[hcip] MPLS Foundation

Catalog

MPLS  Architecture

label

static state MPLS

LDP  Label distribution agreement

LDP  Message type

LDP LSR Establishment process

MPLS  Forwarding process

MPLS  Yes TTL  To deal with

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LSR： Label switching router

MPLS  Domain ： from LSR  Network domain formed by

LER： Label edge router

LSP： Label switching path （ A one-way ）

Ingress：LSP  The input node of ;Transit：LSP  Middle node of ;Egress：LSP  Out node of

MPLS  Architecture

MPLS  The architecture consists of 「 Control plane 」 and 「 Forwarding plane 」 form

Control plane ： Responsible for generating and maintaining routing information and labels . among , Routing information table RIB： from IP  Routing protocol generation , For routing ; Label distribution agreement LDP： Responsible for label assignment 、 The establishment of label forwarding information table 、 The establishment of label exchange path 、 Demolition, etc ; Label information table LIB： Generated by label distribution protocol , Used to manage label information

Forwarding plane ： In charge of general IP  Message forwarding and band MPLS  Forwarding of tags . among , Forwarding information table FIB： from RIB  Extract necessary route information generation , In charge of general IP  Forwarding of messages ; Label forwarding information table LFIB： Label forwarding table for short , By label distribution protocol on LSR  On the establishment of LFIB, Take care of MPLS  Forwarding of tag message

Forwarding equivalence class FEC： Group messages with the same characteristics , Do the same processing when forwarding

label

Label： Tag value field ;Exp： Used to extend , Now it is often used to do Cos, When the device is blocked, send the message with high priority first ;S： Represents the last layer of labels ;TTL： Hops

Special labels ：0 ~ 15;0： Means pop up ;3： Go straight ahead IP  forward

static state LSP  and CR-LSP  Share tags ：16 ~ 1023

dynamic ：1024  And above

static state MPLS

mpls lsr-id「ID」： Used to identify unique LSR
mpls： Enable mpls function （ overall situation 、 Interfaces should be ）
static-lsp ingress「 name 」destin「IP」nexthop「 Next jump 」out-label「 label 」： The downstream 
static-lsp transit「 name 」incoming-interface「 Access interface 」in-label「 label 」nexthop「 Next jump 」out-label「 label 」： In the middle 
static-lsp transit「 name 」incoming-interface「 Access interface 」in-label「 label 」： The downstream 
dis fib

LDP  Label distribution agreement

Responsible for establishing 、 Maintain label exchange path

Local adjacency ： Establish neighbors by multicast ; Distal adjacency ： Establish neighbors by unicast

Local LDP  conversation ： Direct connection ; Distal  LDP  conversation ： It's not directly connected

LDP  neighbor ：5s  once  hello  message ,15s  interrupt ;LDP  conversation ：15s  once keepalive  message ,45s  interrupt

LDP  Message type

Find out （Discovery）： Used to announce and maintain LSR  The existence of

conversation （Session）： For building 、 Maintenance and termination LDP  Conversation between peers

notice （Advertisement）： For building 、 Change and delete FEC  Tag mapping for

notice （Notification）： Used to provide suggestive messages and error notifications

Except that the message is UDP, Others are TCP

LDP LSR Establishment process

  take FEC  Binding to tags , And inform LSP  On the adjacent LSR

（1） By default , When the route changes , If the edge node （Egress） It is found that a new route appears in your routing table and this route does not belong to any existing FEC, Then create a new FEC

（2） if MPLS  The network has labels to assign , Then for FEC  Assign tags , And actively send label mapping messages to the upstream , It contains the assigned tags and bindings FEC  Etc

（3）Transit  After receiving the label mapping information , Judge whether the sender is the FEC  The next jump , if , Then add corresponding entries in its label forwarding table , Then take the initiative to send the specified information to the upstream

（4）Ingress  After receiving the tag, judge whether the sender is the FEC  The next jump , if , Then add corresponding entries in the tag forwarding table , This is complete LSP  establish

MPLS  Forwarding process

MPLS  Yes TTL  To deal with

MPLS  Yes TTL  There are two processing modes ：「 Unified mode the first Mod （Uniform）」「 Pipeline mode （Pipe）」

mpls ldp（ overall situation 、 Interface ）
dis mpls ldp session
dis mpls lsp
dis mpls lsp protocol ldp
lsp-trigger： Trigger setup LSP（ Huawei defaults to 32 The non physical interface of the bit host is turned on ）
diag： Enter diagnostic mode 
dis mpls nhlfe： Check the next hop label forwarding table 
dis mpls ilm： see 
route recursive-lookup tunnel： Open the non tagged public network GBP The route iterates to LSP In the tunnel 
ttl propagate： Common mode 
undo ttl propagate： Pipeline mode