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

["Hesham Soliman (ERA)" <[e-mail]>]

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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