Dear Serhad,
thank you for your valuable comments. We will take them into account in
the revision of the draft (we are now working to prepare the new version)
As discussed in the last WG meeting, we want to setup a design team of
people interested to proceed in the definition of requirements. If you
want to be involved or just be notified of the progress of the work,
please contact Saverio or me.
Cheers,
Stefano
Doken, Serhad wrote:
Saverio,
Additional requirements :
(a) Vertical handover should not put excessive load on the access
network preventing it to serve existing MHs/sessions. For instance,
multiple MHs in the 3G AN approaching a hot spot should not bring
down a Wi-Fi network during/after the handover.
(b) MH should not ping pong between access networks during handover.
Terminal Mobility and Session Mobility can be intertwined. When two
ANs are available to the MH, it may choose to keep the voice session
in AN1 and handover the video to AN2 or move them both to AN2 and
transfer the video part to another MH.
As a desirable requirement, splitting of signaling and media between
different ANs may be possible.
Sec 2, within the description of Terminal mobility you mention IP
subnets. I think you meant IP ANs unless you used in the sense of
NATs.
Other comments :
First paragraph, "...access network can become not available
anymore.." -> access network can become unavailable.
Sec 2, network level mobility bullet, "...to recognize an available
bandwidth" -> to recognize lack of bandwidth
Sec 3, "technologies and difference bandwidth/delay" -> "technologies
and different bandwidth/delay"
Sec 4, "in the same moment" -> "..at the same moment"
Thanks, Serhad
-----Original Message----- From: sipping-bounces@xxxxxxxx
[mailto:sipping-bounces@xxxxxxxx] On Behalf Of Saverio Niccolini
Sent: Monday, November 24, 2008 8:56 AM To: sipping@xxxxxxxx
Subject: Re: draft-niccolini-sipping-siphandover-05.txt
Dear all,
among the contributors it was discussed that is actually good to
keep the discussion on the mailing list to gather more general
feedback from everybody and more specific one from the people
willing to actively contribute (people like John Elwell,
Zaheduzzaman Sarker and Hassnaa Moustafa demonstrated interest in
this).
So far we have received the following comments, that we are going
to take care of: -- we should state clearly that terminal mobility
has a requirement to be able to support a "make before break" style
of handover even if it possible to use the solution to also do
"break before make", we should be able to formalize what "make
before break" means at protocol level in a clear way to be able to
write requirements for this -- provide more detailed summary of
work in 3GPP to avoid people to look for and read the related 3GPP
documents -- add an additional requirement that is to minimize the
packet loss (or avoid it at all) and the reordering problem during
an handover
What is still unclear: -- we should look at SIP-based terminal
mobility requirement in general with vertical handover being one
use case --> what are the requirements missing in the draft for
looking at SIP-based terminal mobility requirement in general?
Any comments?
Thanks, Saverio
============================================================ Dr.
Saverio Niccolini Manager, Real-Time Communications Group NEC
Laboratories Europe, Network Research Division Kurfuerstenanlage
36, D-69115 Heidelberg Tel. +49 (0)6221 4342-118 Fax: +49
(0)6221 4342-155 e-mail: saverio.niccolini@xxxxxxxxxxxx <-- !!!
NEW ADDRESS !!!
============================================================ NEC
Europe Limited Registered Office: NEC House, 1 Victoria Road,
London W3 6BL Registered in England 2832014
-----Original Message----- From: sipping-bounces@xxxxxxxx
[mailto:sipping-bounces@xxxxxxxx] On Behalf Of Ashutosh Dutta
Sent: Monday, November 24, 2008 2:57 PM To: Anton Tveretin Cc:
sipping@xxxxxxxx Subject: Re:
draft-niccolini-sipping-siphandover-05.txt
Anton Tveretin wrote:
Dear All, Here is my contribution to the problem list. I hope
this might help. 1. "Hanging TCP" problem: if, at the time of
handover,
there is a TCP
connection between nodes, this might cause sending packets to
the wrong host (i.e. IP address of the MH changes, and previous
IP is assigned to that host). This is also a security hole.
Just a clarification. SIP-based terminal mobility could be most
useful for SIP-based sessions, where media is mostly RTP/UDP
(e.g., Interactive VoIP, RTP-based streaming). There are
additional complexities to support TCP-based application (e.g.,
tcpchat) using SIP-based terminal mobility, although not
impossible. However, SIP-based terminal mobility cannot be used
for applications that are not initiated using SIP signaling
(e.g., FTP, Telnet).
We had a draft discussing this issue a while back in 2001.
http://www.argreenhouse.com/SIP-mobile/sip_draft4.
One can potentially use any MIP-based solution to avoid such
complexity to support terminal mobility for TCP-based
application.
2. (Related to the previous): How can the CH find out that it
is connected to the same host (MH), but with different IP
address, and not something else? This is especially important
for TLS
connections.
3. Handover collision problem, i.e. during handover process,
the CH also changes its IP address. I don't see any solution
for this problem. IMO the connection will be lost.
Simultaneous mobility problem is a good one. There is currently a
draft in MEXT discussing this specific issue in addition to few
papers that have addressed this specific issue. It also lists
some of the solutions. We should add this one as a requirement.
http://tools.ietf.org/html/draft-wong-mext-simultaneous-ps-01
Since we are discussing the requirement draft, we should not be
discussing possible solutions yet.
Thanks Ashutosh
Sincerely yours.
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--
*******************************************************************
Stefano Salsano
Dipartimento Ingegneria Elettronica
Universita' di Roma "Tor Vergata"
Via del Politecnico, 1 - 00133 Roma - ITALY
http://netgroup.uniroma2.it/Stefano_Salsano/
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Office : (Tel.) +39 06 72597770 (Fax.) +39 06 72597435
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