Anybody know what a "gray-hole hop" is?

Anybody know what a "gray-hole hop" is?

Post by wulf » Wed, 02 Oct 2002 13:42:42



Some Jalaam marketing material (www.jaalam.com) sez  that their
appareNet (tm) NMS product can detect "Black-Hole / Gray-Hole Hops".
I've never heard this terminology before. I assume a black-hole hop is a
packet that get's dropped and instead of being forwarded by a router?
 But what would a gray-hole hop be?

TIA,
--Wulf

 
 
 

Anybody know what a "gray-hole hop" is?

Post by Leonid Rosenboi » Wed, 02 Oct 2002 17:32:37


Wulf,

On some networks when you do traceroute, some of
the intermediate routers will not appears,
becuase they wont send the ICMP Time Exceeded
packets back at you, these I beleive are referred
to as "black hole". They still route these packets
allright.

As to grey holes, it is the first time I encounter this term.

So I did a search on Google, and here is what I found (different
meaniong of black-hole):
http://www.canarie.ca/advnet/workshop_2001/presentations/klassen.ppt

MTU via PMTU Discovery
Most commonly deployed method
Defined in RFC 1191
'Black Hole Router' is a device in a path that does not send a "packet too
big" ICMP message when required
'Grey Hole Router' is a device in a path that send the wrong MTU size in the
"packet too big" ICMP message
Negotiation failure causes some applications to run slowly, or not at all.
Most applications continue to run.
For more information on MTU download the MTU whitepaper at
http://www.jaalam.com


> Some Jalaam marketing material (www.jaalam.com) sez  that their
> appareNet (tm) NMS product can detect "Black-Hole / Gray-Hole Hops".
> I've never heard this terminology before. I assume a black-hole hop is a
> packet that get's dropped and instead of being forwarded by a router?
>  But what would a gray-hole hop be?

> TIA,
> --Wulf


 
 
 

Anybody know what a "gray-hole hop" is?

Post by Martin Kaye » Thu, 03 Oct 2002 20:59:59


I don't know the exact details but a grey-hole is when only some of the
packets 'disappear, as opposed to all of them which would be a black-hole.

I did see a reference to Grey-Holes once on a search from Yahoo.

Regards,

Martin


> Wulf,

> On some networks when you do traceroute, some of
> the intermediate routers will not appears,
> becuase they wont send the ICMP Time Exceeded
> packets back at you, these I beleive are referred
> to as "black hole". They still route these packets
> allright.

> As to grey holes, it is the first time I encounter this term.

> So I did a search on Google, and here is what I found (different
> meaniong of black-hole):
> http://www.canarie.ca/advnet/workshop_2001/presentations/klassen.ppt

> MTU via PMTU Discovery
> Most commonly deployed method
> Defined in RFC 1191
> 'Black Hole Router' is a device in a path that does not send a "packet too
> big" ICMP message when required
> 'Grey Hole Router' is a device in a path that send the wrong MTU size in
the
> "packet too big" ICMP message
> Negotiation failure causes some applications to run slowly, or not at all.
> Most applications continue to run.
> For more information on MTU download the MTU whitepaper at
> http://www.jaalam.com




- Show quoted text -

Quote:> > Some Jalaam marketing material (www.jaalam.com) sez  that their
> > appareNet (tm) NMS product can detect "Black-Hole / Gray-Hole Hops".
> > I've never heard this terminology before. I assume a black-hole hop is a
> > packet that get's dropped and instead of being forwarded by a router?
> >  But what would a gray-hole hop be?

> > TIA,
> > --Wulf