Natural selection is testing this #Altcoins season 🌊. In this cycle, many are once again diving deep into research, searching for “the best” after Bitcoin & @Joseinnewworld makes waves 124 #NFTs — Wow, a strong signal for those still weighing their moves. #eCash $XEC #CryptoNews pic.twitter.com/GB3dRvH01U
— NFToa (@nftoa_) September 26, 2025
The rapid development of communication and information technology, especially in the field of wireless communication, means that the need for mobile is increasing day by day. While for every network transfer, there is a change in the IP (internet protocol) number. Thus, a technology is needed that can perform the function of not changing the IP address even though it moves from one network to another. The technology that can perform this function is Mobile IP. Where in this technology when a host moves from one network to another, there is no change in IP. In other words, a host will have a fixed address even though it always moves networks. The increasing number of hosts on a computer network results in an increasing need for IP so that to meet this need, a larger IP allocation is needed. For this reason, in this Mobile IP technology there are two models, namely for mobile IP version 4 and mobile IP version 6. Mobile IP version 6 supports faster connections because it is supported by tunneling technology. Namely bidirectional tunnel and route optimization. With this Mobile IP, it is expected to make it easier to set up IP.
1. Understanding Mobile IP
In the wired Internet, it is established that an IP address uniquely identifies a node's point of attachment to the Internet. Therefore, a node must be located on the network identified by its IP address in order to receive datagrams addressed to it; otherwise, datagrams addressed to the node will not be delivered. For a node to change its point of attachment without losing its ability to communicate, one of two mechanisms must be in place:
- Nodes must change their IP addresses when they change their connection point to the internet.
- Certain host routes must be propagated throughout the internet provider company.
Both of these alternatives are often unacceptable. The first alternative makes it impossible for a node to maintain a transport layer connection and a higher layer connection when the node changes its location. The second alternative is clearly problematic. This requires a new mechanism to accommodate node mobility across the Internet that allows nodes to change their attachment to the Internet without changing their IP addresses.
The features of this mobile IP include:
- Support Hosts who move around.
- No geographical limitations
- No modifications to IP numbers
- Network security is guaranteed.
2. Official Mobile IP Standards
Mobile IP was approved by the Internet Engineering Steering Group (IESG) in June 1996 and published as a Proposed Standard in November 1996. The Proposed Standard was the first significant step in the evolution of a protocol from an Internet draft to a full Internet standard.
Mobile IP was created by IP Routing for wireless/mobile hosts (mobile IP) which is a collaboration with the IETF which was formed in June 1992. The standard documents for mobile IP follow the RFCs, including:
- RFC 2002, which is the protocol of mobile IP itself.
- RFCs 2003, 2004, and 1701, each of which defines the types of tunneling used in mobile IP.
- RFC 2005, which describes the applicability of mobile IP.
RFC 2006, which describes the mobile IP Management Information Base (MIB). The Mobile IP MIB is a set of variables in a node that implements mobile IP that can be checked or configured by a station manager using the Simple Network Management Protocol version 2 (SNMPv2) contained in RFC 1905.
3. Reasons for Using Mobile IP
The IP address of a host consists of two parts: the higher bits of the address determine the network on which the host is located and the lower bits determine the host number.
IP selects the next hop by determining the network information from the destination IP address of the packet. In contrast, higher-level layers such as TCP manage connection information composed of quadruplets containing the endpoint IP address and its port number. So, when trying to be mobile on the Internet under the existing protocol suite, we face two interrelated problems: a mobile node must change its IP address when moving to another network, so that data packets can be delivered to their destination correctly. In order to remain connected to the Internet, a mobile node must have a fixed IP address. Changing the IP address will cause the connection to be disrupted and eventually dropped.
Mobile IP is designed to solve this problem by allowing each mobile node to have two IP addresses and to properly manage the binding process between the two addresses. One of the IP addresses is a permanent home address that is on the home network and is used for endpoint communication, and the other is a temporary care-of address that indicates the current location of the host. The main purpose of mobile IP is to make mobility easier to recognize to higher level protocols such as TCP and to minimize changes to existing internet infrastructure.
Mengenal Mobile IPv4 (MIPv4)
Mobile IP is intended to allow nodes to move from one IP subnet to another. This is suitable for both homogeneous and heterogeneous media mobility. Mobile IP facilitates the movement of nodes from one Ethernet segment to another as well as the movement of nodes from one Ethernet segment to a wireless LAN, as long as the IP address remains the same after the movement.
Mobile IP is likened to the logic of the post office that occurs in everyday life. Here there are several different entities, namely the own post-office or the old post office in mobile IP is known as the Home Network where to support the work of the home network, there is also a router known as the Home Agent. The post-office is then referred to as the new post-office or the new post-office to be visited, in this mobile IP with the Foreign Network and the same as in the home network, in the foreign network there is also a router known as the Foreign Agent.
Where the host that always moves from network to network is known as Mobile Host. Where this host will register with the home agent when in a new location or Foreign Network. While the Home Agent in the home network will also control the package for the mobile host, and forward it to the foreign agent, which is then sent to the mobile host. For more details will be explained in the architecture and how Mobile IP works in the next sub-chapter.
1. Architecture Mobile IPv4
Mobile IP introduces several new functional entities, namely:
a. Mobile Host A host or router that changes its point of attachment from one network or subnetwork to another. A mobile node can change its IP address. It can continue communication with other Internet nodes at multiple locations using a constant IP address, assuming link layer connectivity to the point of attachment is available.
b. Corresponding Host is the opposing host of the mobile host when it is on the next network, namely the foreign network which contains the Home Agent.
c. Care of Address The address owned by the Mobile Host when it is on the destination network, namely a foreign network which contains a Foreign Agent.
d. Home Agent A router on the home mobile node network that opens a datagram path for delivery to the mobile node when it is away from home and maintains the current location information for the mobile node.
e. Foreign Agent A router on the visited mobile node's network provides routing services to the mobile node while it is registered. The foreign agent closes the path and sends datagrams to the mobile node to which the path has been opened by the mobile node's home agent. For datagrams sent by the mobile node, the foreign agent can serve as the default router for the registered mobile node.
A mobile node is assigned a long IP address on a home network. This home address is administered in the same way as a fixed IP address provided by a fixed host. When away from the home network, a care-of address is associated with the mobile node and reflects the mobile node's current point of attachment.
Gambar 8. Terminologi Mobile IPv4
Information :
- M : Mobile host
- C: Correspondent Host
- H : Home Agent
- F : Foreign Agent.
2. Operations on Mobile IPv4
In general, the operational steps in MIPv4 are as follows:
a. Mobility Agent (home agent and foreign agent) Announces its presence through Agent Advertisement messages. A mobile node can optionally request an Agent Advertisement message from a mobility agent located in the local area through an Agent Solicitation message.
Figure 9. Agent Advertisement
Information :
- Type = 16
- Length = 6+4 *COAs
- R : registration required
- B : busy, no more registrations
- H : home agent
- F : foreign agent
- M : minimal encapsulations
- G :GRE encapsulations
- R = 0, ignored (former Van Jacobson compression)
- T : FA support reverse tunneling
- Reserved : = 0, ignored.
b. Mobile Node receives this Agent Advertisement and determines whether it is on the home network or on a foreign network.
c. When the mobile node detects that it is on its network, it operates without mobility service. If the mobile node returns to its home network and has been registered elsewhere, the mobile node will be re-registered by its home agent through exchanging Registration Request and Request Reply messages with it.
Figure 10. Registration Process
Gambar 11. Registration Request
Information :
- S : simultaneous bindings
- B : broadcast datagram
- D : decapsulations by MN
- M : minimal encapsulations
- G : GRE encapsulations r : =0, ignored
- T : reverse tunneling requested x : =0, ignored.
Gambar 12. Registration Replay
Information :
Example codes :
Registration succesful
0 registration accepted
1 registration accepted, but simultaneous mobility bindings unsuported
Registration denied by FA
65 administravely prohibited
66 insufficient resources
67 mobile node failed authentication
68 home agent failed authentication
69 requested Lifetime too long Registration denies by HA
129 administratively prohibited
131 mobile node failes authentication
133 registration Identification mismatch
135 too many simultaneous mobility binding
e. When a mobile node detects that it has moved to a foreign network, it will be assigned a care-of address on the foreign network. The care-of address can be determined either from a foreign agent advertisement (a foreign agent care-of address) or by an external assignment mechanism such as DHCP (a co-located care-of address).
f. A mobile node operating at a location far from its home agent will have its new care-of address registered with its home agent by exchanging a Registration Request and Registration Reply message with it, possibly through a foreign agent.
g. Datagrams sent to the mobile node home address will be held by the home agent, a path is created by the home agent to the mobile node care of address, received at the end of the channel (either at the foreign agent or the mobile node itself) and finally delivered to the mobile node.
h. In the opposite direction, datagrams sent by a mobile node will generally be delivered to their destination using standard IP routing mechanisms, without having to go through the home agent.
When away from home, Mobile IP uses a path-making protocol to hide the mobile node's home address from router interference between the home network and its current location. The delivery path terminates at the mobile node's care-of address. A care-of address must be an address to which datagrams can be delivered via conventional IP routing. In a care-of address, the original datagram is removed from the delivery path and delivered to the mobile IPv4 address, this is called Triangular Routing.
Figure 13. Triangular Routing
Information :
- Corresp. Node C initializes with the Mobile Node and sends a packet to the MN home address.
- The Home Agent receives the packet and forwards it to the mobile node.
- The mobile node replies directly to Corresp. Node C.
General Mobile IPv6
The design of mobile IPv6 takes advantage of both the experience in the development of mobile IPv6 and the opportunities provided by IPv6. Therefore, mobile IPv6 shares some characteristics with mobile IPv4, but integrates with IPv6 and offers several enhancements.
1. Mobile IPv6 protocol
Mobile IPv6 defines a new IPv6 protocol, a set of messages and processes used to establish relationships between adjacent nodes. The protocol is Neighbor Discovery. Neighbor discovery is a replacement for ARP, ICMP Router Discovery and ICMP redirect used in IPv4 with some new functionality.
The processes carried out by Neighbor Discovery are as follows:
- Router Discovery. The process by which a host searches for routers on a link.
- Prefix Discovery. The process by which hosts search network prefixes for local destination links.
- Parameter Discovery. The process by which hosts discover additional operating parameters, including the default MTU and hop limit for outgoing packets.
- Address autoconfiguration. The process of automatically configuring IP addresses for interfaces.
- Neighbor Unreachability detection. The process by which a node ensures that a neighboring node's IPv6 layer is no longer accepting packets.
- Duplicate Address Detection. The process by which a node ensures that an address to be used has not been used by a neighbor.
2. Operasi Mobile IPv6
Mobile nodes are always expected to be addressed at their home address, whether they are on their home link or far from home. The home address is the IP address assigned to the mobile node with its home subnet prefix on the home link.
While the mobile node is at home, packets are addressed to the home link. While the mobile node is at home, packets are addressed to its home address and then routed to the mobile node link using a routing mechanism.
While the mobile node is attached to several foreign links far from home, it can also be addressed to one or more care-of addresses, which are IP addresses associated with the mobile node that have a subnet prefix from a particular foreign link. The mobile node can obtain its care-of address through conventional IPv6 mechanisms such as stateless or statefull autoconfiguration. As long as the mobile node remains at this location, packets are addressed to this care-of address and then routed to the mobile node. The mobile node can also receive packets from several care-of addresses, such as when it is moving but still reachable on the previous link.
The relationship between a mobile node's home address and care-of address is known as "Correspondent node" for the mobile node. While away from home, a mobile node registers its care-of address primarily with a router on its home link, requesting this router to act as a "home agent" for the mobile node. The mobile node establishes the binding registration by sending a "Binding Update" message to the home agent. The home agent replies to the mobile node by returning a "Binding Acknowledgement" message.
There are two possible communication modes between the mobile node and the correspondent node, namely:
a. The first mode is bidirectional tunneling
This mode does not require support for correspondent mode and is even available if the mobile node does not register its current bindings with the correspondent node. Packets from the correspondent node are routed to the home agent and then tunneled to the mobile node. Packets to the correspondent node are tunneled from the mobile node to the home agent ("reverse tunneled") and then normally from the home network to the correspondent node. In this mode, the home agent uses a Neighbor Discovery proxy to intercept some IPv6 packets addressed to the mobile node's home address on the home link. Each intercepted packet is then tunneled to the mobile node's primary care-of address. This tunneling uses IPv6 encapsulation.
Figure 14. From Correspondent Node to Mobile Node
b. The second mode is route optimization
This mode requires the mobile node to register its bindings to the correspondent node. Packets from the corresponding node can be routed directly to the care-of address of the mobile node. When sending a packet to some destination, the correspondent node checks for any pending bindings for the packet's destination address. If a pending binding for the destination address is found, the node uses a new type of IPv6 routing header to route the mobile packet to the mobile node with the care-of address marked on this binding. Routing packets directly to the mobile node's care-of address allows the use of the shortest communication path. It also eliminates congestion on the mobile node's home agent and home link. In addition, the impact of possible home agent or network failures on the path is reduced. When routing packets directly to the mobile node, the correspondent node adjusts the destination address in the IPv6 header to the care-of address of the mobile node. A new type of IPv6 routing header is also added to the packet to carry it to the specified home address. Similarly, the mobile node adjusts the source address in the IPv6 packet header to its new care-of address. The mobile node adds a new IPv6 destination "home address" option to bring it to its home address. The inclusion of home addresses in these packets makes the use of care-of addresses transparent above the network layer.
Figure 9. From Correspondent Node to Mobile Node
Comparison of Mobile IPv4 with Mobile IPv6
Although Mobile IPv6 shares some features with Mobile IPv4, there are some key differences between the two. These differences include:
- In mobile IPv6 there is no need to employ a special router as a "foreign agent" as in mobile IPv4. Mobile IPv6 operates in multiple locations without the need for a special local router.
- Mobile IPv6 supports route optimization as a fundamental part of the protocol, rather than an extension of the standard.
- Mobile IPv6 route optimization can operate securely even without pre-anggered security associations. It is expected that such route optimization can be performed on a global scale between all mobile nodes and correspondent nodes.
- Most packets delivered to mobile nodes while away from home in mobile IPv6 are sent using IPv6 routing headers rather than IP encapsulation, reducing the workload in mobile IPv4.
- Mobile IPv6 is separated from some parts of the link layer, as used in Neighbor Discovery. This also increases the robustness of the protocol.
- The use of IPv6 encapsulation removes the need in Mobile IPv6 to manage "tunnel soft state".
- The dynamic home agent address discovery mechanism in Mobile IPv6 returns a single reply to the mobile node. The directed broadcast approach is used in IPv4 to return separate replies to each home agent.
Here's how Mobile IP works
- The home agent and foreign agent periodically send agent advertisements which are received by all nodes on the network.
- The mobile node checks the agent advertisement and checks the connection, whether the mobile node is on the home network or a foreign network.
- The mobile node connects to the foreign network and then gets care of address from the advertisement agent.
- The mobile node registers its care of address with its home agent. The mobile node sends a request to the foreign agent to request a connection service to the network.
- The home agent or other routers provide the home address to the mobile node and then assemble packets addressed to the home address of the mobile node. The home agent sends packets to the home address of the mobile node and to the care of address of the mobile node through the tunnel.
- The foreign agent removes the original packet from the tunnel and delivers the original packet to the mobile node.
- Next, the mobile node can send packets to the destination address without going through the tunneling process. At this time, the foreign agent acts as a router.
Or more broadly it can be explained that Mobile IP can work through three major stages, including:
- Agent Discovery
- Registration
- Tunneling
1. Agent Discovery
During the agent discovery phase, the Home Agent and Foreign Agent advertise their services on the network using ICMP Router Discovery Protocol (IRDP). The Mobile Node listens to determine whether it is connected to the home network or a foreign network. IRDP carries the Mobile IP extension that determines whether the agent is a Home Agent, a Foreign Agent, or both; its address maintenance, the type of services to be provided such as reverse tunneling and generic routing encapsulation (GRE); and allows a lifetime registration or moving period for the incoming Mobile Node. Instead of waiting for the IRDP agent, the Mobile Node can send an agent request. This request forces any agent on the channel to send an agent advertisement as soon as possible. If the Mobile Node determines that it is connected to a foreign network, it requires address maintenance. There are two types of address maintenance:
- Care-of address acquired from a Foreign Agent
- Colocated care-of address.
Foreign Agent address maintenance is the IP address of a Foreign Agent that has an interface relationship with a foreign network visited by a Mobile Node. A Mobile Node that obtains this type can share the address with other Mobile Nodes. Collocated address maintenance displays the current position of the Mobile Node on the external network and can be used by only one Mobile Node at a time. When a Mobile Node receives a Foreign Agent advertisement and detects that it has moved out of its home network, it initiates registration.
2. Registration
The Mobile Node is provided with the IP address and mobile connection security (including a shared key) from the Home Agent. In addition, the Mobile Node is provided with the home IP address, or other user identifier, such as the Network Access Identifier. The Mobile Node uses this information along with information it has learned from the Foreign Agent to form a Mobile IP registration request. It adds the registration request to a queue list and sends the registration request to the Home Agent either through the Foreign Agent or directly if it uses collocated address maintenance and does not require registration through the Foreign Agent. If the registration request is sent through the Foreign Agent, the Foreign Agent checks its validity, which includes checking that the request lifetime has not been reached, that the requested encapsulation channel is available, and that the reverse channel is supported. If the registration is valid, the Foreign Agent adds the Mobile Node to the queue list before forwarding it to the Home Agent. If the registration request is invalid, the Foreign Agent sends a reply with an appropriate error code to the Mobile Node.
The Home Agent checks the validity of the registration request, including the authenticity of the Mobile Node. If the registration request is valid, the Home Agent creates a mobility binding (an association of the Mobile Node with its address custodian), a channel to the address custodian, and an inbound route to send packets to the home address through the channel. The Home Agent then sends a reply to the Mobile Node through the Foreign Agent (if the registration request was received through the Foreign Agent) or directly to the Mobile Node. If the registration request is invalid, the Home Agent rejects the request by sending a reply with an appropriate error code. The Foreign Agent checks the validity of the reply, including ensuring that the corresponding registration request is in the queue list. If the reply is valid, the Foreign Agent adds the Mobile Node to the visitor list, establishes a channel to the Home Agent, and creates an inbound route to send packets to the home address. It then sends a registration reply to the Mobile Node.
Finally, the Mobile Node checks the validity of the reply, including ensuring that the corresponding request is in the queue list as well as the proper authenticity of the Home Agent. If the reply is invalid, the Mobile Node rejects the reply. If the valid reply indicates that the registration was accepted, the Mobile Node confirms that the mobility agent is aware of its existence. In the case of collocated address maintenance, it adds a channel to the Home Agent. Next, it sends the packet to the Foreign Agent. The Mobile Node re-registers before its registration lifetime expires. The Home Agent and the Foreign Agent update their mobility connections and visitor entries, respectively, during re-registration. In cases where registration is rejected, the Mobile Node makes the necessary adjustments and attempts to register again. For example, if registration is rejected due to a time difference and the Home Agent sends its timestamp for synchronization, the Mobile Node adjusts its timestamp for future registration requests. Thus, successful Mobile IP registration establishes a routing mechanism to transport packets to and from the Mobile Node while in motion.
3. Tunneling
The Mobile Node sends packets using its home IP address, effectively maintaining its presence on the home network. Even when the Mobile Node moves to a foreign network, its movement is transparent to the corresponding node. Packets addressed to the Mobile Node are routed to its home network, where the Home Agent now captures and forwards them to the care-of address of the Mobile Node. Tunneling has two main functions: encapsulation of the data packets to reach the endpoints of the tunnel, and decapsulation once the packets are delivered to the endpoints. The default tunneling mode is Encapsulate IP within Encapsulate IP. Optionally, GRE and minimal encapsulation within IP can be used. Typically, the Mobile Node sends packets to the Foreign Agent, which routes them to their final destination, the Correspondent Node, as shown in the following figure.
Figure 3.10. Package Delivery
However, this datapath is topologically incorrect because it does not reflect the actual IP network source for the data – rather, it reflects the Mobile Node’s home network. Because the packet shows the home network as its source on the outside network, the access control list on the router on the inside network called ingress filtering drops the packet rather than forwarding it. A feature called reverse tunneling solves this problem by having the Foreign Agent tunnel packets back to the Home Agent when it receives them from the Mobile Node. See Figure 3.11.
Figure 3.11. Reserve Tunnel
Or the package delivery process can be described diagrammatically as follows,
Figure 3.12. Package Delivery Process
4. Mobile IP Application
- On the internet network
- On WIFI
- On cellular network
- GPRS.
5. Conclusion
Mobile IP is a solution for the network layer in carrying out mobility or movement and it is suggested that other mechanisms that are outside the scope of Mobile IP can help to provide a more complete movement solution around it. Unlike other technologies, Mobile IP allows nodes to move on the same media or not.
The mobile node itself defines three important elements that work together to solve this problem, including: mobile node, foreign agent, and home agent.
We see that when a mobile node is in its own network, which can act as a host or router, it does not require additional functions from Mobile IP. For mobile nodes connected to a foreign agent, the mobile node uses tunneling to send packets to the mobile node. The tunnel aims to carry the original packet intended for the mobile node through the care -- of address that has been previously encapsulated in the home agent, then after arriving at the foreign agent the packet will be extracted and forwarded to the destination mobile node. Where when this tunneling process occurs, the tunnel requires the mobile node to report the current care -- of address to the home agent. This process is called registration.
6. QUESTIONS
- What is meant by mobile IP and what are the conditions for using mobile IP?
- How does the mobile IP process occur?
- Difference between Mobile IPv4 and Mobile IPv6?
- How does mobile IP work?
- Name and explain what components are used in mobile IP?