Level 3 Relay  -  NLP actions

Host A          to           Host B
FTP over YB                  FTP over CONS

On entry to Converter

called DTE: Converter (80) address        Calling DTE:  Host A X.121
        YB: 'unique string'                        YB:  'hostA dependant'

NLP Look-ups  (Transition Document section 5.8)

1) Inverse Forward lookup of YB to get HostB's name [eg: uk.ac.ed.hostb]
2) Forward lookup of that name to get NSAP [eg:3882611000015099001001001003]
3) Lookup of NSAP to get X.121 address of HostB

4) Reverse lookup of calling DTE&YB to get HostA's name
5) Inverse Reverse lookup of HostA's name to get 'return call' NSAP


On exit from converter

called DTE: Host B's X.121 address        Calling DTE: Converter X.121 (84)
      NSAP: Host B's NSAP for FTP                NSAP: 'return call' NSAP


Call from Host B to Host A
==========================

On entry to converter


called DTE: Converter X.121 (84)          Calling DTE: HostB X.121
      NSAP: 'Return call' NSAP                   NSAP: HostB's NSAP for FTP


NLP Lookups

1) Inverse Forward lookup of 'return call' NSAP to get Host A's name
2) Forward Lookup of hosta's name to get DTE & YB strings for Host a

3) Reverse lookup of calling NSAP to get Host B's name
4) Inverse Reverse Lookup of Host B's name to get the YB 'unique string' for B

On exit

called DTE: Host A's X.121               Calling DTE: Converter (80) X.121
        YB: 'host dependant' (lookup 2)           YB: 'unique string' for B