mpls - why do we use it and how

[carl_townshend]

Hi all

I have not done much in the way of mpls, I know it uses labels to bascially switch frames through routers, Can anyone tell me the benifits of MPLS ? and also why do we use it ?

Also a very quick technical explanation of how it works on a cisco router would be really helpful

cheers

Carl

[Mohamed Sobair]

Hi,

The staraight answer is that MPLS reduces Costs by emulating those dedicated poitnt to point links over a shared VPN infrastructure cloud.

MPLS also allows for all protocls to be carried overetc : VOIP, Video , IPsec, IP, IPx.

There are so many benefits of using MPlS , here are some:

1- The ability to have Traffic Engineering with MPLS.

2- The ability to have the traffic routed based on source addresses and chose path per hop.

3- The ability to have Overlapping VPNs.

4- The ability to have QoS , Quick Convergence and other features.

5- The forwarding is based on Labels which enhance Network performance.

5- Reduces Costs.

Regards,

Mohamed

[carl_townshend]

Hi there

thanks for that

further questions

1.How does mpls improve QOS?  in what way ?

2.with CEF nowadays why use MPLS?

3.Please explain why you use MPLS with a VRF, cant you just use a VRF on its own ?

4.Can you please explain the Route Distinguisher, and Route Target meanings and why we use them ?

cheers

[Mohamed Sobair]

Hi,

Answers inine:

1- MPLS doesnt improve QoS, but rather, QoS improves MPLS , just like when you implement QoS for normal IP traffic, its also the same with MPLS , priotrizing traffic over another.

2- MPLS introduced earlier before CEF was introduced. however, as I mentioned earlier, its not only a Switching performance is the benefit of MPLS , there are also other benefit just like i mentioned.

3- You can definately use a vrf on its own, However, using Vrf with MPLS is an enhancment introduced into the MPLS.

4- Route Distinguisgher is 64bit value that appended to the Customer IPv4 address 32bit, its must becaust it makes the VPNv4 address unique in the MPLS Network. which is 96bit long., The route Target is an extended community attribute that identify the VPN. with route target you control which routes need to be imported between different VPNs. Cisco Says, at least one of the route target must match for the Routes to be imported into particular VPN.

I hope this answers your inquiry,

Regards,

Mohamed

[carl_townshend]

hi

can you please explain why we would use a VRF with MPLS, what actually happens here ?

[vmiller]

Consider the following:

A nationwide enterprise with thousands of locations. all neatly addressed with 10.x.x.x, can run over the same (carrier provided) MPLS as another enterprise with the same addressing scheme. the difference is the VRF.

Same enterprise outsources sme network management function to a third party, adding a second VRF (with the appropriate RD etc etc) would allow

the same transport to be used for both functions.

The VRF simply carves up the routing table. in conjunction with the RD route target, and the vpnv4 address-family. The net result is more ways to

"route" traffic.

[Mohamed Sobair]

As you can use VRF - Lite without the need of MPLS, The enhancment is to carry VRF also over an MPLS Infrastructure.

The Only added thing is that while the Manadatory protocol to be used is BGP which allows also an MPLS labels to be carried out.

In short,

LAbeled VPNv4/VPNv6  Packets are also carried out with MPLS, while without MPLS, there its a VPNv4 or VPNv6 packet that are not labeled.

Let me know if this answers your question,

Regards,

Mohamed