connecting 3 computers without a router

[Orson Cart]

Suppose I have 3 pizza boxes, each has 2 x 1 Gbps ethernet ports.
If I connect each to both of the others with crossover cables,
I eliminate the delay of a router.
Is this topology used by anybody? Does it have a name?
Any hidden surprises?

[Pascal Hambourg]

Hello,

Orson Cart a écrit :

> Suppose I have 3 pizza boxes, each has 2 x 1 Gbps ethernet ports.
> If I connect each to both of the others with crossover cables,

If the ports have automatic MDI/MDI-X configuration, you can use
straight cables.

> I eliminate the delay of a router.

The device used to interconnect nodes in a network is a switch, not a
router. A router is used to interconnect networks.

> Is this topology used by anybody? Does it have a name?

I would say that's a kind of point-to-point topology.

> Any hidden surprises?

As each link is a separate network, you cannot send a single broadcast
to all hosts.

[Lew Pitcher]

On Dec 26, 5:26 am, Pascal Hambourg <boite-a-s...@plouf.fr.eu.org>
wrote:

Assuming that the OP has enough knowledge to properly set up the three
boxen (assigning proper IP addresses & subnet masks, setting proper
values in his static route definitions, providing proper /etc/hosts
values, etc.), then he /might/ have enough knowledge to be able to
hide the middle boxes two connections under a single "bridge" device.

That way, all three hosts can reside on the same network, with the
middle host moving packets for the end systems across the (hidden)
physical interfaces.

[Pascal Hambourg]

Lew Pitcher a écrit :

>>
>> Orson Cart a écrit :
>>>
>>> Suppose I have 3 pizza boxes, each has 2 x 1 Gbps ethernet ports.
>>> If I connect each to both of the others with crossover cables,
>>>

>>> I eliminate the delay of a router.

[...]

> Assuming that the OP has enough knowledge to properly set up the three
> boxen (assigning proper IP addresses & subnet masks, setting proper
> values in his static route definitions, providing proper /etc/hosts
> values, etc.), then he /might/ have enough knowledge to be able to
> hide the middle boxes two connections under a single "bridge" device.

Middle box ? IIUC the OP's design, each box is directly connected to the
two others, in a triangle topology. A middle box acting as a bridge
introduces at least as much forwarding delay between the two other boxes
as a switch would. Even in the triangle topology, creating a bridge on
each box would require to enable STP (Spanning Tree Protocol) to avoid
loops ; that would effectively disable on of the links and result in one
box being in the middle.

[Mark Evans]

Orson Cart <ex-p...@parts.org> wrote:
>
> Suppose I have 3 pizza boxes, each has 2 x 1 Gbps ethernet ports.
> If I connect each to both of the others with crossover cables,

You are unlikely to need a crossover cable with gigabit ports.
Even fairly recent 10/100 NICS/switches will automatically links
with straight cables.

> I eliminate the delay of a router.
> Is this topology used by anybody? Does it have a name?

You could call it either a "ring" or a set of point to point
links.

[Bernhard Kupfer]

Guess the delay by your systems having to ask their own routing tables
is much higher then the delay a switch (wich routes on OSI Level 2)
would have. Your router has a switch builtin, with the router as
another device on an internal port, not being asked for local
transmissions.

Bernhard

[David Schwartz]

You don't need crossover cables for Gigabit. That topology is used,
it's called point-to-point. What it eliminates is not routing but
switching. Switching delay is generally considered negligible, but
there are some applications where minimizing it helps, and Gigabit
ports tend to be pretty cheap.

DS

[Thad Floryan]

There's a big difference between "cheap" and "inexpensive"; quality
can be inexpensive:

<http://www.newegg.com/Product/Product.aspx?Item=N82E16833106033>

<http://www.intel.com/content/www/us/en/network-adapters/gigabit-network-adapters/gigabit-ct-desktop-adapter.html>

<http://www.intel.com/content/dam/doc/product-brief/gigabit-ct-desktop-adapter-brief.pdf>

[Christian Brandt]

Am 26.12.2011 01:58, schrieb Orson Cart:
> Suppose I have 3 pizza boxes, each has 2 x 1 Gbps ethernet ports.
> If I connect each to both of the others with crossover cables,
> I eliminate the delay of a router.

> Is this topology used by anybody?

Token Ring - dead fish in the water.

> Does it have a name?

emergency solution, misuse of resources.

Connect all ports to a single switch and enjoy 2GBit throughput by port
trunking. This will easily outperform a million times the penalties of a
switch.

> Any hidden surprises?

You might safe 0.1ms by sacrificing nearly all conformity to normal
TCP-Networks. If you do not know what you are doing thing might get
interesting for the uninvolved observer.

Christian Brandt