Page 1136 - 5G Basics - Core Network Aspects

2 Transport aspects

Figure 15-7  TTI structure

The features of access point identifiers (APIs) are:
– Each access point identifier must be globally unique in its layer network.
– Where it may be expected that the access point may be required for path set-up across an inter-
operator boundary, the access point identifier must be available to other network operators.
– The access point identifier should not change while the access point remains in existence.
– The access point identifier should be able to identify the country and network operator which is
responsible for routing to and from the access point.
– The set of all access point identifiers belonging to a single administrative layer network should
form a single access point identification scheme.
– The scheme of access point identifiers for each administrative layer network can be independent
from the scheme in any other administrative layer network.

It is recommended that the ODUk, OTUk and OTS should each have the access point identification scheme
based on a tree-like format to aid routing control search algorithms. The access point identifier should be
globally unambiguous.

The access point identifier (SAPI, DAPI) shall consist of a three-character international segment and a
twelve-character national segment (NS) (see Figure 15-8). These characters shall be coded according to
[ITU-T T.50] (International Reference Alphabet – 7-bit coded character set for information exchange).

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