To Call or To Be Called Behind NATs is Sensitive in Solving the Direct Connection Problem

Abstract

Abstract-In this article, we first depict the call-role sensitivity problem in Network Address Translation (NAT) traversal, and then propose an approach to resolving the problem. The problem is whether a direct connection can be found between two peers across NATs mainly depends on the NAT type at the caller's side. We propose the extra-candidate connectivity check where both peers initiate a direct connectivity check to eliminate the effect of the call role. We have implemented the extra-candidate connectivity check and conducted experiments with 18 different NATs. Experimental results show that our approach can indeed resolve the call-role sensitivity problem, and maximize the direct connectivity rate (DCR) which is improved by 18.71% from the original scheme.

NAT-Compatibility Testbed: An Environment to Automatically Verify Direct Connection Rate

“…This request originated from the new mapped-address will also be dropped by the port restricted cone or symmetric NAT at the callee's side because the NAT did not send packets to that IP address before. Such a problem is caused by the connection tracking, one feature built within the Linux kernel, and called call-role sensitivity problem [10]. Also, this kind of NATs is named Linux-based NATs in [10].…”

“…Such a problem is caused by the connection tracking, one feature built within the Linux kernel, and called call-role sensitivity problem [10]. Also, this kind of NATs is named Linux-based NATs in [10].…”

Can: A context-aware NAT traversal scheme

“…To improve the DCR and efficiency of ICE, this study proposes Context Aware NAT (CAN) traversal scheme. In CAN, user agents (UAs) of hosts obtain network-context information (host location, NAT type, Saikat et al, 2004;Rosenberg et al, 2003;Audet, 2007;Huang andHwang, 2009, whether hairpin translation, Ford et al, 2005;Srisuresh et al, 2008;Kuramochi et al, 2008, is supported and whether connection tracking, Ho et al, 2010;Raste and Kulkarni, 2008, is implemented) in advance. Then both hosts exchange their network-context information to assist in the connectivity check.…”

“…NAT allows IHs within a private network to connect to EHs in a public network (Francis and Egevang, 2001;Ho et al, 2011Ho et al, , 2010. The usage and toleration of NAT ameliorates IPv4 address depletion by allowing globally registered IP addresses to be either reused or shared among several hosts.…”

“…When later NAT X receives outgoing packets from the same session of nodes A and C, it assigns a new mapped-address to this session. Ho et al (2010) proposed an initiator-change method to solve the call-role sensitivity problem. As Fig.…”