No. By the endnode itself. It have no idea where to send it. For
ethernet, DECnet supposedly already knows the MAC address where to send
every packet. Where would it send a packet that isn't to the local
ethernet segment?
All the end node needs to know to send an Ethernet frame is a MAC for the
destination, and if it knows the DECnet node number then it knows the MAC by
definition. Anything beyond that is not its problem.
That's what the bridge program does, right? Moves those DECnet Ethernet
frames, via TCP/IP (or UDP - I forget which you used) over Internet to
another LAN ?
BTW, what do you mean by Ethernet "segment" in the context of the bridge
program? Aren't bridged "segments" by definition the same segment (at least
as far as DECnet messages go)? Or is the bridge itself doing something
smart with DECnet traffic?
Bob
Ennodes only become clever when the first datagram from the remote host returns. After that unnecessary routers are bypassed. Perhaps phase IV+ is different, in phase IV the first packet to a host outside the area is always sent to a router, when present.
Verzonden vanaf mijn draadloze BlackBerry -toestel
-----Original Message-----
From: Johnny Billquist <bqt at softjar.se>
Sender: owner-hecnet at Update.UU.SE
Date: Sun, 17 Jul 2011 19:40:10
To: <hecnet at Update.UU.SE>
Reply-To: hecnet at Update.UU.SESubject: Re: [HECnet] DECnet et al
On 2011-07-17 17.30, hvlems at zonnet.nl wrote:
Bob, endnodes in different areas can only talk to each other if there's no router present. So your scheme only works if all of us shut down all our L1 and L2 routers. Once an endnode sees a router in its area it will send all its off-area datagrams to it. If that router is an L1 router then the other area is seen as unreachable. If it is an L2 router then it must see the other area router.
No, endnodes will be clever and directly talk to other nodes that are
directly connected, even in the presence of a router. But the router is
needed to talk to anything not directly connected.
Johnny
I do need L1 routers (for DDCMP and DSSI circuits) and possibly others do too.
Show net/old is neat and useful when systems are in different rooms !
Hans
Verzonden vanaf mijn draadloze BlackBerry -toestel
-----Original Message-----
From: "Bob Armstrong"<bob at jfcl.com>
Sender: owner-hecnet at Update.UU.SE
Date: Sun, 17 Jul 2011 08:21:12
To:<hecnet at Update.UU.SE>
Reply-To: hecnet at Update.UU.SESubject: RE: [HECnet] DECnet et al
Yes. But any L1 routers need help from L2 routers to get out of area.
Yeah, but given that the routers aren't actually needed for two nodes to
talk (under HECnet circumstances) then we don't actually need the routing
nodes at all. Sounds like their only real use is to be able to do a "SHOW
NETWORK/OLD" and see an nice list of active nodes (which is undeniably
neat)...
So a node configured as an end node in area 'n' can actually communicate
directly, over Ethernet, with another end node in area 'm'? But a L1
routing node in area 'n', in the same physical network topology, would
actually relay its packets for a node in area 'm' via an L2 router? And
does this actually take two L2 routers to hand off the packets, one for area
'n' and one for 'm'?
So (again, in the HECnet situation only) having an L1 router is a real
penalty - where as two end nodes could talk directly, just changing the same
machines to L1 routers would require the same traffic to be handled by two
intermediate nodes.
Or an I confused? That's a bit bizarre.
Bob
On 2011-07-17 19.45, Bob Armstrong wrote:
And so those packets will be tossed.
Tossed by who? The bridge program?
No. By the endnode itself. It have no idea where to send it. For ethernet, DECnet supposedly already knows the MAC address where to send every packet. Where would it send a packet that isn't to the local ethernet segment? It needs to send it to a router, which will forward it. But since there is no router, there is nothing it can do with it. DECnet data traffic is not broadcast...
Just as information - from MIM, the area furthest away is are 59, which is three hops distance. So it packets needs to pass through two intermediate level 2 routers to get to the right area.
Johnny
On 2011-07-17 19.24, Bob Armstrong wrote:
Bob, endnodes in different areas can only talk to each other
if there's no router present. So your scheme only works if
all of us shut down all our L1 and L2 routers.
We don't have to shut down all the routers on HECnet, right? Just
shutting down the router for my area (or the area of anyone else who cares
about the issue) would be sufficient.
Yes... As long as you don't want to talk to anything that is not on the same segment. But since there are machines further away, this sounds like a sad limitation.
Once an endnode sees a router in its area ...
Exactly... If there are no routers in the end node's area, then
communications is direct. Routers for other areas are moot.
No. Communication are only direct to destinations which are on the same segment. The endnode will have no idea what to do if the destination is not on the same segment, and there is no router. And so those packets will be tossed.
Johnny
On 2011-07-17 17.30, hvlems at zonnet.nl wrote:
Bob, endnodes in different areas can only talk to each other if there's no router present. So your scheme only works if all of us shut down all our L1 and L2 routers. Once an endnode sees a router in its area it will send all its off-area datagrams to it. If that router is an L1 router then the other area is seen as unreachable. If it is an L2 router then it must see the other area router.
No, endnodes will be clever and directly talk to other nodes that are directly connected, even in the presence of a router. But the router is needed to talk to anything not directly connected.
Johnny
I do need L1 routers (for DDCMP and DSSI circuits) and possibly others do too.
Show net/old is neat and useful when systems are in different rooms !
Hans
Verzonden vanaf mijn draadloze BlackBerry -toestel
-----Original Message-----
From: "Bob Armstrong"<bob at jfcl.com>
Sender: owner-hecnet at Update.UU.SE
Date: Sun, 17 Jul 2011 08:21:12
To:<hecnet at Update.UU.SE>
Reply-To: hecnet at Update.UU.SESubject: RE: [HECnet] DECnet et al
Yes. But any L1 routers need help from L2 routers to get out of area.
Yeah, but given that the routers aren't actually needed for two nodes to
talk (under HECnet circumstances) then we don't actually need the routing
nodes at all. Sounds like their only real use is to be able to do a "SHOW
NETWORK/OLD" and see an nice list of active nodes (which is undeniably
neat)...
So a node configured as an end node in area 'n' can actually communicate
directly, over Ethernet, with another end node in area 'm'? But a L1
routing node in area 'n', in the same physical network topology, would
actually relay its packets for a node in area 'm' via an L2 router? And
does this actually take two L2 routers to hand off the packets, one for area
'n' and one for 'm'?
So (again, in the HECnet situation only) having an L1 router is a real
penalty - where as two end nodes could talk directly, just changing the same
machines to L1 routers would require the same traffic to be handled by two
intermediate nodes.
Or an I confused? That's a bit bizarre.
Bob
On 2011-07-17 16.55, Bob Armstrong wrote:
Paul Koning wrote:
It is legal to have multiple areas on a single Ethernet;
the routing spec covers that case explicitly. If that is done,
end nodes will communicate directly to a destination on the
Ethernet even if off-area ...
Given that Johnny's bridge program effectively creates a big Ethernet,
does that imply that HECnet end nodes in different areas can communicate
without an area router?
Yes, at least partially.
They can comminucate directly with machines sitting on the same ethernet segment, even if those machines are in another area.
However, I think that an endnode will not pick any router in another area as its designated router.
Johnny
It's the return path I'm worried about.
Say your area has just endnodes. My area has at least one L1 router up and running. How does a node in my area return the traffic since its router won't have a path towards your area. If mu area contains an L2 router then I think it will return an error like "destination area unreachable".
So, yes Johnny's bridge program makes HECnet behave like we're running DECnet (and LAT) on a large flat LAN. But the rules must observed by all: either we're running routers or neither of us do.
At least that's how I read Paul's messages.
Hans
------Origineel bericht------
Van: Bob Armstrong
Afzender: owner-hecnet at Update.UU.SE
Aan: hecnet at Update.UU.SE
Beantwoorden: hecnet at Update.UU.SE
Onderwerp: RE: [HECnet] DECnet et al
Verzonden: 17 juli 2011 19:24
Bob, endnodes in different areas can only talk to each other
if there's no router present. So your scheme only works if
all of us shut down all our L1 and L2 routers.
We don't have to shut down all the routers on HECnet, right? Just
shutting down the router for my area (or the area of anyone else who cares
about the issue) would be sufficient.
Once an endnode sees a router in its area ...
Exactly... If there are no routers in the end node's area, then
communications is direct. Routers for other areas are moot.
Bob
Verzonden vanaf mijn draadloze BlackBerry -toestel
Bob, endnodes in different areas can only talk to each other
if there's no router present. So your scheme only works if
all of us shut down all our L1 and L2 routers.
We don't have to shut down all the routers on HECnet, right? Just
shutting down the router for my area (or the area of anyone else who cares
about the issue) would be sufficient.
Once an endnode sees a router in its area ...
Exactly... If there are no routers in the end node's area, then
communications is direct. Routers for other areas are moot.
Bob
Bob, endnodes in different areas can only talk to each other if there's no router present. So your scheme only works if all of us shut down all our L1 and L2 routers. Once an endnode sees a router in its area it will send all its off-area datagrams to it. If that router is an L1 router then the other area is seen as unreachable. If it is an L2 router then it must see the other area router.
I do need L1 routers (for DDCMP and DSSI circuits) and possibly others do too.
Show net/old is neat and useful when systems are in different rooms !
Hans
Verzonden vanaf mijn draadloze BlackBerry -toestel
-----Original Message-----
From: "Bob Armstrong" <bob at jfcl.com>
Sender: owner-hecnet at Update.UU.SE
Date: Sun, 17 Jul 2011 08:21:12
To: <hecnet at Update.UU.SE>
Reply-To: hecnet at Update.UU.SESubject: RE: [HECnet] DECnet et al
Yes. But any L1 routers need help from L2 routers to get out of area.
Yeah, but given that the routers aren't actually needed for two nodes to
talk (under HECnet circumstances) then we don't actually need the routing
nodes at all. Sounds like their only real use is to be able to do a "SHOW
NETWORK/OLD" and see an nice list of active nodes (which is undeniably
neat)...
So a node configured as an end node in area 'n' can actually communicate
directly, over Ethernet, with another end node in area 'm'? But a L1
routing node in area 'n', in the same physical network topology, would
actually relay its packets for a node in area 'm' via an L2 router? And
does this actually take two L2 routers to hand off the packets, one for area
'n' and one for 'm'?
So (again, in the HECnet situation only) having an L1 router is a real
penalty - where as two end nodes could talk directly, just changing the same
machines to L1 routers would require the same traffic to be handled by two
intermediate nodes.
Or an I confused? That's a bit bizarre.
Bob
