4.5.29	Transit network selection
The purpose of the Transit network selection information element is to identify one requested transit network. The Transit network selection information element may be repeated in a message to select a sequence of transit networks through which a call mus
t pass (see Annex C).
The Transit network selection information element is coded as shown in Figure 4-35 and Table 4-25. The maximum length of this information element is network dependent.










Bits
8
7
6
5
4
3
2
1
Octets
Transit network selection
0
1
1
1
1
0
0
0
      1
Information element identifier
Length of transit network selection contents
      2
1 ext.
Type of network
identification
Network identification plan
      3
0
Network identification (IA5 characters)
      4
    etc.
FIGURE  4-35/Q.931
Transit network selection information element
TABLE  4-25/Q.931
Transit network selection information element

Type of network identification (octet 3)
	Bits
	7  6  5
	0  0  0	User specified
	0  1  0	National network identification (Note 1)
	0  1  1	International network identification
	All other values are reserved.
	NOTE 1 – In the case that "type of network identification" is coded as 010, "national network identification", "national identification plan" is coded according to national specification.
Network identification plan (octet 3)
	Bits
	4  3  2  1
	0  0  0  0		Unknown
	0  0  0  1		Carrier Identification Code (Note 2)
	0  0  1  1		Data network identification code (Recommendation X.121) [21]
	All other values are reserved.
	NOTE 2 – Carrier Identification Codes may be an appropriate method of identifying the network serving the remote user.
Network identification (octet 4)
	These IA5 characters are organized according to the network identification plan specified in octet 3.