According to Cisco, “IP NGN is a platform for the Connected Life.” What does that really mean? It is an infrastructure for voice, video, mobile, and cloud or managed services based on Cisco products, including the CRS Series, ASR Series, and Nexus Series.
Cisco IP NGN carrier Ethernet design incorporates multiple networking technologies to provide optimal flexibility for current and next-generation service offerings:
- Ethernet over MPLS (EoMPLS)
- Layer 3 Protocol Independent Multicast-Source Specific Multicast (PIM-SSM)
- MPLS VPN
- IP over dense wavelength-division multiplexing (IPoDWDM)
- Hierarchal Virtual Private LAN Service (H-VPLS)
- IEEE 802.1ad; as well as emerging Ethernet, IP, and MPLS technologies
Basic Cisco design for NGN Routing + MPLS design must supply Provider Edge (PE)-to-PE Routes (and Label Switched Paths) as well as Single Border Gateway Protocol (BGP) Autonomous System Number (ASN). Furthermore, the PE needs /32 routes to other PEs, and PE placement shouldn’t matter.
Routing + MPLS Design conventional wisdom says
- Advertise infrastructure (e.g., PE) routes in IGP for reachability between PE routers.
- Advertise infrastructure (e.g., PE) labels in LDP to establish a label switch path between PE routers.
- Segment IGP domains (i.e., ISIS L1/L2 or OSPF Areas) to add control. Keep in mind that summarization is not allowed at the borders; this would be disruptive to the label switch path.
The Routing + MPLS Design Conventional Wisdom may not be good enough in environments with large IGP database size, a concern for fast(er) convergence and for network stability, or networks with large LDP databases.
Interior Gateway Protocols
Interior Gateway Protocols come in two flavors: Intermediate System to Intermediate System (ISIS) and Open Shortest Path First (OSPF). Let’s do a quick comparison:
|Dijkstra algorithm||Dijkstra algorithm|
|OSPF natively built to route IPv4 (OSPFv2) or IPv6 (OSPFv3)||IS-IS natively OSI, but supports IPv4, IPv6, Decnet Phase 5, IPX, and Layer 2 routing (TRILL, FabricPath) OSPF ISIS|
|4 network types (5 in a Cisco network)||2 network types|
|11 or 12 LSA Types (OSPFv2 verses OSPFv3)||2 types of LSP|
|6 types of areas 2 types of levels (areas)||2 types of levels (areas)|
|Area number and router ID in the format of IPv4 address for both OSPFv2 and OSPFv3||NET has “area” and system ID embedded in it|
Multiprotocol Border Gateway Protocol
BGP is a distance vector protocol with enhancements: reliable updates, triggered updates only, and path attributes. It is designed to scale to huge internetworks (407,000 routes on the Internet) but not for speed.
Virtual Routing and Forwarding (VRF)
Virtual Routing and Forwarding is a technology implemented in the IP network routers that allows multiple instances of a routing table to exist on the same router at the same time. As each VRF is independent, duplicate (or overlapping) IP subnets can exist in different VRFs without conflicting with each other.
Multi-Protocol Label Switching (MPLS)
MPLS compliments IP technology. It is designed to leverage the intelligence associated with IP Routing and the Switching paradigm. MPLS consists of a Control Plane and a Forwarding Plane. The Control Plane builds a Forwarding Table, while the Forwarding Plane forwards packets to the appropriate interface (based on the Forwarding Table).
The efficient design of MPLS uses Labels to encapsulate IP packets. A Forwarding Table lists Label Values, which are each associated with determining the outgoing interface for every network prefix. Cisco IOS Software supports two signaling mechanisms to distribute labels: Label Distribution Protocol (LDP), and Resource Reservation Protocol/Traffic Engineering (RSVP / TE).
Today’s Services Providers networks have to leverage technology to deal with the demands of clients and their traffic. The networks have to be able perform at or above those expected levels and be flexible enough to handle needs of the future requirements (to a point). This post gave you a taste of some of those technologies and the method that providers are using to scale to much larger networks.
Excerpted and available for download from the Global Knowledge White Paper: Cisco Service Provider Next Generation Networks
SPNGN1 – Building Cisco Service Provider Next-Generation Networks, Part 1
SPNGN2 – Building Cisco Service Provider Next-Generation Networks, Part 2″ target=”_blank”>
SPROUTE – Deploying Cisco Service Provider Network Routing