Philosophy of Building CN2: A Simple, Scalable, and Secure Network for China Telecom

1. Philosophy of Building CN2 Xu Jianfeng China Telecom Corporation http://www.chinatelecom.com.cn

2. Background • Challenges • Total voice traffic and revenue decreases by the end of 2005. The mobile phone and IP phone calls have cannibalized part of the voice traffic businesses • Traditional communication network is unable to support China Telecom’s strategy to become a Comprehensive Information Service Provider. This is due to its lack of capability in offering value-added service and service awareness on a unified network. • High OPEX (Operating Expenses) is required for operating separate networks in a tradition way • The existing ChinaNet is not best choice for NGN, 3G, VPN and other strict SLA demanding services • Opportunities • Acceleration of the Information and Communications Technology (ICT) adoption in government and enterprises would drives the demand for telecom services • Adoption of the SIP-based soft-switch technology • The impending releases of 3G license • Rapid development of the broadband service • Fix and Mobile Convergence ( FMC )

3. Solutions • Migration of voice service from PSTN network to IP-based network • Preparation for 3G-based mobile services • Accelerate the development and deployment of the broadband services base on xDSL access technology • Drive managed service and system integration service • Triple play services and future IP NGN convergence including network convergence, service convergence and application convergence • Built an Integrated IP/MPLS-based multi-service platform — CN2 • CN2：China telecom Next Carrier Network

4. Philosophy of Building CN2 • Simple network topology • Scalable routing architecture • Highest level of redundancy • Highest level of security • Different class service • Day one support for voice , video and data • End to end control and management

5. CN2 Strength • Homogeneous Global Architecture • Single Global ASN(AS4809) • ISIS level2-only with sub-second convergence • MPLS FRR with sub-50ms reroute • Robust Architecture Allows for Unsurpassed Stability • Diffserv-based QOS、MPLS and multicast enabled network • 6PE-based IPV6 network • Offer Layer-2/3 public/private flexible connectivity over IP or MPLS • Leading SLAs via Zero Loss & Speed of Light Delays • Fast automated end to end service provision and fault management utilizing industry leading IP service management solutions, help to greatly reduced OPEX and accelerate service deployment • End to end IP SLA monitoring tool make CN2 a true carrier class network

6. Simple Network Topology • CN2 comprises of two functional planes and four structural layers to offer a seamless connectivity for customers. • The two functional planes are high speed data forwarding plane and service provisioning plane • The four structural layers are core layer, aggregation layer, edge layer and services connecting layer • The high speed data forwarding plane and service offering plane is supported by 4 and 1 vendors respectively. This is to ensure minimum service disruption and better edge services control. SR/PE Service Edge Aggregation SR/PE Core 高速转发层 业务接入层 SR/PE

7. Simple Network Topology(cont) • IP/MPLS Network • All-Optical，Dense Wave Division Multiplexing (DWDM) • SONET/SDH framing • Per flow load-sharing and fail-over load-sharing with ISIS • MPLS is enabled on all network with VPN traffic encapsulated in MPLS and others transported in native IP IP IP MPLS SONET FRAMING DWDM

8. Scalable route architecture • To ensure network’s scalability and security, only infrastructure address blocks are redistributed into the IS-IS (IGP) routing table. Non-infrastructure addresses are redistributed in BGP. Keeping the IS-IS routing table to a minimum would greatly enhance the network stability. • Single Global ASN (AS4809) • BGP Communities are deployed for routes control and netflow-based traffic monitor • CN2 have two type Route reflector • VPN RR for RFC2547-based VPN service,(VRR) • Global RR for global internet routing(GRR) • VPN RR is independent of global RR, both use one level Route Reflector(RR) • Global iBGP: Scaling the Global Internet Routing Table involve the increase in the number of GRR group,each group handles a part of global routes. • VPN iBGP: Likewise, scaling the VPN routing Table involve the increase of VRR group. Example, VPN1-500 is handled by VRR-G1 while VPN501-1000 can be handled by VRR-G2

9. Send Part 1 routes to G1 Send Part 2 routes to G2 Receive Part 1 routes from G1 Receive Part 2 routes from G2 Scalable routing architecture (Cont) • Scaling the Global Internet Routing Table Group 1 for part1 routes Group 2 for Part2 routes Full mesh Peers Full mesh Peers GRR1 GRR2 GRR3 GRR4 Client Client EBGP EBGP Client Client Internet Internet

10. Send/ receive VPN1 routes to/from G1 Send/ receive VPN501 routes to/from G2 Scalable route architecture (Cont) • scaling the VPN routing Table Group 1 for VPN 1-500 routes Group 2 for VPN 501-1000 routes Full mesh Peers Full mesh Peers VRR1 VRR2 VRR3 VRR4 Client Client Client PE Client PE PE PE

11. Highest Level of redundancy • All network links are deployed in pairs over diverse facilities • Only POS interface are used on backbone link to do faster link failures detection • All network links are active (NOT working and protect) • Each PoP’s router pair is connected by multiple routers. Link failure protection is done through IS-IS (layer 3 control) and not dependent on transport layer (layer 2 control) • IS-IS routing protocol • Per flow load sharing between dual pairs • Fail-over load sharing • Sub-second fast convergence for gold service • Three priority LSP flooding and FIB update • MPLS FRR • 1:1 mode FRR is deployed in core layer for 50 links • Sub-50ms reroute time • Built to maintain utilization not to exceed 50% during normal running • As a congestion-free network, CN2 ensures premium priority for delivery of all packets in the core

12. Higher Level of security • Strict uRPF is deployed on all customer access interfaces • Loose uRPF is deployed on interconnected interface • Infrastructure ACLs (iACL) deny external traffic to ALL routers interfaces address. iACL are deployed on edges and borders of the network. No one outside network can reach routers • Infrastructure routes are not distributed to internet or customer • All router access control is managed by AAA servers and syslog • QOS technology would be deployed accordingly to reduce the impact of an attack or worm traffic. • All customer facing routers interfaces do not have IGP turn on. When EBGP are deployed on these interfaces, BGP MD5 hash must be configured

13. Differentiated class service capability • CN2 QoS positioning • QoS is used to allocate limited network resources to different services. Unlike traditional networks of ATM, Frame Relay, and lease circuit services, CN2 provides an uniform network for all these services. To differentiate the services based on the class of importance or contract, QdS is the mechanism in place to segregate and allocate network resources to different class of services. • Example of a QoS policy: 3G and soft-switch traffic can be allocated with at least 50% of the available bandwidth while Vnet can only consume a maximum of 15% of the total bandwidth • QoS are also positioned for traffic congestion management. Under the accidental circumstances of equipment or circuit failures, QoS helps to manage the limited usable network resources to different classes of services. • Better resource utilization is expected from deploying QoS. Having elastic policy to re-allocate the under-utilized resources results in efficient resources utilization.

14. Differentiated class service capability (Cont) • QoS design philosophy • CN2 adhere to DiffServ framework based on IP precedence and MPLS EXP Bit classification. Thus offering 8 classes of service • Initial CN2 service classification is base on 5 basic classes of services. • 1 class for network control traffic • 1 class for CT internal service • 3 classes for service offering • All services are classified, remarked, shaped and rate-limited on the edge of the network to ensure a consistent QOS policy enforcement within the CN2 network • Service resource allocation is based on class of service. GOLD class of service would be allocated with 2 times more redundant resources than BRONZE class of service • Convergence of prefix varies on the traffic class. Prefixes of a GOLD class of traffic would converge faster than prefixes of BRONZE class of traffic

15. Different class service capability • CN2 SLA

16. Corporate Dial QOS edge PE PE PE broadbandaccess Integrated VPN PE PE P P P PE PE MPLS L3 VPN P IP/MPLS platform SDH/DD P PE P PE P IPSecVPN PE P MPLS L2 VPN PE PE ATM/FR PE AoMPLS All services are Edge Functions • Services are enforced and policed on the edges of the network via the SR/PE device. Service comprises of soft-switch, video conference, VPN, Internet, ATM/FR/DDN etc. • To ensure core network’s stability and security, service provisioning, new service deployment and security control are performed on the edge of the network.. • The SOLEresponsibility of the Core Network is packet switching and forwarding

17. Network Capacity and Coverage • Network Capacity and Coverage (by the end of 2005)： • CN2 will provide coverage for 208 cities including Hong Kong, Tokyo, Singapore, London, New York, San Jose, Washington etc. with service offering MPLS/VPN and Internet Services. • 671 routers in total，including 439 P routers，208 PE/SR routers，12 Public RR，and 12 VPN RR • 1267 relay links with a total link bandwidth of 4.231T • Over 800 external interlinkage with a total bandwidth of 2.8T • A total customer access link bandwidth of 650.62G • CN2 uses Cisco 12416 with E3&SIP line cards as PE routers exclusively to ensure a consistent connectivity and configuration management. This would reduce equipment interoperation issue as well as the speed of problem resolution.

18. CN2 service capability • Support MPLS layer 2/3 VPN • L3 VPN(RFC2547) • Ethernet point to point service(Draft-martini) • Ethernet multi point service (Vkompella VPLS) • ATM/FR over MPLS • Support 3 classes of service. GOLD, SILVER and BRONZE. • Support internet & VPN services with SDH、Ethernet/VLAN、ATM/FR/DDN、 L2TPv3, pseudo-wired access • Support network wide multicasts of 600 groups,1.2Gbps end to end multicast traffic • Support network wide 6PE-based IPv6 with wire speed • CN2 uses Cisco 12416 with E3&SIP line cards as PE routers exclusively to ensure a consistent connectivity and configuration management. This would reduce equipment interoperation issue as well as the time of problem resolution, thus be more agile in time to market.

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