Chapter 8 Management Network Connectivity

TCP/IP and OSI Networking

8.6.4 OSI Routing

OSI architecture includes ESs and ISs. The OSI routing scheme includes:

A set of routing protocols that allow ESs and ISs to collect and distribute the information necessary to determine routes. Protocols include the ES-IS and IS-IS protocols. ES-IS routing establishes connectivity among ESs and ISs attached to the same (single) subnetwork.

A routing information base (RIB) containing this information, from which routes between ESs can be computed. The RIB consists of a table of entries that identify a destination (for example, an NSAP), the subnetwork over which packets should be forwarded to reach that destination, and a routing metric. The routing metric communicates characteristics of the route (such as delay properties or expected error rate) that are used to evaluate the suitability of a route compared to another route with different properties, for transporting a particular packet or class of packets.

A routing algorithm, Shortest Path First (SPF), that uses information contained in the RIB to derive routes between ESs.

In OSI networking, discovery is based on announcements. An ES uses the ES-IS protocol end system hello (ESH) message to announce its presence to ISs and ESs connected to the same network. Any ES or IS that is listening for ESHs gets a copy. ISs store the NSAP address and the corresponding subnetwork address pair in routing tables. ESs might store the address, or they might wait to be informed by ISs when they need such information.

An IS composes intermediate system hello (ISH) messages to announce its configuration information to ISs and ESs that are connected to the same broadcast subnetwork. Like the ESHs, the ISH contains the addressing information for the IS (the NET and the subnetwork point-of-attachment address [SNPA]) and a holding time. ISHs might also communicate a suggested ES configuration time recommending a configuration timer to ESs.

The exchange of ISHs is called neighbor greeting or initialization. Each router learns about the other routers with which they share direct connectivity. After the initialization, each router constructs a link-state packet (LSP). The LSP contains a list of the names of the IS’s neighbors and the cost to reach each of the neighbors. Routers then distribute the LSPs to all of the other routers. When all LSPs are propagated to all routers, each router has a complete map of the network topology (in the form of LSPs). Routers use the LSPs and the SPF algorithm to compute routes to every destination in the network.

OSI networks are divided into areas and domains. An area is a group of contiguous networks and attached hosts that is designated as an area by a network administrator. A domain is a collection of connected areas. Routing domains provides full connectivity to all ESs within the domains. Routing within the same area is known as Level 1 routing. Routing between two areas is known as Level 2 routing. LSPs that are exchanged within a Level 1 area are called L1 LSPs. LSPs that are exchanged across Level 2 areas are called L2 LSPs. Figure 8-16shows an example of Level 1 and Level 2 routing.

Note The ONS 15310-MA SDH do not support Level 1/Level 2 routing. Level 1/Level 2 routing is supported by the ONS 15454, ONS 15454 SDH, and the ONS 15600.

Cisco ONS 15310-MA SDH Reference Manual, Release 9.1 and Release 9.2

 

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Cisco Systems 15310-MA manual OSI Routing

15310-MA specifications

Cisco Systems has established itself as a leader in the networking domain, offering a wide array of solutions to meet the needs of modern businesses. Among its impressive product lineup are the Cisco 15310-CL and 15310-MA routers, designed to provide advanced network performance and reliability.

The Cisco 15310-CL is a versatile platform that primarily serves as a carrier-class router aimed at supporting high-speed data and voice services. It is built to handle the demands of large enterprises and service providers, offering a robust design that ensures maximum uptime and performance. One of its standout features is its modular architecture, which enables users to customize their configurations based on specific application needs. This scalability allows for future expansion without the need for a complete hardware overhaul.

Key technologies integrated into the Cisco 15310-CL include high-density Ethernet interfaces and a comprehensive suite of Layer 2 and Layer 3 protocol support. The device is capable of supporting multiple types of connections, including TDM, ATM, and Ethernet. This flexibility makes it an ideal choice for organizations that require seamless migration between various service types. Moreover, with features such as MPLS (Multiprotocol Label Switching) support and advanced Quality of Service (QoS) mechanisms, the router ensures that critical applications receive the necessary bandwidth and low latency required for optimal performance.

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Both models benefit from Cisco's commitment to security and manageability, offering features like enhanced encryption protocols and user authentication mechanisms that help safeguard networks against threats. Additionally, they can be managed through Cisco’s intuitive software tools, simplifying configuration and monitoring tasks for IT administrators.

The Cisco 15310-CL and 15310-MA are ideal solutions for businesses seeking to enhance their network infrastructure, ensuring firms can keep pace with evolving technology demands while maintaining a focus on security and performance. Their combination of advanced features, modular capabilities, and robust support makes them valuable assets in the networking landscape.