odc010012 mpls traffic protection issue1_0

8/13/2019 ODC010012 MPLS Traffic Protection ISSUE1_0

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ODC010012 MPLS Traffic

Protection

ISSUE 1.0

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HUAWEI TECHNOLOGIES CO., LTD. Page 1All rights reserved

IP network with single internet service is

being evolved to multi-service network

with voice, data, and multimedia service.It needs to provide more reliability and

security.

This slide will focus on the protection

and restoration of MPLS traffic.

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References

l VRP5 MPLS Operation Manual

l MPLS Traffic Engineering Learning

Guide



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Upon completion of this course, you

will be able to:

[ Master the mode of trafficprotection

[ Master the principle of path

protection

[ Master the principle of fast reroute



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Chapter 1 Traffic Protection OverviewChapter 1 Traffic Protection Overview

Chapter 2 Path ProtectionChapter 2 Path Protection

Chapter 3 Fast RerouteChapter 3 Fast Reroute

Chapter 4 Comparison of pathChapter 4 Comparison of path

protection and fast rerouteprotection and fast reroute



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Traffic Protection

lWhen the failure of link or node happens, routing protocol

needs several seconds to convergence and restoration.

The factor of traffic switchover speedThe factor of traffic switchover speed

~1-2sLSDB size, CPU occupancy rateRouting recalculation

~5-30sTimers of IGP, network sizeFlooding of routing info.

~s

(POS + APS)

Medium and special platformDetection of link failureConvergence timeFactorsEvents



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The mode of MPLS TE traffic protection

l MPLS TE traffic protection mode mainly includes:

[ Path Protection

[ Fast Reroute, sometimes also called local protection

! Link Protection

! Node Protection



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Path Protection Overview

l Path protection is also called end to end protection, establish

backup LSP to protect important master LSP.

l

Path protection can setup more than one TE tunnel fromsource to end, each tunnel LSP should pass through different

path.

l When master LSP is down, the flow can be switched into

backup LSP tunnel in time.

l

Backup LSP tunnel will be established in advance, and it willnot transit flow but reserve bandwidth in ordinary situation

Path ProtectionPath Protection



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Example for Path Protection

l Primary LSP(RTA-RTB-RTD-RTE) is the best path from source todestination.

l When master LSP is down, the flow will be switched to backup LSP.

l Simultaneity, the source of master tunnel re-setup new LSP.

l Backup LSP (RTA-RTC-RTE) support two type of Backup LSP:

[ Hot-Standby LSP

[ Ordinary Backup LSP

RTA RTB

RTC

RTD RTEPrimary Tunnel

Backup Tunnel



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Hot-standby and Ordinary LSP

l Hot-Standby LSP

[ Hot-Standby LSP needs to be established before flow forwarding.

[ Switchover time is short, about 250 ms.

l Ordinary Backup LSP

[ Ordinary Backup LSP initiate setup backup LSP when the source of

tunnel receive the failure of the master LSP.

[ Once backup LSP is established, the flow will be switched into backup

LSP.

[ Switchover time is long, about 1-2 seconds

HotHot--standby and Ordinarystandby and Ordinary



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Section 1 Fast Reroute OverviewSection 1 Fast Reroute Overview

Section 2 Link ProtectionSection 2 Link Protection

Section 3 Node ProtectionSection 3 Node Protection



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Fast Reroute Technology

l Fast Reroute is usually called local protection, according to the objects to

be protected, it can be divided into:

[ Link Protection

[ Node Protection

lProtection type of Fast Reroute:[ One-to-one Backup

[ Facility Backup

l Fast reroute is temporary protection measure.

l When the protected link or node is failed, the flow will be switched to

backup tunnel.

l Advertise failure information to the source of tunnel to trigger tunnel re-

optimization.

l Switchover time is less than 50 ms, more quickly than path protection.

FRR ConceptFRR Concept



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Protection Type of Fast Reroute

l One-to-one Backup

[ One backup LSP protect one master LSP, this mode is

usually called Detour LSP.

[ Only one label in forwarding process.

l Facility Backup

[ One backup LSP protect more than one LSP, this mode is

usually called Bypass LSP.

[ Two labels in forwarding process.

l Most of the vendors support Facility Backup.



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Fast Route Terms

l PLR (Point of Local Repair) : the source of backup LSP

l MP (Merge Point): the endpoint of backup LSP

l NHop (Next-hop Router ): only one hop from PLR router

l NNHop (Next-next-hop Router ): two hops from PLR router

FRR TermsFRR Terms



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Example for FRR

RTA

RTB

RTC

RTD

RTE

RTF

RTG

RTH

Path: RTA,RTC,RTE,RTG

Path: RTC,RTD,RTF,RTE

Path: RTC,RTD,RTF,RTH,RTG

Primary tunnel

Backup tunnel0(NHop)

Backup tunnel0(NNHop)

l RTC is PLR

l RTE is the MP of tunnel0, RTG is the MP of tunnel1

l RTE is the NHop of PLR RTC

l RTG is NNHop of PLR RTC!



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Link Protection

l Establish a protected tunnel from PLR to MP to protect the link between PLR

and NHop.

l Link protection only protect the link between PLR and MP.

l

One backup tunnel to protect more than one LSP tunnel, maybe it will bringnetwork congestion when flow is switched.

l When protected link is down, all the flow in this link will be switched to

backup LSP in 50 ms. Simultaneously, the source of the master LSP carry

out tunnel re-optimization as soon as it received the link failure information.

Link ProtectionLink Protection



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Implementation of Link Protection

l Four steps of link protection implementation:

[ Pre-failure configuration

[ Failure detection

[ Connectivity restoration

[ Post-failure signaling

Implementation StepImplementation Step



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Pre-failure configuration

l The steps of Pre-failure configuration:

[ Obtain the label of MP

! The flag of Label Recording Requested in Session_Attribute Class

is set as 0x02

[ Enable FRR function in the source of tunnel

! Enable "mpls te fast-reroute# in tunnel interface

! The flag of "Local protection is desired# in Session_Attribute Class

is set as 0x01

[ Enable link protection in PLR

! Configure backup tunnel to NHop

! Tie the Protected Link to the Backup Tunnel

PrePre--failure configurationfailure configuration



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Master LSP Establishment

RT8

RT2

RT6

RT4

RT7

RT1 RT5

RT9

Pop

14

37

Setup: Path (R1Setup: Path (R1-->R2>R2-->R4>R4-->R9)>R9)

Labels Established on Resv messageLabels Established on Resv message



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Backup LSP Establishment

Setup: Path (R2Setup: Path (R2-->R6>R6-->R7>R7-->R4)>R4)

Labels Established on Resv messageLabels Established on Resv message

Pop

22

17

RT8

RT2

RT6

RT4

RT7

RT1 RT5

RT9



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Failure detection

l Commonly used failure detection methods:

[ Aim at physical media, for example SDH/SONET APS

[ Aim at point to point link, for example PPP keepalive

[ RSVP-TE expansion, hello message

[ BFD (Bidirectional Failure detection)

[ MPLS OAM

Failure DetectionFailure Detection



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Traffic Switchover

l When the protected link is down, PLR is responsible to switch the flow to

backup LSP :

[ Affirm the backup LSP is ready or not, label is ready or not?

[ Clear the flag bit of Local Protection Desired in Session_Attribute class.

[ IP address value in IPV4 Tunnel Sender Address of Sender_Template

is set as the IP address of PLR output interface .

[ The value of RSVP_Hop class is set as the IP address of PLR output

interface .

[ Generate new ERO object

[ Refresh RRO object

[ The label stack of PLR will be changed, from one label to two labels.

Traffic SwitchoverTraffic Switchover



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After the failure of link

RT8

RT2

RT6

RT4

RT7

RT1

RT5

RT9

PushPush 37

PopPop 22

SwapSwap 37->14

PushPush 17

SwapSwap 17->22

PopPop 14

Label Stack: R1 R2 R6 R7 R4 R937 17 22 14 None

14 14

Primary Tunnel



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Post-failure Signaling

l The process of post-failure signaling:

[ Upstream signal advertisement

[ IGP routing information advertisement

[ Downstream signal advertisement

PostPost--failure Signalingfailure Signaling



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Upstream Signaling Advertisement

l When the protected link is down, PLR will send Path_Error message to

the source of the TE tunnel.

l Normally, the master LSP will be broke down when received Path_Error

message.

l

Now, the master LSP is protected by backup LSP, we need to hold theUP state of master LSP. Don$t close the master LSP tunnel.

l Expand new features of Path_Error Message, add Code=25(Notification),

Subcode=3(Tunnel locally repaired).

l The function of expansion is to show that the master LSP have been

locally protected, please don$t break down the master LSP, only carry outthe Tunnel re-optimization.



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IGP Routing Information Advertisement

l There are two types of failure information advertisement:

[ RSVP Path_Error Message

[ IGP routing information

l Normally, RSVP Path_Error message arrived in the source of

TE tunnel quicker than IGP flooding.

l After the interrelated operation of the source of TE tunnel, TE

tunnel receives IGP information of link failure. How to deal with

it ?

[ The source of TE tunnel should ignore IGP flooding

advertisement.



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Downstream Signaling Advertisement

l When the protected link is down, MP node don $t receive the

path message from upstream in several intervals, MP will send

Path_Tear message to the downstream to break down the

master LSP.

l For the sake of the master LSP hold "UP# state, PLR need to

continuously send Path message along the backup LSP.

l Simultaneously, MP node will continue to send Path message

to downstream node to maintain the soft-state of master LSP.



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Signalling Process After Link Failure

RT4RT1 RT2 RT3

Path Tear

Resv Tear

Resv Tear

No Link Protection

RT4 waits forrefresh

Path Error

Resv in place

Link Protection



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Node Protection

l Node protection: Establish a protected tunnel from PLR (RT2) to NNHop(RT4).

l Node Protection can protect NHop(RT3) node and the link of PLR(RT2) to NHop(RT3).

RT8

RT2

RT6

RT3

RT7

RT1

RT5

RT9

RT4



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Comparison of Link Protection and Node

Protection(1)

l Need to enable FRR function in the source of TE tunnel.

l PLR node need to tie the protected link to the backup tunnel.

l The process of failure detection.

l Flow switchover process after link or node failure.

l Signaling process after failure.

SamenessSameness



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Comparison between Link Protection and Node

Protection(2)

l Backup tunnel is different:

[ Link protection: PLR->NHop

[ Node protection: PLR->NNHop

l The protected object is different:[ Link protection: the link between PLR and NHop

[ Node protection: NHop node and the link between PLR and NHop

l The allocation of label is different:

[ Link protection: need to know the label which NHop node distribute to

PLR node[ Node protection: need to know the label which NNHop node distribute

to NHop node.

DifferentiaDifferentia



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Comparison between Path Protection and

Fast Reroute

Performance ComparisonPerformance Comparison

1:N

1:N

1:1

Protection

Mode

GoodPLR->NHOP Link

and NHop Node

50 msNode Protection

GoodPLR->NHop Link50 msLink Protection

Not goodLSP250 msPath Protection

ScalabilityProtected ObjectSwitchover

Time

Protection mode



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Question?

l How many types of traffic protection?

l What is the difference between link protection and node

protection?

l What is the difference between path protection and local

protection?



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l The main mode of traffic protection and

restoration:

[ Path protection

[ Local protection

! Link protection

! Node protection

SummarySummary



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