# A Hierarchical Mapping System for Flat Identifier to Locator Resolution Based on Active Degree
## 1 Introduction
LISP [6] uses EID (Endpoint Identifier) representing the endpoint identifier, and RLOC (Routing Locator) representing the locators of routers and network interfaces. LISP-ALT, LISP-CONS, LISP-EMACS, LISP-NERD are the different resolving systems of LISP according to the differences of storing and querying mapping. Although different query and storage mechanisms are designed for resolving EID-to-RLOC, they all require the structure of EID to be aggregatable. TLMS [8] proposes a two-level mapping model based on the PUSH/PULL mechanism, in which the actual mapping information is stored in bottom level and the upper level stores the reachability information of location of the actual mapping item locates. LMS [9] designs a hierarchical mapping system, but its identifier ELOC (identify endpoint) still uses a format similar to IP, which required ELOC is aggregative. For a global locator or local locator, the aggregation requirement for EID or ELOC actually reflects the location information. In fact, for a network which uses the ID/Locator separation mechanism, the identifier should not contain any location information. That is, the identifier should be non-structural or flat. This makes it possible to find the storage position of an identifier-to-locator mapping  
Figure 1: Universal Network (UN): A kind of ID/Locator separation network. only through two ways: flooding or storage based on specific rules advanced which the finder also knows. However, because the number of AIDs, the identifier in the UN, is huge, and one AID can map to any RID in theory, we must store mapping information based on specific rules advanced. In addition, mobility causes frequent mapping updates. Numerous mobile endpoints require controlling the cost and delay caused by the mapping item updates. Distinguishing the endpoints based on their mobile feature can improve the efficiency of mapping items resolving. Reference [10] proposed a mapping method based on energy level, but the construction method of the top layer is not deeply expressed, and its performance analysis is slightly insufficient. This paper concentrated on the question of how to provide a locator resolution service for flat identifiers under the ID/Locator separation architecture using the replacement of addresses based on Reference [10]. The main goal is reducing the delay of mapping resolution from ID to locator. We achieve the goal mainly by the following four methods: (1) Architecture: the mapping items storage architecture for resolving is divided into three different levels according to the different activity items stored. (2) Mapping items flow mechanism: based on the push mechanism, updated mapping items will be stored in the appropriate position; change the storage position dynamically according to the activity of an item; policy report (PR) is used for an identifier according to the different mobility of the corresponding endpoint. (3) Location awareness construction method of the top layer: using the Markov decision process to construct the top layer CHORD, thus keeping the consistency between the physical topology and the logical topology. This paper is organized as follows. In Section 2 we present the overall framework of resolution. Section 3 focuses on the related process and mechanism of identification resolving. Section 4 focuses on the construction method of the top layer. Section 5 focuses on the performance analysis of the proposed method.