Integrating Mobile IP with
Ad Hoc Networks
作者：Yu-Chee Tseng,Chia-Ching Shen(nctu)
Wen-Tsuen Chen(nthu)
報告者：王生見
1
content


1. Abstract
2. Mobile IP and MANETS






Related work in internet computing
3. Network architecture
4. Communication scenarios
5. Intra-Manet and inter-Manet routing scenarios
6. Broadcast routing scenario
7. Integration and implementation







TTL in IP packets
Agent advertisement
Agent solicitation
ARP
Broadcast
Destination address and TTL
Configuration of IEEE 802.11b NICs
2
Abstract




Ubiquitous computing has added a new
feature, mobility, to the world of computing
and communications.
Mobile IP and mobile ad-hoc network(MAnet)
Application
Integrating
3
Mobile IP and Manet
Figure1 mobile IP transmission scenario.
4
Related work in internet computing(1/5)


Mobile IP was originally designed to support
macro mobileity
Researchers have developed two other
internet protocols

Cellular IP and the handoff-aware wireless access
internet infrastructure (Hawaii)
5
Related work in internet computing(2/5)

Cellular IP



Uses a hierarchical approach to minimize
registrations to home agents as a mobile host
roaming around.
A foreign agent can provide services to multiple
base station.
As long as the same foreign agent’s base stations
cover the mobile host, no reregistration is required,
thereby significantly reducing handoff delay.
6
名詞解釋(home agents and foreign agent)

Home Agent：


主要是傳遞資訊給從這個Home network離開的
Mobile Nodes，並且維護mobile node目前的位置
資訊。
Foreign Agent：

與Home Agent合作，完整地去傳遞資訊給從home
network離開的mobile node。
7
Related work in internet computing(3/5)

Hawaii protocol



Adopts a domain-based approach in which base
stations can be connected as a tree.
It uses specialized path setup schemes that install
host-based forwarding entries in specific routers
to support intradomain routing.
Unlike cellular IP

Hawaii breaks the gateway-foreign-agent tie and thus is
more tolerant to gateway failure, which simplifies
gateway design.
8
Related work in internet computing(4/5)

Other research has addressed using Manet
to provide continuous internet access via
mobile IP.


This includes extending mobile IP to let mobile
hosts use a care-of address even if they are more
than one hop away from a foreign agent.
It also resolves the conflict between mobile IP and
Manets in managing routing tables.
9
名詞解釋(care-of address)

暫時位址（Care-of Address）：

一個表示當Mobile Host不在Home Network時，在
網路上接點的IP位址。
10
Related work in internet computing(5/5)

Compared to earlier efforts that focused on
only a single Manet

Consider the existence of multiple Manets in
same vicinity


With mobile agents and mobile hosts negotiating foreign
agents’ service ranges
Improves Manets flexibility and reduces mobile
agents’ service overhead
11
Network architecture
Figure2 proposed network architecture.
12
Communication scenarios


Our proposed network architecture can
accommodate several different
communication scenarios.
In discussing the possible combinations


We assume that DSDV supports all corresponding
Manet routings
Although any proper routing protocol is applicable
13
名詞解釋(DSDV)
Destination-Sequenced Distance-Vector routing



Destination-Sequenced Distance-Vector Routing
 傳統Bellman-Ford路由選擇演算法所改良而發展出來的，一個以
routing table為基礎的通訊協定。
每一個行動節點必須儲存一個routing table，其中紀錄所有與該節
點可能進行連結的節點及距離(no of hops)
 routing table內的每筆紀錄同時也包含了一個sequence number，這是
用來判斷是否有些路徑比較老舊，以避免routing table的產生。
DSDV基本上和網際網路上的Distance-Vector Routing相同，只是多
了destination sequence number的紀錄
 當網路topology變動比較不頻繁時，並不需要將routing table的所有
資料進行交換，DSDV在每個節點內再加了一個table，用來記錄其
routing table從上次交換至今所更改的部分
 如果更改很多，就進行全部資料的交換，稱為full dump封包，如果
改變很少，就只針對改變部分交換，稱為incremental封包。
14
Intra-Manet and inter-Manet routing
scenarios
15
Inter-Manet routing scenarios in overlaid
Manets
16
Broadcast routing scenario
17
Integration and implementation(1/9)
System architecture of our implementation.
18
Integration and implementation(2/9)

TTL in IP packets


Each IP datagram has a TTL field to control its
internet lifetime.
Routing inside Manets



Implementation is based on the DSDV protocol.
Each host maintains a forwarding table that lists
all available destinations along with the next hop
leading to each destination.
Our prototype made some modifications to the
DSDV protocol

Because Manets can overlap in our architecture.
19
Integration and implementation(3/9)

Agent advertisement


Manets multihop nature requires setting the TTL
to N and decreasing the value by one for each
reboadcast
No rebroadcast is necessary when the TTL is
equal to 0
20
Integration and implementation(4/9)

Agent solicitation



A mobile host can multicast an Agent_Soliciation
message to locate a nearby mobile agent.
The original TTL value should be recorded in the
packet’s payload so that when the gateway
receives the packet.
It can recover its distance to the requesting mobile
host.
21
Integration and implementation(5/9)

ARP


Instead,The host registers the MAC-to IP address
mapping when it receives an
Agent_Advertisement message.
Our network architecture



Enabling the address resolution protocol in foreign
networks to send requests and replies as usual.
Because many nomadic hosts can exist in a Manet
These networks should relay packets of any destination
without using a subnetmask.
22
Integration and implementation(6/9)

Broadcast


When it receives the packet, the gateway
decapsulates it and broadcasts it with a TTL equal
to N.
To prevent broadcast datagram from looping back
to the source host

The broadcast daemon also records broadcast
datagram that it has encapsulated recently.
23
Integration and implementation(7/9)

Destination address and TTL


In view of the fact that the M value that Manets
use should be at least as large as the N
(N->TTL,M->hop)
We recommend setting M equal to 2N



Which guarantees that intra-Manet communication can
always occur directly without encapsulation.
In the worst case, a packet has to travel from a Manet’s
boundary to the gateway
In addition, communication between nearby Manets is
likely to occur without going through mobile IP

Thus the packet will not undergo encapsulation.
24
Integration and implementation(8/9)

In our frame work


The network should function correctly, but some
routes may not exist even if some hosts are
physically neighbors.
Our system is based on Linux Redhat and
implements two daemons, DSDVd and MIPd.
25
Integration and implementation(9/9)

DSDVd



MIPd



periodically multicasts user datagram protocol packets
to help maintain the hosts’ forwarding tables.
System calls write proper entries from the forwarding
table into the kernel’s routing table.
Uses raw sockets for advertisement, encapsulation, and
decapsulation, and it uses normal sockets for
registration.
Unix system calls perform proxy ARP.
In addition, the IP forwarding option at each
mobile hosts must be turned on.
26
報告結束
27