ROAM Design

Figure: Upon changing its address from $R$ to $R'$, a receiver needs only to update its trigger. This change is transparent to the sender.

In this section, we describe ROAM, which provides an end-to-end architecture for Internet host mobility on top of $i3$.

Achieving host mobility using $i3$is straightforward. A mobile host that changes its address from $R$ to $R'$ as a result of moving from one subnetwork to another can preserve end-to-end connectivity by simply updating each of its existing triggers from $(id, R)$ to $(id, R')$, as shown in Figure 3.

ROAM exhibits the following desirable properties:

Efficient routing. ROAM takes into account the mobility pattern of the end-hosts to improve $i3$'s ability to provide low latency stretch (see Section 4.1).

Efficient handoff. ROAM implements fast handoff and multicast-based handoff to reduce packet loss during handoffs (see Section 4.2).

Fault tolerance. Since triggers are periodically refreshed, ROAM recovers gracefully from server failure. If a server fails, the triggers stored at that server are inserted at another server the next time they are refreshed.³ Section 7.1.4 evaluates ROAM's robustness through simulation.

Simultaneous mobility. The sending and receiving hosts can move simultaneously while $i3$serves as an anchor point for the two sides of the communication channel.

Location privacy. ROAM allows end-hosts the flexibility of choosing triggers to not reveal any location information. Section 4.3 discusses the tradeoffs between location privacy and routing efficiency.

Personal/session mobility. Unlike Mobile IP, ROAM allows a user to redirect a new session or migrate an active one from one application or device to another when a better choice becomes available (see Section 4.4).

Next, we describe efficient routing, efficient handoff, location privacy, and personal/session mobility in more detail. The key to achieving these properties is the ability of end-hosts to control the location of a trigger in $i3$. Since fault tolerance and simultaneous mobility follow directly from $i3$'s properties, we do not discuss them here.