Zte ZXR10 GER, Руководство пользователя

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ZXR10 GER (V2.6.03) General Excellent Router User Manual Volume-I
276 Confidential and Proprietary Information of ZTE CORPORATION
Border router of MPLS determines the QoS type of an MPLS
packet according to the parameters (such as source/destination
IP address, port ID and TOS value) in the IP packet.
For IP packets to the same destination, different forwarding
paths can be set up according to the requirements for TOS
values, to meet the requirements for transmission quality. In the
meantime, the management of special routes also can solve the
problem of load balance and congestion on the network
efficiently. When congestion occurs in a network, MPLS sets new
forwarding routes that disperse the traffic to ease the network
congestion.
MPLS Label Header
An MPLS label is inserted between an L2 header and an L3
packet. Therefore, an MPLS label header is also called a shim
header. The length of an MPLS label header is four bytes,
containing a 20-bit label, a 3 test bits, a 1-bit stack bottom tag
and 8-bit TTL (Time-To Live).
A router sending an MPLS packet needs to use a method to
notify a router receiving the packet. The transmitted packet is
not a pure IP packet, but an MPLS datagram. For Ethernet
packets, Ethernet types 8847 and 8848 (in hexadecimal notation)
are used to label MPLS packets; while for PPP packets, the
protocol field is set to “8282” (in hexadecimal notation) to label
MPLS packets.
MPLS LDP
LDP label binding is an association relation between a
destination prefix and a label. Labels used for label binding are
locked from a label set called “label space”.
LDP supports two types of label spaces:
„
Label space per interface uses the label resources of the
interface. For example, the LC-ATM interface uses VPI/VCI as
a label. Based on different configurations, an LDP instance
can support or may not support one or multiple interface
label spaces.
„
LDP instance supports a label space shared by all interfaces
in a platform range. Except the LC-ATM interface, ZXR10
T64/T128 uses the label space per platform on all the other
interfaces.
LDP uses six bytes to name a label space, called LDP identity
(LDP Id), which is composed of two parts:
„
First four bytes indicate the router ID of the router that has
the label space.
Border Router
MPLS Label
Header
MPLS LDP
Label space
per interface
Label space
per platform
LDP identity