Question about SLA responder: ENSARI study question

[hfakoor222]

Studying for the ensari eam,  one of the questions in the book is:

In which of the following situations would you require an IP SLA responder?
a. Testing one-way delay for voice packets
b. Testing connectivity for a fl oating static route
c. Testing connectivity for First-Hop Resiliency Protocol
d. Testing round-trip time with an ICMP echo

The answer is a, however i thought it was d, as i thought the echo may have needed a responder.

Could someone elaborate as to why a is the answer?

Thanks

[Peter Paluch · Accepted solution]

Hello,

IP SLA responder is a component of Cisco IOS/IOS XE. It is a functionality for special measurements or protocols that need a specific processing on the destination device. Measuring one-way delay for voice packets would be such an application because you cannot just send voice packets to an arbitrary host - if there is no software receiving and processing those packets, they will be discarded without processing.

ICMP echo - or ping - is a basic functionality implemented in every TCP/IP driver. Every device supporting IP supports pings, so you do not need a special software for that.

The documentation and some in-depth discussion on IP SLA Responder functionality can be found here:

https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/ipsla/configuration/xe-16-12/sla-xe-16-12-book/sla-overview.html#GUID-C2E58A98-D907-4EF2-949B-0AD59FD3D4D4

Once again, an IP SLA Responder is not just any device that will respond to SLA probes (such as pings) - rather, it is a Cisco device running IOS or IOS XE that allows more specialized measurements than just the ones using the simple and ubiquitous mechanisms.

Please feel free to ask further!

Best regards,
Peter

[hfakoor222]

Thanks, I will be adding the link to the white-papers I will be reading later

[MHM Cisco World]

one-way delay

This I think trick' 

So yes I think answer is A

please check below 

[hfakoor222]

Thanks

[MHM Cisco World]

You so so welcome' I will try run lab' hope ntp this time work and show you how delay measures in responder.

[MHM Cisco World]

@hfakoor222  for you Friend and all see post 
as I mention and check some icmp or other (jiiter and delay) need ip sla responder 
the responder is send timestamp to sender and sender calculate the delay.  (this timestamp not send when we use icmp-ech)
check the wiresharke capture 
if you want lab just ask and I will share here. 
by the way finally NTP work LOL...
have a nice summer 
MHM

[hfakoor222]

Thanks, helped clear some things up  

[MHM Cisco World]

You are so welcome.

MHM