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The ns Manual (formerly ns Notes and Documentation)1 - NM Lab at ...

The ns Manual (formerly ns Notes and Documentation)1 - NM Lab at ...

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target_target_encapsul<strong>at</strong>orreg_agent_MH IP address01decapsul<strong>at</strong>or_Hierarchicalclassifierslevel nown IP address255defaulttarget_entry_level 2level 1defaulttarget_Rtg Agenttarget_uptarget_LLdowntarget_ChannelFigure 16.4: Schem<strong>at</strong>ic of a Wireless MobileIP BaseSt<strong>at</strong>ion Nodemodel of a SRNode.<strong>The</strong> MobileNode/MIPBS node routinely broadcasts beacon or advertisement messages out to MHs. A solicit<strong>at</strong>ion from amobilenode gener<strong>at</strong>es an ad th<strong>at</strong> is send directly to the requesting MH. <strong>The</strong> address of the base-st<strong>at</strong>ion sending out beacon isheard by MH <strong>and</strong> is used as the COA (care-of-address) of the MH. Thus as the MH moves from its n<strong>at</strong>ive to foreign domai<strong>ns</strong>,its COA changes. Upon receiving reg_request (as reply to ads) from a mobilehost the base-st<strong>at</strong>ion checks to see if it is theHA for the MH. If not, it sets up its decapsul<strong>at</strong>or <strong>and</strong> forwards the reg_request towards the HA of the MH.In case the base-st<strong>at</strong>ion is the HA for the requesting MH but the COA doesnot m<strong>at</strong>ch its own, it sets up an encapsul<strong>at</strong>or <strong>and</strong>sends reg-request-reply back to the COA (address of the FA) who has forwarded the reg_request to it. so now all packetsdestined to the MH reaching the HA would be tunneled through the encapsul<strong>at</strong>or which encapsul<strong>at</strong>es the IP pkthdr with aIPinIP hdr, now destined to the COA i<strong>ns</strong>tead of MH. <strong>The</strong> FA’s decapsul<strong>at</strong>or recives this packet, removes the encapsul<strong>at</strong>ion164

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