一、查看3GPP TS 24.301
9.9.4 EPS Session Management (ESM) information elements
See subclause 10.5.6.1 in 3GPP TS 24.008 [13].
二、查看3GPP TS 24.008
三、查看3GPP TS 23.003
可以得知，APN的长度最大是100字节。
四、一个APN的例子
1980 Jan 6 00:49:41.677 [2D] 0xB0E2 LTE NAS ESM Plain OTA Incoming Message -- Activate default EPS bearer context request Msg
Subscription ID = 1
pkt_version = 1 (0x1)
rel_number = 9 (0x9)
rel_version_major = 5 (0x5)
rel_version_minor = 0 (0x0)
eps_bearer_id_or_skip_id = 5 (0x5)
prot_disc = 2 (0x2) (EPS session management messages)
trans_id = 6 (0x6)
msg_type = 193 (0xc1) (Activate default EPS bearer context request)
lte_esm_msg
act_def_eps_bearer_context_req
eps_qos
qci = 9 (0x9) (QC9)
oct4_incl = 0 (0x0)
oct5_incl = 0 (0x0)
oct6_incl = 0 (0x0)
oct7_incl = 0 (0x0)
oct8_incl = 0 (0x0)
oct9_incl = 0 (0x0)
oct10_incl = 0 (0x0)
oct11_incl = 0 (0x0)
oct12_incl = 0 (0x0)
oct13_incl = 0 (0x0)
oct14_incl = 0 (0x0)
oct15_incl = 0 (0x0)
access_point
num_acc_pt_val = 25 (0x19)
acc_pt_name_val[0] = 5 (0x5) (length)
acc_pt_name_val[1] = 67 (0x43) (C)
acc_pt_name_val[2] = 77 (0x4d) (M)
acc_pt_name_val[3] = 78 (0x4e) (N)
acc_pt_name_val[4] = 69 (0x45) (E)
acc_pt_name_val[5] = 84 (0x54) (T)
acc_pt_name_val[6] = 6 (0x6) (length)
acc_pt_name_val[7] = 77 (0x4d) (M)
acc_pt_name_val[8] = 78 (0x4e) (N)
acc_pt_name_val[9] = 67 (0x43) (C)
acc_pt_name_val[10] = 48 (0x30) (0)
acc_pt_name_val[11] = 48 (0x30) (0)
acc_pt_name_val[12] = 50 (0x32) (2)
acc_pt_name_val[13] = 6 (0x6) (length)
acc_pt_name_val[14] = 77 (0x4d) (M)
acc_pt_name_val[15] = 67 (0x43) (C)
acc_pt_name_val[16] = 67 (0x43) (C)
acc_pt_name_val[17] = 52 (0x34) (4)
acc_pt_name_val[18] = 54 (0x36) (6)
acc_pt_name_val[19] = 48 (0x30) (0)
acc_pt_name_val[20] = 4 (0x4) (length)
acc_pt_name_val[21] = 71 (0x47) (G)
acc_pt_name_val[22] = 80 (0x50) (P)
acc_pt_name_val[23] = 82 (0x52) (R)
acc_pt_name_val[24] = 83 (0x53) (S)