# Comparative Analysis of Producer Mobility Management Approaches in Named Data Networking
## 3 Analysis of Scheme Designs
### Map-Me  
Map-Me is composed of two variant schemes: Map-Me Interest Update (Map-Me-IU) and Map-Me Interest Notification (Map-Me-IN). Map-Me-IU sets the path between the old and new PoA so that any incoming consumer interest packet to the old PoA can be forwarded to the new PoA. Map-Me-IN includes an additional complementary scheme to IU, which allows for consumer interests to follow a mobile producer as it moves using a \"scope discovery\" procedure. Map-Me-IN, referred to also as full Map-Me, is based on IN and scope discovery and also deploys the IU technique periodically. An illustrative example of Map-Me operation is shown on Figure 3 and further explained shortly. * **Scheme Operation** Map-Me operations rely on the use of a sequence numbers which is maintained at the producer, initialized to zero, and incremented at each new attachment with a new PoA. Additionally, the sequence numbers are kept in an additional FIB structure within each node, called the temporary FIB buffer (TFIB), to keep a record of the chronological sequence of the mobility of the producer. We describe each of the two schemes next:  
Figure 2: Example of AFIRM operation. 1. Map-Me-IU Triggered by producer mobility, and after the attachment of the producer to a new PoA and face creation, a special interest packet called an interest update (IU) is sent from the new PoA to the old PoA by following the name of the prefix advertised by the producer. The IU contains a tag field (to recognize it is an IU by the routers) and a copy of the current sequence number at the producer. When the routers receive an IU, the action they take depends on comparing the sequence number of the IU with the sequence number in the TFIB associated with the same prefix. If the IU sequence number is greater than the sequence number in the TFIB, then this indicates that the IU is coming from a recent location of the mobile producer. Therefore, the face from which the IU arrived is copied to the FIB, the sequence number is copied in the TFIB, and the IU is further propagated. In the second case, if the IU sequence number is smaller than the sequence number in the TFIB, then this indicates that the IU is coming from an older location of the mobile producer, and consequently, the IU is dropped. In the third case, if the IU sequence number is equal to the sequence number in the TFIB, the IU is also ignored, as this case may occur as a result of a multi-cast forwarding. 2. Map-Me (Map-Me-IN) Triggered by producer mobility, at each new attachment to an edge PoA, a special interest packet called an interest notification (IN) is sent by the producer. The neighboring PoAs keep a trace of this (a breadcrumb). The IN contains a tag field (to specify it is an IN) and a copy of the current sequence number of the producer. INs are used as breadcrumbs for the \"scope discovery\" process. In this scope discovery, when an interest reaches the old PoA and does not find the producer at the associated face, as indicated in the FIB, the interest is tagged with a \"discovery\" flag (hence becoming a scope interest) and gets a copy of the sequence number from the TFIB of the old PoA. Then, the scope interest is broadcasted. Upon receiving a scope interest, a router first compares the sequence number of the received scope interest and that in its TFIB. In case there is no information about the prefix in the TFIB or a smaller or equal sequence exists in its TFIB, the scope interest packet is dropped. Otherwise, if the TFIB has a higher sequence number than the scope interest packet but there is no valid forwarding information in the FIB, then this means that a recent IN has been attached to this PoA, and the scope interest is moving in the same direction of the producer. Then, the sequence number from the TFIB is copied into the scope interest, which is then further broadcast to the one-hop neighbors. This process is repeated until the producer is found. Next, we provide an example of Map-Me operation.