RE: [Seamoby] Revised Section 4 of CAR issues draft

["Govind Krishnamurthi" <[e-mail]>]

Hello Hesham,
Thanks for your comments.

Govind.
>
>
>I'm happy with the new modifications.
>
>Hesham
>
>   > -----Original Message-----
>   > From: Hemant Chaskar [mailto:[e-mail]]
>   > Sent: Wednesday, January 16, 2002 3:57 AM
>   > To: [e-mail]
>   > Subject: [Seamoby] Revised Section 4 of CAR issues draft
>   >
>   >
>   > Hi,
>   >
>   > Here is the revised text for Section 4 of CAR discovery
>   > issues draft. The
>   > text has been finetuned. I hope that it is now clear
>   > enough. If there are no
>   > more concerns on Section 4, we can submit the problem
>   > statement draft with
>   > this text for Section 4, to IESG.
>   >
>   > Hemant
>   >
>   > -------------------------------snip-------------------------
>   > ---------
>   >
>   > 4. APPROACHES TO CANDIDATE ACCESS ROUTER DISCOVERY
>   >
>   > In this section, we describe three approaches to CAR discovery,
>   > namely the Anticipated CAR Discovery (discovery prior to
>   > handoff), Dynamic
>   > CAR
>   > Discovery (discovery at the time of handoff) and Hybrid CAR
>   > Discovery.
>   >
>   > 4.1 Anticipated CAR Discovery
>   >
>   > In Anticpated CAR Discovery, CAR discovery is performed at some
>   > point prior to the MN performing a handoff. This can be performed in
>   > a number of ways and with various entities particpating in
>   > the process.
>   > One illustrative method for Anticipated CAR Discovery is
>   > given below.
>   >
>   > In this method, an AR currently serving an MN can identify
>   > a set of CARs for
>   > the MN's handoff, at some point prior to handoff. This
>   > information is then
>   > available at the time of handoff as input to the TAR
>   > Selection Algorithm.
>   > Another
>   > input to the TAR Selection Algorithm may be the preferences
>   > expressed by the
>   > MN
>   > prior to the handoff, or preferences enforced by the
>   > administrative control.
>   > At
>   > the time of handoff, it may only be required to provide
>   > input to the TAR
>   > Selection
>   > Algorithm about the reachability of neighboring ARs from
>   > the MN. This
>   > reachability
>   > information is usually in the form of the identity of the
>   > AP to which the MN
>   > can listen to, and the current AR has to resolve this AP
>   > identity to the
>   > GAAR's IP address.
>   >
>   > The advantage of Anticipated CAR Discovery is that the
>   > handoff can be
>   > executed
>   > quickly because much of the information needed by the TAR Selection
>   > Algorithm
>   > is collected in advance of handoff.
>   >
>   > Anticipated CAR Discovery is depicted in Figure 1.
>   >
>   >
>   >
>   > -----------------------------------------------------------------
>   >    |                     All routers
>   >          |
>   >    |                          |  Discovery of ARs whose
>   > coverage     |
>   >    |                          |  areas overlap (GAARs) with
>   > that of  |
>   >    |                          v  the current AR
>   >          |
>   >    |           Local map of GAARs at current AR
>   >          |
>   >    |                          |
>   >          |
>   >    |                          |   Capability identification
>   >          |
>   >    |                          v
>   >          |
>   >    |      CARs for MN's handoff identified at current AR
>   >          |
>   >    |                          |
>   >          |
>   >
>   > --------------------------|--------------------------------------
>   >                               |
>   >                               |   Predefined preferences of the MN
>   >          AR Reachability      |   and administrative preferences
>   >            for the MN         |
>   >                 |             |             |
>   >                 v             v             v
>   >              TAR Selection Algorithm executed at the time of
>   >              handoff to determine unique TAR for MN's handoff
>   >
>   >               Figure 1: Anticipated CAR Discovery
>   >
>   >
>   > 4.2 Dynamic CAR Discovery
>   >
>   > In Dyanmic CAR discovery, CAR discovery is performed at the
>   > time the MN is
>   > about to undergo handoff. Again, this can be performed in a
>   > number of ways
>   > and with various entities particpating in the process. One
>   > illustrative
>   > method
>   > for Dynamic CAR Discovery is given below.
>   >
>   > According to this method, an MN dynamically obtains
>   > information about the
>   > available
>   > ARs for handoff, along with their capabilities. This is
>   > done after the
>   > handoff trigger
>   > is generated. When the MN detects an AR that has
>   > capabilities matching its
>   > preferences,
>   > the MN may notify the currently serving AR to perform a
>   > handoff to this AR
>   > using one or
>   > more of the seamless handoff protocols. The advantage of
>   > this method is that
>   > the MN
>   > has fine-grained control over the TAR selection. However,
>   > this method
>   > generates more
>   > radio traffic during the CAR discovery step. This is
>   > because capability
>   > information is
>   > sent to the MN over the air. Also, it is required that the
>   > MN can receive
>   > IP-level
>   > capability information from the GAARs and negotiate
>   > requirements with the
>   > GAARs, while
>   > still being connected to the current AR.
>   >
>   >
>   > Dynamic CAR Discovery is shown in Figure 2.
>   >
>   >
>   >
>   > --------------------------------------------------------------
>   >       |
>   >          |
>   >       |                 GAARs identified at handoff time
>   >          |
>   >       |                           |
>   >          |
>   >       |                           | Capability
>   > identification        |
>   >       |                           |
>   >          |
>   >       |                           v
>   >          |
>   >       |            CARs for MN's handoff identified
>   >          |
>   >       |                           |
>   >          |
>   >
>   > ---------------------------|----------------------------------
>   >                                   |
>   >                                   | TAR selection at the
>   >                                   |    time of handoff
>   >                                   v
>   >                         Unique TAR identity
>   >
>   >                   Figure 2: Dynamic CAR Discovery
>   >
>   >
>   > 4.3 Hybrid CAR Discovery
>   >
>   > In practice, a hybrid of the Anticipated and Dynamic CAR discovery
>   > approaches
>   > may be used. For example, in the hybrid approach, the GAAR
>   > discovery and
>   > much
>   > of the capability identification may be performed prior to
>   > handover, while
>   > the
>   > remaining capability identification may happen during the
>   > handover process.
>   > But,
>   > there are other alternatives too.
>   >
>   > _________________________________________________________________
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