Well, there is really no reason why areas would be tied to geographical separation. You can spread out nodes that are in one area over the whole world as well.
There are both L1 hello messages, and L2 hello messages.
These are used to build the connection topography matrix for the routers.
What areas really brought to the table was a hierarchy where you could also more easily separate administration of the network.
All L1 routers within one are must be able to communicate with all other L1 routers within the area, by just talking directly, or via other L1 routers in the area.
All L2 routers must be able to talk to all other L2 routers, either directly or using only other L2 routers.
Both are obvious requirements when you think of the hello messages, which are not routed, but broadcast on all interfaces. So a scenarion of
A(L2) - B(L1) - C(L2)
would mean that A and C could not exchange L2 hello messages, which means they will not know of each other, or what connectivity the other node have.
Also worth mentioning is that all L2 routers also are L1 routers.
Johnny
On 2011-07-17 00.03, hvlems at zonnet.nl wrote:
Exactly my point Johnny. The original function for areas was to identify different geograhical locations. Same LAN area routing just wasn't part of the design. The rule is that area routers must always be adjacent to make the connection. In those days (30 years ago) that always meant poiint-to-point connections.
ISTR that there is a L2 hello message for that purpose.
Verzonden vanaf mijn draadloze BlackBerry -toestel
-----Original Message-----
From: Johnny Billquist<bqt at softjar.se>
Sender: owner-hecnet at Update.UU.SE
Date: Sat, 16 Jul 2011 23:52:42
To:<hecnet at Update.UU.SE>
Reply-To: hecnet at Update.UU.SESubject: Re: [HECnet] DECnet et al
On 2011-07-16 23:46, Paul Koning wrote:
On Jul 16, 2011, at 5:40 PM,<hvlems at zonnet.nl> wrote:
Ok, so the convention that the output of the SHO NET command always lists the area router with the highest address is just a display rule. It has nothing to do with an "active" area router then?
I can't find the rule for what L2 adjacent router to pick if you're an L1 router going out of area. It may be that this is where "highest" kicks in.
For non-adjacent L2 routers, the L1 router doesn't have any idea which router is represented by the "nearest L2 router" pseudo-address zero. It can't know that.
I don't know all the details here, and instead of starting to read
through documentation, perhaps you know, Paul, if L1 routers knows
*which* nodes in the area are L2 routers?
Because L1 routers knows the shortest paths to all nodes within it's
area, if I don't remember wrong.
However, an L1 router can never know which L2 router is the better for
reaching a specific area, since L1 routers have no idea of the area
topology.
But I *think* that L1 routers knows the type of nodes of all nodes in
the local area, so they should easily be able to figure out where the
closest L2 router is. But that is based on the assumption that they know
the type of each node in the area.
Johnny
paul
------Origineel bericht------
Van: Paul Koning
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: 16 juli 2011 23:25
On Jul 16, 2011, at 3:42 PM, Johnny Billquist wrote:
On 2011-07-16 19.18, hvlems at zonnet.nl wrote:
I'm not sure what the router rules are. There are 63 areas, each with
one actove area router. There may be more routers configured as an area
router in one area; the one with the highest (?) DECnet address is
selected as the active one.
As far as I know, there can be more than one active area router. Just look at what the next hop are for different nodes in your node list... :-)
The way it works is that address 0 in the level 1 routing data corresponds to "nearest L2 router". Any L2 router contributes to that. The L1 routers don't know or care who is the nearest L2 router, they only care which direction to send to get there.
paul
Verzonden vanaf mijn draadloze BlackBerry -toestel
Exactly my point Johnny. The original function for areas was to identify different geograhical locations. Same LAN area routing just wasn't part of the design. The rule is that area routers must always be adjacent to make the connection. In those days (30 years ago) that always meant poiint-to-point connections.
ISTR that there is a L2 hello message for that purpose.
Verzonden vanaf mijn draadloze BlackBerry -toestel
-----Original Message-----
From: Johnny Billquist <bqt at softjar.se>
Sender: owner-hecnet at Update.UU.SE
Date: Sat, 16 Jul 2011 23:52:42
To: <hecnet at Update.UU.SE>
Reply-To: hecnet at Update.UU.SESubject: Re: [HECnet] DECnet et al
On 2011-07-16 23:46, Paul Koning wrote:
On Jul 16, 2011, at 5:40 PM,<hvlems at zonnet.nl> wrote:
Ok, so the convention that the output of the SHO NET command always lists the area router with the highest address is just a display rule. It has nothing to do with an "active" area router then?
I can't find the rule for what L2 adjacent router to pick if you're an L1 router going out of area. It may be that this is where "highest" kicks in.
For non-adjacent L2 routers, the L1 router doesn't have any idea which router is represented by the "nearest L2 router" pseudo-address zero. It can't know that.
I don't know all the details here, and instead of starting to read
through documentation, perhaps you know, Paul, if L1 routers knows
*which* nodes in the area are L2 routers?
Because L1 routers knows the shortest paths to all nodes within it's
area, if I don't remember wrong.
However, an L1 router can never know which L2 router is the better for
reaching a specific area, since L1 routers have no idea of the area
topology.
But I *think* that L1 routers knows the type of nodes of all nodes in
the local area, so they should easily be able to figure out where the
closest L2 router is. But that is based on the assumption that they know
the type of each node in the area.
Johnny
paul
------Origineel bericht------
Van: Paul Koning
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: 16 juli 2011 23:25
On Jul 16, 2011, at 3:42 PM, Johnny Billquist wrote:
On 2011-07-16 19.18, hvlems at zonnet.nl wrote:
I'm not sure what the router rules are. There are 63 areas, each with
one actove area router. There may be more routers configured as an area
router in one area; the one with the highest (?) DECnet address is
selected as the active one.
As far as I know, there can be more than one active area router. Just look at what the next hop are for different nodes in your node list... :-)
The way it works is that address 0 in the level 1 routing data corresponds to "nearest L2 router". Any L2 router contributes to that. The L1 routers don't know or care who is the nearest L2 router, they only care which direction to send to get there.
paul
Verzonden vanaf mijn draadloze BlackBerry -toestel
--
Johnny Billquist || "I'm on a bus
|| on a psychedelic trip
email: bqt at softjar.se || Reading murder books
pdp is alive! || tryin' to stay hip" - B. Idol
On 2011-07-16 23:46, Paul Koning wrote:
On Jul 16, 2011, at 5:40 PM,<hvlems at zonnet.nl> wrote:
Ok, so the convention that the output of the SHO NET command always lists the area router with the highest address is just a display rule. It has nothing to do with an "active" area router then?
I can't find the rule for what L2 adjacent router to pick if you're an L1 router going out of area. It may be that this is where "highest" kicks in.
For non-adjacent L2 routers, the L1 router doesn't have any idea which router is represented by the "nearest L2 router" pseudo-address zero. It can't know that.
I don't know all the details here, and instead of starting to read through documentation, perhaps you know, Paul, if L1 routers knows *which* nodes in the area are L2 routers?
Because L1 routers knows the shortest paths to all nodes within it's area, if I don't remember wrong.
However, an L1 router can never know which L2 router is the better for reaching a specific area, since L1 routers have no idea of the area topology.
But I *think* that L1 routers knows the type of nodes of all nodes in the local area, so they should easily be able to figure out where the closest L2 router is. But that is based on the assumption that they know the type of each node in the area.
Johnny
paul
------Origineel bericht------
Van: Paul Koning
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: 16 juli 2011 23:25
On Jul 16, 2011, at 3:42 PM, Johnny Billquist wrote:
On 2011-07-16 19.18, hvlems at zonnet.nl wrote:
I'm not sure what the router rules are. There are 63 areas, each with
one actove area router. There may be more routers configured as an area
router in one area; the one with the highest (?) DECnet address is
selected as the active one.
As far as I know, there can be more than one active area router. Just look at what the next hop are for different nodes in your node list... :-)
The way it works is that address 0 in the level 1 routing data corresponds to "nearest L2 router". Any L2 router contributes to that. The L1 routers don't know or care who is the nearest L2 router, they only care which direction to send to get there.
paul
Verzonden vanaf mijn draadloze BlackBerry -toestel
--
Johnny Billquist || "I'm on a bus
|| on a psychedelic trip
email: bqt at softjar.se || Reading murder books
pdp is alive! || tryin' to stay hip" - B. Idol
On Jul 16, 2011, at 5:40 PM, <hvlems at zonnet.nl> wrote:
Ok, so the convention that the output of the SHO NET command always lists the area router with the highest address is just a display rule. It has nothing to do with an "active" area router then?
I can't find the rule for what L2 adjacent router to pick if you're an L1 router going out of area. It may be that this is where "highest" kicks in.
For non-adjacent L2 routers, the L1 router doesn't have any idea which router is represented by the "nearest L2 router" pseudo-address zero. It can't know that.
paul
------Origineel bericht------
Van: Paul Koning
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: 16 juli 2011 23:25
On Jul 16, 2011, at 3:42 PM, Johnny Billquist wrote:
On 2011-07-16 19.18, hvlems at zonnet.nl wrote:
I'm not sure what the router rules are. There are 63 areas, each with
one actove area router. There may be more routers configured as an area
router in one area; the one with the highest (?) DECnet address is
selected as the active one.
As far as I know, there can be more than one active area router. Just look at what the next hop are for different nodes in your node list... :-)
The way it works is that address 0 in the level 1 routing data corresponds to "nearest L2 router". Any L2 router contributes to that. The L1 routers don't know or care who is the nearest L2 router, they only care which direction to send to get there.
paul
Verzonden vanaf mijn draadloze BlackBerry -toestel
Ok, so the convention that the output of the SHO NET command always lists the area router with the highest address is just a display rule. It has nothing to do with an "active" area router then?
------Origineel bericht------
Van: Paul Koning
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: 16 juli 2011 23:25
On Jul 16, 2011, at 3:42 PM, Johnny Billquist wrote:
On 2011-07-16 19.18, hvlems at zonnet.nl wrote:
I'm not sure what the router rules are. There are 63 areas, each with
one actove area router. There may be more routers configured as an area
router in one area; the one with the highest (?) DECnet address is
selected as the active one.
As far as I know, there can be more than one active area router. Just look at what the next hop are for different nodes in your node list... :-)
The way it works is that address 0 in the level 1 routing data corresponds to "nearest L2 router". Any L2 router contributes to that. The L1 routers don't know or care who is the nearest L2 router, they only care which direction to send to get there.
paul
Verzonden vanaf mijn draadloze BlackBerry -toestel
On Jul 16, 2011, at 3:42 PM, Johnny Billquist wrote:
On 2011-07-16 19.18, hvlems at zonnet.nl wrote:
I'm not sure what the router rules are. There are 63 areas, each with
one actove area router. There may be more routers configured as an area
router in one area; the one with the highest (?) DECnet address is
selected as the active one.
As far as I know, there can be more than one active area router. Just look at what the next hop are for different nodes in your node list... :-)
The way it works is that address 0 in the level 1 routing data corresponds to "nearest L2 router". Any L2 router contributes to that. The L1 routers don't know or care who is the nearest L2 router, they only care which direction to send to get there.
paul
On Jul 16, 2011, at 1:18 PM, <hvlems at zonnet.nl> <hvlems at zonnet.nl> wrote:
The Montagar licenses include all the DECnet licenses. There is no reason to limit yourself (today) to endnode functionality. SHOW NETWORK(/OLD) gives useful information.
I'm not sure what the router rules are. There are 63 areas, each with one actove area router. There may be more routers configured as an area router in one area; the one with the highest (?) DECnet address is selected as the active one.
No, an L1 router will pick the nearest L2 router (lowest cost path to it). End nodes will send to the elected designated router for the first packet, and will (depending on the exact version) send subsequent traffic back to the router that sent it the reply. (That's the "previous hop cache" which in the original Phase IV started out as the "on-Ethernet" cache but was later generalized.)
There are limits on the number of routers. There are counters in NCP, executer max circuits and exec maximum routers.
Max routers is the max adjacent routers on Ethernet; it does not limit the total number of routers in the area.
paul
On 2011-07-16 19.22, hvlems at zonnet.nl wrote:
The restriction was for level-1 (or circuit) routing and was introduced
when the Alpha was new (no Itanium yet, Alpha was king of the hill).
Ethernet was to be the network for all sites.
Ethernet is a different domain than DECnet routing. You need DECnet routing even with Ethernet. And Alphas can officially act as level 1 routers. It is level 2 (area) routers they supposedly can not be.
AFAIK there is still no DDCMP support for decnet on alpha.
Right.
Johnny
Verzonden vanaf mijn draadloze BlackBerry -toestel
------------------------------------------------------------------------
*From: * "Steve Davidson" <jeep at scshome.net>
*Sender: * owner-hecnet at Update.UU.SE
*Date: *Sat, 16 Jul 2011 11:28:12 -0400
*To: *<hecnet at Update.UU.SE>
*ReplyTo: * hecnet at Update.UU.SE
*Subject: *[HECnet] DECnet routing on Alpha platforms
While it is true that HP does not officially support Alpha's as routers
(according to their web site), it works just fine!
I suspect, but do not know for sure, that this was more of a marketing
ploy to push Itanium over Alpha.
If you go the emulated route (i.e. VAX 3900) this becomes a non-issue as
VAXen ARE supported as DECnet routers.
-Steve
On 2011-07-16 19.18, hvlems at zonnet.nl wrote:
I'm not sure what the router rules are. There are 63 areas, each with
one actove area router. There may be more routers configured as an area
router in one area; the one with the highest (?) DECnet address is
selected as the active one.
As far as I know, there can be more than one active area router. Just look at what the next hop are for different nodes in your node list... :-)
There are limits on the number of routers. There are counters in NCP,
executer max circuits and exec maximum routers.
Yes. But that is a limit on broadcast routers, and relates to adjacent routers that you want to keep track of.
On first generation VAX systems routing overhead was deemed too high.
I think it's wrong to say it was deemed "too high", as that is very subjective. But running as an endnode takes much less resources, so unless you want to run as a router, it would perhaps be benificial.
IMO this may be the case with 11/750's and slower but a MicroVAX II
could easily keep up with the traffic on a LAN with more than 1100
decnet hosts in 8 areas.
Well, a PDP-11 can keep up with it as well. (Although I have not tried anything slower than a PDP-11/70.) But it do take some CPU power, as well as memory.
Johnny
Hans
Verzonden vanaf mijn draadloze BlackBerry -toestel
------------------------------------------------------------------------
*From: * "Steve Davidson" <jeep at scshome.net>
*Sender: * owner-hecnet at Update.UU.SE
*Date: *Sat, 16 Jul 2011 11:23:46 -0400
*To: *<hecnet at Update.UU.SE>
*ReplyTo: * hecnet at Update.UU.SE
*Subject: *[HECnet] DECnet et al
Mark,
When I install DECnet on VMS I always use the DNVETRTG license. This way
I do not have to care about the system's role - I may change it at will
On another note, the node SGC:: is an emulated system that is always
running as an area router. This way I always have a gateway to the rest
of HECnet and the cost to run the system is minimal. DECnet has limits
as to the total number of area routers so just adding a router may not
be the best answer. The HECnet backbone is not at that limit yet... If
you were to use an emulated system as a router then it would not matter
which of the other systems you brought up - they would all be able to
see the rest of HECnet.
I should mention though that a cluster with a cluster alias MUST be a
router. It can be a level-1 or level-2 (area) though...
-Steve
