rename HELLO cells to VERSIONS cells.

         4 -- DESTROY     (Stop using a circuit)    (See Sec 5.4)

         5 -- CREATE_FAST (Create a circuit, no PK) (See Sec 5.1)

         6 -- CREATED_FAST (Circuit created, no PK) (See Sec 5.1)

         7 -- HELLO       (Negotiate versions)      (See Sec 4.1)

         7 -- VERSIONS    (Negotiate versions)      (See Sec 4.1)

         8 -- NETINFO     (Time and MITM-prevention) (See Sec 4.2)

   The interpretation of 'Payload' depends on the type of the cell.

   RELAY cells are used to send commands and data along a circuit; see

   section 5 below.

   HELLO cells are used to introduce parameters and characteristics of

   VERSIONS cells are used to introduce parameters and characteristics of

   Tor clients and servers when connections are established.

4, Connection management

   Upon establishing a TLS connection, both parties immediately begin

   negotiating a connection protocol version and other connection parameters.

4.1. HELLO cells

4.1. VERSIONS cells

   When a Tor connection is established, both parties normally send a HELLO

   cell before sending any other cells.  (But see below.)

   When a Tor connection is established, both parties normally send a

   VERSIONS cell before sending any other cells.  (But see below.)

         NumVersions            [1 byte]

         Versions               [NumVersions bytes]

   are able and willing to support.  Parties can only communicate if they

   have some connection protocol version in common.

   Version 0.1.2.0-alpha and earlier don't understand HELLO cells, and

   therefore don't support version negotiation.  Thus, waiting until

   the other side has sent a HELLO cell won't work for these servers: if they

   send no cells back, it is impossible to tell whether they have sent a

   HELLO cell that has been stalled, or whether they have dropped our own

   HELLO cell as unrecognized.  Thus, immediately after a TLS connection has

   been established, the parties check whether the other side has an obsolete

   certificate (organizationName equal to "Tor" or "TOR").  If the other party

   presented an obsolete certificate, we assume a v0 connection.  Otherwise,

   both parties send HELLO cells listing all their supported  versions.  Upon

   receiving the other party's HELLO cell, the implementation begins using

   the highest-valued version common to both cells.  If the first cell from

   the other party is _not_ a HELLO cell, we assume a v0 protocol.

   Version 0.1.2.0-alpha and earlier don't understand VERSIONS cells,

   and therefore don't support version negotiation.  Thus, waiting until

   the other side has sent a VERSIONS cell won't work for these servers:

   if they send no cells back, it is impossible to tell whether they

   have sent a VERSIONS cell that has been stalled, or whether they have

   dropped our own VERSIONS cell as unrecognized.  Thus, immediately after

   a TLS connection has been established, the parties check whether the

   other side has an obsolete certificate (organizationName equal to "Tor"

   or "TOR").  If the other party presented an obsolete certificate,

   we assume a v0 connection.  Otherwise, both parties send VERSIONS

   cells listing all their supported  versions.  Upon receiving the

   other party's VERSIONS cell, the implementation begins using the

   highest-valued version common to both cells.  If the first cell from

   the other party is _not_ a VERSIONS cell, we assume a v0 protocol.

   Implementations MUST discard cells that are not the first cells sent on a

   connection.

   administrator.

   Each address contains Type/Length/Value as used in Section 6.4.  The first

   address is the address of the interface the party sending the HELLO cell

   address is the address of the interface the party sending the VERSIONS cell

   used to connect to or accept connections from the other -- we include it

   to block a man-in-the-middle attack on TLS that lets an attacker bounce

   traffic through his own computers to enable timing and packet-counting

   attacks.

   The second address is the one that the party sending the HELLO cell

   The second address is the one that the party sending the VERSIONS cell

   believes the other has -- it can be used to learn what your IP address

   is if you have no other hints.