Ram: /* Sending */ Typo fix

2014-01-26T11:20:03Z

Sending: Typo fix

← Older revision		Revision as of 11:20, 26 January 2014
Line 64:		Line 64:
	Send a /QA/D child for the local hub and each neighbouring hub, whether or not the		Send a /QA/D child for the local hub and each neighbouring hub, whether or not the
	hub has actually forwarded the query. If a hub has not forwarded the query, it was		hub has actually forwarded the query. If a hub has not forwarded the query, it was
	still effectively searched as the QHT indicated it could not ~~field~~ a matching object.		still effectively searched as the QHT indicated it could not find a matching object.

	=== Receiving ===		=== Receiving ===

Dcat at 04:11, 1 January 2009

2009-01-01T04:11:38Z

← Older revision		Revision as of 04:11, 1 January 2009
Line 1:		Line 1:
			{{Packets}}

	= /QA - Query Acknowledgement =		= /QA - Query Acknowledgement =

Spooky: typo

2005-04-05T19:11:39Z

typo

← Older revision		Revision as of 19:11, 5 April 2005
Line 61:		Line 61:

	Send a /QA/D child for the local hub and each neighbouring hub, whether or not the		Send a /QA/D child for the local hub and each neighbouring hub, whether or not the
	hub ~~was~~ actually forwarded the query. If a hub ~~was~~ not forwarded the query, it was		hub has actually forwarded the query. If a hub has not forwarded the query, it was
	still effectively searched as the QHT indicated it could not field a matching object.		still effectively searched as the QHT indicated it could not field a matching object.

Dcat at 19:28, 20 March 2005

2005-03-20T19:28:54Z

New page

= /QA - Query Acknowledgement =

The query acknowledgement packet is used to inform a search client that a target
hub has received its [[Q2|query]] and is processing it. It also provides information for the
search client's hub cache, expanding knowledge of the network and ensuring hubs
are not searched more than once in a given query.

== Sending ==

Send a query acknowledgement packet only when operating in hub mode, and only
when the query was not received from a hub via a TCP link. Acknowledgements
should only be sent after verifying the query key authentication.

== Receiving ==

When a query acknowledgement is received, update the local hub cache as
necessary:

* Hubs which have been searched should not be sent this query again
* New suggested hubs should be added and refreshed
* Any "back-off" time should be recorded and honoured.

== Payload ==

A GUID identifying the query being acknowledged.

== Children ==

This packet has several child packet types defined at the current time:

* /QA/TS - Timestamp
* /QA/D - "Done" or Completed Hub
* /QA/S - "Search" or New Hub
* /QA/RA - Retry After
* /QA/FR - From Address

== /QA/TS - Timestamp ==

The /QA/TS child provides a timestamp representing the current universal time at the
sending node. This can be used as a reference when considering other timestamps in
the packet, allowing them to be adjusted to eliminate differences between the time
setting on the local and remote node.

=== Sending ===

This child is optional but recommended.

=== Payload ===

A 32-bit integer representing the current UNIX time, or time(NULL).

=== Children ===

This packet has no known children at the current time.

== /QA/D - Done Hub ==

References a hub which has now been queried, and should not be queried again.

=== Sending ===

Send a /QA/D child for the local hub and each neighbouring hub, whether or not the
hub was actually forwarded the query. If a hub was not forwarded the query, it was
still effectively searched as the QHT indicated it could not field a matching object.

=== Receiving ===

Upon receiving a /QA/D child, add the hub to the cache, freshen its timestamp and
mark it as queried in this search. Do not query this node again for several minutes.

=== Payload ===

A network/node address followed by a 16-bit leaf count.

=== Children ===

This packet has no known children at the current time.

== /QA/S - Search Hub ==

References a hub which was not searched in this operation, but could be searched
later if it has not already been touched.

=== Sending ===

Send a /QA/S child for every unique hub in the local hub cluster which is not a direct
neighbour. Optionally select some recent cached hubs and send /QA/S children for
them also, to make up at least 10 in total.

=== Receiving ===

Upon receiving a /QA/S child, add the hub to the cache and/or freshen its
timestamp.

=== Payload ===

A network/node address, optionally followed by a 32-bit last-seen timestamp. This
makes detecting the address family slightly harder, but the compactness is
worthwhile. Timestamps are omitted for hubs in the local hub cluster, which should
make up the majority.

=== Children ===

This packet has no known children at the current time.

== /QA/RA - Retry After ==

Advises the search client that the hub does not wish to be contacted again for a
specified period of time. Queries earlier than this time may result in a longer-term
ban.

=== Sending ===

Send this child, with or without executing the search if the hub's resources are
becoming saturated. It provides an indirect means of flow control.

=== Receiving ===

Upon receiving a /QA/RA child, record the retry after interval and do not send any
requests to the hub until the period has expired.

=== Payload ===

A 16 bit or 32 bit integer specifying the delay in seconds until the hub may be
contacted again.

=== Children ===

This packet has no known children at the current time.

== /QA/FR - From Address ==

This child is used when a query acknowledgement is forwarded from a proxy hub to
a firewalled leaf node. It advises the leaf of the original sender.

=== Sending ===

When a hub receives a /QA packet for a search originated by one of its leaves, it
should forward the /QA to the appropriate leaf after adding a /QA/FR child with the
remote hub's network address.

=== Receiving ===

If this child is present and the /QA packet was received via TCP from a local hub, the
node address within should be used as the remote hub's node address. This
information is often reflected in the first /QA/D child, however this is not always
present.

=== Payload ===

A network address which may omit the port number.

=== Children ===

This packet has no known children at the current time.

QA - Revision history

Ram: /* Sending */ Typo fix

Dcat at 04:11, 1 January 2009

Spooky: typo

Dcat at 19:28, 20 March 2005