Packet Loss & RTT Calculation
Method
Banjarmasin
June 1, 2017
NOKIA PACKET LOSS CALCULATION METHOD
1. Nokia uses Two Way Active Protocol Measurement Protocol (TWAMP) based on RFC5357, and further
simplified to TWAMP Light.
2. TWAMP is a way to have an indication of quality and performance of the IP MOBILE BACKHAUL by
exchange test packets between two TWAMP entities, further known as TWAMP Sender and TWAMP
Reflector
3. Measures Round Trip Time (RTT), Packet Loss Rate (PLR) and additionally Packet Delay Variation (PDV).
4. Since User Plane is the traffic for end user, Nokia set the TWAMP parameters that reflect U-Plane
traffic (IP Address of TWAMP Sender and Reflector, Packet Size, DSCP)
5. In 3G network, use NodeB as TWAMP Sender and RNC as TWAMP Reflector that will indicate the
performance of the IP MOBILE BACKHAUL of an IuB interface. Nokia set 3 sessions to imitate RT
Traffic, NRT Traffic and HSPA Traffic.
NodeB
Sent TWAMP Messages
(vrf IuB)
Reflected TWAMP Messages
(vrf IuB)
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Access
Router
RNC
NOKIA PACKET LOSS METHOD
5. For LTE Network, to better reflect the condition of IP MOBILE BACKHAUL for S1-U interface, it is
suggested to have TWAMP Reflector or UDP Echo at SGW site. Since still does not have TWAMP
Reflector at SGW site yet, it is agreed to use RNC that co-located with Access Router to indicate
performance of ACCESS IP MOBILE BACKHAUL.
Note that we can not measure the quality of end-to-end transport (eNB to SGW) performance because of
that, only up until Access Router only.
eNB
Sent TWAMP Messages
(vrf lte-uplane)
Reflected TWAMP Messages
(vrf lte-uplane)
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Access
Router
RNC
TWAMP Packet Loss Measurement
1.
2.
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06/06/2017
Since test packets contain sequence numbering, it
is possible to measure Packet Loss Rate by TWAMP
Sender
Session Reflector copies the sequence number
from received test packet to the packet that is to
be transmitted back
TWAMP RTT Measurement
1. RTT Measurement if use TWAMP Reflector
RTT = (RTSS-TTSR) + (RTSR-TTSS)
T
S
G
T
S
G
TWAMP
Sender
TTSS
RTSR
TWAMP message containing TTSS
T
S
G
Reflected TWAMP message containing
TTSS, RTSR,and TTSR
T
S
G
RTSS
TTSR
TSG:
TTSS :
RTSR:
TTSR:
RTSS:
TWAMP
Reflector
Time Stamp Generator
Transmit TimeStamp at Sender
Receive TimeStamp at Receiver
Transmit TimeStamp at Receiver
Receive TimeStamp at Sender
2. RTT Measurement if use UDP Echo
RTT = RTSS-TTSS
T
S
G
TWAMP
Sender
T
S
G
TTSS
TWAMP message containing TTSS
Reflected TWAMP message containing
TTSS
RTSS
TSG:
TTSS :
RTSS:
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06/06/2017
Time Stamp Generator
Transmit TimeStamp at Sender
Receive TimeStamp at Sender
UDP Echo
Server
NOKIA 3G TWAMP FORMULA
IP TWAMP Packet Lost Ratio (%)
=
100 * lostTwampMessages
txTwampMessages
Round Trip Time (miliseconds)
=
maxRTT_15Min
1000
Packet Delay Variation (miliseconds)
=
(maxRTT_15Min – avgRTT_15Min)
1000
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NOKIA 4G TWAMP FORMULA
IP TWAMP Packet Lost Ratio (%)
=
100 * lostTwampMessages
txTwampMessages
Round Trip Time (miliseconds)
=
maxRTT_15Min
1000
Packet Delay Variation (miliseconds)
=
(maxRTT_15Min – avgRTT_15Min)
1000
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06/06/2017
ERICSSON 3G PACKET LOSS FORMULA
1. Ericsson uses counters related to frame loss to monitor High Speed data service in the downlink
direction.
Packet Loss SpiXX (%)
=
100 * IuBDataStreams.pmHsDataFramesLostSpiXX
IuBDataStreams.pmHsDataFramesReceivedSpiXX+IuBDataStreams.pmHsDataFramesLostSpiXX
RBS
RNC
MAC-d
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With the use of Sequence Number in MAC PDU, receiver
can detect if there’s a frame loss that can be an
indication that there’s packet loss in the transport
network
ERICSSON 3G RTT FORMULA
2. Ericsson uses maximum dynamic delay between RNC and RBS on the radio network layer based on
Node synchronization.
RTT (miliseconds)
=
2 * pmIubLinkDynamicDelayMax
RNC
15. CCH FP (FACH): DL Node Synchronisation (T1)
sampleIntervalSup
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16. CCH FP (FACH): UL Node Synchronisation (T1, T2, T3)
RBS
ERICSSON 4G PACKET LOSS & RTT FORMULA
1. Ericsson uses counters related to SCTP of X2-MME logical connection between eNB and MME
SCTP Data Chunk Retransmission Rate (%) =
100 * pmRtChunks
pmRtChunks + pmOutDataChunks
eNB
MME
S1-MME
SCTP will retransmit data if there’s a
packet loss indication
X2-AP
Adj eNB
2. No RTT measurement method
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Summary
ERICSSON
Items to be
Measured
Protocol
Remarks
NOKIA
Protocol
Remarks
Similar Measurement with Ericsson
HSUPA congestion rate in Iub =
100*SUM
(IUB_DELAY_CC_DELAY_IND
+HW_OVERL_CC_DELAY_IND
3G Packet Loss
Rate
+IUB_LOSS_CC_FRAME_LOSS_IND
Frame Protocol of Only measures packet loss
HSPA
rate of HSPA Traffic
TWAMP Light
based on
RFC5357
3G RTT
4G Packet Loss
Rate
4G RTT
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Node
Synchronization
(over FACH)
Only measures delay of node
synchronization
SCTP of S1-MME
interface
Only measures SCTP traffic
(Control Plane). Since SCTP is
for Signaling, it will be given
higher priority than User Plane
Traffic.
No measurement
+IUB_DELAY_CC_FRAME_LOSS_IND
Strength :
Parameters can be set to imitate
+HW_OVERL_CC_FRAME_LOSS_IND)
the traffic that wanted to be
------------------------------measured (RT, NRT, HSPA, NBAP,
SUM (MISSED_EDCH_FRAMES
S1-MME, S1-U, X2-AP etc)
+DELAYED_EDCH_FRAMES
+SUCC_REC_EDCH_FRAMES)
Dependency :
Need peers that is set as TWAMP
N/A
Reflector or UDP Echo
S1 interface SCTP unsuccessful
transmission ratio = 100 - (100*
sum(SCTP_S1CHSNT)
/
sum(SCTP_S1CHSNT+SCTP_S1CHRS
NT))