3com 3031 Instruccion De Instalación

C

HAPTER

 55: MPLS L2VPN C

ONFIGURATION

Figure 183   Networking for L2VPN

MPLS L2VPN offers the following benefits:

■

Support multiple link-layer protocols to provide L2VPN services based on 
different media on the MPLS network, including ATM (ATM ALL5 and ATM cell 
relay), FR, VLAN, Ethernet, PPP, HDLC etc. 

■

Support multiple network layer protocols, such as IP, IPv6, IPX and SNA.

It provides multiple services, including L3VPN, QoS etc. 

■

Excellent scalability. MPLS L2VPN only establishes L2 connections for users and 
does not import and manage the routing information of users. Thus, the load 
on PE and the entire SP network can be significantly reduced. Thereby, the SP 
can support more VPNs and provide the access service for more subscribers.

■

Guaranteed reliability and privacy of subscriber route. As MPLS L2VPN is not 
required to import routing information of subscribers, it has neither needs nor 
means to obtain and process routes of subscribers. Thus, it guarantees the 
privacy of subscribers’ routes.

MPLS L2VPN frames are in such format:

Figure 184   MPLS L2VPN frame format

Control word: It is unnecessary to transmit the L2 frame as a whole in transmitting 
12VPN packets over MPLS network. All required is to distract the L2 frame header 
at the ingress and to add it at the egress. But for AAL5 and FR encapsulation at the 
link layer, extra information needs to be contained in L2 frame header. Control 

VPN A

VPN A

VPN B

VPN B

CE

CE

CE

CE

PE

PE

PE

VC

VC

LSP

P

P

VPN A

VPN A

VPN B

VPN B

CE

CE

CE

CE

PE

PE

PE

VC

VC

LSP

P

P

    Control word                 Label stack                       L2  PDU

  Tunnel label            VC label