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Simplified MPLS Through IPsec over 1500-byte Media Overview


When you transmit a virtual private LAN service (VPLS) frame over a Layer 3 IP network, you need to encapsulate the MPLS packet into generic routing encapsulation (GRE) and then transmit the frame across the IP network. However, when you transmit VPLS over GRE over 1500-byte media such as the Internet, the VPLS frame is corrupted at the receiving end. Hence, it is not possible to send a 1500-byte Ethernet frame across a VPLS service running over the Internet. The Ethernet frame beyond 1448 bytes (24byte GRE + 20byte IP + 2*4byte MPLS) is blocked. Hence, the VPN traffic forwarded over 1500-byte media must be fragmented.

Juniper Networks® Branch SRX Series Services Gateways provide a solution for IPsec encapsulated packet fragmentation and reassembly.