Re: [mpls-linux-general] A smaller network for label stack example

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On Wed, Nov 17, 2004 at 11:13:49AM +0100, ed...@ti... wrote:
> Many questions for you James, please answer me:
> 1) when i pass from MPLS to IP i've seen that label space stay already setted,
> how can i remove this setting? (i've tryed mplsadm2 -D -L eth0:0 without
> success)

mplsadm2 -L eth0:-1

> 2) I've test PHP way, seeing settings of LER (in the last example WINDOWS)
> i've seen that it has already ILM setted, can this setting invalid my test
> in any way (if i'm right the link between the last LSR and the LER in PHP
> way must be all IP, isn't it?)

mpls-linux does not do proper PHP.  Proper PHP would result in a LSR forwarding
an unlabeled IP packet without doing a IP lookup.  mpls-linux will always
do an IP lookup on unlabeled packet.

> 3) You have told me that "At the point of exiting the IP stack it is redirected
> to MPLS via the special nexthop 0x4." what dooes it mean? NHLFE is an entry
> in /mpls/out  table, can you explain me better?

I think the best way for you to understand what that means is to read the code.
Start looing in linux/net/ipv4/route.c look in the function called
rt_set_nexthop().  See how it calls spec_nh->func() in the case of MPLS
spec_nh->func() is mpls_set_nexthop() which can be found in
linux/net/mpls/mpls_output.c.  Notice how mpls_set_nexthop sets dst->child?
Now go look at linux/net/ipv4/ip_output.c  Look for the function
ip_finish_output2().  Notice what happens is dst->child is set?
In the case of MPLS dst_output() calls mpls_output() which can be
found in linux/net/mpls/mpls_output.c

> I'd like to send packets from different source to the same destination trough
> my MPLS network, if i've understtod your explanation you set an LSP with
> 0X2 NHLFE and an other opne with 0X3, These LSP originate from the source
> of traffic to the LER, after you forward these packets trought LSP 0x4.
> In my intention source and destination of packets are IP hosts, label stack
> in my idea is made by one from the I-LER to the E-LER and one that explain
> which hosts has generated traffic forwarded.

The example I sent you does exactly that.  IP packets from 2 different hosts
get sent on different LSPs destined for the same host.

> Can you help me?
> 
> 
> 
> 
> 
> 
> >-- Messaggio Originale --
> >From: "James R. Leu" <jl...@mi...>
> >To: ed...@ti...
> >Cc: mpl...@li...
> >Subject: Re: [mpls-linux-general] A smaller network for label stack example
> >Reply-To: jl...@mi...
> >Date: Tue, 16 Nov 2004 11:54:30 -0600
> >
> >
> >Lets look at the case where you want traffic from different hosts using
> >different LSPs:
> >
> >You use iptables to differentiate the traffic from the two different hosts.
> >
> >    iptable -A OUTPUT -s 2.2.2.2/32 -j MARK --set-mark=2
> >    iptable -A OUTPUT -s 3.3.3.3/32 -j MARK --set-mark=3
> >
> >You then need to make sure you have a route installed for the
> >destination which points to a NHLFE:
> >
> >    ip route add 4.4.4.4/32 via 192.168.2.1 spec_nh 0x8847 0x4
> >
> >Where 0x4 is the key for a NHLFE which was created like this:
> >
> >    mplsadm2 -A -O 0
> >    (key 0x2)
> >    mplsadm2 -A -O 0
> >    (key 0x3)
> >    mplsadm2 -A -O 0
> >    (key 0x4)
> >    mplsadm2 -O 0x2 -o push:gen:200:set:eth0:ipv4:192.168.2.1
> >    mplsadm2 -O 0x3 -o push:gen:300:set:eth0:ipv4:192.168.2.1
> >    mplsadm2 -O 0x4 -o nffwd:0xf:0x2:0x2:0x3:0x3
> >
> >NOTE: the format of the nffwd command is '<mask>:<mark:nhlfe>:<mark:nhlfe>...'
> >
> >Explaination:
> >
> >Traffic arrives at the LER with source 2.2.2.2 and destination 4.4.4.4.
> >Iptables looks at the source and 'marks' the packet with 0x2.
> >(the mark is internal to the kernel, it is called a nfmark).  The packet
> >continues through the IP stack.  At the point of exiting the IP stack
> >it is redirected to MPLS via the special nexthop 0x4.  In the MPLS stack
> >the NHLFE 0x4 looks to the nfmark on the packet and uses it to forward
> >it to another NHLFE, if the nfmark is 0x2 the packet is further handled
> >by NHLFE 0x2.  NHLFE 0x2 pushes and label and send that packet.
> >
> >If you would like to add another level of stacking you could do it two
> >different ways.  Either have NHFLE 0x2 and 0x3 do multiple pushes or you
> >could have the fwd to another NHLFE which does a push and the final set.
> >The details of this are left as an excersise for the reader.
> >
> >
> >On Tue, Nov 16, 2004 at 06:26:56PM +0100, ed...@ti... wrote:
> >> Hi
> >>  i'd like to set a label stack between PCLENTO1 and TOSHIBA (see the
> attachment)
> >> After my test should be this: i receive on WINDOWS traffic from 2 host
> >(that
> >> represent 2 network) that is destinated to network
> >>  linked with TOSHIBA and i would that, through my network packets are
> labelled
> >>  basing on host it come from (packets from host A with a label, packets
> >> from
> >>  be with an other one). How can i do this?
> >>  I've seen label stack example on mailing list and my answer is: instruction
> >>  for r3 in the example is for PCLENTO1, those for R4 is for TOSHIBA and
> >> noone
> >>  for R2 in the example, aren't they?
> >>  Thanks a lots for all help you give me
> >> 
> >> __________________________________________________________________
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> >> 
> >> 
> >> 
> >
> >
> >
> >-- 
> >James R. Leu
> >jl...@mi...
> >
> >
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> 
> 
> __________________________________________________________________
> Tiscali Adsl 2 Mega Free: naviga gratis tutto l'anno!
> Supera tutti i limiti di velocita' con Tiscali Adsl 2 Mega Free.
> Sei libero da costi fissi e, se ti abboni entro il 25 novembre,
> navighi gratis fino al 31 dicembre 2004 e non paghi il costo di adesione.
> http://abbonati.tiscali.it/adsl/
> 
> 
> 

-- 
James R. Leu
jl...@mi...