239 foo, even if you could reach it.
>
> - there is no way to have multiple anycast addresses within an AS
>
> - load balancing is tough
>
> These may all be solved, though... it's hard to tell without a protocol
> description.
>
> Regards
> Marshall Eubanks
>
> > On Fri, 5 Jul 2002, Barry Raveendran Greene wrote:
> >
> > > FYI - for those scratching their heads on "anycast" .....
> > >
> > > I just pushed out a paper on anycast by Chris Metz. Good foundation
> > > material.
> > >
> > > http://www.cisco.com/public/cons/isp/essentials/ip-anycast-cmetz-03.pdf
> > >
> > > > -----Original Message-----
> > > > From: owner-nanog () merit edu [mailto:owner-nanog () merit edu]On Behalf Of
> > > > Bill Woodcock
> > > > Sent: Friday, July 05, 2002 4:56 AM
> > > > To: Marshall Eubanks
> > > > Cc: nanog () merit edu
> > > > Subject: Re: Internet vulnerabilities
> > > >
> > > >
> > > >
> > > >     > But the only IPv4 anycast
> > > >     > that I know of does use MSDP :
> > > >     >
> > > > http://www.ietf.org/internet-drafts/draft-ietf-mboned-anycast-rp-08.txt
> > > >     > Is there a different proposal ? What's the RFC / I-D name ?
> > > >
> > > > You seem to be confusing anycast with something complicated.  It's not a
> > > > protocol, it's a method of assigning and routing addresses.
> > > >
> > > >                                 -Bill