Subject: [core] Fwd: FW: I-D Action: draft-zheng-core-coap-lantency-evaluation-00.txt

From: Zhen Cao <[email-masked]>
Date: Mon, 4 Jul 2016 12:34:28 +0800

FYI.

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Sent: Monday, July 04, 2016 11:16 AM
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Subject: I-D Action: draft-zheng-core-coap-lantency-evaluation-00.txt

A New Internet-Draft is available from the on-line Internet-Drafts directories.

        Title           : CoAP Latency Evaluation
        Authors         : Fei Zheng
                          Baicheng Fu
                          Zhen Cao
        Filename        : draft-zheng-core-coap-lantency-evaluation-00.txt
        Pages           : 9
        Date            : 2016-07-03

Abstract:
   This document presents the evaluation results of CoAP in terms of
   various latency metrics over UDP/TCP under different network
   environments.  We conduct experiments via both GPRS and WiFi.  We
   also evaluate how the latency metrics are impacted by the background
   traffic.

The IETF datatracker status page for this draft is:
https://datatracker.ietf.org/doc/draft-zheng-core-coap-lantency-evaluation/

There's also a htmlized version available at:
https://tools.ietf.org/html/draft-zheng-core-coap-lantency-evaluation-00

Please note that it may take a couple of minutes from the time of
submission until the htmlized version and diff are available at
tools.ietf.org.

Internet-Drafts are also available by anonymous FTP at:
ftp://ftp.ietf.org/internet-drafts/

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---

From: "Carles Gomez Montenegro" <[email-masked]>
Date: Mon, 4 Jul 2016 10:58:28 +0200

Hi Zhen,

Thanks a lot for this draft!

A few comments/questions:

- Did you measure the native packet loss rate?

- In Table 3 (Wi-Fi), latency of CoAP-CoCoA is the same regardless of the
manually introduced packet loss rate. I would expect some C-RTT increase
with packet loss rate increase... Which is the reason why C-RTT increase
does not happen? Or is there maybe some increase below the millisecond
granularity?

- I noticed that ICMP RTT for GPRS is 572 ms, while obtained C-RTT is
often lower than that value. I guess that is due to the size of the ICMP
packets used to measure the ICMP RTT? (It would be good to indicate the
size of such packets)

- In GPRS, we also observed a slight retry ratio increase for CoAP-CoCoA
in low congestion GPRS scenarios. However, the retry ratio was
significantly lower for CoAP-CoCoA (compared to CoAP-RAW) in moderate to
high congestion conditions. It would be interesting to measure what
happens for different offered loads.

- Which window size did you use for TCP?

Minor:

- Is the CoAP client (over UDP) encapsulating the messages as CONs?

- Apparently there is a jump from section 4.2 to 4.4.

- Section 4.4:  s/as composed to/as opposed to

- Reference [COAPCC]: s/Networks magazine/Communications magazine

Cheers,

Carles

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---

From: Zhen Cao <[email-masked]>
Date: Tue, 5 Jul 2016 15:06:56 +0800

Hi Carles,

Thanks for feedback.

> - Did you measure the native packet loss rate?

not really.  many paper has studied this, native packet loss rate for
cellular network is rather low in steady environment, because 3gpp
stack is very good at fast retransmission.

> does not happen? Or is there maybe some increase below the millisecond

We only notice sub-ms increase in this set of data.  Because the data
is averaged for the 100 rounds, several retransmissions do not account
much probably.

> packets used to measure the ICMP RTT? (It would be good to indicate the

ICMP packet size is smaller than CoAP+UDP.   ICMP Ping request is 40 bytes.

> happens for different offered loads.

CoAP-RAW by default retries after 2 seconds.  If the RTT is higher
than 2s, CoAP-RAW will definitely be more aggressive than CoAP-CoCoA
which calculates RTO based on SmoothedRTT. So what's your RTT?

> - Which window size did you use for TCP?

Default on Android, which is TEN.

> - Is the CoAP client (over UDP) encapsulating the messages as CONs?

Yes,.
> - Reference [COAPCC]: s/Networks magazine/Communications magazine

we will correct the above three nits.

Many thanks,
Zhen

---

From: "weigengyu" <[email-masked]>
Date: Tue, 5 Jul 2016 16:01:53 +0800

Hi，

Some questions:
1. How large the NS is set for CoAP- Cocoa?
2. The ICMP latency is measured when the FTP background traffic is exiting, 
or not?
3. For CoAP over TCP on GPRS, how many are the allocated bufffers inside the 
andoid terminal?

Regards,

Gengyu WEI
Network Technology Center
School of Computer
Beijing University of Posts and Telecommunications
-----原始邮件----- 
From: Zhen Cao
Sent: Tuesday, July 05, 2016 3:06 PM
To: Carles Gomez Montenegro
Cc: [email-masked] ; [email-masked] WG
Subject: Re: [core] Fwd: FW: I-D Action: 
draft-zheng-core-coap-lantency-evaluation-00.txt

Hi Carles,

Thanks for feedback.

Yes,.

Many thanks,
Zhen

>>         Filename        : 
>> draft-zheng-core-coap-lantency-evaluation-00.txt
>>         Pages           : 9
>>         Date            : 2016-07-03
>>
>> Abstract: