Node Route Cache and Addressed Packet Forwarding - Revision history

Spooky at 18:39, 5 April 2005

2005-04-05T18:39:07Z

← Older revision		Revision as of 18:39, 5 April 2005
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			[[Known Hub Cache and Hub Cluster Cache\|<< Known Hub Cache and Hub Cluster Cache]] \| [[Query Hash Tables\|Query Hash Tables >>]] \| [[Main_Page\|Main Page]]

			__TOC__
	== Introduction ==		== Introduction ==

Kath: /* Push Handshaking */

2005-03-27T17:09:24Z

Push Handshaking

← Older revision		Revision as of 17:09, 27 March 2005
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	Note that unlike the Gnutella1 case, no purpose-specific information is provided. The		Note that unlike the Gnutella1 case, no purpose-specific information is provided. The
	pushed connection can now be used for any purpose a normally established TCP link		pushed connection can now be used for any purpose a normally established TCP link
	could adopt, including but not limited to:		could adopt, including, but not limited to:

	* Gnutella2 network connection		* Gnutella2 network connection
Line 92:		Line 92:
	* Etc		* Etc

	Gnutella2 implementations are however strongly advised to provide backward		Gnutella2 implementations are however, strongly advised to provide backward
	support for the Gnutella1 push handshake, even if not supporting Gnutella1 directly.		support for the Gnutella1 push handshake, even if not supporting Gnutella1 directly.
	This is because applications supporting both protocols may be unable to determine in		This is because applications supporting both protocols may be unable to determine in
	advance whether the host they are pushing to is Gnutella1 or Gnutella2.		advance, whether the host they are pushing to is Gnutella1 or Gnutella2.
	The legacy-style push handshake looks like:		The legacy-style push handshake looks like:

Kath: /* Addressed Packet Forwarding */

2005-03-27T17:06:18Z

Addressed Packet Forwarding

← Older revision		Revision as of 17:06, 27 March 2005
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	Any Gnutella2 packet may be addressed to a particular destination node by GUID.		Any Gnutella2 packet may be addressed to a particular destination node by GUID.
	Upon receiving an addressed packet, it should be immediately forwarded either to		Upon receiving an addressed packet, it should be immediately forwarded either to
	the destination, or toward it. Addressed packets should not be interpreted locally		the destination, or toward it. Addressed packets should not be interpreted locally,
	unless the destination address matches the local GUID.		unless the destination address matches the local GUID.

Kath: /* Introduction */

2005-03-27T17:03:11Z

Introduction

← Older revision		Revision as of 17:03, 27 March 2005
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	Each Gnutella2 node must maintain a dynamic node route cache to map node GUIDs		Each Gnutella2 node must maintain a dynamic node route cache to map node GUIDs
	to appropriate destinations. The route cache is consulted when a packet needs to be		to appropriate destinations. The route cache is consulted when a packet needs to be
	dispatched to or toward a GUID-addressed node. GUID-addressing is used over		dispatched to, or toward a GUID-addressed node. GUID-addressing is used over
	network-addressing in a number of situations.		network-addressing in a number of situations.

Dcat at 04:19, 20 March 2005

2005-03-20T04:19:44Z

@@ Line 69: / Line 69: @@
 This mechanism is used to request that a "firewalled" leaf initiate a "reverse
 connection" or "call-back" to an elected address. The root packet type "/[[PUSH]]" is
-used, and is documented in the following sections.
+used.

Dcat at 00:00, 20 March 2005

2005-03-20T00:00:07Z

New page

== Introduction ==

Each Gnutella2 node must maintain a dynamic node route cache to map node GUIDs
to appropriate destinations. The route cache is consulted when a packet needs to be
dispatched to or toward a GUID-addressed node. GUID-addressing is used over
network-addressing in a number of situations.

== Data ==

Each entry in a node route cache will have:

* The GUID of the target node
* The local TCP connection providing the best route to the node, or
* A UDP endpoint for the node or the best route to the node

== Performance ==

A route cache needs to be addressable by GUID, and must implement a refresh
mechanism to store routes for an appropriate amount of time based upon route hits.
Many schemes exist to engineer efficient lookup systems, such as hash tables, twotable
exchanges and balanced trees.

The route cache is similar to the several GUID mapping caches involved in old
Gnutella applications, with two key differences:

* Each entry may map to a local address or a UDP endpoint
* There is only one unified route cache for all purposes

== Applications ==

GUIDs are used to identify virtual entities within the network, such as nodes (node
GUIDs), searches (search GUIDs) and other transactional requests. The GUIDs
associated with these entities can then be committed to the route cache and mapped
to reflect the easiest route back to the owner of the object.

All nodes should be aware of their directly connected neighbours, and treat these
node GUIDs as a special case that need never expire.

== Addressed Packet Forwarding ==

Any Gnutella2 packet may be addressed to a particular destination node by GUID.
Upon receiving an addressed packet, it should be immediately forwarded either to
the destination, or toward it. Addressed packets should not be interpreted locally
unless the destination address matches the local GUID.

Loops are avoided by placing restrictions upon forwarding:

* If received from a leaf via TCP, a packet may be forwarded anywhere
* If received from a hub, a packet may only be forwarded to a leaf
* If received via UDP, a packet may not be forwarded via UDP

Note that these restrictions apply only to generically addressed packets. Some packet
types have specific forwarding rules which override these. These rules allow any
node to be reached in two hops.

Packets are addressed by including a special child packet as the first child of the root
packet. The child packet is named "TO", so its full name would be "/?/TO" where ? is
the root packet name. The address packet's payload consists of a 16 byte GUID, and
it has no children defined at the current time.

== Reverse Connection (Push) Requests ==

Addressed packet forwarding can be used to deliver any valid Gnutella2
communications to leaf nodes that are unable to accept TCP or UDP traffic directly.
The packet is simply sent to one of the hubs to which the target leaf is attached, or a
hub in the same hub cluster, and the forwarding rules will allow the packet to reach
its destination.

This mechanism is used to request that a "firewalled" leaf initiate a "reverse
connection" or "call-back" to an elected address. The root packet type "/[[PUSH]]" is
used, and is documented in the following sections.