# T-Move: A Light-Weight Protocol for Improved QoS in Content-Centric Networks with Producer Mobility
## 3 Related Work
### Producer Mobility in Information-Centric Networks  
Very little work has been reported on producer mobility for CCN/NDN. The authors in [18] survey various techniques to handle mobility in information-centric networks. As discussed in Section 1, there are three major approaches to producer mobility--anchor-based, rendezvous point-based, and anchorless. Anchor-based solutions (e.g., [25; 26; 27]) have special network nodes called _anchors_ that keep track of the mobile producer and reroute interests to its current location. Rendezvous-based approach (e.g., [28; 29; 30; 31]) works in a similar way where a rendezvous node redirects interests to the mobile producer. The major difference between these two approaches is that the anchor is a node that belongs to the home domain of the producer, whereas the rendezvous point may be anywhere in the network.  
The disadvantage of the above approaches is that the anchor/rendezvous point becomes a network performance bottle neck. Also, failure of an anchor/rendezvous point results in loss of information about current content location. Anchorless approach to producer mobility does not need require special nodes such as anchors or rendezvous points. Instead, special messages (called interest updates) are sent to the routers, which change their FIB entries for the mobile content to reflect the new face on which interests must be forwarded to reach the producer's new location. Ref. [29] proposes one such anchorless scheme where the FIB entries are updated, while more recently, Ref. [32] proposed MobiCCN, which uses greedy routing to handle mobile producers. Each node in the network is assigned a virtual coordinate and when a producer moves it sends a greedy update to a special router called its _host router_. All the routers along the path of this update update the FIB entry to be the face on which the update is received. This allows them to send future interests for that content to the new location. MobiCCN performs well, but requires special nodes acting as host routers and virtual coordinates to be assigned to nodes. MAP-Me [11] has been proposed to provide anchorless producer mobility in information-centric networks. MAP-Me uses Interest Updates by mobile producers to update the FIB entries. None of the above approaches to mobility leverage the fact that content can be retrieved not only from the producer, but also from the routers that cache it.  
Our mobility support solution is based on proactive content-pushing, as it ensures uninterrupted access to data. Proactive content-pushing to a nearby router when the producer moves has been studied in [9; 10]. In these papers, content is pushed to a nearby router even when the producer receives no interest for it. Since content gets cached at the router, it can be retrieved from the router's CS if the producer moves away. While [9] gives no simulation results, [10] considers a very small network with 9 routers and just one producer and one consumer with 10 interests/s and a mobility rate of 15 m/s for evaluation. In [33], the authors propose a scheme that pushes content proactively to increase availability and evaluate it for larger topologies. However, content is pushed upon creation in any network other than the home network. As mentioned in Section 1, proactively pushing content that may never be requested unnecessarily increases traffic and adversely effects cache memory management at routers.  
T-Move is an anchorless, proactive content-pushing solution in the sense that it does not require special nodes. It goes a step further from anchorless solutions that merely update the FIB entries to reroute interests--it pushes content (based on trendiness) at routers where it is most likely requested from and sends FIB updates so that the content _or_ its cached copy can be found by interests. This decreases the retrieval time of content. T-Move also reduces the number of FIB updates by dropping them wherever possible, thus decreasing the traffic substantially in mobile environments such as vehicle-to-infrastructure networks.