Zte ZXR10 GER, Руководство пользователя

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ZXR10 GER (V2.6.03) General Excellent Router User Manual Volume-I
274 Confidential and Proprietary Information of ZTE CORPORATION
and management information) of the mails are coded in a
certain method to facilitate rapid and efficient mail processing
and speed up the routing of the mails to individual destinations.
The basic concept of MPLS is the assignment of labels, that is,
labels are bound with network layer routes.
Basic MPLS routing mode is routing hop by hop, which permits a
forwarding mechanism simpler than packets and can implement
faster routing. Since the common label allocation method and
generic routing protocols are used in multiple types of media
(such as packets, cells and frames), MPLS supports efficient
definite routing mode (such as QoS) that can be used to fulfill
different purposes, common traffic engineering method and
other operation modes.
Label Distribution Protocol (LDP)
LDP (Label Distribution Protocol) is the core protocol of MPLS.
LDP works in conjunction with standard network layer routing
protocols and distributes label information among different
pieces of equipment on an MPLS network in the connectionless
working mode.
MPLS also can use the work mode in which resources are
reserved but no definite connection is set up, that is, protocols
RSVP and RSVP-LSP-TUNNEL are used to serve traffic
engineering.
In addition, CRLDP (Constrained-based Routing LDP) executes
some routes with definite paths.
LDP divides Forwarding Equivalence Class (FEC) based on IP
prefixes. In an MPLS network, internal gateway protocols are
used to discover the information about IP prefixes. When a Label
Switch Router (LSR) discovers such information, it will distribute
a label to the FEC and advertise the label to all upstream LDP
neighbors.
Hop-by-hop dynamic label distribution of LDP leads to the
generation of a series of labeled paths, called Label Switched
Paths (LSPs). Along these LSPs, the label traffic can pass the
MPLS backbone to reach a designated destination. With this
capability, a service provider can deploy MPLS-based IP VPN, as
well as the IP + ATM service over multi-proxy MPLS networks.
The propagation process of IP packets through the MPLS
backbone is as follows.
„
An ingress border LSR receives a packet, puts the packet into
an FEC and then uses the outgoing label corresponding to
the FEC to label the packet. For a unicast IP route based on
destination address, the FEC corresponds to a destination
subnet.
Hop by hop
routing
LDP function
Forwarding
Equivalence
Class
Hop- By-Hop