Subject: [mobile-ip] MIP QoS requirements draft - modification to Section 3.3.2

From: "Hemant Chaskar" <[email-masked]>
Date: Wed, 24 Apr 2002 18:54:35 +0000

I received some comments privately that the text in Section 3.3.2 of 
draft-ietf-mobileip-qos-requirements-02.txt, is not clear enough. In 
response to that, I propose the following modification to this text. Please 
let me know if you have any comments, else I will go ahead and incorporate 
it in the next version (03) of the draft.

Thanks,
Hemant

Old text:
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2. Interactions with link-layer support for QoS:

The QoS mechanism MAY provide some information to the link layers for them 
to support the required QoS. Since a vast number of devices using Mobile IP 
will be connected to the Internet via wireless links, QoS parameters 
relevant for wireless links, such as error rate, MAY have to be included in 
the set of IP-level QoS parameters to be possibly considered by the 
underlying link layer.

An example scenario will be two UDP streams requiring different levels of 
error protection at the link layer. For such cases, an IP-layer QoS 
mechanism may indicate some generic parameters such as acceptable IP packet 
loss rate to link layers.

New text:
-----------

2. Interactions with wireless link-layer support for QoS:

Since a vast number of devices using Mobile IP will be connected to the 
Internet via wireless links, the QoS mechanism for Mobile IP MAY provide 
some information to the wireless link layers for them to support the 
required QoS.

An example scenario that may benefit from such information is that of the 
two UDP streams associated with the same media, but requiring different 
levels of error protection at the wireless link layer due to certain 
characteristics of their respective encoding schemes. The packets of these 
two streams are equally delay sensitive (so as to maintain playout 
synchronization at the receiver), and hence, may be treated equally (as 
regards queuing) by IP layer. But they may need to be transmitted on 
wireless channels of different error characteristics(say different FEC 
coding or power levels).

The QoS information included for the benefit of wireless link layers SHOULD 
be such that it is meaningful both ways: to applications that reside over IP 
so that they can choose the IP service of certain QoS characteristics and to 
wireless link QoS managers so that they can then map this information to the 
details of lower layer mechanisms and their parameters.

In the example scenario described above, such a QoS information could be 
expressed as the acceptable loss rate of IP packets in the UDP stream. This 
parameter enables the UDP application to choose the IP service having QoS 
that matches its requirements, and it also enables the wireless link QoS 
managers to choose the right wireless channel to transmit the packets of 
this UDP stream.

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