HUAWEI SE2900 Session Border Controller V300R002C10. Technical White Paper for IP. Issue 01. Date HUAWEI TECHNOLOGIES CO., LTD.

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1 V300R002C10 Issue 01 Date HUAWEI TECHNOLOGIES CO., LTD.

2 2016. All rights reserved. No part of this document may be reproduced or transmitted in any form or by any means without prior written consent of Huawei Technologies Co., Ltd. Trademarks and Permissions and other Huawei trademarks are trademarks of Huawei Technologies Co., Ltd. All other trademarks and trade names mentioned in this document are the property of their respective holders. Notice The purchased products, services and features are stipulated by the contract made between Huawei and the customer. All or part of the products, services and features described in this document may not be within the purchase scope or the usage scope. Unless otherwise specified in the contract, all statements, information, and recommendations in this document are provided "AS IS" without warranties, guarantees or representations of any kind, either express or implied. The information in this document is subject to change without notice. Every effort has been made in the preparation of this document to ensure accuracy of the contents, but all statements, information, and recommendations in this document do not constitute a warranty of any kind, express or implied. Huawei Technologies Co., Ltd. Address: Website: Huawei Industrial Base Bantian, Longgang Shenzhen People's Republic of China support@huawei.com i

3 About This Document About This Document Purpose This document briefly describes the IP functions and networking solutions provided by Huawei SE2900 Session Border Controller, involving IP-related features, networking, networking reliability, and typical configuration examples. This document helps engineers understand how to deploy the SE2900 on carriers' networks. Intended Audience This document is intended for: Carrier managers and planning and design engineers Huawei sales and marketing staff Technical support engineers Maintenance engineers Symbol Conventions The symbols that may be found in this document are defined as follows. Symbol Description Indicates an imminently hazardous situation which, if not avoided, will result in death or serious injury. Indicates a potentially hazardous situation which, if not avoided, could result in death or serious injury. Indicates a potentially hazardous situation which, if not avoided, may result in minor or moderate injury. Indicates a potentially hazardous situation which, if not avoided, could result in equipment damage, data loss, performance deterioration, or unanticipated results. NOTICE is used to address practices not related to personal injury. ii

4 About This Document Symbol Description Calls attention to important information, best practices and tips. NOTE is used to address information not related to personal injury, equipment damage, and environment deterioration. Change History Changes between document issues are cumulative. The latest document issue contains all the changes made in earlier issues. This issue is used for a first office application (FOA) site. iii

5 Contents Contents About This Document... ii 1 Overview IP Service Overview VRF Service Overview IP Networking Features Overview Port Interface Eth-trunk IPv4 Address IPv6 Address IPv4/IPv6 Dual Stack IP Routing VRF/VRF Networking Reliability Active/Standby Processes Active/Standby Ports Load Balancing Active/Standby Routes ARP Probe IPv6 Neighbor Discovery BFD Overview Port Classification Dual-plane Load Balancing Networking Dual-plane Load Balancing Networking Using Eth-Trunk Interfaces Single-plane Load Balancing Networking Using Eth-Trunk Interfaces Active/Standby Networking Interconnection with VRRP-enabled Routers IPv6 Networking iv

6 Contents 4.9 VRF Networking Networking Limitations Port IPv4 Address IPv6 Address Routing BFD Acronyms and Abbreviations v

7 1 Overview 1 Overview 1.1 IP Service Overview The SE2900 is an SBC that participates in the implementation of solutions, such as VoBB, RCS, VoLTE, convergent conference, NGN, and one network. The SE2900 is deployed at the border of different parts of an IP network or at the border of different IP networks to control voice, video, and data sessions. The functions of the SE2900 include access control, security, QoS, media transcoding, media firewall, media/signaling proxy, NAT traversal, firewall traversal, flexible routing, network redundancy, and encrypted transmission of signaling/media. Figure 1-1 shows the networking in which the SE2900s are interconnected with other devices using IP-based media and signaling channels. 1

8 1 Overview Figure 1-1 SE2900 networking Carrier network NMS NMS Client NMS Server BOSS IMS (VoBB/RCS/VoLTE/Conference) Management plane H.323 GW NGN I-SBC Management channel Bill System CCF CSCF ATS SoftX3000 DNS Core network A-SBC Media channel Signaling channel Access network Remote I-SBC PCRF MME AG Cable MGW GGSN PGW Fixed BB CS 3G PS LTE POTS VoBB UE/RCS UE/SIP PON CS UE RCS UE/SIP UE VoLTE UE From the perspective of IP bearer, the access and core networks, as well as the media and signaling channels, are all used to connect SE2900s to other devices. At present, the SE2900 can interconnect with routers and switches. Figure 1-2 shows the networking in which the SE2900 interconnect with routers. Figure 1-2 Interconnection between the SE2900 and routers Router 1 Access Network/ Core Network Router 2 2

9 1 Overview In this networking, the SE2900 is directly connected to routers through ports, and no switching device exists between the SE2900 and routers. The SE2900 forwards traffic to router 1 and router 2 using static routes. Figure 1-3 shows the networking in which the SE2900 interconnect with switches. Figure 1-3 Interconnection between the SE2900 and switches LAN Switch 1 Access Network/ Core Network LAN Switch 2 In this networking, the SE2900 is directly connected to switches through ports, and no device exists between the SE2900 and switches. The SE2900 forwards traffic to LAN Switch 1 and LAN Switch 2 using active/standby ports or static routes. In the preceding networking modes, IP-related service features must be deployed to meet carriers' requirements on interconnection compatibility and reliability. For details about the features, see Chapter 2 "IP Networking Features." Different features are used in different networking solutions. For details about how to use the features in specific networking solutions, see Chapter 4 "Networking Solutions." 1.2 VRF Service Overview Virtual routing and forwarding (VRF) is a technology used to establish multiple virtual routers on a physical router on the IP network. Every VRF has its own routing table, IP address, and interface. VRF can be used to separate IP addresses from routes on a VPN. VRF allows multiple instances of a routing table to co-exist within the same router on the VPN. VPN1 VPN2 CE Site1 Service provider's backbone PE Site4 CE PE PE VPN2 CE Site2 VPN1 Site3 CE 3

10 1 Overview The preceding figure shows a typical BGP/MPLS IP VPN network. Site 1 and site 3 belong to VPN1, and site 2 and site 4 belong to VPN2. As site 1 and site 2 belong to different VPNs, the IP addresses used to connect the PE to site 1 and site 2 may be the same. To prevent address overlap, VRF must be configured on the PE, so that the interfaces connecting the PE to site 1 and site 2 can be classified into different VRFs to separate IP addresses from routes. VRF provides the network separation and address overlap functions to resolve the IPv4 address exhaustion issue. Using the VRF feature, the SE2900 can be connected to different VPNs with the same IP address and supports the overlap of access-side addresses, the overlap of core-side addresses, and the overlap of core and access network addresses ~ ~ ~ Core network Core network Core network Core network A-BAC full proxy A-BAC full proxy A-BAC full proxy BRAS Access network 1 BRAS Access network 2 BRAS Access network BRAS Access network to to to

11 2 IP Networking Features 2 IP Networking Features 2.1 Overview 2.2 Port Ports on SE2900 service boards (SPUA0 and SPUA1) are classified into GE optical/electrical ports and 10GE optical ports. The ports can work in full-duplex mode. GE ports comply with 1000Base SFP standards. They can be configured as GE optical ports by inserting GE optical modules, or as GE electrical ports by inserting electrical port modules, depending on the network environment. CAUTION Electrical modules can be inserted into ports 0, 2, 4, and 6. For the ease of plug and unplug, do not use ports 1, 3, 5, and 7 for electrical modules. 10GE optical ports comply with 10GBase SFP+ standards. A 10GE optical port can be degraded to a GE optical interface by running MOD PORT. Positions of ports on the SPUA0/SPUA1 Ports on SE2900 XMUs are classified into 10M/100M/1000M auto-sensing Ethernet electrical ports, Fabric-plane cascading ports, and Base-plane cascading ports. 5

12 2 IP Networking Features 10M/100M/1000M auto-sensing Ethernet electrical ports comply with 1000Base-TX physical layer specifications and are compatible with 10Base-T and 100Base-TX physical layer specifications. Fabric-plane cascading ports, which are QSFP+ ports, comply with 40GBASE-XR4 standards. MPO multimode optical fibers are used for the ports. Base-plane cascading ports comply with 1000Base-TX physical layer specifications and are compatible with 10Base-T and 100Base-TX physical layer specifications. Positions of ports on the MXUA0 2.3 Interface SE2900 service boards use interfaces to exchange packets with other devices on the network. All service packets are sent or received by interfaces. An interface carries various attributes, such as the interface IPv4/IPv6 address, subnet mask, Address Resolution Protocol (ARP) proxy, MTU, and network interface working mode. Interfaces are classified into main interfaces and subinterfaces. Main interface: You can configure a main interface on a physical interface by setting attributes, such as the MTU and network interface working mode. Subinterface: You can configure subinterfaces on a main interface to send or receive VLAN packets. Every virtual local area network (VLAN) on a main interface must be configured with subinterfaces. Eth-trunk interface: Eth-trunk is an interface trunking technology which bundles multiple Ethernet physical interfaces to a logical interface. The logical interface is an Eth-trunk interface, (also called a load-balancing group or link aggregation group) and the bundled physical interfaces are member interfaces. 2.4 Eth-trunk An Eth-trunk interface has three operating modes: Active/standby mode: On an Eth-trunk interface, only one member link is in the Up state, and this link is called the primary link. All the other links are backup links. When the primary link goes Down, traffic on this link is switched to other links automatically. Load-balancing mode: On an Eth-trunk interface, each member link is in the Up state, and traffic is load balanced among these links. Static Link Aggregation Control Protocol (LACP) mode: On an Eth-trunk interface, M member links are primary links and N member links are backup links. When the primary 6

13 2 IP Networking Features links go Down, traffic on the links is switched to one backup link which is of top priority among N backup links. LACP provides a standard negotiation mechanism for a switching device. This ensures that the switching device can automatically create and enable an aggregation link according to its configurations. After the aggregation link is created, LACP is responsible for maintaining the link status. When the link aggregation condition is changed, LACP automatically adjusts or disables the aggregation link. The member interfaces of an Eth-trunk can be deployed on the active and standby SPUs that house the same HRU module and cannot be deployed for different HRUs. The Eth-trunk function is used to guarantee network reliability and increase interface bandwidth at low cost. The Eth-trunk interface in active/standby mode is applicable to the networks which have high network reliability but low interface bandwidth requirements. The Eth-trunk interface in load-balancing mode is applicable to the networks which have high interface bandwidth requirements. The Eth-trunk interface in static LACP mode is applicable to the networks which have high network reliability and high interface bandwidth requirements. Trunk, as a link aggregation technology, can increase the bandwidth by binding multiple physical interfaces to a trunk interface. Nevertheless, the trunk technology is weak in fault detection, and can detect only the link disconnection, but not other faults, such as the link layer fault and link misconnection. The Link Aggregation Control Protocol (LACP) is introduced as an alternative, which can improve the fault tolerance of the trunk, ensure the high reliability of the member links Eth-trunk Interface in Active/standby Mode Figure 2-1 shows the networking for an Eth-trunk interface in active/standby mode. Member interfaces of the Eth-trunk interface connect to different routers and only one member interface is in the active state. In active/standby mode, one Eth-trunk link is in the active state and the other Eth-trunk link is in the standby state. When the active member interface is faulty, traffic is switched to the standby member interface. Figure 2-1 Networking for an Eth-trunk interface in active/standby mode Router B Router A Eth-trunk Backup link SBC Primary link The SE2900 can automatically detect the status of physical interfaces but cannot automatically obtain the status of physical links. In the networking for an Eth-trunk interface in active/standby mode, if the primary link is faulty but the active interface is normal in the physical state, the SE2900 cannot detect this situation. Consequently, the SE2900 does not 7

14 2 IP Networking Features transmit the data to the peer device through the standby interface and backup link, causing communication failures. To avoid preceding communication failures, apply the Address Resolution Protocol (ARP) probe function on the Eth-trunk interface in active/standby mode. An active/standby switchover is performed on the Eth-trunk interface if the ARP probe function is enabled, the physical status of the active interface is normal but the link is faulty, or the peer device is detected faulty by the active interface Eth-trunk Interface in Load-balancing Mode Figure 2-2 shows the networking for an Eth-trunk interface in load-balancing mode. Member interfaces of the Eth-trunk interface connect to a router and operate in the active state. Traffic is load balanced among member links according to configured weights. In this mode, all Eth-trunk links are in the active state. When one physical interface is faulty, traffic is load balanced among available physical interfaces. Figure 2-2 Networking for Eth-trunk interfaces in load-balancing mode Router B Router A Eth-trunk 2 Eth-trunk 1 Backup link SBC Primary link In an Eth-trunk interface in load-balancing mode, the number of member interfaces in the Up state will have an impact on the status and bandwidth of the Eth-trunk interface. To minimize the impact of member link changes on an Eth-trunk link, you need to set the minimum number of active member links in the Eth-trunk link Eth-trunk Interface in Static LACP Mode LACP, as specified in the IEEE 802.3ad, is the protocol to implement dynamic link aggregation and de-aggregation. LACP enables information exchange between both ends through Link Aggregation Control Protocol Data Units (LACPDUs). In static LACP mode, after member interfaces are added into the trunk, each end sends LACPDUs to inform the peer end of its system priority, MAC address, member interface priorities, interface numbers, and keys. After being informed of the information, the peer end compares the information with that saved on itself, and selects interfaces that can be aggregated. Then, through the LACP negotiation, both ends agree on the active interfaces and active links. As shown in Figure 2-3, you need to manually create an Eth-trunk in static LACP mode on the SE2600 and Router A and add member interfaces to the Eth-trunk. Then the member interfaces are enabled with LACP, and devices at both ends can send LACPDUs to each other. 8

15 2 IP Networking Features Figure 2-3 LACPDUs sent in static LACP mode As shown in Figure 2-4, after devices at both ends select the Actor, both devices select active interfaces according to the priorities of interfaces on the Actor. Then active interfaces are selected, active links in the LAG are specified, and load balancing is implemented among these active links. Figure 2-4 Selecting active interfaces in static LACP mode In static LACP mode, if a device at one end detects the following events, a link switchover is triggered in the LAG if any of the following conditions is met. An active link goes Down. LACP discovers a link failure. An active interface becomes unavailable. When any of the preceding triggering conditions is met, the link switchover occurs in the following order: The faulty link is disabled. The backup link of the highest priority is selected to replace the faulty active link. The backup link of the highest priority becomes the active link and then forwards data. 2.5 IPv4 Address SE2900 service boards support two types of IP addresses for packer sending, receiving, and processing: interface IP addresses and service IP addresses. An interface IP address is configured for a main interface or subinterface to directly communicate with neighboring network devices instead of processing services. 9

16 2 IP Networking Features All the IP addresses involved in the communication between the SBC and other network devices are called service IP addresses. Service IP addresses include but are not limited to the access-side media address, access-side signaling address, core-side media address, and core-side signaling address. Service IP addresses do not directly communicate with neighboring network devices. Interfaces or interface IP addresses are used in routing or ARP proxy mode to achieve the communication. 2.6 IPv6 Address IPv6 is the second generation Internet protocol at the network layer. It is also termed as IP next generation (IPng).It is a standard released by IETF as an IPv4 update. Significantly, IPv6 is different from IPv4 in that the address length is increased from 32 bits to 128bits.With its simplified packet headers, sufficient address spaces, hierarchical address structure, flexible extension headers, and enhanced neighbor discovery mechanism, IPv6 technologies will be the appropriate substitute of the IPv4 technologies. Generally, IPv6 technologies properly resolve the problem of IP address insufficiency, are compatible with existing network applications, support smooth transition from IPv4, and interwork with IPv4 networks. IPv6-related concepts are as follows: 1. IPv6 header format Figure 2-5 Comparison between an IPv4 header and an IPv6 header Version IHL TOS Total length Identification Flags TTL Protocol Header Checksum Source address(32bits) Destination address(32bits) Options Fragment Offset Version Traffic Class Flow Label Payload Length Next Header Hop Limit Source Address(128bits) Basic header IPv4 header Destination Address(128bits) Nextheader Extension Header Data Extension headers Nextheader Extension Header Data IPv6 header In the preceding figure, the IPv4 and IPv6 headers in the same color have the same function. The following table lists the explanations to these headers: IPv4 Header IPv6 Header Comparison Version (4bit) Version (4bit) These two fields have the same function. Each of these fields refers to the Internet protocol version. For an IPv6 header, the Version field is set to 6. 10

17 2 IP Networking Features IPv4 Header IPv6 Header Comparison IHL (4bit) - The IPv6 header does not carry this field. This 4-bit header indicates the header length, covering the length of all option fields. That is, the IPv4 header length is not fixed. In IPv6 packets, extension headers are used instead of option fields. The total header length of a basic IPv6 header is 40 bits. Type of service (8bit) Traffic class (8bit) These two fields have the same function. The Traffic class field in an IPv6 header is similar to the Type of Service field in an IPv4 packet. This field uses DSCP to mark IPv6 packets and indicate how the IPv6 packets to be processed. - Flow label (20bit) This field is only available in IPv6 packets and used to identify IPv6 data streams. However, no details on the management and processing of the stream tags are available in current standard. After this field is set in IPv6 packets, devices that receive the IPv6 packets categorize the IPv6 packets into different streams based on the value of this field and process them accordingly. Due to this field, QoS assurance can be implemented on IPv6 packets that carry IPSec payloads. Total length (16bit) Payload length (16bit) These two fields have the same function. These fields are used to indicate the payload lengths in the IPv4 and IPv6 packet, respectively. A valid payload refers to the datagram that follows the IP headers. In IPv6 packets that carry extension headers, the valid payload follows the extension headers. Identification (16bit) - This field is unavailable in IPv6 packets because packet fragmentation is different in IPv4 and IPv6. In IPv4 packets, the flags field, offset field, and this field are related to packet fragmentation. This field is specified at the source. If an IPv4 packet is fragmented, each fragment carries this field so that all fragments can be assembled into the original packet after they arrive at the destination. 11

18 2 IP Networking Features IPv4 Header IPv6 Header Comparison Flags (3bit) - This field is unavailable in IPv6 packets because packet fragmentation is different in IPv4 and IPv6. In an IPv4 packet, this field is 3 bit long. Only two bits are used: one bit is used to identify whether this IPv4 packet can be fragmented, and the other bit is used to indicate whether the current segment is the last one. Fragment offset (13bit) - This field is unavailable in IPv6 packets because packet fragmentation is different in IPv4 and IPv6. This field specifies the offset of a particular fragment relative to the beginning of the original IP packet. Protocol (8bit) Next header (8bit) These two fields have the same function. This field in an IPv6 packet indicates the information types of the extension headers that follow the basic IPv6 headers. The information types defined for this field are the same as those defined in the protocol field in IPv4 packets. Header checksum (16bit) - Checksums are available at layer 2 and layer 4, and therefore the checksum at layer 3 is redundant. In IPv6, the header checksum at layer 3 is subtracted. TTL (8bit) Hop limit (8bit) These two fields have the same function. In an IPv6 packet, this field specifies the maximum number of hops that the IPv6 packet can pass, and is the same as the TTL field in an IPv4 packet. Source address (32bit) Destination address (32bit) Source address (128bit) Destination address (128bit) These fields indicate the source IP address of an IPv4 packet and an IPv6 packet, respectively. In an IPv6 packet, the source IP address is 128 bits long. These fields indicate the destination IP address of an IPv4 packet and an IPv6 packet, respectively. In an IPv6 packet, the destination IP address is 128 bits long. Option (variable length) - In IPv6 packets, extension headers are used instead of options, reducing the overhead consumed during packet transmission. 12

19 2 IP Networking Features 2. IPv6 address format A 128-bit IPv6 address can be represented in either of the following formats: X:X:X:X:X:X:X:X An IPv6 address is a series of hexadecimal numerals separated by colons (:).Specifically, each IPv6 address contains eight 16-bit hexadecimal numerals, each of which is represented by four hexadecimal digits. The following is an example IPv6 address: 2031:0000:130F:0000:0000:09C0:876A:130B To simplify handwriting, the leading zeroes in each 16-bit block can be omitted. Therefore, the preceding IPv6 address can be simplified as follows: 2031:0:130F:0:0:9C0:876A:130B In addition, if two or more consecutive blocks are all zeroes, double colons (::) can be used to further simplify the IPv6 representation. Therefore, the preceding IPv6 address can be further simplified as follows: 2031:0:130F::9C0:876A:130B In each IPv6 address, only one double-colon (::) can be used. If two or more double-colons are used, the number of zeroes in each 16-bit block cannot be determined when the IPv6 address is restored to its 128-bit version. X:X:X:X:X:X:d.d.d.d In the preceding format, each X represents a high-order 16-bit block consisting of several hexadecimal digits, and each d represents a low-order 8-bit block consisting of several decimal digits. In fact, the four low-order 8-bit blocks constitute a standard IPv4 address. Note that the SE2900 supports IPv6 addresses in the first format but not those in the second format. When configuring IP addresses on the SE2900, you can use any IPv6 addresses that comply with RFC 4291 and RFC 5952.The IPv6 addresses output by the SE2900 are mainly in the format defined in RFC 4291, and certain output IPv6 addresses are in the format defined in RFC IPv6 address structure An IPv6 address consists of the following two parts: Network prefix: The length of the network prefix is variable in bits. The network prefixes in an IPv6 address and an IPv4 address are used to identify the network to which the address belongs. Interface identifier: The length of the interface identifier is the difference between 128 and the length of the network prefix. It is similar to the host ID in an IPv4 address. Figure 2-6 shows the structure of the IPv6 address 2001:A304:6101:1::E0:F726:4E58 /64. Figure 2-6 Structure of the IPv6 address 2001:A304:6101:1::E0:F726:4E58 /64 Network prefix 64 bits 2001:A304:6101:0001 Interface identifier 64 bits 0000:00E0:F726:4E58 13

20 2 IP Networking Features SPUs on the SE2900 support two types of IPv6 addresses for packet sending, receiving, and processing and they are interface IPv6 addresses and service IPv6 addresses. 2.7 IPv4/IPv6 Dual Stack The SE2900 supports IPv4/IPv6 dual stack defined in RFC 4213.You can configure an IPv4 address and an IPv6 address on an interface and use the interface to access IPv4 and IPv6 networks. 2.8 IP Routing Routing information is used to guide packet transmission. Routing is a process of selecting routes for packets. On the SE2900, a routing table is saved on every VRF, and every routing entry in the table specifies an SE2900 physical interface used to transmit a packet to a subnet or host. The packet can then be sent to the next network device along the path or directly sent to the destination host. The following concepts are associated with IP routing: 1. Routing attributes Destination address: It is used to identify the destination address or network of an IP packet. Network mask: Combined with the destination address, it is used to identify the network segment on which the destination host or router resides. Output interface: It indicates the interface from which an IP packet is forwarded. Next-hop IP address: It specifies the IP address of the next network device to which an IP packet is transmitted. Priority: It is used to select the optimal route. A destination address may correspond to different next hops. The route with the highest priority (smallest priority value) is selected as the optimal route. Route status: It specifies whether a route is active or not. If the routing status is active, the route is available. If the routing status is inactive, the route is unavailable. 2. Routing table A routing table saves the routing information discovered by a routing protocol. On the SE2900, a routing table is saved on every VRF. Every routing entry in the routing table contains the destination address, subnet mask, discovery protocol, routing priority, next-hop address, and egress information. 3. Routing principle If multiple routes are destined for the same network address, routes are selected in compliance with the following rules: The route with the longest next-hop mask is preferred. If the length of the next-hop mask is the same, the route with the higher priority is preferred. 14

21 2 IP Networking Features The rule for selecting equal-cost routes is that signaling packets are distributed based on the source and destination IP addresses and media packets are distributed based on the stream ID. 4. Route classification Direct route After an IP address is configured for a router interface, the router generates a 32-bit host route whose IP address is the same as the configured IP address and the network route located in the same network segment as the configured IP address. A direct route is discovered by a link-layer protocol. For a host route, the IP address of the host is the destination address and the next-hop address is Static route A static route is a special route that is manually configured by the network administrator. On a network with a simple networking structure, correctly configuring the static route can guarantee network security and network bandwidth. Default route A default route is a special static route that is used when the SE2900 cannot find any matched routing entry. In a routing table, the default route is expressed as the route to the network with the subnet mask Using the default route can reduce the routing time and bandwidth required for packet forwarding. The benefit of using the default route is especially significant when the SE2900 processes service traffic of a large number of subscribers. 2.9 VRF/VRF6 VRF is a technology that uses multiple routing instances to independently send and receive packets to achieve network isolation and network address overlapping. Virtual routing instances are independent of each other, with their respective routing entries, interfaces, and IP addresses. Because the routing instances are independent, overlapping IP addresses or subnet segments can be used in different VRF instances without conflicting with each other. VRF is implemented on both the IPv4 and IPv6 protocol stack and VRF configurations on both protocol stacks are independent from each other. On a VRF network, the SBC groups networks into different VRF instances to access or isolate networks with overlapping segments. Every VRF instance is logically considered as an independent SBC. The objects in a VRF instance are as follows: A group of interfaces that are bound to the same VRF instance: The interfaces include both main interfaces and subinterfaces. An interface can belong to only one VRF instance. A group of IP addresses and subnets configured for the same interface: The IP addresses and subnets configured for different VRF instances can overlap. A group of independent service IP addresses: The service IP addresses of different VRF instances can overlap. An independent routing table in which the segments of different VRF instances can overlap A default VRF instance is created during system initialization of the SBC. The instance includes a global route, all the unbound interfaces, and all the IP addresses for which no VRF 15

22 2 IP Networking Features instance is specified. In addition, carriers can create multiple VRF instances that are independent of each other. 16

23 3 Networking Reliability 3 Networking Reliability 3.1 Active/Standby Processes The SE2900 provides two boards, with one deployed with the active control-plane PCU and forwarding-plane HRU and the other deployed with the standby control-plane PCU and forwarding-plane HRU. This design prevents single point of failure from the process level to the board level. The following figure shows the deployment of the active/standby PCUs and HRUs. OMU SPU Configuration channel PCU Backup channel for data forwarding Configuration channel PCU SPU Synchronization channel for data forwarding HRU Backup channel for data forwarding HRU Service packets Control-plane PCU: is responsible for processing background data, interface failure/restoration, and packets (such as ARP and BFD packets), adding, modifying, or deleting data (such as ARP and routes) based on control packets, and synchronizing the forwarding data to the forwarding process. The active and standby PCUs back up for each other to forward data. Forwarding-plane HRU: is responsible for receiving and sending IP packets and forwarding packets at a high speed. The HRU receives the forwarding data synchronized from the PCU. The active and standby HRUs back up for each other to forward data. The active and standby PCUs and HRUs enhance reliability by: 17

24 3 Networking Reliability Data forwarding on the HRU is not affected upon the switching between or the resetting of the active and standby PCUs. The call loss is within milliseconds upon HRU switching. 3.2 Active/Standby Ports Active/standby ports are used on a Layer 2 network to improve system reliability. The following figure shows the networking of the active/standby 1GE SFP 10GE SFP+ ports. Access Network Slot 1 and slot 3, working as backup for each other, are connected to two LAN switches. If the active port or the connection on the active port fails, services are switched from the active port to the standby port. This solution has the following characteristics: 1. Services are not switched on the HRU when port switching occurs. 2. Port switching is performed within milliseconds (a minimum of 200 milliseconds). This design brings a small call loss upon a single point of failure on a port, achieving high service reliability. 3.3 Load Balancing The SE2900 supports load balancing that allows multiple routes with the same destination address and priority. If these routes are matched, all of them are adopted. Signaling packets are forwarded to the destination address based on the source and destination IP addresses and media packets are forwarded to the destination address based on the stream ID, achieving load balancing. 18

25 3 Networking Reliability 3.4 Active/Standby Routes The SE2900 supports active and standby routes to improve network reliability. Users can configure multiple routes destined for the same destination as required. The route with the highest priority serves as the active route, and the routes with lower priorities serve as the standby routes. Normally, the SE2900 adopts the active route to forward data. When a fault occurs on the line, the active route becomes inactive and the SE2900 selects the route with the highest priority among the standby routes to forward data. In this manner, the switching between the active and standby routes is performed. If the active route restores, the route with the highest priority changes from the inactive state to the active state and the SE2900 re-selects a route. As the active route is with the highest priority, the SE2900 selects the active route to forward data. In this manner, the switching from the standby route to the active route is achieved. 3.5 ARP Probe The SE2900 can perform self-checks on the port status but fail to automatically obtain the link-layer status. If the physical status of a port is normal but the link becomes faulty, data cannot be sent to the peer device; as a result, the communication is interrupted. To prevent this issue, users can enable APR probe in the active/standby or VRRP networking to enhance network reliability. The ARP probe function is used to send ARP requests to the peer device within a specified period. The ARP response from the peer device is used to determine the network link status. If the number of times the system fails to receive a response within the specified period reaches the threshold or the failure rate within the specified period reaches the threshold, the ARP probe is considered failed, the network link fails, and a probe failure alarm is generated. The SE2900 participates in port switching arbitrary and triggers port switching. ARP probe can be classified into gateway probe and active/standby probe based on the peer path detected by the standby port. In gateway probe mode, the active and standby ports on the SE2900 regularly use the IP addresses configured on the ports to send ARP requests for the MAC addresses of gateway addresses. An IP address must be configured on the standby port to implement the probe. In active/standby probe mode, the active port of the SE2900 regularly uses the configured address to send the ARP request for the MAC address associated with the gateway address. The standby port regularly uses IP address to send the ARP request for the MAC address associated with the active port address. In comparison with the gateway probe mode, the active/standby probe mode uses less interface IP addresses and therefore is recommended. 3.6 IPv6 Neighbor Discovery IPv6 neighbor discovery (ND) is a technology that enables the SE2900 to check the status of network connections based on the response to the Neighbor Solicitation message initiated by the SE2900.If the SE2900 does not receive any response after initiating the maximum number of consecutive Neighbor Solicitation messages or the percentage of Neighbor Solicitation messages that are not responded within a period reaches the upper limit, the ND process fails. In this case, an alarm indicating the failure is generated and the interface switchover is 19

26 3 Networking Reliability implemented. Based on how IPv6 ND is implemented for the standby interface, IPv6 ND can be implemented as follows: 1. In the gateway mode, the SE2900 sends Neighbor Solicitation messages through both the active and standby interfaces to request the MAC address of the gateway. In this mode, the standby interface must be configured with an independent IPv6 address. 2. In the active/standby mode, the SE2900 sends Neighbor Solicitation messages through the active interface to request the MAC address of the gateway and sends Neighbor Solicitation messages through the standby interface to request the MAC address of the active interface. In this mode, the IP address of the standby interface is an all-zero IPv6 address. On live networks, this mode is recommended. 3.7 BFD Bidirectional forwarding detection (BFD) provides a simple method of detecting the stream transmission capability for a link or system, aiming at improving the link fault detection and restoration efficiency. BFD provides light-load and short-period detection for the faults on the channel between neighboring forwarding engines. The channel faults can be about the interface, data link, or even the forwarding engine. BFD can be used to rapidly detect faults about the communication between neighboring devices so that the devices can quickly locate the fault and switch traffic to the backup link, which speeds up network convergence and ensures normal service operation. The mechanism reduces the impacts of device or link faults on services and improves network usability. After the BFD-enabled device establishes peer relationships with neighboring systems, every system monitors BFD probe packets sent from other systems at the negotiated rate. The monitoring period can be specified at the millisecond level. On the SE2900, BFD can be performed in asynchronous mode or query mode. The difference between the synchronization and query modes lies in the detection location. In synchronization mode, the local end sends BFD control packets within a specified period, and the remote end checks the transmitted BFD control packets. In query mode, the local end checks the transmitted BFD control packets. Details are as follows: Asynchronous mode In this mode, BFD control packets are transmitted between systems within a specified period. If the SE2900 does not receive the BFD control packets sent from the peer system within the period, the session is considered Down. Query mode In this mode, every system is assumed to use an independent method of confirming the connections to other systems. Once a BFD session is established, the system stops sending BFD control packets. The system continues with sending periodic BFD control packets until the connectivity needs to be verified. If the SE2900 does not receive any response to the BFD control packets within the detection period, the session is considered Down. If the SE2900 receives a response to the BFD control packets, no BFD control packet is transmitted. The SE2900 does not support the query mode when it functions as the local end but supports a reply to the query packets sent from the peer system. When BFD is bound to a static route and the static route changes from the active state to inactive state upon a fault, traffic switches from the static route to a load-balancing or standby route. If BFD detects that a fault is rectified, the static route changes from the inactive state to the active state, and the route re-transmits traffic. 20

27 3 Networking Reliability The SE2900 supports both BFD for IPv4 and BFD for IPv6. 21

28 4.1 Overview The SE2900 can interconnect with Layer 2 (LAN Switch) and Layer 3 (router) devices. Different interconnection solutions are used based on the conditions of carriers' networks. At present, the common networking solutions are Layer 2 active/standby networking, dual-plane load balancing networking, VRRP networking, and VRF networking with address overlapping. Table 4-1 lists the solutions. Table 4-1 Networking solutions Networking Solution Interconnected Device Description Remarks Dual-plane load balancing networking Dual-plane router The SE2900 is connected to a dual-plane load-balancing router, such as a PE, in direct or side connection mode. Packets are forwarded to the two planes in load-balancing mode. Active/standby networking Dual-plane switch The SE2900 is connected to switches in direct or side connection mode. Packets are forwarded to the master switch in active/standby port mode. Interconnection with VRRP-enabled routers VRRP-enabled router On an existing VRRP network, the SE2900 is interconnected with VRRP-enabled routers in active/standby port mode. VRF networking Different networks with overlapping address segments The SE2900 groups networks into different VRF instances to access two or more networks with overlapping address segments. 22

29 4.2 Port Classification Port Overview MXUA0 Ports The SE2900 supports two types of boards: MXU and SPU. The MXU provides functions including device management, alarm management, and service configuration. The SPU provides functions including access control, security, QoS, media transcoding, media firewall, media/signaling proxy, NAT traversal, firewall traversal, flexible routing, network redundancy, and encrypted transmission for signaling/media. Figure 4-1 shows ports on the MXUA0. Table 4-2 lists the specifications of the ports. Figure 4-1 Ports on the MXUA0 Table 4-2 Specifications of ports on the MXUA0 Board Name Port Name Function Description Port Quantity MXUA0 LAN port O&M network port The port mode is 10/100/1000M Base-T auto-negotiation. The port type is RJ-45. The cable type is CAT5E. The port has two indicators. 2 RS232 network port Serial port for system commissioning The port type is RJ-45. The cable type is DB9-RJ45. The standard RS232 network port provides channels for program loading, communication, commissioning, and monitoring. 1 RS485 network port Serial port for power distribution monitoring The port type is RJ-45. The cable type is DB9-RJ45. The standard RS485 network port monitors the PDB status. 1 Fabric port Fabric-plane cascading port The port mode is 40G BASE-XR4 The port type is QSFP+. The cable type is 2 23

30 Board Name Port Name Function Description Port Quantity MPO. Fabric ports are used to implement Fabric cascading between the active and standby subracks. Base port Base-plane cascading port The port mode is 10/100/1000M Base-T auto-negotiation. The port type is RJ-45. The cable type is twisted pair. Base ports are used to implement Base cascading between the active and standby subracks SPUA0/SPUA1 Ports Figure 4-2 shows ports on the SPUA0/SPUA1. Table 4-3 lists the specifications of the ports. Figure 4-2 Ports on the SPUA0/SPUA1 Table 4-3 Specifications of ports on the SPUA0/SPUA1 Board Name Port Name Function Description Port Quantity SPUA0/S PUA1 SFP port 1GE signaling/mana gement port The port type is LC jumpering square optical fiber connector. The cable type is optical fiber. SFP ports are used for signaling and management. 4 SFP+ port 10GE signaling/medi a port The port type is LC jumpering square optical fiber connector. The cable type is optical fiber. SFP+ ports are used for signaling/media transmission. 4 24

31 4.2.4 Service-based Port Allocation Both the SPUA0 and SPUA1 are equipped with 4*1GE and 4*10GE ports. Figure 4-3 shows the service functions of different ports on an SPU. In this section, ports are expressed in the format of GE Subrack ID-Slot ID-Interface number. For example, port 2 in slot 1 subrack 0 is expressed as GE If only one SE2900 is deployed, the default subrack ID is 0. Figure 4-3 Port allocation on the SPU 1GE SFP 10GE SFP signaling port 4 Reserved port 4 port media port port Reserved signaling/media port (small user capacity) port (small user capacity) The rules for port allocation are as follows: GE0-1-0 and GE0-4-0 are used to access access-side signaling traffic and some media traffic. GE0-1-4 and GE0-4-4 are used to access core-side signaling traffic. Port 4 in slots 3 and 6 does not need to access core-side signaling traffic and therefore is reserved. Ports 0 and 1 in all slots are used to access access-side media traffic. The current service traffic requires only one port, that is, port 0. Ports 2 and 3 in all slots are used to access core-side media traffic. The current service traffic requires only one port, that is, port 2. A 10GE optical port can be degraded to a GE optical port if the media traffic rate on the ISU is less than or equal to1.6 Gbit/s and that on the ESU is less than or equal to 2.4 Gbit/s. Ports 5 and 7 can be added to access access-side media traffic and core-side media traffic respectively as the service traffic increases. GE electrical ports are used if the access-side media traffic is less than or equal to 0.8 Gbit/s. In this case, only ports 0, 2, 4, and 6 are available. Ports in slots 1 and 4, as well as ports in slots 3 and 6, work in active/standby or load-balancing mode. Every board must be allocated with access-side and core-side media ports. All access-side or core-side ports must be connected to the same network. 25

32 In the case of multi-subrack cascading, every board in a subrack must be allocated with access-side and core-side media ports. and core-side signaling ports reside only in subrack 0, as shown in Figure 4-4. Figure 4-4 Port allocation in other subracks Subrack 1 1GE SFP 10GE SFP Reserved port 0 1 media port 2 3 port Lawful interception port signaling/media port (small user capacity) port (small user capacity) 4.3 Dual-plane Load Balancing Networking Networking Scenario The SE2900 is directly connected to routers. The routers are deployed on a dual-plane network where both planes can forward service packets. 26

33 4.3.2 Networking Figure 4-5 networking where dual-plane load balancing is implemented 1GE SFP 10GE SFP+ signaling and media media Router 1 Router 2 Access Network As shown in Figure 4-5, two routers are deployed in load-balancing mode on the access-side network where both planes can forward service packets. In this situation, use the specified traffic model to calculate the number of required cables on each board based on the traffic volume and distribution. The product of the port quantity and port bandwidth must be no less than the service bandwidth required by the specified board. If a base board supports a maximum number of 40,000 concurrent audio sessions, the codec type is G.711, the packetization time is 20 ms, and the Ethernet bandwidth required by a session flow is 95.2 kbit/s, the bandwidth required is x 95.2 kbit/s = Gbit/s. In this case, only one 10GE port needs to be configured on the board to access access-side media traffic. These specifications can also be used to calculate the high bandwidth required by video traffic. In this document, the bandwidth required when the number of accessed UEs reaches the upper limit is used as an example for the scenarios where bandwidth requirements are not specified. On the live network, the bandwidth required depends on the actual service traffic. Pay attention to the following items for networking: Services in slots 1 and 4, as well as services in slots 3 and 6, back up each other. No real active/standby relationship exists between SE2900 service boards. Inside the SE2900, processes that back up each other are deployed on different boards. In the case of a service failure, processes are switched as the minimum switching objects. Ports on service boards are managed by HRU processes for sending and receiving packets, and the active and standby HRU processes are deployed on adjacent boards. Therefore, the boards work in active/standby mode in IP forwarding. GE0-1-0 and GE0-4-0 are used to access access-side signaling traffic and some media traffic. The two ports belong to different network segments. Every pair of boards has its own media service addresses. GE0-1-0 and GE0-4-0 on the two boards are used to implement load balancing. Media traffic is evenly distributed on the two ports in route load-balancing mode, as shown in Figure