The LISP technology is a kind of solution based on the host identifier and host location identifier separation, as shown in FIG. 1, its realization way is as follows:
The site network (usually referring to the user network) is separated with the transmission network (usually referring to the operator network), and the address space is divided into an Endpoint Identifier (EID, representing an address within the site network) address space and a Routing Locator (RLOC, representing reachability within the edge router network) address space. The routing information within the side network in the network, that is, EID address information, is not released to the transmission network, and two site networks are connected through the tunnel which is across the transmission network and established between an Ingress Tunnel Router (ITR) and an Egress Tunnel Router (ETR). The maintenance of the information of the mapping from the EID to the RLOC is realized through a single mapping system by the site network.
When the data need to be forwarded, the data package producer in the site network forwards the generated data package to the ITR, the ITR initiates a mapping request to the mapping system, to obtain a mapping relationship between the destination EID address and the RLOC address of the destination site ETR. The ITR caches the mapping relationship, and performs the LISP encapsulation on the data package according to the mapping relationship, and then sends the encapsulated data package to the ETR of the destination site through the tunnel. After performing the de-capsulation on the received data package, the ETR of the destination site forwards the data package to a receiver in the site according to the destination EID address carried in the data package.
As shown in FIG. 1, the mapping plane is illustrated by taking the Alternative Logical Topology (ALT) mapping system as an example, and the Map Resolver (MR) and the Map Server (MS) are used in the mapping system. Wherein, the MR is used for receiving a mapping request of the LISP encapsulation sent by the ITR, and sending the mapping request to a corresponding MS according to the EID prefix routing information in the mapping network; and the MS is used for storing the mapping information registered by the ETR, and forwarding the received mapping request to the corresponding ETR.
The related technology also involves the support to the mobility by the LISP technology. In the LISP mobility research, each Mobile Node (MN) can be regarded as an LISP site, and the MN can execute part of the functions of the ETR and the ITR. Therefore, one MN device maintains two identifications: one is the identifier of the MN, and the identifier usually is not changed; and another is the location identifier of the MN, and the MN can obtain the identifier dynamically when the MN moves to a new location. As the scene shown in FIG. 2, the identifier of the MN is indicated by the EID of the MN, and can be abbreviated as MEID. When the new location of the MN is in an LISP site, the location identifier obtained dynamically by the MN in the site is one EID in the site address space, indicated by the EID of that site, and abbreviated as SEID. The MN regards the obtained SEID address as the RLOC address, and registers the mapping relationship from the MEID to the SEID with the corresponding MS in the mapping system.
Based on the scene illustrated in FIG. 2, in the related technology, a correspondent Node of the MN, for example, one Static Node (SN) in some LISP site 1 as shown in FIG. 2, wants to establish a communication connection with the MN in the site 2. The location of the SN will not usually change in regard to the MN, and the location identifier will not usually change either. When the ITR in the site 1 receives the data package, sent by the SN, of which the destination address is the MEID, the ITR in the site 1 performs the mapping cache searching; if there is no mapping information corresponding to the MEID in the cache, then the ITR in the site 1 sends the mapping request to the mapping system, and obtains the mapping relationship from the MEID to the SEID through the MS corresponding to the MN. The ITR performs the LISP encapsulation on the data package according to the mapping relationship, and the destination address of the encapsulated data package is the SEID. If there is no mapping item corresponding to the SEID in the ITR cache, then the ITR needs to visit the mapping system again to obtain the mapping information from the SEID to the RLOC address of the ETR of the LISP site where the MN locates (ETR RLOC, abbreviated as ERLOC), and performs the LISP encapsulation again on the above-mentioned encapsulated data package according to the mapping information, and then sends out the data package. Therefore in the scene illustrated in FIG. 2, the ITR may need to perform the mapping searching twice, and needs to perform two layer-LISP encapsulations on the data package which is sent to the MN by the SN.
It needs to be illustrated that in the above-mentioned scene, besides the SN in the LISP site, the correspondent Node which wants to establish a communication connection with the LISP MN can also be the MN in the LISP site, the SN in the non-LISP field, or the MN in the non-LISP field. When the correspondent Node is the SN in the non-LISP field, the processes of twice-mapping searching and two layer-LISP encapsulation are performed by the Proxy ITR (PITR) device; and when the correspondent Node is the MN in the non-LISP field, the processes of twice-mapping searching and two layer-LISP encapsulation are all completed by the sender MN itself; when the correspondent Node is the MN in the LISP site, the sender MN of the data package obtains the mapping information from the MEID to the SEID of the destination MN at first, performs the LISP encapsulation on the data package, then sends the encapsulated data package to the ITR of the site where the present MN locates according to the default setting, and the ITR obtains the mapping information from the SEID to the ERLOC and then performs the second layer LISP encapsulation on the data package.
Based on the above-mentioned scenes, if the LISP MN moves to a new LISP site each time and obtains the EID of the site as the location identifier, when the correspondent Node outside the site initiates a connection to the MN for the first time, the processes of twice-mapping searching and twice-mapping encapsulation are all required to be performed, which causes the waste of the system resources and will increase the overhead of the message transmission after multiple encapsulations.