Zte ZXR10 5900E series Configuration Manual page 10

ZXR10 5900E Series Configuration Guide (VPN)
If the type field is 0, AN field covers four bytes.
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If the type field is 1, AN field covers two bytes.
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If the type field is 2, AN field covers two bytes.
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The RD is only used between PEs and CEs to differentiate IPv4 addresses of different
VPNs. The ingress generates an RD and converts the received IPv4 route of the CE into
a VPN-IPv4 address. Before advertising the route to the CE, the egress PE converts the
VPN-IPv4 route into an IPv4 route.
MPLS VPN Principle
MPLS VPN adopts L3 technology. Every VPN has its own VPN-ID. Every VPN user can
only communicate with the members belonging to the same VPN, and only VPN members
can enter the VPN.
In MPLS VPN, the service provider (SP) allocates a RD to every VPN. The RD is unique
in SP network.
Forwarding table contains a unique address, called VPN-IP address, which is formed
through the connection of the RD and user IP address. The VPN-IP address is unique
in the network. The address table is stored in the forwarding table.
BGP is a routing information distribution protocol, which uses multi-protocol extension
and common attributes to define VPN connectivity. In MPLS VPN, BGP only advertises
messages to the members in the same VPN, and provides basic security by means of
traffic split.
Data is forwarded by using LSP. The LSP defines a special path that cannot be changed,
to guarantee the security. Such a label-based mode can provide confidentiality like frame
relay and ATM. The SP associates a special VPN to an interface, and packet forwarding
is decided by ingress labels.
VPN forwarding table contains a label that corresponds to the VPN-IP address. The label
is used to send data to the corresponding destination. Since the label replaces the IP
address, user can keep its own address structure. The data can be transmitted without
Network Address Translation (NAT). According to the data ingress, the corresponding
switch will select a special VPN forwarding table that only contains a valid destination
address in VPN. Router selects a specified VPN forwarding table according to the ingress.
The VPN forwarding table contains the valid destination addresses only.
CE advertises routing information on the user's network to the PE by means of static route,
default route, routing protocols RIP, OSPF, IS-IS or BGP.
CE sends the routing information to PE by static route, default router or routing protocol,
such as Routing Information Protocol (RIP), Open Shortest Path First (OSPF) and
Intermediate System-to-Intermediate System (IS-IS).
Meanwhile extended multi-protocol BGP is used between PEs to transmit VPN-IP
information and the corresponding labels (VPN label, called inner label hereinafter).
SJ-20150114102049-016|2015-03-10 (R1.0)
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