Packet switching and label switching in MPLS

MPLS ---- Multi protocol label switching technology

Packet exchange

Data consists of packets , after , It is continuously transmitted in each network node , Finally, we reach our goal
The problem of inefficient packet switching and forwarding ：
1、 In the whole process of packet exchange , You need to query the routing table first and then check ARP Cache two tables to complete the forwarding process , Leading to low efficiency
2、 Matching principle of routing table ---- The longest matching principle causes the query efficiency of the routing table not to be too high
3、 There is a recursive lookup process in the routing table
4、IP The head is a variable length head , Lead us to IP When the head is read, it needs to be processed by software , Unable to find fast based on hardware

Control level
The data flow direction of the routing protocol , The purpose is to obtain the routing information of unknown network segments , Generate routing table
Data level
The device forwards specific data information based on the improved routing table , Its direction is exactly opposite to the flow of the control layer

Changes in packet exchange
1、 Process exchange
The earliest packet switching
Every packet needs to check the routing table first , I'll see later ARP Cache the table to determine the content of the two-layer package
2、 Fast packet switching
Stream based packet switching
One time routing , Exchange many times
3、 Cisco's express switching technology
CEF technology
It can greatly improve the forwarding efficiency of routing

Label switching

Label switching is between two-layer and three-layer packaging , Add a label that has a mapping relationship with the routing entry , Then maintain a table that records the correspondence and forwarding interface , Bring tagged data to the device , Look at the label first , Then forward based on the maintained tag forwarding table , There is no need to view the three-tier content . Because the label itself is short and fixed length , therefore , Its forwarding efficiency will be higher than that of packet switching .
But label exchange needs to label the packet first , Then you need to pop up the tag before reaching the target , therefore , Label switching only improves the efficiency in the forwarding process , On the whole, the improvement of intersecting packet exchange is not obvious

Control level
be based on FEC Assign tags , And get other LSR For the same FEC Assigned tags , after , Record generation LIB surface , Then combine FIB Generate LFIB surface
Data level
The device is based on LFIB surface , Forward according to the tag

Inbound LSR
MPLS The boundary of the domain , When a packet without a tag comes in LSR On , He needs to press labels into the packets
transit LSR
Complete the label replacement action LSR equipment
Departure LSR
It's also MPLS The boundary of the domain , Complete the pop-up action of the label

Label exchange can be done better ：
1、 For resolution BGP The routing black hole of
2、MPLS VPN
3、MPLS TE ---- Flow engineering

Build static LSP：

1、 Ensure routing conditions
Static only requires the border device to have round-trip routing information
2、 To configure LSR
Inbound LSR
1. to LSR To configure LSR-ID
2. Activate MPLS
3. Build static LSP
Configure transit LSR
Configuration battle LSR