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Security and Tunneling Overhead

IPsec is an IETF protocol suite for secure transmission of IP packets. IPsec can operate in two modes Transport mode or Tunnel mode. In Transport mode, encryption is applied only to the payload of the IP packet, whereas in Tunnel mode, encryption is applied to the whole IP packet, including the header. When the IP header is encrypted, the intermediate routers can no longer analyze and route the IP packet. Therefore, in Tunnel mode, the encrypted IP packet must be encapsulated in another IP...

Impact of Voice Samples and Packet Size on Bandwidth

DSP coverts analog voice signal to digital voice signal using a particular codec. Based on the codec used, the DSP generates so many bits per second. The bits that are generated for 10 milliseconds (ms) of analog voice signal form one digital voice sample. The size of the digital voice sample depends on the codec used. Table 1-6 shows how the digital voice sample size changes based on the codec used. The number of voice bytes for two digital voice samples using different codecs is shown in the...

Distributed Versus Centralized Call Control

Two major call control models exist distributed call control and centralized call control. The H.323 and SIP protocols are classified as distributed, whereas the MGCP protocol is considered as a centralized call control VoIP signaling protocol. In the distributed model, multiple devices are involved in setup, maintenance, teardown, and other aspects of call control. The voice-capable devices that perform these tasks have the intelligence and proper configuration to do so. Figure 1-3 shows a...

Layer 2 QoS CoS on 8021QP Ethernet Frame

The IEEE defined the 802.1Q frame for the purpose of implementing trunks between LAN devices. The 4-byte 802.1Q header field that is inserted after the source MAC address on the Ethernet header has a VLAN ID field for trunking purposes. A three-bit user priority field (PRI) is available also and is called CoS (802.1p). CoS is used for QoS purposes it can have one of eight possible values, as shown in Table 3-2. Table 3-2 CoS Bits and Their Corresponding Decimal Values and Definitions Table 3-2...

QoS Pre Classify Applications

Two commonly used tunneling protocols that are relevant to VPNs, discussed in the ONT course, are GRE and IPsec. Because these tunneling protocols, at the tunnel end points, encapsulate the original IP packet and use a new IP header, the original IP header is no longer available to the QoS mechanisms on the outbound (egress) interface. The good news is that the original ToS byte of an IP packet is copied to a ToS byte of the new IP header. Therefore, if the QoS mechanisms on the egress...

Cisco IOS Commands to Configure NBAR

To enhance the list of protocols that NBAR recognizes through a PDLM, download the PDLM from CCO and copy it into the flash or on a TFTP server. Next, enter the following command, which refers to the PDLM name in URL format Router(config) ip nbar pdlm pdlm-name The URL, for example, can be flash citrix.pdlm, referring to the citrix.pdlm file in flash memory. The URL can also refer to a file on a TFTP server, such as tftp 192.168.19.66 citrix.pdlm. To modify the port number that NBAR associates...

The Diff Serv Model Differentiated Services Code Point DSCP and Per Hop Behavior PHB

The DiffServ model was briefly discussed in Chapter 2, IP Quality of Service. Within the DiffServ architecture, traffic is preferred to be classified and marked as soon (as close to the source) as possible. Marking of the IP packet was traditionally done on the three IP precedence bits, but now, marking (setting) the six DSCP bits on the IP header is considered the standard method of IP packet marking. NOTE Some network devices cannot check or set Layer 3 header QoS fields (such as IP...

Current Wireless LAN QoS Implementation

Wireless RF is an OSI Layer 2 technology, and its QoS is currently based on 802.11e or WMM specifications. With the addition of WLANs, to maintain end-to-end QoS in a network, it is necessary to perform mapping between Layer 2 (802.1p) priority or Layer 3 DSCP (or IP precedence) and 802.11e priority (or WMM access category). If a wireless AP connects to an access port (non-trunk port, lacking 801.1p marking) of a LAN switch, the Layer 2 802.11e (or WMM) marking of data coming from the wireless...

Trust Boundaries

End-system devices such as personal computers, IP phones, IP conference devices, and video conference gateways, plus switches and routers at different levels of the network hierarchy, can mark the IP packets or the encapsulating frames such as 802.1Q P. One of the design and policy decisions you have to make is where to place your network trust boundary. The trust boundary forms a perimeter on your network your network respects and trusts (does not override) the markings that the devices on or...

Low Latency Queuing

Neither WFQ nor CBWFQ can provide guaranteed bandwidth and low-delay guarantee to selected applications such as VoIP that is because those queuing models have no priority queue. Certain applications such as VoIP have a small end-to-end delay budget and little tolerance to jitter (delay variation among packets of a flow). LLQ includes a strict-priority queue that is given priority over other queues, which makes it ideal for delay and jitter-sensitive applications. Unlike the plain old PQ,...

QoS Service Level Agreements SLAs

An SLA is a contractual agreement between an enterprise (customer) and a service provider regarding data, voice, and other service or a group of services. Internet access, leased line, Frame Relay, and ATM are examples of such services. After the SLA is negotiated, it is important that it is monitored for compliance of the parties involved with the terms of the agreement. The service provider must deliver services as per the qualities assured in the SLA, and the customer must submit traffic at...

WAN Edge QoS Implementations

WAN edge QoS configurations are performed on CE and PE devices that terminate WAN circuits. Commonly used WAN technologies are Frame Relay and ATM. Important QoS features implemented on the CE and PE devices are LLQ, compression, fragmentation and interleaving, policing, and shaping. Figure 6-6 shows a customer site connected to a provider IP network through a Frame Relay connection between a CE device and a PE device. Note that a similar connection between the CE and the PE devices exists at...

Traffic Shaping and Policing

Traffic shaping and policing are two different mechanisms for traffic conditioning. Both mechanisms measure the rate of different traffic classes against a policy or SLA. SLA stands for service level agreement, and it is usually set up between an enterprise and a service provider with regard to bandwidth, traffic rates, reliability, availability, QoS, and billing matters. Traffic shaping usually buffers the traffic that is in excess of the policy agreement. Policing either drops the excess...

QoS Pre Classification Deployment Options

Many QoS features that are supported on physical interfaces are also supported on, and are often required on, tunnel interfaces. A QoS service policy that is normally applied to a physical interface can also be applied to a tunnel interface. In that situation, you must answer two questions 1. Does the QoS policy classify an IP packet merely based on the ToS byte 2. If the QoS policy classifies traffic based on fields other than or in addition to the ToS byte, should the classification be done...

Calculating the Total Bandwidth for a VoIP Call

Calculating the bandwidth that a VoIP call consumes involves consideration for all the factors discussed thus far. Some fields and protocols are required, each of which might offer implementation alternatives. Other protocols and fields are optional. You use the bandwidth consumed by each VoIP call to calculate the total bandwidth required for the aggregate of simultaneous VoIP calls over LAN and WAN connections. This information is required for the following purposes Designing and planning...

And EAP Authentication Protocols

IEEE developed the 802.1x standard, called Extensible Authentication Protocol (EAP), so that LAN bridges switches can perform port-based network access control. 802.1x was therefore considered a supplement to the IEEE 802.1d standard. The 802.1x (EAP) standard was quickly discovered and adopted for wireless LAN access control. Cisco Systems has supported the 802.1x authentication since December 2000. Cisco Systems, Microsoft, and other vendors have developed several variations of EAP different...

Voice Gateway Functions on a Cisco Router

The Cisco family of voice gateways, including integrated services routers (ISR), provide connectivity between analog interfaces, digital interfaces, and IP Telephony devices. Examples of analog interfaces are FXS and FXO. Examples of analog devices are analog phones, fax machines, and modems. T1 E1 and BRI are examples of digital interfaces. A PBX is usually connected to a gateway using T1 E1 interfaces, even though using an E& M interface is also possible. You can set up a gateway...

Cisco Unified Call Manager Functions

Cisco CallManager (CCM) is call processing software it is the main component of the Cisco Unified Communication System. CCM supports the MGCP, H.323, SIP, and SCCP IP Telephony signaling protocols. Within the MGCP context, CCM acts as the CA and controls MGCP gateways, and within the SCCP context, it controls the IP phones (Skinny Clients). CCM interacts with H.323 and SIP devices. Cisco CallManager version 5.0 supports SIP clients, such as SIP-based IP phones. CallManager servers form a...

Rogue Access Point Detection

The process flow of a rogue AP being detected in a WLAN environment is based on the LWAPs already being powered up and associated to their controllers. The WLC detects a rogue AP and immediately notifies WCS, which creates a rogue AP alarm that appears in the lower-left corner of the user interface pages. Simply selecting the indicator displays the Rogue AP Alarms page. The alarms for rogue APs are naturally listed on the Rogue Access Point Alarms page. This page details the severity, the rogue...

Layer 2 12 QoS Mpls Exp Field

MPLS packets are IP packets that have one or more 4-byte MPLS headers added. The IP packet with its added MPLS header is encapsulated in a Layer 2 protocol data unit (PDU) such as Ethernet before it is transmitted. Therefore, the MPLS header is often called the SHIM or layer 2 1 2 header. Figure 3-3 displays an MPLS-IP packet encapsulated in an Ethernet frame. The EXP (experimental) field within the MPLS header is used for QoS purposes. The EXP field was designed as a 3-bit field to be...

Network Based Application Recognition NBAR

NBAR is a Cisco IOS feature that can be used to perform three tasks Traffic statistics collection Because NBAR can discover which applications and protocols are running on your network and display volume and statistics about them, you can use it as a powerful yet simple tool to form the definitions of your network traffic classes (BAs). You can also use NBAR within class-based (CB) marking or other MQC-based tools to classify packets for purposes such as marking, policing, and queuing. NBAR is...

Foundation Summary Dqt

The Foundation Summary is a collection of information that provides a convenient review of many key concepts in this chapter. If you are already comfortable with the topics in this chapter, this summary can help you recall a few details. If you just read this chapter, this review should help solidify some key facts. If you are doing your final preparation before the exam, the information in this section is a convenient way to review the day before the exam. Wireless LANs (WLANs) are extensions...

FirstInFirst Out Priority Queuing Round Robin and Weighted Round Robin Queuing

FIFO is the default queuing discipline in most interfaces except those at 2.048 Mbps or lower (E1). The hardware queue (TxQ) also processes packets based on the FIFO discipline. Each queue within a multiqueue discipline is a FIFO queue. FIFO is a simple algorithm that requires no configuration effort. Packets line up in a single FIFO queue packet class, priority, and type play no role in a FIFO queue. Without multiple queues and without a scheduling and dropping algorithm, high-volume and...

Router and Security Device Manager SDM QoS Wizard

Cisco SDM is a web-based device-management tool for Cisco routers. With SDM, router deployment and troubleshooting of network and VPN connectivity issues becomes simpler. Proactive management through performance monitoring is also accomplished using SDM. Cisco SDM supports a range of Cisco IOS Software releases and is available on many Cisco router models (from Cisco 830 Series to Cisco 7301) on several router models, SDM is preinstalled. Cisco SDM offers smart wizards that provide step-by-step...

WLSE Software Features

Network management of system-wide autonomous APs through CiscoWorks WLSE has these major software features Configuration One CiscoWorks WLSE console supports up to 2500 APs. Configuration changes can be performed in mass, individually, or in defined groups as desired or on a schedule time. All Cisco Aironet APs are supported. Fault and policy monitoring WLSE monitors device faults and performance threshold conditions such as memory, CPU, associations, Lightweight Extensible Authentication...

The Need for Wireless LAN QoS

They are mostly implemented as extensions to, but are occasionally deployed as overlays to, wired LANs, or replacements for wired LANs. The difference between wired and wireless LANs is in the physical layer and in the MAC layer. Please note that Logical Link Control (LLC) and MAC are considered upper and lower sublayers of the OSI Layer 2 Data Link Control (DLC) layer, respectively. Upper-layer protocols and applications such as IP, TCP, and FTP run identically...

Cisco Unified Wireless Networks

The Cisco Unified Wireless Network is a total-enterprise solution composed of five comprehensive elements. The Cisco Unified Wireless Network enables the use of advanced wireless services and addresses security concerns. It also addresses deployment, control, and the management of WLAN components and RF. Following are the five elements of Cisco Unified Wireless Network Client devices Use the Cisco Compatible Extensions program to help ensure interoperability. The Cisco Compatible Extensions...

Configuring Encryption and Authentication on Lightweight Access Points

In this section, you will learn how to navigate through the GUI of a WLC (Cisco WLC2006, specifically) to configure encryption and authentication on a lightweight AP (Cisco AP1020, specifically). The specific tasks shown are configuring open authentication, static WEP authentication, WPA with PSK, web authentication, and 802.1x authentication. Open authentication means that you are interested neither in authenticating the client user nor in encrypting the data exchanged between the wireless...

Header Compression

Header compression reduces serialization delay and results in less bandwidth usage, yielding more throughput and more available bandwidth. As the name implies, header compression compresses headers only for example, RTP header compression compresses Real-time Transport Protocol (RTP), User Datagram Protocol (UDP), and IP headers, but it does not compress the application data. This makes header compression especially useful for cases in which application payload size is small. Without header...

Data Link Overhead

Transmitting an IP packet over a link requires encapsulation of the IP packet in a frame that is appropriate for the data link layer protocol provisioned on that link. For instance, if the data link layer protocol used on a link is PPP, the interface connected to that link must be configured for PPP encapsulation. In other words, any packet to be transmitted out of that interface must be encapsulated in a PPP frame. When a router routes a packet, the packet can enter the router via an interface...

Protocols Used in Voice Encapsulation

Even though the term VoIP implies that digitized voice is encapsulated in IP packets, other protocol headers and mechanisms are involved in this process. Although the two major TCP IP transport layer protocols, namely TCP and UDP, have their own merits, neither of these protocols alone is a suitable transport protocol for real-time voice. RTP, which runs over UDP using UDP ports 16384 through 32767, offers a good transport layer solution for real-time voice and video. Table 1-5 compares TCP,...

Class Based Weighted Fair Queuing

CBWFQ addresses some of the limitations of PQ, CQ, and WFQ. CBWFQ allows creation of user-defined classes, each of which is assigned to its own queue. Each queue receives a user-defined (minimum) bandwidth guarantee, but it can use more bandwidth if it is available. In contrast to PQ, no queue in CBWFQ is starved. Unlike PQ and CQ, you do not have to define classes of traffic to different queues using complex access lists. WFQ does not allow creation of user-defined classes, but CBWFQ does...

WCS Configuration Examples

The WCS configuration first requires an authorized login. Several configuration steps must take place after the initial authorized login, such as adding devices and site maps. The Cisco WCS Server login involves three major steps Step 1 Start Microsoft Internet Explorer version 6.0 or later. Step 2 Enter https localhost in the address bar when the Cisco WCS user interface is on a Cisco WCS server. Enter https wcs-ip-address when the Cisco WCS interface is on any other workstation. Step 3 Enter...

WCS System Features

The Cisco WCS operating system manages all data client, communications, and system administration functions and performs radio resource management (RRM) functions. Moreover, WCS manages systemwide mobility policies using the operating systems security solution and coordinates all security functions using the operating system security framework. Three user interfaces exist for Cisco WCS. The first is a full featured CLI that can be used to configure and monitor individual controllers. The second...

Modular QoS Command Line Interface MQC

Cisco introduced MQC to address the shortcomings of the legacy CLI and to allow utilization of the newer QoS tools and features available in the modern Cisco IOS. With the MQC, traffic classification and policy definition are done separately. Traffic policies are defined after traffic classes. Different policies might reference the same traffic classes, thereby taking advantage of the modular and reusable code. When one or more policies are defined, you can apply them to many interfaces,...

The Nyquist Theorem

The number of samples taken per second during the sampling stage, also called the sampling rate, has a significant impact on the quality of digitized signal. The higher the sampling rate is, the better quality it yields however, a higher sampling rate also generates higher bits per second that must be transmitted. Based on the Nyquist theorem, a signal that is sampled at a rate at least twice the highest frequency of that signal yields enough samples for accurate reconstruction of the signal at...

Benefits of Packet Telephony Networks

Many believe that the biggest benefit of packet telephony is toll bypass, or simply long-distance cost savings. However, because the cost of a long-distance call to most parts of the world has decreased substantially, this is not even one of the top three reasons for migrating to packet telephony networks in the North American market. The main benefits of packet telephony networks are as follows More efficient use of bandwidth and equipment, and lower transmission costs Packet telephony...

Call Admission Control CAC

Call admission control is a feature that is configured to limit the number of concurrent calls. Usually, because the bandwidth of the WAN link is much less than LAN links, CAC is configured so that WAN bandwidth does not get oversubscribed by VoIP calls. CAC complements QoS configurations. For instance, if a strict priority queue with enough bandwidth for three voice calls is configured on all routers between two phones, although there are fewer than four concurrent calls, all will be good...

Definition of QoS and the Three Steps to Implementing It

Following is the most recent definition that Cisco educational material provides for QoS QoS is the ability of the network to provide better or special service to a set of users or applications or both to the detriment of other users or applications or both. The earliest versions of QoS tools protected data against data. For instance, priority queuing made sure packets that matched an access list always had the right of way on an egress interface. Another example is WFQ, which prevents small...

Measuring Traffic Rates

The operating systems on Cisco devices measure traffic rates using a bucket and token scheme. The token and bucket scheme has a few variations single bucket with single rate, dual bucket with single rate, and dual bucket with dual rates. The Cisco ONT course covers only the single bucket with single rate model. To transmit one byte of data, the bucket must have one token. Tokens are put into the bucket at the rate equivalent to the SLA rate for example, for a Frame Relay virtual circuit, the...