Subject: Re:draft-zhang-mobopts-multicast-dma-00.txt

From: 张 冰怡 <[email-masked]>
Date: Fri, 27 May 2005 08:40:10 +0000

Hi, everyone
  I am the leader of the IP lab of College of Electronics and Information 
Engineering, Beijing Jiaotong University, Beijing 100044, P.R.China. I also 
is a professor and the president of this college. I am glad to contribute 
our draft to this work group and get your help and comment about it.  
First, I give an introduction as follows:
  IPv6 will replace IPv4 gradually in next generation network. Along with 
the development of the wireless IP technologies, more and more people have 
the chance to use wireless equipment accessing network. They will likeing 
this method gradually and being in the habit of accessing wireless network. 
Now there are more than 200 millions of mobile terminal users such as 
mobile phone users in China. Multicast is also a hot point and many 
research have been studyed in it. There have been many multicast route 
protocols, such as DVMRP, MOSPF, MSDP, BGMP and PIM-SSM and so on. 
Unfortunately they are not suit to mobility wireleless network. Supporting 
the mobility and multicast will becomes the inevitable function in next 
generation network. So how to support multicast in mobile IPv6 network is a 
inevitable question. The research in mobile multicast is important and 
necessary. 
However we face the challenge to combine mobile IP with multicast now. 
There are many difficulties during the researches. First the existing IP 
multicast protocols can’t satisfy the needs of node for mobility. Second 
the handoff time of mobile node and the delay used in rejoining in 
multicast group is too long , so it can’t meet the requirement of QoS yet. 
Third the reconstruction of multicast tree caused by the MN handoff in the 
subnet frequently burden the network load. Fourth the existing mobile IP 
multicast protocols have the problems of triangle route and tunnel 
congregation. Above all the optimization design for mobile multicast route 
is very important.
  For conquerving the above problems, we propose a DMA (Dynamic Multicast 
Agent) approach in our draft. The DMA approach is based on the porposed 
MIP-BT (Mobile IP – Bidirectional tunnel) and MIP-RS (Mobile IP – Remote 
Subscription). The MIP-BT use a bi-directional tunnel between a MN with its 
HA to support mulcast in mobile network. The MIP-RS using a multicast 
router in a foreign subnet being visited to support multicast in mobile 
network. These two methods can remain the multicast communications when MNs 
move, but there are some disadvantages about them. To MIP-BT, the triangle 
route problem will add the network cost and the tunnel congreation problem 
can not be solved yet. To MIP-RS, when the handoff occures frequently, the 
rejoin of a MN and the reconstruction of multicast tree will cause too long 
delay and too much cost.
  The DMA conquers the problems in MIP-BT and MIP-RS. The DMA approach 
includes three concepts of MSA (Multicast subnet Agent), DMA and Tunnel 
State. The approach is a combination of MIP-BT and MIP-RS, and it is also a 
hybrid solution of movement based method and distance based method. Such a 
configuration allows MNs to optimize multicast routes, and meanwhile reduce 
the number of handoffs by selecting new multicast agents dynamically. In 
addition to weakening the triangle route problem and diminishing the 
influence of handoff to multicast
  A throughness flow chart of DMA approach, the operation of MSA and 
dynamic multicast agent selection all have been given. The mathmatics 
analysis and simulation in NS are also completed. The results in simulation 
denote that DMA approach can effectively reduces the reconstructing of 
multicast tree and the multicast packages can be forwarded through optimal 
path. The DMA approach can improving the network performance effectively 
and adapt to the mobile IPv6 multicast.
  At last, I hope you can give your generous help and comments to make it 
wonderful. 
Best regards with many thanks 

Hong-Ke Zhang

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