5 Iur Data Transport for Common Transport Channel Data Streams

5 I_ur Data Transport for Common Transport Channel Data Streams

25.4243GPPRelease 17TSUTRAN Iur interface data transport & transport signalling for Common Transport Channel data streams

Tools: ARFCN - Frequency Conversion for 5G NR/LTE/UMTS/GSM

5.1 Introduction

This clause specifies the transport layers that support Common Channels (FACH, RACH, DSCH [TDD], USCH [TDD], HS-DSCH) Iur data streams.

There are two options for the transport layer of the Common Channels data streams in Iur and Iub:

1) ATM based Transport (ATM transport option)

2) IP based Transport (IP transport option)

The following figure shows the protocol stacks of the two options.

Protocol stack for ATM transport option Protocol stack for IP transport option

Figure 1: Transport network layer for DCH data streams over Iur and Iub interfaces

5.2 ATM Transport Option

ATM (ITU-T Rec. I.361 [1]), AAL type 2 (ITU-T Recommendations I.363.2 [2] and ITU-T Rec. I.366.1 [3]) is used as the standard transport layer for RACH, FACH, USCH [TDD], DSCH [TDD] and HS-DSCH Iur data streams.

These AAL2 connections are established via the transport signalling protocol described in clause 5.

Figure 1 shows the protocol stack for the transport of RACH, FACH, USCH [TDD], DSCH [TDD] and HS-DSCH Iur data streams using the ATM Transport Option. Service Specific Segmentation and Re-assembly (SSSAR) is used for the segmentation and re-assembly of AAL2 SDUs (i.e. SSSAR is only considered from ITU-T Recommendation I.366.1 [3]).

5.3 IP Option

UDP (IETF RFC 768 [19]) over IP shall be used as the transport for RACH, FACH, USCH [TDD], DSCH [TDD] and HS-DSCH data streams on Iur. The data link layer is as specified in subclause 4.2.

An IP UTRAN Node shall support IPv6 (IETF RFC 2460 [16]). The support of IPv4 (IETF RFC 791 [17]) is optional.

Note: This does not preclude single implementation of IPv4.

IP dual stack support is recommended for the potential transition period from IPv4 to IPv6 in the transport network.

The transport bearer is identified by the UDP port number and the IP address (source UDP port number, destination UDP port number, source IP address, destination IP address).

IP Differentiated Services code point marking (IETF RFC 2474 [18]) shall be supported. The mapping between traffic categories and Diffserv code points shall be configurable by O&M. Traffic categories are implementation-specific and may be determined from the application parameters.