Кстати, к вопросу об упущенных возможностях в части мобильности
>Our original view of X's use included highly mobile individuals (students moving between classes), and a hope, never generally realized for X, was the migration of applications between X servers.

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>Bridges emulate CLNP -- an ISO version of IP. CLNP (ISO 8473) was rather close to IP but better in many ways. CLNP had a hierarchical addressing and offered a mobility within a campus: a user can move his computer from one router (connectivity point on campus) to another without any need to change addresses and other protocol settings. CLNP integrated a telephone network -- regular telephone numbers can serve as (a part of) node address.
>When the limitations of IP became apparent, CLNP looked like a deserving successor.
>Unfortunately, CLNP was developed by ISO -- an anathema to IETF. Therefore, CLNP had no chances within IETF. This is very sad.