Linux 2.4 as a router, when is it appropriate?

Linux 2.4 as a router, when is it appropriate?

[Russell Leighton]

Could someone please tell me (or refer me to docs) on when
using the Linux on PC hardware as a router is an appropriate
solution and when one should consider a "real" router (e.g., Cisco)?

I have heard that performance wise, if you have a fast CPU,
much memory and good NICs that Linux can be as good
all but the high end routers. Are there important missing
features or realiability issues that make using Linux not
suitable for "enterprise" use?

Thanks.

Russ

Re: Linux 2.4 as a router, when is it appropriate?

[Alan Cox]

> I have heard that performance wise, if you have a fast CPU,
> much memory and good NICs that Linux can be as good
> all but the high end routers. Are there important missing
> features or realiability issues that make using Linux not
> suitable for "enterprise" use?

CPU and RAM isnt that important. Your normal limit is the PCI bus bandwidth.
At gigabit speeds that becomes a bottleneck, followed by RAM bandwidth.

Re: Linux 2.4 as a router, when is it appropriate?

[Hirling Endre]

On Fri, 3 May 2002, Russell Leighton wrote:

> Could someone please tell me (or refer me to docs) on when
> using the Linux on PC hardware as a router is an appropriate
> solution and when one should consider a "real" router (e.g., Cisco)?

I have a Linux-based router and it can handle about as much as a cisco
7206vxr with GE interfaces. I think both of them reaches the bandwidth
limit of the PCI bus. The PC can be much better with 64bit/66MHz PCI
buses or you can even buy motherboards with 100 or 133MHz PCI-X slots. I
guess those can drive 3 or 4 GE interfaces at gigabit speed.

You need a cisco when you care about interface density, you have
interfaces you can't buy for a PC or you need to route protocols other
than IP or proprietary to cisco.

endre

RE: Linux 2.4 as a router, when is it appropriate?

[George Bonser]

I have used Linux/Zebra in production as a route reflector. That
machine was simply a BGP peer of the others and not directly in the
traffic path. That configuration had several commercial border routers
(actually L2/3 switches) collecting full Internet routes from their
upstream peers. These border routers fed their routing table via BGP
to the Linux route reflector. The Linux/Zebra box aggregated the
table, applied various policy to the routes received, and sent the
resulting table on to the core routers.

The reason for using Linux in this case was the large amount of memory
required for handling all the peers. Zebra handled it just fine and
you can just keep adding RAM to a PC. To get the same capability in a
commercial unit you have to get some very expensive iron.  This
allowed the border units to be relatively inexpensive with only enough
RAM to handle 1 Internet peer with full routes and kept the core
router CPU free to handle traffic rather than process routes so it
could also be a lower cost unit than would otherwise be required.

The unit was in production for over a year without a single reboot.




> -----Original Message-----
> From: linux-kernel-owner@vger.kernel.org
> [mailto:linux-kernel-owner@vger.kernel.org]On Behalf Of
> Russell Leighton
> Sent: Friday, May 03, 2002 6:25 AM
> To: linux-kernel@vger.kernel.org
> Subject: Linux 2.4 as a router, when is it appropriate?
>
>
>
> Could someone please tell me (or refer me to docs) on when
> using the Linux on PC hardware as a router is an appropriate
> solution and when one should consider a "real" router (e.g., Cisco)?
>
> I have heard that performance wise, if you have a fast CPU,
> much memory and good NICs that Linux can be as good
> all but the high end routers. Are there important missing
> features or realiability issues that make using Linux not
> suitable for "enterprise" use?
>
> Thanks.
>
> Russ
>
>
>
> -
> To unsubscribe from this list: send the line "unsubscribe
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Re: Linux 2.4 as a router, when is it appropriate?

[David S. Miller]

   From: Russell Leighton <russ@elegant-software.com>
   Date: Fri, 03 May 2002 09:25:12 -0400

   Could someone please tell me (or refer me to docs) on when
   using the Linux on PC hardware as a router is an appropriate
   solution and when one should consider a "real" router (e.g., Cisco)?

The most heavily accessed ftp site in europe uses Linux machines
exclusively as it's routers.

Re: Linux 2.4 as a router, when is it appropriate?

[David S. Miller]

   From: Mathieu Chouquet-Stringer <mathieu@newview.com>
   Date: 05 May 2002 22:27:52 -0400

   And what kind of traffic are you speaking of (I mean how much megs/teras
   per day)?
   
We're talking about several hundred kilo packet per second routing
over gigabit.

   

Re: Linux 2.4 as a router, when is it appropriate?

[Mathieu Chouquet-Stringer]

davem@redhat.com ("David S. Miller") writes:
>    From: Russell Leighton <russ@elegant-software.com>
>    Date: Fri, 03 May 2002 09:25:12 -0400
> 
>    Could someone please tell me (or refer me to docs) on when
>    using the Linux on PC hardware as a router is an appropriate
>    solution and when one should consider a "real" router (e.g., Cisco)?
> 
> The most heavily accessed ftp site in europe uses Linux machines
> exclusively as it's routers.

And what kind of traffic are you speaking of (I mean how much megs/teras
per day)?

-- 
Mathieu Chouquet-Stringer              E-Mail : mathieu@newview.com
    It is exactly because a man cannot do a thing that he is a
                      proper judge of it.
                      -- Oscar Wilde

Re: Linux 2.4 as a router, when is it appropriate?

[Mathieu Chouquet-Stringer]

On Sun, May 05, 2002 at 07:18:05PM -0700, David S. Miller wrote:
>    From: Mathieu Chouquet-Stringer <mathieu@newview.com>
>    Date: 05 May 2002 22:27:52 -0400
> 
>    And what kind of traffic are you speaking of (I mean how much megs/teras
>    per day)?
>    
> We're talking about several hundred kilo packet per second routing
> over gigabit.

Impressive (thanks for this quick reply).
-- 
Mathieu Chouquet-Stringer              E-Mail : mathieu@newview.com
    It is exactly because a man cannot do a thing that he is a
                      proper judge of it.
                      -- Oscar Wilde

Re: Linux 2.4 as a router, when is it appropriate?

[Hirling Endre]

On Mon, 2002-05-06 at 04:18, David S. Miller wrote:
    
> We're talking about several hundred kilo packet per second routing
> over gigabit.

What kind of hardware are those routers?

endre

Re: Linux 2.4 as a router, when is it appropriate?

[Bill Davidsen]

On Fri, 3 May 2002, Russell Leighton wrote:

> 
> Could someone please tell me (or refer me to docs) on when
> using the Linux on PC hardware as a router is an appropriate
> solution and when one should consider a "real" router (e.g., Cisco)?
> 
> I have heard that performance wise, if you have a fast CPU,
> much memory and good NICs that Linux can be as good
> all but the high end routers. Are there important missing
> features or realiability issues that make using Linux not
> suitable for "enterprise" use?

  Professional routers may support non-IP protocols which Linux doesn't,
and the non-IP protocols which are in Linux are far less less used than
IP. That does not mean they don't work, but somewhat untrodden ground.

  For IP, particularly for tricky, messy, nasty stuff, I do prefer
Linux/iptables. I'm looking forward to having time to see how well UML and
iptables play, so I can have a whole DMZ full of "machines" to test some
challenging setups.

  Throughput and latency are pretty competitive with any commercial
router, given good hardware. I believe preempt does improve latency, but I
really haven't had a case where I needed to worry about it, Linux is fast
as-is.

-- 
bill davidsen <davidsen@tmr.com>
  CTO, TMR Associates, Inc
Doing interesting things with little computers since 1979.