Testing the Network. from Cables to Packets to Applications. Harshang Pandya Psiber Data Pte. Ltd.

Transcription

1 Testing the Network from Cables to Packets to Applications Harshang Pandya Psiber Data Pte. Ltd. Content Courtesy Sara Johnson

2 Challenges Faced by Enterprise Network Engineers Increasing complexity of network issues Insufficient budget - less training, fewer instruments customer cannot wait for problems to be fixed - high dependency on IT infrastructure

3 Typical Networking Issues Cabling and PoE related Connectivity related Networking stack/protocol related network link performance applications and services -VoIP

4 Trouble-shooting Wiring issues Wiremap testing- verify proper cable wiring and display: Reversed pairs Split pairs Crossed pairs Opens or shorts Length - Measures the distance to an open or short for each wire pair in a cable out to 100 meters or 300 feet

5 PoE Verification and Measurement Knowing actual power demand for each device allows proper allocation of power for each port within the capability of PoE source Verify PoE source before connecting a PoE devide Inline PoE - determine the actual power used by a powered device verify compliance with device specifications Information Includes Wire pairs that are powered Voltage Actual current draw Power in Watts Wire pair polarity

6 Basic Connectivity Tests Far End Identification Locating Far End of the Cable Locate a punch down or trace a cable using a Probe Tone cadence and frequency are adjustable Locating Switch/Hub Port Determine which port of a hub or switch is wired to a particular wall jack by blinking the link LED on the port Adjustable blink rate ensures compatibility with most switches and hubs

7 Ping Quick Check of Network Link Verifies connection to another device on the network Provides round trip time for a packet to be transmitted and the response received The received packet is compared to the transmitted packet to determine if any packet corruption has occurred Trace Route Shows all the hops the packet took on the round trip Link Configuration Test Verifies connectivity Displays connected speed and duplex mode Shows speed and duplex capabilities of far end device Determines wire polarity (normal or reversed) Master/slave assignment for 1000BaseTx links IP information Display

8 Port Compatibility Test with Dual-port Testers Shows whether the devices on either side of the tester are port compatible Shows the highest common connection speed of the 2 device when connected into each other Highlights incompatibility if there is no common connection speed

9 Port Info (LLDP/CDP) Layer 2 protocol used by network devices for advertising their identity and capabilities on the local network Information that may be retrieved include: system name and description port name and description IP management address system capabilities (switching, routing, etc.)

10 Networked Devices Information Devices are listed by Device Type, MAC address or IP address Listed devices can be limited to local addresses or on the entire network Devices are detected by monitoring traffic or through a discover broadcast Active discover will display DNS names of devices when they have been assigned by a DNS server

11 Device Information Helps Track Unwanted Users The devices screen shows all the devices on the network Identified an unknown user A recently installed router with wireless capabilities did not have security Turning off the wireless allowed for a secure site!

12 Expert Help From Testers Automates Fault Finding Detects problems such as: Link speed mismatch CRC errors Jabbers Runt frames IP packet fragments IP/TCP/UDP header errors Provides recommended solution for each problem

13 Case Study: Expert Help Tracks Bad Router A high number of TCP header errors detected from a specific IP address The IP address of the device was shown as a router The router was working but added bad packets to the network slowing user access The router was replaced and the TCP header errors stopped

14 Network Traffic Metrics - Troubleshooting and Optimization Vitals Real time analysis of every frame received Provides the number and percentage of good and bad frames indicating the health of the network Breakdown of frames that are unicast, multicast or broadcast Protocols A List of all protocols detected with the total number of packets and the percentage of the total traffic Certain protocols such as IPv4 and IPv6 can be expanded to show the sub-protocols Top Talkers Identifies the top transmitting devices on the network Find someone playing online games or downloading large files

15 Case Study: Protocol Analysis Rectifies Server Performance Problem: Storage server occasionally does not receive files sent by a device Solution: Place the tester inline between the server and a switch and perform file transfer. Monitor the protocol traffic to observe if network receives all packets sent by device Isolate the problem to either network or to the server

16 Traffic Generation Used to determine how a network will perform under various loading conditions Continuous or burst modes Adjustable packet size and transmission rate Using the other port (on a dual-port tester) or a second tester as a Link Partner provides detailed packet statistics

17 RFC 2544 Network Link Performance Test Generates traffic and measures performance metrics in accordance with IETF RFC 2544 Throughput, Latency, Packet Loss, Back-to-back Frames Conducted using the two independent ports on a single unit or used with a second unit located remotely on a network A cable certifier tests only cables not active devices. A stress test is used on segments that consist of cables and active devices

18 Network Application Tests - VoIP Track different VoIP calls providing: From-to IP addresses Call start and stop times Call duration Number of attempted and successful registrations with the VoIP server Statistics include: RTP Frames RTCP Frames Misordered Frames Lost Frames Restarts Packet Jitter

19 Frame Capture Allows Deep Dive in Protocols Frame Capture Capabilities in Hand held testers allows post-processing of complex protocol traffic Capture with simple and handy setup with real-time filters Process off-line using sophisticated tools like WireShark

20 Summary Cable testing, link detection, ping and trace route verify point to point and cross network connectivity. PoE test ensures adaquate provisioning of PoE Detailed packet monitoring, filtering and capture provide the ability to identify and solve complex problems. Flexible traffic generation and structured stress tests demonstrate network performance under varying load conditions. Service tests provide statistics and measurements required to ensure proper performance of services like VoIP. A must-have for network technicians: a single solution for analyzing and troubleshooting networks from the cabling to the packet.