Re: MN behaviors to uplink data packets during a handoff

Hi Jee,

Yes, you described exactly the behavior of the current OPNET model. The 
last known good interface comes into the picture if you have a mobile 
router with multiple roaming interfaces.

- Jay

At 03:07 AM 7/28/2003 +0100, Jee J.Z. wrote:
>Hi Jay,
>
>You are quite right. So after several times try and fail, link layer drops
>the packet.
>
>Another question is in OPNET MIPv4 model, what do "the last known agent" and
>"the last known good interface"  mean? If the MN gets an agent advertisment
>from a new FA, while haven't got any adversitments from its old FA recently,
>then the new FA immediately becomes the last known agent? If so, at this
>time the MN turns to send packets to the new FA without waiting for the
>registration reply, and whether these packets from the unauthorized MN would
>be served depends on whether the new FA would provide service to them?
>
>Many thanks,
>Jee
>
>
>----- Original Message -----
>From: "Jay J Lee" <[email protected]>
>To: "Jee J.Z." <[email protected]>; <[email protected]>
>Sent: Monday, July 28, 2003 2:02 AM
>Subject: Re: [mobile-ip] MN behaviors to uplink data packets during a
>handoff
>
>
> > Hi,
> >
> > I am not an expert on WLAN behavior but I do not think it should hold
> > packets when it looses connectivity with the AP.  The main reason for that
> > is that this type of condition is best handled (at least currently) by the
> > upper layer (most likely transport layer).
> >
> > Let's say you have a TCP session going on and you lost connectivity with
> > your AP for 10 seconds then reconnects.  If the TCP session was terminated
> > then the MAC layer is left with stale data that nobody can process if it
> > were queueing packets (for other than the purpose of limited retries).
>With
> > UDP, you most likely want to receive the most current packets transmitted
> > rather than the ones transmitted 10 seconds ago (real time video anyone?).
> >
> > Again, I am strictly talking about real life devices and their
> > implementations.  I have seen similar proposals (smarter link layers) in
> > several research papers. They were not necessarily related to Mobile IP
>but
> > on improving wireless network performance in general.
> >
> > Good luck, - Jay
> >
> >
> > At 05:03 PM 7/24/2003 +0100, Jee J.Z. wrote:
> > >Hi Jay and all,
> > >
> > >Thank you very much for your reply.
> > >
> > >According to your comments, can I think this way that the disruption to
> > >uplink stream caused by a handoff is largely depending on the link layer
> > >technology and the Mobility Agent (or the administrative domain)
>behaviors?
> > >That is,
> > >
> > >For example, as far as I know, Mobile Nodes in WLAN make sure there is an
> > >Access Point reachable before everytime they send out a frame. In this
>case,
> > >even if the MN loses contact with any AP for some time, IP packets would
>not
> > >be lost, instead, they queue up at the link layer and wait for the link
>data
> > >frame to be sent out. (?)
> > >
> > >When the MN is in registration process with a new FA, it sends out data
> > >packets to the new FA as long as it knows the FA's MAC address. Whether
>to
> > >offer service to the unauthorized MN (at least before the successful
> > >registration reply comes back) depends on the policy the new FA (or the
> > >admistrative domain it belongs to) deploys. If it does not, uplink data
> > >packets are discarded by it during the registration process. If it does
> > >offer service, there could be no uplink data packets lost in WLAN. (?)
> > >
> > >However, it is not WLAN, things might be different. (?)
> > >
> > >Regards,
> > >Jee
> > >
> > >
> > >----- Original Message -----
> > >From: "Jay J Lee" <[email protected]>
> > >To: "Ji Zhang" <[email protected]>; <[email protected]>
> > >Sent: Thursday, July 24, 2003 3:59 AM
> > >Subject: Re: [mobile-ip] [Mobile IP] MN behaviors to uplink data packets
> > >during a handoff
> > >
> > >
> > > > Hi,
> > > >
> > > > I believe these are all implementation time decisions.
> > > >
> > > > For #1, if you are talking about MIPv4, what is happening within the
>IP
> > > > layer should not affect the link layer.  If it still has upper layer
> > > > packets to send out it will continue to do so.  The link/MAC layer
>does
> > >not
> > > > and should not know what happens at the other layers other than the
> > >packets
> > > > it receives from them.  Although with MIPv6 there are proposals for
> > > > inter-layer communications.
> > > >
> > > > For #2, the OPNET MIPv4 simulation model, for example, keeps sending
>the
> > > > data packets to the last known agent (HA or FA) on the last known good
> > > > interface whether it is lost or in the process of registration.  This
> > > > decision was made because once you start queueing packets and managing
> > > > them, the implementation becomes expensive considerably in the
>simulation
> > > > domain as well as for the OSes in the real devices.
> > > >
> > > > Hope this helps, - Jay
> > > >
> > > >
> > > > At 09:37 PM 7/23/2003 +0100, Ji Zhang wrote:
> > > > >Hi all,
> > > > >
> > > > >Could anybody offer me some instructions on the behaviors of a Mobile
> > >Node
> > > > >to
> > > > >uplink (MN-->FA) data packets during a handoff?
> > > > >
> > > > >For example,
> > > > >1. when the MN loses link contact with the old FA (before getting an
> > >agent
> > > > >advertisement), are all uplink data packets stored up at the link
>layer?
> > > > >2. when the MN is aware of agent advertisements are missing, at the
>same
> > > > >time it sends an agent solicitation, should it stop sending data
>packets
> > > > >until
> > > > >it gets an agent advertisement (or even until the registration is
> > > > >successful)?
> > > > >
> > > > >Many thanks,
> > > > >Jee
> > > >
> > > >
> >
> >