Challenges in testing transport layer networks - swisst.net Challenges in testing transport layer networks ... Slide Title • Wired network ... • Network equipment cost reductions

Challenges in testing

transport layer networks

Juraj Urminsky

Business Development Manager CEE

Anritsu EMEA

28/10/2015

Copyright© ANRISTU2

Slide Title

Agenda

1. Network traffic growth

2. History of networks

3. Why the network change

4. Testing approaches and recommendations

5. OTN – What is it and Where it came from and Why

6. OTN – mappings , network structure and testing

( FEC ITU-T O.182)

7. Ethernet - reasons for testing, method of testing

( RFC 2544 , Y.1564)

8. Mobile Front-haul Verification - CPRI

3 Copyright© ANRISTU

Slide Title

• Wired network traffic requirements have greatly increased after the IT bubble

• After 2000 network requirements expanded rapidly in the most advanced countries

o Due to pre bubble network role-out this 1st Wave was manageable

• 2nd Wave leaded due to BRIC’s countries in 2005.

o This required large fiber and core network investment by the operators

• Smart phone data requirements commenced the 3rd Wave ~ 2010

pushing or exceeding network abilities from the 1st & 2nd Waves

• Network equipment cost reductions mean dollar value is almost flat

o But total data traffic is continually ramping up…

Network traffic growth

(Year)20102000

(Traffic)

2005

- 100G moving to the

core network.

- Network moving to

OTN + Ethernet.

- GigE speed to mobile.

- Full 10G metro/core at

price point reduction

- Start 40G installation

- Mobile network move

from ATM to Ethernet.- Start 10G to metro/core

- Spread Ethernet

3rd Wave

Smart Phone

1st Wave

Forward Country

2nd Wave

BRICsWhen

and how

big is the

4th

Wave ??

?


Slide Title

History of Networks

• Wired network (Telecom)

– PDH / DSn (32 / 24 voice channels or 2Mbits / 1.5Mbits) (CCITT) – ITU-

T G.703

– SDH / SONET (52Mbits to 40Gbits)

• First standardized late mid to late 1980’s (CCITT) – ITU-T G.803

– OTN (2.6Gbits to 100Gbits)

• First standardized in 2001 – ITU-T G.709

• Major update in 2009 to 2012

• Wired network (Ethernet)

– LAN developed by Xerox in 1973

– 10Base5 - First standardized early 1980’s – IEEE 802.5

– 10Base2 / 10Base-T / 10Base-X in 1985 / 1990 / 1998 – IEEE 802.3

– 100Base-TX/T4/T2 and 100Base-FX/SX/BX/LX10 in 1995 – IEEE 802.3u

– 1GigE or 1000Base-XX appeared in June 1998 – IEEE 802.3z

Later in 1999 IEEE 802.3ab for UTP or in 2004 IEEE 802.3ah for “first mile

– 10GBase-XX in 2002 as IEEE 802.3ae, lat. version 2012 IEEE 802.3-2012

– 40G/100G standard ratified in June 2010 as - IEEE 802.3ba

http://www.nmedia.net/docs/ccitt/1988/

http://www.itu.int/rec/T-REC-G.703/en

http://www.nmedia.net/docs/ccitt/1988/



http://www.ieee802.org/5/www8025org/

http://www.ieee802.org/3/purchase/index.html









Slide Title

Transformation of the Network

3G

4G

RRH

T1/E1

Central Office

T1/E1

RRH

RF

Over Fiber

Base Station

Carrier Class

Ethernet

over OTN

Ethernet

RRH

Business Connection

Next Gen

Backhaul network

Node B

ROADM

Core

Network

with MPLS-

TP or PBB-

TE over

OTN

T1/E1

TDM

(SDH/SONET)SDH/

SONET

T1/E1

RF 2G

3G

• Common Carrier Class Network

– From Mobile to Core

– From Copper to Fiber

– From 2G to 4G

• Common Carrier Class Network

(changes)

– Removal of T1/E1 where possible

– Core changes to ROADM, OTN,

MPLS-TP. Ethernet

– Migrate over time to remove

SDH/SONET

Legacy

Backhaul network

InterfacesT1/E1 SDH/SONET Ethernet


Slide Title

Why the network change

• Is the movement from SDH to OTN or Ethernet (MPLS-TP / PBB-TE) required

– Change is slow (years) due to Cost, Reliability

– Cores are commonly moving to OTN while services are often over Ethernet

• What is the reason for the network change

– Demand for data and data intensive services, HD Video, HD Video conferencing, Live document sharing/collaboration

• Expanding the metro network (moving serves closer to customers)

• What the networks of tomorrow will look like

– Ethernet / MPLS to the Operator or Metro

• Lower rates (sub 1.24Gbps) managed by MPLS

– OTN in the Core / Metro / Access

• Higher rates (above 1.24Gbps) managed by OTN

Eth / OTN

Metro

ROADMROADM

OTN

Core

Eth OTN

Metro

Eth / OTN

Metro

10G * 20

100G

10G *

20

100G

* 1


Slide Title

Testing approaches

• Out-of-service testing

– Installation and commissioning and troubleshooting of SDH/SONET lines

– System stressing through generation of alarms, error, pointer operations

and frequency offset

– Test synchronization circuits

– Round Trip Delay measurements

• In-service testing

– Alarm and error monitoring for both sides of the SDH/SONET line

– Frequency-deviation measurements

– G.826/G.828/G.829/M.2100 error-performance measurements on live traffic

• M.2100 parameters

– Errored Seconds (ES) - 1 sec in available time with 1 bit error

– Several Errored Seconds (SES) - 1 sec in available time with a BER > 10E-3 or alarm

– Unavailable time (UAT) - 1 sec in available time with a BER > 10E-3 or alarm

– Available time (AT) - A new AT starts at the beginning of 10 consecutive non-SES

events


Slide Title

Error performance recommendations SDH/PDH

• G.821

– Defined for out-of-service PRBS based bit error measurements at 64 kbit/s

– "Interim guidelines" for use at higher bit rates and for in-service use

– Now obsoleted

• G.826

– Based on block error measurements

– Defined for in-service error measurement at 2 Mbit/s and higher

– Defined for all relevant PDH and SDH rates plus for ATM

– Out-of-service measurements are briefly mentioned

– G.828 and G.829 are defined for SDH error performance

• M.2100

– Defined for both in-service and out-of-service applications

– Based on bit error measurements

– Defined for 64 kbit/s and all relevant PDH rates

– M.2101 defines SDH error performance

– M.2110 and M.2120 defines practical use of M.2100


Slide Title

Error performance recommendations OTN

• G.8201

– Error performance parameters and objectives for multi-operator

international paths within optical transport networks

– Defines error performance parameters and objectives for international

ODUk paths transported by the OTN. Allocation principles can be applied

to the design of error performance for national or private ODUk paths. Is

based upon a block-based measurement concept using error detection

code (EDC) and EDC usage inherent to the path under test. Simplifies in-

service measurements, events, parameters and objectives are defined

accordingly. In addition to path performance assessment, tandem

connection monitoring is covered.

• M.2401

– Error performance limits and procedures for bringing-into-service and

maintenance of multi-operator international paths and sections within an

optical transport network

– Gives error performance objectives, limits and procedures for bringing-

into-service (BIS) and maintenance of multi-operator international ODUk

Paths and OTUk Sections in an OTN.


Slide Title

OTN

– Originally designed for long haul networks released in 1999 to 2001

– With OAM allowing supervision for the Operator at the different layers of the

OTN network (OTU, ODU, and OPU)

– And FEC (Forward Error Correction) allowing longer error (correctable)

free transition lengths

– Capable of carry all traffic types Legacy(SDH/SONET) and new

(PBB/MPLS/IP/FC)

– Flexibility of OTN’s mapping is the key strength of the technology

Optical Amp Optical ADMDigital Amp

Customer EquipOptical ADM

Digital AmpCustomer Equip

OTS OTS

OMS

OCh (Channel)

OTU (Section)

ODU (Path)

OPU (Payload) – Customer traffic


Slide Title

OTN structure

• A network can be divided into Optical and Data domains

– Optical: DWDM, Optical switching, Optical amplification etc

– Data: network elements look at the header information

• Within the Data Domain

– OTU (Optical channel Transport Unit)

• Switching and monitoring point

• Associated with point to point network elements

– OPU (Optical channel Payload Unit)

• Associated with an end to end switching point

• Can be associated with an end customer

– Multiple OTU’s can be utilized to form a single OPU


Slide Title

ITU-T O.182 Standard

Error Correction Curve

• FEC performance tests using Poisson distribution random errors was adopted by ITU-T O.182 in July 2007

• Reproducible / accurate FEC error correction tests are performed by generating truly random signal errors (Poisson distribution)

– Generating true random errors stress the OTN FEC

– Allows a much lower BERT measurement ensuring testing to the limit or beyond the switching equipment's ability

• Required to test the true performance / threshold of an OTN network

Bad Random

Distribution

Good Random

Distribution


Slide Title

Testing of OTN

• OTN overhead tells us the location of an issue via the Maintenance signals

– Correctly evaluating this information quickly identifies where testing should commence

– Priority of restoration can be identified via affected Layer SM is higher priority (likely a core issue) than PM (possibly customer issue)

• The customer(s) or section of the network affected, TCM identify to a customer or segment level.

– High priority customers can be looked at first.

– Understanding the different TCM levels analysing or injecting errors identifies the actual section affected

• Testing both direction in pass-through mode overwriting the overhead is key to a deep evaluation, simulate issues (viewing both the forward and backward errors)


Slide Title

Testing of OTN

• Dividing the network allowing in-depth

analysis across layers

– Testing from client signal to OTN

layer

• Y.1564 over GigE ↔ ODU1

↔ ODU2 ↔ OTU2

• Testing from the core to the client

– Sub-dividing the network into logical

segments, Core, Metro, Access

• Confirming throughput of a customers HQ using

Ethernet to the core

– Offer customer facing reports showing

committed bandwidth even though Regional

Offices are configured with lower BW than

HQ

– Confirm OTN overhead using customer

type payload, Voice, Video Data (not BERT)

an view errors related to each level.


Slide Title

Ethernet

• LAN technology that is now becoming dominant data-transmission technology

• A number of protocols were developed to migrate from LAN to Carrrier-Class

like OAM, VLAN, PBB-TE, MPLS-TP

- Ethernet frame

PreambleMAC

Destination

MAC

DestinationEthertype

Length

Payload FCS

(CRC)

7 bytes 6 bytes 6 bytes 2 bytes 4 bytes

Interframe gap

12 bytes

MT1000A Training FY 2014

DA

SA

TPID

Payload

FCS

802.1

Ethernet

TPID

VID

TPID

FCS

DA

SA

Payload

802.1Q

VLAN

TPID

C-VID

TPID

FCS

TPID

S-VID

DA

SA

Payload

802.1ad

PB

TPID

I-SID

FCS

TPID

B-VID

B-DA

B-SA

Payload =

802.1ad Frame

With or without

FCS

802.1ah

PBB

Q-TAG S-TAG

C-TAG

I-TAG

B-TAG


Slide Title

Ethernet – Network issues

Typical root causes of issues in network

• Top talker

– Top talker occupies a major part of

the network, slowing it down.

• Network attack

– One node is accessed from many

sites, which occupies the network.

• Error Frames

– Error frames causes re-transmission

and waste the network capacity.

Target

node


Slide Title

Ethernet – Reasons for testing

– SLA (Service Level Agreement)

• Customer places the telecom operator under legal agreements

during the sales cycle

– Confirm the network

• Ensure when the customer turns up his equipment the end points

are connected

– If there are issues not detected at install operator would have

to resend engineers to look into the issue

– Confirms routing end to end of the telecom network

• Bandwidth as per customer agreement

– Check the routers throughout the network are configured

correctly

– Ensure the customer is getting what he is paying for

• Network Delay

– Ensure the circuit is capable of carrying all types of traffic


Slide Title

Ethernet – How to test

BERT (Bit Error Rate Test),

– Commonly requested as customers are comfortable with this technology.

IETF RFC2544

• Commonly referred to as the reference point for testing Ethernet

– Originally designed for network elements, adopted by telecom operators

– Performance characteristics like – Throughput, Frame Loss, Latency,

Burst

ITU-T Y.1564

• Becoming the reference point for testing Ethernet networks

– Completes a quick test to confirm connectivity (Service Configuration Test)

– Completes a detailed test with all services running (Service Performance

Test)

• Closer to customer traffic than RFC2544 (test simultaneous connections)

MultiStream

• Not a standard but customers confirm the network using it

– Simple straight forward check of the network

http://www.ietf.org/

http://www.ietf.org/


Slide Title

Ethernet – Multistream testing

• Multi-stream Network Quality Evaluation

Network and Service Quality (QoS)

VLAN QoS Test

Traffic Generation

Monitoring


Slide Title

Ethernet – Benefit of Multistream testing

• By sending several streams of traffic with different priority settings the user can

verify that high priority traffic is transported better (i.e. has lower frame loss

ratio) through a congested network than low priority traffic.

• VoIP traffic is often given a high priority in order to ensure the quality of the

service

– In some cases the DSCP/TOS byte is used to give high priority

– In other cases high priority is given to selected TCP/UDP port numbers

• In some cases operators allocate a certain amount of traffic capacity to each

type of traffic in a link with limited capacity.

• By sending several streams of traffic with different type indications the user

can verify that each type of traffic get the allocated capacity

– Type of traffic can be indicated with VLAN tags


Slide Title

Ethernet – Symmetrical / Asymmetrical testing

– Traditional network are symmetrical in their nature,

• SDH, ATM, Frame Relay, ISDN all normally have the same uplink and

downlink speeds.

– Many newer technologies adopt asymmetrical links,

• WiMax, xDSL normally have a different uplink (much less, 5 to 10

times) than downlink speed.

• With different network architecture often different testing methodologies are

required.

– A reflector has more value in symmetrical than asymmetrical networks.

– Master Slave testing allows for better characterization of a asymmetrical

network.

• Combining the best of both testing type is the best method to adopt.

• Understanding the network architecture is required to fully characterize a

network.


Slide Title

Ethernet – What is coming next

– 400GbE –

• IEEE P802.3bs

• Objectives of reaching 100,500, 2000, 10 000 meters over MMF and

SMF cables specification.

• Expecting to be ratified first half of 2017.

• Possible configuration might be 16x25Gbs, 8x50Gbs or 4x100Gbs.

• EEE - energy efficient Ethernet objectives were adopted by project to

support to reduce operational costs and environmental footprint.


Slide Title

Mobile Front-haul Verification

• C-RAN

– the mobile fronthaul is configured from centralized Base Band Units

(BBU) and multiple Remote Radio Head (RRH) units connected via

general-purpose interfaces, such as the Common Public Radio Interface

(CPRI) or Open Base Station Architecture Initiative (OBSAI).

– Minimizing number of BBU’s per antenna cuts operator costs (rent,

power, HW, etc.)

Locating BBU 15 km or more from multiple RRH requires reliable

connection

– CPRI runs over C-RAN with two main layers:

• Layer 1: Physical transport

• Layer 2: Several areas

C-RAN main interest is L1 in-band protocol;

understanding this area allows

operator to troubleshoot alarms and errors


Slide Title



Slide Title


- TEST case 1 :

- Test the line between BBU and RRH ( REC and RE) ,

- System testing, installation testing

- Line could be : optical, CPRI over OTN or CPRI over radio link

- BER test and Delay measurements ( max 200-400micros)

- TEST case 2:

– Connect to the actual equipment (REC or RE) to verify that it is alive

– Signal level and frequency measurement

– Optical cable ends may be checked with Video Inspection Probe (VIP)

– Monitor control word K30.7 – indicates error in the 8B/10B line code (CPRI option 1-7 only) – and 8B/10B code violations

– Check equipment behaviour

» Check that the equipment can reach the “Passive Link” state

» Confirming HDLC layer (Layer 2) network is connecting

» Check the equipment’s behaviour when alarms are generated

- TEST case 3:

– Monitoring of the actual line between REC (Radio Equipment Control) -(master) and RE (Radio Equipment) - (slave)

– Utilizing dual port in through mode or monitor

– Monitor interactive behaviour of equipment

– For maintenance or in-service troubleshooting


Slide Title

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• Transport

• Optical

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Slide Title

T h a n k Yo u

Challenges in testing transport layer networks - swisst.net Challenges in testing transport layer networks ... Slide Title • Wired network ... • Network equipment cost reductions

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