Requirements for the Wiring Closet

Transcription

1 WHITE PAPER Requirements for the Wiring Closet Advanced Wiring Closet Features Today, as nearly every segment of the networking industry is buffeted by change, most network managers face a fundamental question: To what extent can an integrated architecture and infrastructure be maintained? This paper details how to provide advanced functionality in the wiring closet by leveraging tight product integration and extending multilayer services from the network core. Advanced functionality will have to be provided by wiring closet devices in order to effectively support emerging applications. Multicast Support Most applications in use today operate between one receiver and one sender. In many of today s newer applications, one sender will transmit to a group of receivers simultaneously. These important applications will help increase an organization s ability to communicate and collaborate, which lends a competitive advantage. Examples include the transmission of corporate messages to employees, video and audio conferencing for remote meetings and telecommuting, replicating databases and Web site information, live transmission of multimedia training and university courses, communications of stock quotes to brokers, collaborative computing, transmission over networks of live TV or radio news and entertainment programs, Microsoft s NetShow and NetMeeting, and Precept, Inc. s IPTV. The technology that enables these applications is multicast. The ability to effectively support multicast traffic is a requirement in the wiring closet. The architecture of the Cisco Catalyst 5000 Family of LAN switches is especially suited to handle multicast traffic. With wire-speed performance, these switches can transmit traffic from multiple multicast sessions out of all ports simultaneously. This capability has been demonstrated in a testbed at Microsoft running Microsoft s NetShow application (see Figure 1) on a fully loaded Catalyst 5500 supporting 264 clients. Microsoft is deploying its multicast applications campus-wide using a LAN switching infrastructure of Catalyst 5000 Family switches. Page 1 of 9

2 Figure 1 Catalyst 5500 Supporting Multiple Microsoft NetShow Sessions However, supporting wire-speed multicast transmission is not the only issue confronting network managers who wish to support these applications. The central issue is that wiring closet switches operate at the data link or Media Access Control (MAC) layer and inherently do not have the intelligence to transmit multicast traffic. The result is that multicast traffic is broadcast to all switch ports. At this point, the wiring closet bandwidth is paralyzed, impacting the performance of all production applications. Figure 2 Multicast Traffic is Broadcast to All Ports in the Wiring Closet Page 2 of 9

3 Recognizing that most customers have deployed Layer 2 switches in the wiring closet (and will continue to do so for cost and ease-of-deployment reasons) and that IP multicasting is quickly becoming a reality in enterprise networks, Cisco is taking an industry-leading approach to ensure the success of both. One result is CGMP Cisco Group Management Protocol a dynamic protocol that extends multicast intelligence to the high-performance Catalyst switch family. Cisco used its proven expertise in router-based IP multicasting to build this protocol. CGMP To better manage IP multicast distribution, Cisco leverages the intelligence of core routers or multilayer switches by enabling these devices to communicate with Layer 2 wiring closet switches. CGMP is a Cisco-developed protocol that allows Catalyst switches in the wiring closet to learn about the existence of multicast clients from Cisco routers and Layer 3 switches. The net result with CGMP is that IP multicast traffic is delivered only to those clients who are interested in the traffic. All other clients who have not explicitly requested the traffic will not receive it. CGMP is a feature that has been shipping since 1997 in standard Catalyst switch software, which makes it an attractive feature from both a cost and deployment perspective. Figure 3 CGMP Enables Intelligent Multicast Transmission NetFlow Feature Card Another mechanism for extending multilayer intelligence into the wiring closet is through the deployment of the NetFlow feature card (NFFC or NFFC2). The NFFC or NFFC2 is a daughter card for the Supervisor Engine that runs in a Catalyst 5000 Family switch. With NFFC technology, a Catalyst switch can examine Layer 3 and Layer 4 packet information without negative performance impact. This powerful feature greatly improves the functionality of the switch, increasing its effectiveness in managing traffic in the wiring closet. IGMP Snooping One benefit of NFFC technology in the wiring closet is IGMP snooping. The Internet Group Management Protocol (IGMP) runs between multicast clients and routers. IGMP is defined by Request for Comments (RFC) 1112 and almost all emerging multicast applications use IGMP. The process of a video client initiating a multicast session starts with the client sending an IGMP join message toward the video server. A switch using IGMP snooping can detect this IGMP join message and can use the information Page 3 of 9

4 within this message to learn about the multicast session. Multicast traffic destined for the video client will be contained to that video client s switch port. Without IGMP snooping, the switch would broadcast the multicast traffic to all ports, wasting network bandwidth and negatively impacting the performance of all stations attached to the switch. Figure 4 With IGMP Snooping, a Layer 2 Switch Can Independently and Intelligently Handle Multicast Traffic Protocol Filtering Another benefit of NFFC technology in the wiring closet is automatic protocol filtering. An NFFC-enabled switch can detect what type of client stations (i.e., IP and IPX) are attached to it by reading the header of all packets originating from the client stations. The switch will automatically shield client stations from unnecessary protocol broadcasts. For example, an IP-only client station will no longer see IPX broadcasts from IPX stations within the same virtual LAN (VLAN). Network managers are granted ultimate flexibility with this protocol-filtering capability. If desired, network managers can turn off the feature for all ports on the switch, for only specified VLANs on the switch, or on a port-by-port basis. They can also override protocol filtering on a port by allowing certain protocol broadcast types to be transmitted. Protocol filtering in the wiring closet improves bandwidth efficiency and end-station performance by freeing the end-station CPU from interrupts to process unnecessary broadcast traffic. Figure 5 Automatic Per-Port Protocol Filtering Page 4 of 9

5 Quality of Service The goal of quality of service (QoS) is to provide better and more predictable network services by providing dedicated bandwidth, controlling jitter and latency, and improving loss characteristics. As part of an intelligent network, services such as QoS are essential throughout the enterprise. QoS functionality must be supported end to end to be an effective tool, so QoS support must also be provided by wiring closet switches. The mechanism that will enable QoS is called policy management. Policy management allows the network to be mapped into the enterprise s profit drivers. Cisco delivers policy management software with Cisco Assure. Cisco Assure policy networking is a further step to the tight integration of applications and network infrastructure. Cisco Assure provides the automatic translation of business requirements to network services such as QoS. Examples of this include Weighted Random Early Detection (WRED) and the Resource Reservation Protocol (RSVP), two more recent Cisco IOS technologies, to provide end-to-end QoS control. WRED in the wiring closet can be used to monitor traffic levels in order to prevent congestion and ensure priority traffic delivery. RSVP establishes end-to-end bandwidth guarantees to readily support mission-critical and bandwidth-intensive multimedia applications. The Catalyst 5000 Family also supports 802.1p and 802.1Q for client stations using these standards. Cisco Assure policy networking will be the glue that binds these QoS mechanisms together, delivering effective and consistent end-to-end QoS support. The NetFlow feature card II is part of the CiscoAssure end-to-end QoS solution. Deployed in a wiring closet, the NFFC II can identify user applications and classify traffic with the appropriate priority level. It enables admission control at the network edge to prevent unauthorized applications from being allowed on the network. The NFFC II can classify user data as high or low priority, based upon physical source port, source/destination MAC address, or network- and transport-layer source/destination addresses. With the NFFC II, the Catalyst 5000 Family switches are QoS edge devices that are application aware. In Figure 6, Catalyst 5000 Family switches identify and classify mission-critical enterprise resource planning (ERP) application traffic as high priority. This priority is maintained from the wiring closet through the campus backbone until the data is delivered to the ERP server in the data center. During periods of network congestion, low-priority traffic (such as that originated from the game software Doom ) is dropped. Furthermore, the network administrator can choose to completely filter certain applications, not allowing any of the filtered traffic to traverse the backbone network. Figure 6 CiscoAssure in the Wiring Closet for an End-to-End QoS Solution Wiring Closet Set ERP = High Set DOOM = Low ERP ERP Si Si C5509 with NFFCII C5500 with NFFCII DOOM Campus Backbone ERP Server Enterprise networks increasingly need to support a broad spectrum of business applications. New applications such as videoconferencing or voice (telephone) traffic will demand a guaranteed level of service to minimize jitter, delay, and loss with assigned bandwidth. Sophisticated QoS mechanisms throughout the enterprise will be needed so that all traffic is delivered within acceptable limits. Page 5 of 9

6 Reliability Layer 2 wiring closet switches use the Spanning-Tree Protocol to recover from link failure and guard against data loops forming in the network. When the primary link fails, the spanning-tree algorithm will select a new path, while ensuring that there is never more than one path connecting two points. The convergence time of the Spanning-Tree Protocol is normally 50 seconds. This long delay can cause many client/server sessions to time-out. Cisco has developed a way to greatly improve Spanning-Tree Protocol convergence on its LAN switches. With the Cisco features PortFast, UplinkFast, and BackboneFast, Spanning-Tree Protocols will converge in less than five seconds after a fault on an uplink. Figure 7 UplinkFast Preserves Client Sessions with Fast Failover Performance While most networking vendors support the Spanning-Tree Protocol, some do not allow multiple spanning-tree domains. A single spanning-tree domain is inherently less reliable than multiple smaller spanning-tree domains in large network designs, because misbehaved bridge protocol data unit (BPDU) packets are not contained but traverse the entire network. Cisco provides a separate spanning-tree domain per VLAN. Each VLAN is, therefore, completely isolated from its neighbors. Load Sharing Data over Separate Paths Cisco uses Inter-Switch Link (ISL) to provide Layer-2 link redundancy and load sharing between the wiring closet and the core network. With ISL trunks, redundant load-sharing uplinks are provided by dividing the traffic into two different VLANs. For example, consider a wiring closet switch connected to a core layer switch by two ISL trunks. On the wiring closet switch itself, half of the users are assigned to VLAN1 and the other half to VLAN2. One ISL trunk provides the primary path for traffic on VLAN1 and a secondary path for traffic on VLAN2. The second ISL link is the reverse. If either trunk fails, all the traffic is carried on a single ISL trunk. This link redundancy is possible because each VLAN is a separate spanning-tree domain. Providing link redundancy and load sharing is part of building a resilient network in the wiring closet. Page 6 of 9

7 Figure 8 Load-Sharing Traffic over Dual-Homed Wiring Closet Uplinks Uplink Scalability and Flexibility Since most traffic traverses the uplink as it travels between clients in the wiring closet and centralized servers in the network core, the uplink is the real measure of maximum performance provided by a wiring closet switch, not the performance rating of the switch itself. Imagine a switch with infinite forwarding capacity. Now connect a 100-Mbps uplink to the core. No matter how fast this switch can forward packets, the maximum performance end users connected to this switch will experience is 100-Mbps throughput to servers in the core of the network. Clearly, scaling uplink capacity is important. Cisco s Catalyst 5000 Family of LAN switches supports Gigabit Ethernet. As a migration path beyond Gigabit Ethernet, the Catalyst 5000 switches also support Gigabit EtherChannel technology, which employs multiple, standard Gigabit Ethernet links that are configured in parallel between switches. Traffic is load shared over the parallel gigabit links, for an aggregate data rate of up to 8 Gbps. Cisco s Gigabit EtherChannel implementation is done in hardware, so load sharing over multiple Fast Gigabit links does not impose a performance penalty. For Asynchronous Transfer Mode (ATM) users, the Catalyst switches support DS3, OC-3, and OC-12 ATM uplinks. Fast EtherChannel is a technology similar to Gigabit EtherChannel because it builds upon the established Fast Ethernet specification to bring higher bandwidth in steps. It uses multiple, standard, full-duplex IEEE Fast Ethernet links between pairs of switches, servers, or routers and establishes a scalable fat pipe to carry higher aggregate-data rates than any single link can accommodate. Configured as parallel point-to-point Fast Ethernet links, users can choose the bandwidth they require up to 800 Mbps or more by selecting the number of links to dedicate as a Fast Ethernet trunk. Fast EtherChannel technology can also be used to solve distance limitations imposed by Gigabit Ethernet. Using multimode fiber and a short-wavelength laser (SX), Gigabit Ethernet cannot travel beyond 260 meters. With a long-wavelength laser (LX) over multimode fiber, the distance can be increased to 550 meters, but at a much greater cost. Fast EtherChannel links can reach the same distances as regular Fast Ethernet links, up to 2 km over multimode fiber. Cisco s Fast EtherChannel implementation is completed in hardware, so load sharing over multiple Fast Ethernet links does not impose a performance penalty. Cisco s hardware implementation also provides subsecond fault-tolerant operation, which means that network traffic from a failed link will be automatically redirected to remaining links with subsecond convergence time. Page 7 of 9

8 User Mobility A universal requirement across all campus switched internetworks is the need to minimize the costs associated with user mobility. These include station and switch port reconfiguration costs when users are moved between wiring closets, as well as the cost of updating the tracking tools based on the new location of users. The need for authentication and security, especially when users are allowed open access to the network, is often coupled with user mobility. CiscoWorks for Switched Internetworks (CWSI) provides an automated VLAN authentication approach that verifies a user s station address prior to permitting access, and a newly developed tracking tool that maintains user location and identity as part of the embedded database functions. These management functions work seamlessly with Dynamic Host Configuration Protocol (DHCP), which automates TCP/IP addressing, and with the underlying topology services of CWSI that can pinpoint the user location within the topology map. Network Management Network management has always been a concern for the wiring closet. Switches should be able to support the four groups of Remote Monitoring (RMON), statistics, alarms, events, and history, which give a baseline of network health. The ability to capture more information should involve the use of a network probe (so as not to affect the performance of the switch itself) and port mirroring techniques. Management via embedded RMON agents and Enhanced Switch Port Analyzer capability, coupled with centralized management through CiscoWorks for Switched Internetworks, prepares Catalyst switched networks to support future policy-based management. Understanding traffic patterns and bandwidth utilization requires effective switch, router, and probe instrumentation as well as traffic analysis and reporting tools. Traffic data collection helps engineers to quickly analyze network problems and determine usage patterns for network planning and analysis purposes. RMON offers a common agent technology for traffic data collection and the reporting to network management applications. These two components, collection and reporting, provide the basis for traffic management within switched internetworks. One of the primary functions within CWSI is a mature traffic management application for reporting and analyzing RMON-collected traffic data, including comprehensive reporting of the switch and individual port data collected by the RMON agents within these devices. In addition, the traffic reporting functions within CWSI work with Cisco s dedicated SwitchProbe devices or network analysis module, which offer RMON and RMON2 capabilities for LAN applications. CWSI includes features such as automated switch report generating capabilities, which greatly reduce administrative setup times, autoroving functionality for gathering traffic data up through Layer 7, and automated launching functions from Cisco s graphical device management application. Conclusion In the last several years, local-area networking and the wiring closet have been revolutionized by the exploding use of LAN switching. Companies continue to replace hubs with switches for gains in bandwidth and services in the wiring closet. The wiring closet should be viewed simply as an extension of the core network. To gain end-to-end support of advanced multilayer features, customers do not need to deploy a complex and expensive solution of Layer 3 switches in the wiring closet. Existing Layer 2 wiring closet switches such as the Catalyst 5000 Family can support advanced features by leveraging the intelligence of multilayer core switches. Cisco delivers tight platform/software integration across the product line. By deploying Catalyst Family switches, customers can build an integrated architecture and infrastructure that enable multilayer services throughout the entire campus network. Page 8 of 9

9 Corporate Headquarters Cisco Systems, Inc. 170 West Tasman Drive San Jose, CA USA Tel: NETS (6387) Fax: European Headquarters Cisco Systems Europe s.a.r.l. Parc Evolic, Batiment L1/L2 16 Avenue du Quebec Villebon, BP Courtaboeuf Cedex France Tel: Fax: Americas Headquarters Cisco Systems, Inc. 170 West Tasman Drive San Jose, CA USA Tel: Fax: Asia Headquarters Nihon Cisco Systems K.K. Fuji Building, 9th Floor Marunouchi Chiyoda-ku, Tokyo 100 Japan Tel: Fax: Cisco Systems has more than 200 offices in the following countries. Addresses, phone numbers, and fax numbers are listed on the Cisco Connection Online Web site at Argentina Australia Austria Belgium Brazil Canada Chile China Colombia Costa Rica Croatia Czech Republic Denmark Dubai, UAE Finland France Germany Greece Hong Kong Hungary India Indonesia Ireland Israel Italy Japan Korea Luxembourg Malaysia Mexico The Netherlands New Zealand Norway Peru Philippines Poland Portugal Puerto Rico Romania Russia Saudi Arabia Singapore Slovakia Slovenia South Africa Spain Sweden Switzerland Taiwan Thailand Turkey Ukraine United Kingdom United States Venezuela Copyright 1999 Cisco Systems, Inc. All rights reserved. Printed in USA. Catalyst, Cisco, Cisco IOS, Cisco Systems, the Cisco Systems logo, Switch Probe, and EtherChannel are registered trademarks of Cisco Systems, Inc. in the U.S. and certain other countries. All other trademarks mentioned in this document are the property of their respective owners. (9811R) 1/99LW