BFD Features - ActForNet S9700...2 Contents BFD introduction and protocol features BFD on S9700 –...

BFD Features

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Session Objectives

At the end of the session, the participants should:

Understand advantages of BFD implementation on S9700

Understand when to use BFD on S9700

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Contents

BFD introduction and protocol features

BFD on S9700 – snapshot

BFD on S9700 – software implementation details

BFD on S9700 – configuration

Summary

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Why BFD Lightweight hello protocol over different protocols IPv4, MPLS…

Used for fast (often sub-second) communication failure detection

Single, common & standardized mechanism

Independent of specific routing, VRRP and other client protocols

dst UDP port 3784 & 4784 (4784 is used for multi-hop BFD)

RFC 5880

SRU (Supervisor)

OSPF VRRP PIM BGP Etc.

BFD

IS-IS

So lots protocols could leverage this lightweight BFD to achieve fast hello without more CPU burden.

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BFD Advantages

Many protocols use same hellos-reduce control plane load

No impact due to sup switchover, unless the route down

ms-level fault detection performance

Proprietary one-arm-echo BFD function can be used with device which does

not support BFD

Proprietary multicast BFD can be used to detect the L2 link and the specific

member in a trunk, and bind the interface state.

Associating with oam protocol , notifies the link faults

Associating with the protocols running on the ring network

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Summary

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BFD on S9700: Snapshot

Software support start: V200R001

Hardware support:

All current and future I/O modules

Centralized packet processing

Master CPU transmit/receive BFD packets

with OAM Chip, we could do hardware offload

SRU-D has already integrated OAM FPGA, so no extra cost.

MCU(S9703) is done by a process in CPU.

BFD packets sent with TOS-EXP

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S97’s BFD Modes brief

Asynchronous mode – Supported from S9700

Systems establish BFD session and periodically exchange control packets

If some number of control packets missed (default is 3 ) session declared down

One ARM Echo mode – Huawei proprietary mode

Worked with other devices does not support BFD

Multicast BFD – Huawei proprietary mode

Could run at L2 links, no IP interface needs.

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Async timer negotiate My desc = foo

Your desc = xxx

Required Rx = 50ms

Desired Tx = 100ms

My desc = bar Your desc = foo Required Rx = 60ms Desired Tx = 40ms

My desc = foo Your desc = bar Required Rx = 50ms Desired Tx = 100ms

R1 R2

R1

R1

R2

Handshake Complete Session is UP

Compare min-RX from peer vs self Desire TX, the slower win

So send @ 100ms

Compare min-RX from peer vs self Desire TX, the slower win.

So send @ 50ms

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BFD one-arm-mode – Huawei

proprietary Application scenario

Connect with a 3rd party device, which doesn’t support BFDv1

3rd Device

Only BFD echo frames No control frames exchange

Trigger hooked clients

sth. Fails

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Multicast BFD – Huawei proprietary

Application scenario

Test a link if no IP address could be specified.

L2 Link or unnumbered interface

Specify a dedicated 224.x.x.x mc-IP-address The MC address must be same in 2 devices.

BFD control frames with multicast

address

Capture this mc-addr. Need avoid conflict.

Capture this mc-addr. Need avoid conflict.

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S97 BFD software features (1) Static BFD

Dynamic BFD

Triggered by protocol, like: OSPF, BGP, IS-IS, MPLS LDP, RSVP-

TE, PWE3、PIM.

BFD for single hop & multi-hop

BFD for supervisor’s switch-over

S97’s BFD session won’t teardown when supervisor do a switch-

over.

BFD for static route / OSPF / BGP / IS-IS

BFD for PIM

BFD for VRRP

BFD for FRR (LDP FRR/ TE FRR /VPN FRR /VLL FRR)

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S97 BFD software features (2) BFD over Ports

L3 GE & 10GE ports

VLAN-IF interface

L3 dot1Q interface

L3 Eth-trunk Logical

Single BFD session for whole trunk

When BFD run over trunk, BFD packets are sent over some link

members using hashing.

L2 port

Need Huawei proprietary multicast BFD.

Eth-trunk Per-link

Separate BFD sessions for each link in interface for resiliency

Need Huawei proprietary multicast BFD session.

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S97 BFD software features (3)

BFD Interface support

Static LSP

LDP LSP

MPLS TE

VLL PW

No detective for backup PW

No support for PW over TE

VPLS PW

No support for PW over TE

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BFD vs Per-Protocol Timers

Per-Protocol Timers:

Single interface may have 2-3+ protocols establishing adjacency

E.g., VRRP, PIM, OSPF on each vlanif/subinterfaceI

Tuning down timers for every protocol increases inband and CPU

utilization. This wastes CPU effort and link bandwidth

Configuration complexity

BFD:

One BFD session can track link-state for all client protocol sessions

between an IP node pair

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Contents





Summary

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BFD on S9700 Software Architecture

OSPF RIP PIM BGP IS-IS Etc.

BFD

Switching Route Unit

Hardware

I/O Module

Hardware

I/O Module

Hardware

I/O Module

BFD Client

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Client Behavior – OSPF

OSPF 1 BFD 1 OSPF 2 BFD 2

Establish OSPF Adj

Establish OSPF Adj

OSPF FULL OSPF FULL

Register OSPF neighbor IP with BFD

BFD notifies OSPF

OSPF Registered BFD packets

Register OSPF neighbor IP with BFD

OSPF Registered BFD packets

Send OSPF Hellos

Send OSPF Hellos

Device Fails BFD notifies OSPF

OSPF Adj removed

OSPF de-Registered De-register neighbor IP with BFD

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Client Behavior – PIM

PIM 1 BFD 1 PIM 2 BFD 2

Send PIM Hellos

Send PIM Hellos

PIM Adj PIM Adj

Register neighbor IP with BFD BFD notifies PIM

PIM Registered BFD packets

Register neighbor IP with BFD

PIM Registered BFD packets

Send PIM Hellos

Send PIM Hellos

Device Fails BFD notifies PIM

PIM Adj removed

PIM de-Registered De-register neighbor IP with BFD

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Client Behavior –static routes

static route 1 BFD 1 static route 2 BFD 2

Track static route with BFD

Add a static BFD configuration

BFD packets


BFD packets

Device Fails BFD notifies static

route static route turn to

inactive

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Proprietary BFD: one-arm-echo (1)

static route 1 BFD 1

Third-part device without BFD function


Add a static BFD configuration one-side only

BFD packets IP loop

BFD notifies static route static route turn to

inactive sth. Fails

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One-arm-echo vs Echo

Unlike standard echo mode. one-arm-echo only send echo BFD frames, no BFD control frame exchange.

Be carefully, by default echo frames use self-interface-ip as src & dst ip, so you should disable some security check function along with the path.

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BFD Interoperability

Tested with:

NE40E

C7600

S9500

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Contents





Summary

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BFD Configuration (1)

Pre-configuration Tasks

Before configuring BFD, complete the following tasks:

1. Connecting each interface correctly

2. Configuring IP addresses for Layer 3 interfaces

Data Preparation

To configure BFD, you need the following data.

1. BFD configuration name

2. Peer IP address, local interface type and number for the directly-connected link

detected by BFD, and default multicast address used by BFD if it checks the

physical layer status of the link

3. BFD session parameters: local and remote discriminators

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BFD min-tx-interval <10-1000> min-rx-interval < 10-1000 > multiplier <3-50>

Global or per-interface control of BFD timers

Interval –frequency in msec at which to send BFD messages

Multiplier: BFD declared down if no packet received within (interval*multiplier)

msec

Default is interval = 10 msec and multiplier = 3

failover detection in 30 msec

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one arm echo config:

bfd cfg-name bind peer-ip peer-ip [ vpn-instance vpn-instance-

name ] interface interface-type interface-number [ source-ip source-

ip ] one-arm-echo

Notice:

1) only in sing-hop BFD

2) Only need local discriminate. “discriminator local discr-value ”.

3) “min-echo-rx-interval interval” could set the echo interval, default is 10ms.

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BFD Configuration: other parameters

WTR configured (default 0) [WTR is a timer to hold when BFD

session state change from down to up.]

Run: wtr wtr-value

Set the priority of BFD packets (default 7, lowest priority 0)

Run: tos-exp tos

Configure the number of the default destination port for the multi-hop

BFD control packet

Run: multi-hop destination-port { 3784 | 4784 }

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BFD Configuration Example 1

BFD for OSPF

1 Display the system view:

Run: system-view

2 Display the OSPF view:

Run: ospf process-id

3 Establish BFD sessions for OSPF:

Run: bfd all-interfaces enable

4 Specify the value for each parameter used to establish a BFD session(Optional):

Run: bfd all-interfaces { min-rx-interval receive-interval | min-tx-interval

transmit-interval | detect-multiplier multiplier-value } *

5 Check the information about the BFD session:

Run: display ospf [process-id ] bfd session interface-type interface-

number [ router-id ] or

display ospf[process-id ] bfd session { router-id | all }

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BFD Configuration Example 2

BFD for PIM

1 Display the system view:

Run: system-view

2 Display the interface view (Interface type must be VLANIF):

Run: interface interface-type interface-number

3 PIM BFD is enabled :

Run: pim bfd enable

4 PIM BFD parameters are adjusted.

Run: pim bfd { min-tx-interval tx-value | min-rx-interval rx-value | detect-multiplier

multiplier-value }*

5 check information about a PIM BFD session :

Run: display pim [ vpn-instance vpn-instance-name | all-instance ] bfd session

statistics

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BFD Configuration example 3

one-arm-bfd example

src & dst ip is local interface IP address by default

Also could change it by CLI: src IP= Loopback IP, dst IP = local

interface IP

Src-MAC = local interface MAC, dst-MAC = peer’s MAC

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BFD Configuration example 4

Multicast BFD example

bfd 1 bind peer-ip default-ip interface ?

Eth-Trunk Ethernet-Trunk interface

Ethernet Ethernet interface

GigabitEthernet GigabitEthernet interface

When use MC-BFD @ Eth-trunk

1) Multi MC-BFD sessions for individual link

2) (Optional) Associate BFD with port status

3) (Optional) Set min-active link parameter in Eth-Trunk

For example:

A 4 links Eth-trunk. If 3 member links down, then teardown the eth-trunks.

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BFD Monitoring

CLI and XML available to obtain BFD information and status

Run: <SwitchA> display bfd session all verbose

BFD MIB

Clear BFD statistics in the user view

Run: reset bfd statistics { all | discriminator discr-value }

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BFD troubleshooting

• Make sure pre-configuration requirements are met.

• Make sure neighbor supports BFD except one-arm-echo scenario.

• Make sure neighbor supports running BFD over same type of interface (i.e trunk).

• Debugs

Enable the debugging of the BFD module

Run: debugging bfd { all | defect-detect | error | event | fsm | ha | packet | process

| product-interface | session-management | timer }

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Contents





Summary

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Summary Top 5 things to remember

Dedicated HW offload the CPU’s BFD process burden

Support both single hop & multi-hop mode

Proprietary BFD one arm echo mode

Worked with other 3rd device, which don’t support BFDv1

Proprietary multicast BFD

Worked in L2 links

BFD trigger interface status & BFD action

Copyright©2012 Huawei Technologies Co., Ltd. All Rights Reserved. The information in this document may contain predictive statements including, without limitation, statements regarding the future financial and

operating results, future product portfolio, new technology, etc. There are a number of factors that could cause actual results and developments to

differ materially from those expressed or implied in the predictive statements. Therefore, such information is provided for reference purpose only and

constitutes neither an offer nor an acceptance. Huawei may change the information at any time without notice.

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BFD Features - ActForNet S9700...2 Contents BFD introduction and protocol features BFD on S9700 –...

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