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How to Diagnose and Fix

Network Performance Problems

John S. Graham

Global Research NOC

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Synopsis

Network Performance Problems

Definitions

Network Testing

Going Loopy

Purpose

Taxonomy

Testing New Leased Lines

Dedicated Test Sets

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Network Contribution to Poor

Performance

1. Incorrect MTU Configuration

1. Standardized IP MTU of 9000 Bytes

2. Check end-to-end: ping -M do -c 1 -s

8972

2. Causes of Packet Loss in the Network

1. Due to a Congested Line

2. Due to a Line Introducing Transmission Errors

3. Process Switching by a Router in the Path

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iPerf Testing

A UDP iPerf test will probe the network for packetloss

Always employ a UDP test:

Eliminate Layer-IV Flow Control from affecting results Simplex test selectively probes one direction (Source

Sink orSinkSource)

The bitrate can be operator controlled

Use a modest packet rate for testing

High-bitrate tests do not reveal additional information

Excessive test traffic may cause congestion!

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Whos the Villain? MYRouter Interface

Or THEIRCircuit?

10G Circuit Over DWDM Ring

Direct Router-to-Router Adjacency over 10GE Interfaces

Kansas City

Houston

Miami

Atlanta

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Representation of DWDM Circuit

Tributary Side Line Side

Cross-Connect Termination Points

Tributary Side Line Side

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Soft Loop Classification

Facility Loops

Loop is applied to fiber side of CTP

Equipment (akaTerminal) Loops

Loop is applied to cross-connect side of CTP

Supported Only on Tributary CTP

Infinera DTN

Four Possible Configurations

Supported on Trib & Line CTPs

Ciena CoreDirector

Eight Possible Configurations

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A Bestiary of Loops

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Testing From a Router

1. Identify Far-End IP Address

2. Configure ARP Mapping : {IP}FE {MAC}NE

3. Clear Egress Interface Counters

4. Send Measured Number of Pings to {IP}FE5. EITHER Looped Network Clear of Errors

1. UCAST_IN = UCAST_OUT = Pings TTL

6. OR Looped Network Introduced Errors

1. UCAST_IN < UCAST_OUT

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Testing a New Leased Line

10G Leased Line

iperf -c 192.168.8.1

-u -b10m

Juniper MX960 Brocade MLX-16

A/32

B/32

192.168.8.1 A/32192.168.8.1 B/32

4

2

1

3

Static Route

Firewall Rule (Inbound)

P2P VLAN

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A Typical Ethernet Tester

2 10G Ports (XFP Optics)

Management

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Network Testers vsSoftware Probes

Network Testers

Do not process packetheaders.

Operator can design packetswith any combination of

protocols Header fields may contain

any value

Optimized for packet

counting Will accept, identify and

count every inbound frame;even those returned by aloop

Software Probes

Only accept packets with

valid headers.

Packet design severely

restricted.

Many header fields not

accessible

Accurate packet counting

difficult with standard tools

Unable to operate in

conjunction with a looped

network connection