odp500059 bfd technology issue1.0_20070312_a

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ODP500059 BFD Technology

ISSUE 1.0


Objectives

Upon completion of this course, you will be able to:

Describe BFD Technologies Evolution

Describe BFD Technologies Principle

Describe BFD Application


Contents

1.1. Technology HistoryTechnology History

2.2. Technology AnalysisTechnology Analysis

3.3. Technology ApplicationTechnology Application

4.4. Standard ReferenceStandard Reference


The Problem of Failure Detection

An increasingly important feature of networking equipment is the rapid detection of communication failures between adjacent systems, in order to more quickly establish alternative paths.

Currently, detection can come fairly quickly in certain circumstances when data link hardware comes into play (such as SONET alarms) .

However, there are media that do not provide this kind of signaling (such as Ethernet), and some media may not detect certain kinds of failures in the path, for example, failing interfaces or forwarding engine components.

Simple situation is that link line connected to Optical network. When Optical internal link down, router does not know.

Another is when two router connect to by LAN switch .When LAN switch fails. The Ethernet interface between Router and Switch still works. But the connection of two routers fails.


Technology History

Routing protocol30S hello


1.1.1.1/30 1.1.1.2/30



1.1.1.1/30 1.1.1.2/30

ms BFD message based on UDP

ms BFD message based on UDP

Interface is up

Interface is up


Technology History

If the SDH system between two router is down, but the link between SDH

and router is still up. So The unique way to detect the status of link is by

protocol with long time;

We need one mechanism to detect the end-to-end failure and provide

protection of link.

SDHSDH

X

Routing protocol Hello


BFD Protocol Overview

Faster convergence of routing protocols, particularly on shared media (Ethernet)

Semantic separation of forwarding plane connectivity and control plane connectivity

Detection of forwarding plane-to-forwarding plane connectivity (including links, interfaces, tunnels etc.)

A single mechanism that is independent of media, routing protocol, and data protocol

Requiring no changes to existing protocols


Mile-stone of BFD

• Aug 04 Submit the base protocol specification to theIESG to be considered as a Proposed Standard.

• Aug 04 Submit BFD encapsulation and usage profile for single-hop IPv 4 andIPv 6 adjacencies to the IESG to be considered as a Proposed Standard

Aug 04 Submit BFD encapsulation and usage profile for MPLSLSPs to the IESG to be considered as a Proposed Standard

Nov 04 Submit BFD MIB to the IESG to be considered as Proposed Standard.

Feb 05 Submit BFD encapsulation and usage profile for multi-hop IPv 4 andIPv 6 adjacencies to the IESG to be considered as a Proposed Standard

Draf t base-002004.7

Draf t base-012005.2

Draf t base-022005.3 Draf t base-03

2005.7

•

•

•


Contents






BFD Packet Architecture

0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1

Vers DiagST

ATP F C A D R Detect Mult Length

My Discriminator

Your Discriminator

Desired Min TX Interval

Required Min RX Interval

Required Min Echo RX Interval

From:draft-ietf-bfd-base-03.txt

• For Ethernet media, packet content is Ethernet + IP + UDP + BFD• For BFD control packet, UDP port is 3784


BFD -- Two BFD Modes

Asynchronous Mode Control packets flow in each

direction

Echo Mode Slower control packets, echo

packets loop through remote system


down

Packet transmit

down

init

init

down => init

init => up

down => init

init => up

A B

:Point of changing state

(in sending packet)

: Point of changing state(Local)

XX => YY : Resault of changingstate (Local)

BFD DOWN : DOWN state in packet

BFD INIT : INIT state in packet

BFD UP : UP state in packet

BFD Session Connection Establishment


BFD Detection Time

Asynchronous Mode In Asynchronous mode ， detection location is at the peer side. Detection Time = Peer DM(the value of Detect detect-multiplier

received from the remote system) * max ( bfd.RMRI (bfd RequiredMinRxInterval), last received DMTI( Desired Min Tx Interval ).

Echo Mode In Echo Mode , detection location is at the local side. Detection Time = bfd.DM * max( bfd.RMRI,last received DMTI).

Attention: Don’t think it is the fixed RMRI and DMTI. Generally it is assigned by the link, delay and jitta.For Example, the transmission link is 1ms delay for 200KM.So you can first ping the link node or calculate.


BFD Configuration

Step Action Command

1 Enter system view. system-view

2 Enter BFD configuration view.

bfd cfg-name [ bind peer-ip ip-address

[ interface interface-name interface-type

interface-number]

3Configure the local or remote

discriminator.discriminator { local discr-value | remote discr-value }

4Configure the minimum sending

interval.min-tx-interval interval

5Configure the minimum receiving

interval.min-rx-interval interval

6 Configure the local detection multiplier. detect-multiplier multiplier


Contents






BFD Application

IGP liveliness detection

Edge network availability

Host reach ability (e.g. media gateways)

Switched Ethernet integrity


BFD for IGP

ISIS Neighbor

BFD Neighbor

RouterA RouterB

BFDBFD

Shows a simple network with two routers running ISIS and BFD. • When ISIS discovers a neighbor it sends a request to the local BFD

process to initiate a BFD neighbor session with the ISIS neighbor router. • The BFD neighbor session with the ISIS neighbor router is established .• The BFD neighbor session with the ISIS neighbor router is torn down• BFD notifies the local ISIS process that the BFD neighbor is no longer reachable• The local ISIS process tears down the ISIS neighbor relationship

192.168.10.2 192.168.10.1

ISIS ISIS

Interface interface-type interface-numberIsis fast-sense


R

R

Layer2 link

Layer2 link TSR

TSR

MGW

IP Core

BFD

BFD Application in Media Gateway

• BFD protocol is completely integrated with the media gateway platform and is used to keep the connection between the gateway and the edge router.

• BFD protocol can detect failures in the Ethernet or independent network segment.

• BFD protocol can alternatively build redundant paths between the gateway and the router. Once failures are detected and confirmed, the BFD can trigger a corresponding changeover mechanism in all routes, transmission, and tunnel systems to ensure network reliability.


VRRP + BFD

BFD is based on the unicast. But VRRP is based on the multicast . So in fact VRRP + BFD solve the 90% issues. If there several VRRP routers. Then VRRP + BFD can not solve the problem. When we apply the BFD + VRRP, we can reduce the time from 3s ( 1S for VRRP hello , 3times ) to less than 500ms.

10.100.10.11

10.100.10.12 10.100.10.13 10.100.10.14

10.100.10.1

10.100.10.2 10.100.10.3

Dts A

，Src

10.100.10.12, next

hop 10.100.10.1

Dst

A，

Src

10.1

00.1

0.12

, nex

t

hop

10.1

00.1

0.1

BFD detection


Mobile IP Bearer Network

The CMCC national IP backbone is the biggest Softswitch Bearer Network in the world, which is a total solution deployed with Huawei’s IP Bearer and Softswitch products.Carrier-class network design and service deployment; end-to-end total solution; abundant commercial experience based on Expert Teams from different areas.Carrier-class reliability; switch over time<=50ms; carrier-class QoS guarantee; CAC mechanism.

The CMCC national IP backbone is the biggest Softswitch Bearer Network in the world, which is a total solution deployed with Huawei’s IP Bearer and Softswitch products.Carrier-class network design and service deployment; end-to-end total solution; abundant commercial experience based on Expert Teams from different areas.Carrier-class reliability; switch over time<=50ms; carrier-class QoS guarantee; CAC mechanism.

SH1

GZ1

XA1

CD1

WH1

NJ1

BJ2

SH2GZ2

XA2

CD2WH2

SY2NJ2

UMG8900

BJ1 SY1

NE5000E NE5000E

SoftX3000

UMG8900

UMG8900

SoftX3000

SoftX3000

UMG8900

UMG8900

UMG8900

NE40E

NE40EGZ1

GZ2


Contents






Standard Reference

Bidirectional Forwarding Detection

draft-ietf-bfd-base-02

draft-ietf-bfd-base-03

BFD for IPv4 and IPv6 (Single Hop)

draft-ietf-bfd-v4v6-1hop-02

BFD for Multihop Paths

draft-ietf-bfd-multihop-02

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Thank You

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odp500059 bfd technology issue1.0_20070312_a

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