待讨论问题-IETFTools.PPT

Page * The challenges in Femtocell synchronization The Femtocell network architecture shows that a public network is used to establish the connectivity between the femtocell and core network elements, This presents a set of unique challenges: Femtocell synchronization security Femtocell synchronization connectivity Femtocell synchronization network scalability Page * Security Issue The security is mandatory since the Gateway and Clock server communicate to the Femtocells via a public backhaul broadband connection (also known as the 3GPP iuh interface or Femtocell Forum Fa interface). The important point worth noting is the large number of Femtocells that might have to be served, as well as the additional bandwidth overhead IPSec represents to the offered load (bandwidth consumption) of synchronization messages. The 3GPP has considered some of the security aspects with respect to synchronization performance. The [3GPP.33.820] report lists the following: 1. it may be possible to leave some of the messages unprotected, but there might be security risks. Care should be taken in considering which messages are protection or not. 2. there may be bandwidth, delay and delay variation problems if all the messages (eg., [IEEE1588]) are to be protected. 3. if delays become excessively long, reliance on internal clock might be important and requires further investigation. Page * Connectivity Issue The Home GW provides Internet sharing for home devices. One of the challenges is to define the end-to-end connectivity model between the femtocell and clock server when a function such as network address translation (NAT) is present within the Home GW. network address translation (NAT) protects the internal home network, but prevents the direct connection between devices sitting in the home network and devices that are outside (reachable through the public Internet). With respect to synchronization, this could limit the ability of a femtocell to communica