Screenshot of the Hamachi Client, showing a joined network and other users. |
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| Developer(s) | LogMeIn Inc. |
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| Stable release | 2.1.0.124 / August 16, 2011 |
| Operating system | Microsoft Windows, Mac OS X, Linux (beta) |
| Type | P2P, VPN |
| License | Proprietary (Free for non-commercial use) |
| Website | www.logmeinhamachi.com www.hamachi.cc www.vpn.net |
Hamachi is a zero-configuration virtual private network (VPN) shareware application that is capable of establishing direct links between computers that are behind NAT firewalls without requiring reconfiguration (when the user's PC can be accessed directly without relays from the Internet/WAN side ); in other words, it establishes a connection over the Internet that emulates the connection that would exist if the computers were connected over a local area network. It is currently available as a production version for Microsoft Windows and Mac OS X, and as a beta version for Linux.
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Hamachi is a centrally-managed VPN system, consisting of the server cluster managed by the vendor of the system and the client software, which is installed on end-user computers. Client software adds a virtual network interface to a computer, and it is used for intercepting outbound as well as injecting inbound VPN traffic. Outbound traffic sent by the operating system to this interface is delivered to the client software, which encrypts and authenticates it and then sends it to the destination VPN peer over a specially initiated UDP connection. Hamachi currently handles tunneling of IP traffic including broadcasts and multicast. The Windows version also recognizes and tunnels IPX traffic.
Each client establishes and maintains a control connection to the server cluster. When the connection is established, the client goes through a login sequence, followed by the discovery process and state synchronization. The login step authenticates the client to the server and vice versa. The discovery is used to determine the topology of the client's Internet connection, specifically to detect the presence of NAT and firewall devices on its route to the Internet. The synchronization step brings a client's view of its private networks in sync with other members of these networks.
When a member of a network goes online or offline, the server instructs other network peers to either establish or tear down tunnels to the former. When establishing tunnels between the peers, Hamachi uses a server-assisted NAT traversal technique, similar to UDP hole punching. Detailed information on how it works has not been made public. The vendor claims "...to successfully mediate P2P connections in roughly 95% of all cases ..." This process does not work on certain combinations of NAT devices, requiring the user to explicitly set up a port forward. Additionally 1.0 series of client software are capable of relaying traffic through vendor-maintained 'relay servers'.
In the event of unexpectedly losing a connection to the server, the client retains all its tunnels and starts actively checking their status. When the server unexpectedly loses client's connection, it informs client's peers about the fact and expects them to also start liveliness checks. This enables Hamachi tunnels to withstand transient network problems on the route between the client and the server as well as short periods of complete server unavailability.
Hamachi is frequently used for gaming and remote administration. The vendor provides free basic service and extra features for a fee.
In February 2007, an IP-level block was imposed by Hamachi servers on parts of Vietnamese Internet space due to "the scale of the system abuse originating from blocked addresses". The company is working on a less intrusive solution to the problem.
Each Hamachi client is assigned an IPv4 address from the 5.0.0.0/8 address block when it logs into the system for the first time. This assignment is however unofficial, as RIPE NCC has the rights to making assignments in that range.[1] Organizations using these address ranges in products or services may experience problems when more specific Internet routes attract traffic that was meant for internal hosts, or alternatively find themselves unable to reach the legitimate users of those addresses because those addresses are being used internally.[2] The IP address is henceforth associated with the client's public crypto key. As long as the client retains its key, it can log into the system and use this IP address.
The 5.0.0.0/8 network is used to avoid collisions with private IP networks that might already be in use on the client side, specifically, 10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16.
Additionally, using a separate network prefix creates a single broadcast domain between all clients. This makes it possible to use LAN protocols that rely on IP broadcasts for discovery and announcement services over Hamachi networks.
The 5.0.0.0/8 address block was allocated by IANA[1] to RIPE NCC in November 2010. Some prefixes from the range are currently being announced by the RIPE NCC debogon project.[3] Hamachi users will not be able to connect to any Internet IP addresses within the range as long as the Hamachi client is running.
The following considerations apply to Hamachi's use as a VPN application:
The current builds of Hamachi are available for the following operating systems:
Prior to versions 1.0.2.0 and 1.0.2.1 for the Windows release,[8] many Windows Vista users had experienced compatibility and connection issues while using Hamachi. As of March 30, 2007, the software now includes Vista tweaks, which answer these OS-related problems, among other specific solutions.[9]
Hamachi has a freeware version but the server side is not open source. This means it is difficult to assess the actual robustness of the tool's security. Also, while the tool is free for personal use at this time there are no guarantees that it will remain free.
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