Design Specification Information, 2011 NPI S4 - SGSN

Contents

1 Revision History.....................................................................................3

2 Introduction.............................................................................................4

3 MkVI: Current Hardware Status.............................................................4

4 S3-S4 Architecture.................................................................................54.1 S3...............................................................................................54.2 S4...............................................................................................64.3 S16.............................................................................................64.4 S6d.............................................................................................64.4.1 S6d/Gr Selection Feature...........................................................6

5 MkVI+: Hardware Status after Upgrade................................................6

6 PEB-based Routing................................................................................9

7 IP Requirements...................................................................................11

8 Upgrade Procedure..............................................................................138.1 Prerequisites.............................................................................138.1.1 Software....................................................................................138.1.2 Hardware..................................................................................138.1.3 CIQ...........................................................................................148.1.4 CLI Scripts................................................................................148.2 Hardware Upgrade...................................................................148.2.1 Replacement of boards............................................................148.2.2 Cabling......................................................................................148.3 New Configuration....................................................................158.3.1 DNS Configuration....................................................................15

9 Alarms & Counters...............................................................................15

10 References............................................................................................15

1 Introduction

The document describes, at high level, the steps needed to upgrade hardware of 3G SGSN, from MkVI to MkVI+, and how to deploy the new S3/S4 interfaces and PEB based routing.

2 MkVI: Current Hardware Status

Currently the 3G SGSN 2009A is deployed on MkVI 1500/4. The architecture layout is shown in Figure 1.

Figure 1: Hardware Architecture of MkVI 1500/4

In this setup the IBASv4 boards are being used for traffic routing. The physical connectivity is shown in Figure 2.

3 S3-S4 Architecture

The new release 8 has introduced four (4) new SGSN interfaces. They are:

3.1 S3

The new S3 interface provides inter-system mobility between S4-SGSN and MME. GTPv2-C messages are transferred over the S3 interface. It facilitates Routing Area Update (RAU) from MME to S4-SGSN and Tracking Area Update (TAU) from S4-SGSN to MME, and Inter-Radio Access Technology (IRAT) Packet-Switched (PS) Handover between LTE and WCDMA.

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Figure 2: Current 3G SGSN Physical Connectivity

3.2 S4

S4 interface is an IP-based protocol between S4-SGSN and Serving Gateway (SGW). The S4 interface includes GTPv2-C signaling for control plane and GTPv1-U payload for user plane. It includes the activation, modification, deactivation of EPS bearers in the EPC and carries user data packets between S4-SGSN and SGW.

3.3 S16

Using GTPv2-C S16 interface facilitates signaling between different S4-SGSNs. It facilitates inter-SGSN Routing Area Update (RAU).

3.4 S6d

The S6d interface connects S4-SGSN to HSS. It allows the HSS to keep track of which S4-SGSN is serving the UE and to provide S4-SGSN with subscriber and authentication data.

3.4.1 S6d/Gr Selection Feature

4 MkVI+: Hardware Status after Upgrade

Major hardware differences between MkVI and MkVI+, including physical connectivity, are:

1. All six (6) PEBv4 are replaced with PEBv5 at slots 1/1, 1/21, 2/1, 2/21, 3/1 and 3/21.

2. All ten (10) IBASv4 boards are replaced with IBACv4 boards at slots 1/2, 1/4, 1/6, 1/7, 2/11, 2/12, 2/14, 2/15, 3/11 and 3/12.

3. PEB-based routing is introduced. 1 Gbps fiber optic physical termination will take place on IBACv4 boards. Jumper cables will be required to connect the physical termination points with the routers.

4. Except for O&M and Gr all other interfaces connectivity to the SGSN is changed from electrical Ethernet to fibre optic Ethernet; 1000 Base-LX SMF links with connector type “LC” at S4-SGSN.

Figure 3 shows the hardware architecture of MkVI+. A comparison with Figure 1 depicts the differences between boards and board roles in the current MkVI configuration and the future MkVI+ configuration.

In PEB-based routing, to be described later, the physical connectivity of interfaces terminating at S4-SGSN changes. Also the roles of certain PIUs are dependent on Traffic-Mix-Optimization (TMO), to be described later. These changes are depicted in Figure 4 and Table 1.

Figure 3: Hardware Architecture MkVI+

InterfaceSlot

Internal External

OAM/NTP/LI1.6:01.7:0

1.6:01.7:0

Gr1.6:11.7:1

1.6:11.7:1

S3/S161.1:1

1.21:12.11:12.12:1

Iu-U2.1:2

2.21:22.1:2

2.21:2

Iu-C2.1:0

2.21:02.14:02.15:0

S4/DNS2.1:1

2.21:12.14:12.15:1

Gn3.1:2

3.21:23.1:2

3.21:2

S6d3.1:1

3.21:13.11:13.12:1

Table 1: Interface connectivity

Figure 4: MkVI+/8 with PEB-based routing

In Table 1 Internal slots are where the traffic routers are present, while External slots are where the physical connection to the S4-SGSN terminates. The interfaces which make use of the PEB-based routing have different Internal and External slots.

5 PEB-based Routing

In MkVI+ PEB-based routing is available. The benefit is increased capacity via freed IBAC PIUs and new 10 Gbps ports. As noted earlier it comes with a cabling and configuration change as external routing is moved from IBAS boards of MkVI to PEB boards of MkVI+.

For the 1 Gbps interfaces using PEB-based routing, the physical connectivity to the SGSN terminates at the media converter of the IBACv4 boards, as the 1 Gbps Ethernet ports on PEBv5 are electrical and not optic. The media converter, as the name implies, converts the media from optic to electrical so that it can connected to the PEBv5 boards. Jumper cables are then used to complete the connection to the PEBv5 boards.

When PEB-based routing is used, it is possible to optimize the roles of some of the boards through TMO. In Figure 3 for some PIUs it is stated that they may change role, which is possible by the use of TMO configuration. For each PIU that may change role, it is noted for which TMO step (/1 – /8) it will take the role as either a control plane of a user plane PIU. For MkVI+, TMO configuration is available for all access types except for pure MME (LTE). In this document TMO /8 is assumed which allows for maximum number of control plane boards. However, this is subject to change depending on traffic pattern.

The software requires redeployment to activate the increased capacity. During reconfiguration there will be traffic downtown. It is recommended that:

The upgrade should be carried out in two separate maintenance windows, at least.

The SGSN should be in pool so that users are not affected while it is being upgraded.

In the recommended three (3) magazine deployment, eight (8) IP interface PIUs (IBACv4) and six (6) PEBv5 PIUs are available for routing. Before planning the reconfiguration, the following needs to be considered:

Only Ethernet based interfaces can be moved to PEBv5 PIUs. Iu cannot be moved if ATM is used. If Iu uses both ATM and Ethernet it is not possible to move the Iu Ethernet interfaces because it is not possible to have one VPN on both IBAS and PEBv5 PIUs.

IPsec and GRE are not supported on PEBv5 PIUs and therefore no instances of IPsec and GRE can be used by IP interfaces on PEBv5 PIUs.

IPv6 is not supported on PEBv5 PIUs.

It is possible to use both 1 Gbps and 10 Gbps interfaces on a PEBv5 PIU but one certain network can not use both types. For example, Gn cannot use both 1 Gbps and 10 Gbps Ethernet interfaces.

For Gn and Iu it is recommended to prioritize the PEBv5 PIUs in a lower magazine before the PEBv5 PIUs in a higher magazine. This minimizes inter magazine communication, that is, start using the PEBv5 PIUs in magazine 3, followed by the PEBv5 PIUs in magazine 2 and finally the PEBv5 PIUs in magazine 1.

6 IP Requirements

The new interfaces come with their own set of IP requirements. New physical Ethernet IPs and Service IPs are required. They are listed in Tables 2 and 3, respectively.

Physical port Network IP Subnet OSPF Area

1-6-0 GomReuse earlier assignment

Reuse earlier assignment


1-7-0 GomReuse earlier assignment



1-6-1 SS7-CN-1 (Gr)Reuse earlier assignment



1-7-1 SS7-CN-2 (Gr)Reuse earlier assignment



1-1-1 S3-S16 New required New required New required1-21-1 S3-S16 New required New required New required

2-1-2 Iu-UReuse earlier assignment



2-21-2 Iu-UReuse earlier assignment



2-1-0 Iu-CReuse earlier assignment



2-21-0 Iu-CReuse earlier assignment



2-1-1 S4-DNS New required New required New required2-21-1 S4-DNS New required New required New required

3-1-2 GnReuse earlier assignment



3-21-2 GnReuse earlier assignment



3-1-1 S6d-1 New required New required New required3-21-1 S6d-2 New required New required New required

Table 2: Physical Ethernet IP Interfaces

Service Network IP Network PrefixCDR-FTP

GomReuse earlier assignment

/32

CDR-GTP-PLI-CLI-UNTPOAM

CN-SS7-1 SS7-CN-1 (Gr)Reuse earlier assignment

/32

CN-SS7-2 SS7-CN-2 (Gr)Reuse earlier assignment

/32

Gn-GTP-CGn


/32Gn-GTP-U

DNS S4-DNS New required New required

Iu-GTP-U Iu-UReuse earlier assignment

/32

Iu-SS7-1 Iu-CReuse earlier assignment

/32


/32


/32


/32

S16-GTP-C S3-S16 New required New requiredS3-GTP-C S3-S16 New required New requiredS4-GTP-C

S4-DNS New required New requiredS4-GTP-UCN-S6d-1 S6d-1 New required New requiredCN-S6d-2 S6d-2 New required New required

Table 3: Service IP Requirements

7 Upgrade Procedure

7.1 Prerequisites

Before the node is upgraded, certain prerequisites need to be met.

7.1.1 Software

Installed software is SGSN 2011B. Required user access to GSS, Terminal Server and SGSN is available.

7.1.2 Hardware

Following hardware is required:

SGSN MkVI+ hardware upgrade kit.

Cables from a MkVI+ upgrade kit.

Transceivers for fiber optic connection termination.

Except for Gom and Gr all other 1 Gbps interfaces coming to the SGSN are via optic fibre. The support for 1 Gbps fiber optic termination is only on the IBACv4 boards. Due to this the physical termination for these interfaces on the S4-SGSN is on the IBACv4 boards. The media converter on these boards converts the optical signal to an electrical one. Jumper cables are used to connect the media converter on the IBACv4 boards with the 1 Gbps slots on the PEBv5 boards to ensure PEB-based routing. Table 2 details the cable requirements.

Connection Link Type (Cable) Link Size (Gbps)OAM/NTP/LI (termination at

SGSN)Electrical (RPM 113 6449) 1

Gr (termination at SGSN) Electrical (RPM 113 6449) 1S3/S16 (termination at SGSN) Fiber Optic (TSR 391 3043) 1

S3/16 (jumper cable) Electrical (TSR 491 602) 1Iu-U (termination at SGSN) Fiber Optic (TSR 391 3043) 10Iu-C (termination at SGSN) Fiber Optic (TSR 391 3043) 1

Iu-C (jumper cable) Electrical (TSR 491 602) 1S4/DNS (termination at

SGSN)Fiber Optic (TSR 391 3043) 1

S4/DNS (jumper cable) Electrical (TSR 491 602) 1Gn (termination at SGSN) Fiber Optic (TSR 391 3043) 10S6d (termination at SGSN) Fiber Optic (TSR 391 3043) 1

S6d (jumper cable) Electrical (TSR 491 602) 1Table 4: Connection and Cable Requirements

GSS and Terminal Server connectivity is available. HSS, MSC, other MMEs/SGSNs, SGW, NTP, DNS and RNCs are ready to be connected.

7.1.3 CIQ

CIQ is complete. All the interface networks are provisioned for the SGSN in routers, switches and firewalls.

7.1.4 CLI Scripts

The CLI scripts for the reconfiguration of the node, based on the CIQ, are present, checked and ready.

7.2 Hardware Upgrade

The hardware upgrade is a two step procedure; replacement of boards and installation of new cabling. Before proceeding with the upgrade, the following steps need to be performed:

1. Validate all prerequisites are met.

2. Back up SGSN.

3. Move subscribers out of the SGSN to other pool members.

4. When all subscribers are removed take the SGSN out of the pool and network.

7.2.1 Replacement of boards

1. Switch off power to the SGSN.

2. Replace all six (6) PEBv4 boards with PEBv5 boards, including cabling.

3. Replace all ten (10) IBASv4 boards with IBACv4 boards at slots 1/2, 1/4, 1/6, 1/7, 2/11, 2/12, 2/14, 2/15, 3/11 and 3/12.

7.2.2 Cabling

1. Connect existing electrical Ethernet Gom and Gr interface cables to their old positions.

2. Connect new optical Ethernet interfaces to their specific ports as in Table 1, Slot – External.

3. Connect jumper cables between electrical Ethernet output of media converter on IBACv4 boards and electrical Ethernet ports of PEBv5 boards; between Table 1, Slot – External and Slot – Internal.

4. Verify ALL cabling before continuing!

7.3 New Configuration

1. Power up the SGSN.

2. Unblock and ensure full functionality of all replaced boards.

3. Load the CLI files.

4. Confirm all interfaces are working.

5. Back up S4-SGSN.

7.3.1 DNS Configuration

8 Alarms & Counters

The alarm modifications from SGSN 2009A to 2011B are listed in:

The counter modifications from SGSN 2009A to 2011B are listed in:

9 References

[1] Description of IBACv4

[2] Description of PEBv5

[3] General Routines For Replacing Hardware

[4] Replacing an IBAS, IBS7, or IBTE

[5] Replacing a PEB

Design Specification Information, 2011 NPI S4 - SGSN - AT&T, USA

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