This debate between Layer 2 VPN services based on MPLS and Layer 3 MPLS VPNs are widely asked and is considered to be largely theoretical; Layer 2 VPN service is not widely available yet. If you wish to have more knowledge regarding the same, join the courses offered by the SPOTO and have relevant knowledge for your studies.
But the two are different enough for potential customers of one or both of the services so as to consider now how they might fit into current networks. At the recent MPLScon 2006 conference, businesses that would be utilizing MPLS services talked about Layer 2 vs. Layer 3 services in some detail, and it would be quite apparent that neither one would be defeating the other.
Actually, the IP network tends to work over the MPLS. The idea of MPLS is that a series of labels could be applied to a given packet or frame that could consequently be used to switch it through a network. In the case of an L3VPN, it would be meaning that rather than the traditional mechanism of looking at the destination IP address, routing devices have looked at one or more previously applied labels to make the decisions of forwarding.
The key point in the above scenario is that the actual contents of the packet aren’t actually considered. Once a given packet is being labeled the intervening devices would be simply forwarding it on the basis of whatever LSP have been signaling. In the case of an L3VPN, the packet is considered to be a fully formed IP packet. In the case of an L2VPN a frame from a particular interface would have been added a label and is forwarded. This might be considered being a full Ethernet frame i.e. with or without an 802.1q header, an HDLC frame from a serial link, one or more cells from an ATM PVC, etc.
One of the major differences between L2 and L3 VPN is the mechanism utilized to signal and set up the overlay network. L3VPN (RFC2547bis) would be extending the BGP protocol so as to allow PE’s for signaling which routes are available within which VPN’s. There would be more possible ways to put together a layer 2 network like, straight point-to-point links, multipoint, translational, etc, and there are also more mechanisms in use in the industry which could be utilized to signal these various topologies.
Layer 3 MPLS VPNs would be exemplify by fully meshed architectures that enable, for example, multicast conferencing in support of projects which would involve a dispersed workgroup. Layer 2 MPLS technology is considered to be limited in this area because it doesn’t scale quite well as Layer 3.
Some businesses like the Layer 3 options that would be obtainable now because the service provider takes over all the WAN routing, whereas, with a Layer 2 WAN, like the MPLS-based VPLS (virtual private LAN services), businesses would have to handle the routing on their own, customers noted.
Outsurcing of routing tables would also be seen as a weakness of Layer 3 VPN services because many corporations do not want to relinquish control or even share their routing schemes with any other corporation, not even their service provider. They prefer Layer 2 network services, like the frame relay or ATM, that are simpler in architecture as well as allow customers to retain control of their own routing tables.
Thus, you would have gone through the various differences between the L2VPN and L3VPN. If you have more query regarding it, or regarding any IT Certification, you could visit the SPOTO and gain the knowledge through their expert professionals.