On 7/26/23 9:45 PM, Jon Perryman wrote:
"HOME" was not in UNIX TCP so z/OS is the only doc available.
Based on a previous comment about HOME controlling the IP address that
remote systems saw newly initiated connections coming from, this concept
is in, and has been for a long time, Linux. This is the source IP
chosen as part of routing. -- This very much so became a thing with
policy based routing in the early 2000s if not before.
There is in fact many features that were (and probably still are)
specific to z/OS
I'll give you "were". I question "still are".
(e.g. HOME, VIPA, port balancing, port forwarding, sysplex
workload balancing and much more).
By default Linux uses what is called the weak host model which means
that the IP addresses belong to the kernel (IP stack) and not to an
interface. It's trivial to move any given IP address around to
different interfaces. -- There's some minutia to moving IPs, but I
assume there is minutia to VIPA too.
Port balancing seems to be quite similar to what is usually called "load
balancing" in Open Systems. Linux kernel has this capability built in
in at least a couple of different ways.
I don't know what "port forwarding" means in z/OS context, but port
forwarding connections from one IP address and port pair to another is
so common that $75 dollar routers running Linux / *BSD have been doing
it for 25 years. I can't even successfully do a search for what it
means on the mainframe because of all the other collissions that I find
in IBM i, AIX, and that's on top of all the other non-IBM related results.
I don't know if sysplex workload balnacing has a counter part, but I
strongly suspect that load balancers described above and / or clusters
of servers account for much of this all be it likely in a different way.
z/OS needed a more robust TCP because of sysplex.
I would never have considered using z/OS for a networking Swiss Army
Knife. Linux and *BSD or a Cisco / Juniper router jump to the top of
that list.
Linux, Windows, Unix and others are single machines with unique resources.
That is their most common configuration. But Linux and *BSD in
particular can do so much more if you want them to.
For instance, DB2 on z/OS can be accessed from any z/OS within a sysplex
Sure.
Depending on the middleware, you can get the same IP / service instance
to be accessible from multiple machines in a cluster.
but DB2 on Linux is available
from a single machine which cannot be transferred to another Linux.
I don't know about DB2, but I an quite certain that there are multiple
ways to have the same IP be accessible from multiple machines.
There are even ways to transfer the connections between machines.
There are ways to synchronize firewall state between multiple machines.
I'm quite certain that how things would be done on the mainframe are
different than how they would be done on Linux.
But I'm also fairly certain that Linux can do most of, if not all of,
what you have mentioned.
Thank you for the additional information Jon.
Grant. . . .
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