Basic Voice Encoding: Converting Analog Signals to Digital Signals (PDF)

Basic Voice Encoding: Converting Analog Signals to Digital Signals ◼ Step 1: Sample the analog signal. ◼ Step 2: Quantize sample into a binary expression. ◼ Step 3: Compress the samples to reduce bandwidth. BIT - NET 4007 Slide 82...

Basic Voice Encoding: Converting Analog Signals to Digital Signals ◼ Step 1: Sample the analog signal. ◼ Step 2: Quantize sample into a binary expression. ◼ Step 3: Compress the samples to reduce bandwidth. BIT - NET 4007 Slide 82  Basic Voice Encoding:Converting Digital Signals to Analog Signals ◼ Step 1: Decompress the samples. ◼ Step 2: Decode the samples into voltage amplitudes, rebuilding the PAM signal. ◼ Step 3: Reconstruct the analog signal from the PAM signals. BIT - NET 4007 Slide 83  Common Voice Codec Characteristics ITU-T Codec Bit Rate (kbps) Standard G.711 PCM 64 G.726 ADPCM 16, 24, 32 G.728 LDCELP (Low Delay CELP) 16 G.729 CS-ACELP 8 CS-ACELP, but with less G.729A 8 computation BIT - NET 4007 Slide 84  Mean Opinion Score BIT - NET 4007 Slide 85  DSP Used for Conferencing ◼ DSPs can be used in single- or mixed-mode conferences: Mixed mode supports different codecs. Single mode demands that the same codec to be used by all participants. ◼ Mixed mode has fewer conferences per DSP. BIT - NET 4007 Slide 86  Voice Transport in VoIP Networks ◼ Analog phones connect to voice gateways. ◼ Voice gateways convert between analog and digital. ◼ After call is set up, IP network provides: Packet-by-packet delivery through the network Shared bandwidth, higher and variable delays BIT - NET 4007 Slide 87  Jitter ◼ Voice packets enter the network at a constant rate. ◼ Voice packets may arrive at the destination at a different rate or in the wrong order. ◼ Jitter occurs when packets arrive at varying rates. ◼ Since voice is dependent on timing and order, a process must exist so that delays and queuing issues can be fixed at the receiving end. ◼ The receiving router must: Ensure steady delivery (delay) Ensure that the packets are in the right order BIT - NET 4007 Slide 88  VoIP Protocol Issues ◼ IP does not guarantee reliability, flow control, error detection or error correction. ◼ IP can use the help of transport layer protocols TCP or UDP. ◼ TCP offers reliability, but voice doesn’t need it…do not retransmit lost voice packets. ◼ TCP overhead for reliability consumes bandwidth. ◼ UDP does not offer reliability. But it also doesn’t offer sequencing…voice packets need to be in the right order. ◼ RTP, which is built on UDP, offers all of the functionality required by voice packets. BIT - NET 4007 Slide 89  Protocols Used for VoIP Voice Feature TCP UDP RTP Needs Reliability No Yes No✓ No ✓ Reordering Yes Yes ✓ No Yes✓ Time- stamping Yes No No Yes✓ Contains As little as Overhead possible unnecessary information Low✓ Low✓ Multiplexing Yes Yes ✓ Yes✓ No BIT - NET 4007 Slide 90  Voice Encapsulation ◼ Digitized voice is encapsulated into RTP, UDP, and IP. ◼ By default, 20 ms of voice is packetized into a single IP packet. BIT - NET 4007 Slide 91  Voice Encapsulation Overhead ◼ Voice is sent in small packets at high packet rates. ◼ IP, UDP, and RTP header overheads are enormous: For G.729, the headers are twice the size of the payload. For G.711, the headers are one-quarter the size of the payload. ◼ Bandwidth is 24 kbps for G.729 and 80 kbps for G.711, ignoring Layer 2 overhead. BIT - NET 4007 Slide 92  RTP Header Compression ◼ Compresses the IP, UDP, and RTP headers ◼ Is configured on a link-by-link basis ◼ Reduces the size of the headers substantially (from 40 bytes to 2 or 4 bytes): 4 bytes if the UDP checksum is preserved 2 bytes if the UDP checksum is not sent ◼ Saves a considerable amount of bandwidth BIT - NET 4007 Slide 93  When to Use RTP Header Compression ◼ Use cRTP: Only on slow links (less than 2 Mbps) If bandwidth needs to be conserved ◼ Consider the disadvantages of cRTP: Adds to processing overhead Introduces additional delays ◼ Tune cRTP—set the number of sessions to be compressed (default is 16). BIT - NET 4007 Slide 94  How the Packetization Period Impacts VoIP Packet Size and Rate ◼ High packetization period results in: Larger IP packet size (adding to the payload) Lower packet rate (reducing the IP overhead) BIT - NET 4007 Slide 95  Data-Link Overhead Is Different per Link Data-Link Frame Ethernet Trunk Ethernet MLP Protocol Relay (802.1Q) Overhead 18 6 6 22 [bytes] BIT - NET 4007 Slide 96  Security and Tunneling Overhead ◼ IP packets can be secured by IPsec. ◼ Additionally, IP packets or data-link frames can be tunneled over a variety of protocols. ◼ Characteristics of IPsec and tunneling protocols are: The original frame or packet is encapsulated into another protocol. The added headers result in larger packets and higher bandwidth requirements. The extra bandwidth can be extremely critical for voice packets because of the transmission of small packets at a high rate. BIT - NET 4007 Slide 97  Total Bandwidth Calculation Procedure ◼ Gather required packetization information: Packetization period (default is 20 ms) or size Codec bandwidth ◼ Gather required information about the link: cRTP enabled Type of data-link protocol IPsec or any tunneling protocols used ◼ Calculate the packetization size or period. ◼ Sum up packetization size and all headers and trailers. ◼ Calculate the packet rate. ◼ Calculate the total bandwidth. BIT - NET 4007 Slide 98  Bandwidth Calculation Example BIT - NET 4007 Slide 99  Quick Bandwidth Calculation Total packet size (bits) ——————————— Packetization Period Total packet size = All headers + payload Parameter Value Layer 2 header 6 to 18 bytes IP + UDP + RTP headers 40 bytes Payload size (20-ms sample interval) 20 bytes for G.729, 160 bytes for G.711 Nominal bandwidth 8 kbps for G.729, 64 kbps for G.711 Example: G.729 with Frame Relay: Total bandwidth requirement = (6 + 40 + 20 bytes) * 8 ————————————— = 26.4 kbps 20 ms BIT - NET 4007 Slide 100  Enterprise Voice Implementations ◼ Components of enterprise voice networks: Gateways and gatekeepers Cisco Unified CallManager and IP phones BIT - NET 4007 Slide 101  Deploying CAC ◼ CAC artificially limits the number of concurrent voice calls. ◼ CAC prevents oversubscription of WAN resources caused by too much voice traffic. ◼ CAC is needed because QoS cannot solve the problem of voice call oversubscription: QoS gives priority only to certain packet types (RTP versus data). QoS cannot block the setup of too many voice calls. Too much voice traffic results in delayed voice packets. BIT - NET 4007 Slide 102  Example: CAC Deployment ◼ IP network (WAN) is only designed for two concurrent voice calls. ◼ If CAC is not deployed, a third call can be set up, causing poor quality for all calls. ◼ When CAC is deployed, the third call is blocked. BIT - NET 4007 Slide 103  Cisco Unified CallManager Functions Call processing Dial plan administration Signaling and device control Phone feature administration Directory and XML services Programming interface to external applications Cisco IP Communicator BIT - NET 4007 Slide 104  Example: Signaling and Call Processing BIT - NET 4007 Slide 105  Enterprise IP Telephony Deployment Models Deployment Model Characteristics Single site ◼ Cisco Unified CallManager cluster at the single site ◼ Local IP phones only Multisite with ◼ Cisco Unified CallManager cluster only at a centralized call single site processing ◼ Local and remote IP phones Multisite with ◼ Cisco Unified CallManager clusters at distributed call multiple sites processing ◼ Local IP phones only Clustering over WAN ◼ Single Cisco Unified CallManager cluster distributed over multiple sites ◼ Usually local IP phones only ◼ Requirement: Round-trip delay between any BIT - NET 4007 pair of servers not to exceed 40 ms Slide 106  Single Site ◼ Cisco Unified CallManager servers, applications, and DSP resources are located at the same physical location. ◼ IP WAN is not used for voice. ◼ PSTN is used for all external calls. Note: Cisco Unified CallManager cluster can be connected to various places depending on the topology. BIT - NET 4007 Slide 107  Multisite with Centralized Call Processing ◼ Cisco Unified CallManager servers and applications are located at the central site while DSP resources are distributed. ◼ IP WAN carries data and voice (signaling for all calls, media only for intersite calls). ◼ PSTN access is provided at all sites. ◼ CAC is used to limit the number of VoIP calls, and AAR is used if WAN bandwidth is exceeded. ◼ Cisco SRST (Survivable Remote Site Telephony) is located at the remote branch. Note: Cisco Unified CallManager cluster can be connected to various places depending on the topology. BIT - NET 4007 Slide 108  Multisite with Distributed Call Processing ◼ Cisco Unified CallManager servers, applications, and DSP resources are located at each site. ◼ IP WAN carries data and voice for intersite calls only (signaling and media). ◼ PSTN access is provided at all sites; rerouting to PSTN is configured if IP WAN is down. ◼ CAC is used to limit the number of VoIP calls, and AAR is used if WAN bandwidth is exceeded. Note: Cisco Unified CallManager cluster can be connected to various places, depending on the topology. BIT - NET 4007 Slide 109  Clustering over WAN ◼ Cisco Unified CallManager servers of a single cluster are distributed among multiple sites while applications and DSP resources are located at each site. ◼ Intracluster communication (such as database synchronization) is performed over the WAN. ◼ IP WAN carries data and voice for intersite calls only (signaling and media). ◼ PSTN access is provided at all sites; rerouting to PSTN is performed if IP WAN is down. ◼ CAC is used to limit the number of VoIP calls; AAR is used if WAN bandwidth is exceeded. Note: Cisco Unified CallManager cluster can be connected to various places, depending on BIT - NET the 4007topology. Slide 110  NET 4007 Multimedia Networking VoIP QoS BIT - NET 4007 Slide 111  Converged Network Realities ◼ Converged network realities: Constant small-packet voice flow competes with bursty data flow. Critical traffic must have priority. Voice and video are time-sensitive. Brief outages are not acceptable. BIT - NET 4007 Slide 112  Converged Network Quality Issues ◼ Lack of bandwidth: Multiple flows compete for a limited amount of bandwidth. ◼ End-to-end delay (fixed and variable): Packets have to traverse many network devices and links; this travel adds up to the overall delay. ◼ Variation of delay (jitter): Sometimes there is a lot of other traffic, which results in varied and increased delay. ◼ Packet loss: Packets may have to be dropped when a link is congested. BIT - NET 4007 Slide 113  Increasing Available Bandwidth ◼Upgrade the link (the best but also the most expensive solution). ◼ Improve QoS with advanced queuing mechanisms to forward the important packets first. ◼ Compress the payload of Layer 2 frames (takes time). BIT -◼NET 4007 Compress IP packet headers. Slide 114  Using Available Bandwidth Efficiently Voice 1 1 Voice (Highest) LLQ RTP header Data 2 2 compression 4 3 2 1 1 (High) Data 3 3 3 Data CBWFQ (Medium) TCP header compression Data 4 4 4 4 (Low) ◼ Using advanced queuing and header compression mechanisms, the available bandwidth can be used more efficiently: Voice: LLQ and RTP header compression Interactive traffic: CBWFQ and TCP header compression BIT - NET 4007 Slide 115  Types of Delay ◼ Processing delay: The time it takes for a router to take the packet from an input interface, examine the packet, and put the packet into the output queue of the output interface. ◼ Queuing delay: The time a packet resides in the output queue of a router. ◼ Serialization delay: The time it takes to place the “bits on the wire.” ◼ Propagation delay: The time it takes for the packet to cross the link from one end to the other. BIT - NET 4007 Slide 116  Ways to Reduce Delay ◼ Upgrade the link (the best solution but also the most expensive). ◼ Forward the important packets first. ◼ Enable reprioritization of important packets. ◼ Compress the payload of Layer 2 frames (takes time). ◼ Compress IP packet headers. BIT - NET 4007 Slide 117  Reducing Delay in a Network ◼ Customer routers perform: TCP/RTP header compression LLQ Prioritization ◼ ISP routers perform: Reprioritization according to the QoS policy BIT - NET 4007 Slide 118  The Impacts of Packet Loss ◼ Telephone call: “I cannot understand you. Your voice is breaking up.” ◼ Teleconferencing: “The picture is very jerky. Voice is not synchronized.” ◼ Publishing company: “This file is corrupted.” ◼ Call center: “Please hold while my screen refreshes.” BIT - NET 4007 Slide 119  Types of Packet Drops ◼ Tail drops occur when the output queue is full. Tail drops are common and happen when a link is congested. ◼ Other types of drops, usually resulting from router congestion, include input drop, ignore, overrun, and frame errors. These errors can often be solved with hardware upgrades. BIT - NET 4007 Slide 120  Ways to Prevent Packet Loss ◼ Upgrade the link (the best solution but also the most expensive). ◼ Guarantee enough bandwidth for sensitive packets. ◼ Prevent congestion by randomly dropping less important packets before congestion occurs. BIT - NET 4007 Slide 121  What Is Quality of Service? Two Perspectives ◼ The user perspective Users perceive that their applications are performing properly Voice, video, and data ◼ The network manager perspective Need to manage bandwidth allocations to deliver the desired application performance Control delay, jitter, and packet loss BIT - NET 4007 Slide 122  Different Types of Traffic Have Different Needs Sensitivity to ▪ Real-time applications especially QoS Metrics Application sensitive to QoS Examples Packet Interactive voice Delay Jitter Loss Videoconferencing Interactive Voice and Video Y Y Y ▪ Causes of degraded performance Congestion losses Streaming Video N Y Y Variable queuing delays Transactional/ ▪ The QoS challenge Interactive Y N N Manage bandwidth allocations to Bulk Data deliver the desired application Email N N N performance File Transfer Control delay, jitter, and packet loss Need to manage bandwidth allocations BIT - NET 4007 Slide 123  Cisco IOS QoS Tools ◼ Queue management: PQ CQ WFQ CBWFQ ◼ Congestion management QoS Toolbox WRED ◼ Link efficiency Link fragmentation and interleave RTP and CRTP ◼ Traffic shaping and traffic policing BIT - NET 4007 Slide 124  Priority Queuing PQ puts data into four levels of queues: high, medium, normal, and low. BIT - NET 4007 Slide 125  Custom Queuing CQ handles traffic by assigning a specified amount of queue space to each class of packet and then servicing up to 17 queues in a BIT - NETround-robin 4007 fashion. Slide 126  Weighted Fair Queuing WFQ makes the transfer rates and interarrival periods of active BIT - NEThigh-volume 4007 conversations much more predictable. Slide 127  Weighted Random Early Detection WRED provides a method that stochastically discards packets if congestion begins to increase. BIT - NET 4007 Slide 128  Implementing QoS Step 1: Identify types of traffic and their requirements. Step 2: Divide traffic into classes. Step 3: Define QoS policies BIT - NET 4007 for each class. Slide 129  Step 1: Identify Types of Traffic and Their Requirements ◼ Network audit: Identify traffic on the network. ◼ Business audit: Determine how important each type of traffic is for business. ◼ Service levels required: Determine required response time. BIT - NET 4007 Slide 130  Step 2: Define Traffic Classes Scavenger Less than Best Effort Class BIT - NET 4007 Slide 131  Step 3: Define QoS Policy ◼ A QoS policy is a network- wide definition of the specific levels of QoS that are assigned to different classes of network traffic. BIT - NET 4007 Slide 132  Quality of Service Operations How Do QoS Tools Work? Classification Queuing and Post-Queuing and Marking (Selective) Dropping Operations BIT - NET 4007 Slide 133  Three QoS Models Model Characteristics Best effort No QoS is applied to packets. If it is not important when or how packets arrive, the best- effort model is appropriate. Integrated Services Applications signal to the network that the (IntServ) applications require certain QoS parameters. Differentiated The network recognizes classes that require QoS. Services (DiffServ) BIT - NET 4007 Slide 134  Best-Effort Model ◼ Internet was initially based on a best-effort packet delivery service. ◼ Best-effort is the default mode for all traffic. ◼ There is no differentiation among types of traffic. ◼ Best-effort model is similar to using standard mail—“The mail will arrive when the mail arrives.” ◼ Benefits: Highly scalable No special mechanisms required ◼ Drawbacks: No service guarantees BIT - NET No 4007service differentiation Slide 135  Integrated Services (IntServ) Model Operation ◼ Ensures guaranteed delivery and predictable behavior of the network for applications. ◼ Provides multiple service levels. ◼ RSVP is a signaling protocol to reserve resources for specified QoS parameters. ◼ The requested QoS parameters are then linked to a packet stream. ◼ Streams are not established if the required QoS parameters cannot be met. ◼ Intelligent queuing mechanisms needed to provide resource reservation in terms of: Guaranteed rate Controlled load (low delay, high throughput) BIT - NET 4007 Slide 136  IntServ Functions Control Plane Routing Selection Admission Control Reservation Setup Reservation Table Data Plane Flow Identification Packet Scheduler BIT - NET 4007 Slide 137  Benefits and Drawbacks of the IntServ Model ◼ Benefits: Explicit resource admission control (end to end) Per-request policy admission control (authorization object, policy object) Signaling of dynamic port numbers (for example, H.323) ◼ Drawbacks: Continuous signaling because of stateful architecture Flow-based approach not scalable to large implementations, such as the public Internet BIT - NET 4007 Slide 138  The Differentiated Services Model ◼ Overcomes many of the limitations best-effort and IntServ models ◼ Uses the soft QoS provisioned-QoS model rather than the hard QoS signaled-QoS model ◼ Classifies flows into aggregates (classes) and provides appropriate QoS for the classes ◼ Minimizes signaling and state maintenance requirements on each network node ◼ Manages QoS characteristics on the basis of per-hop behavior (PHB) ◼ You choose the level of service for each traffic class Edge End Station Edge Interior Edge DiffServ Domain End Station BIT - NET 4007 Slide 139  Methods for Implementing QoS Policy Method Description Legacy CLI ◼ Coded at the CLI ◼ Requires each interface to be individually configured ◼ Time-consuming MQC ◼ Coded at the CLI ◼ Uses configuration modules ◼ Best method for QoS fine tuning Cisco AutoQoS ◼ Applies a possible QoS configuration to the interfaces ◼ Fastest way to implement QoS Cisco SDM QoS wizard ◼ Application for simple QoS configurations BIT - NET 4007 Slide 140  Modular QoS CLI ◼ A command syntax for configuring QoS policy ◼ Reduces configuration steps and time ◼ Configures policy, not “raw” per-interface commands ◼ Uniform CLI across major Cisco IOS platforms ◼ Uniform CLI structure for all QoS features ◼ Separates classification engine from the policy BIT - NET 4007 Slide 141  Modular QoS CLI Components BIT - NET 4007 Slide 142  Step 1: Creating Class Maps: “What Traffic Do We Care About?” ◼ Each class is identified using a class map. ◼ A traffic class contains three major elements: A case-sensitive name A series of match commands An instruction on how to evaluate the match commands if more than one match command exists in the traffic class ◼ Class maps can operate in two modes: Match all: All conditions have to succeed. Match any: At least one condition must succeed. ◼ The default mode is match all. BIT - NET 4007 Slide 143  Configuring Class Maps ◼ Enter class-map configuration mode. Specify the matching strategy. router(config)# class-map [match-all | match-any] class-map-name ▪ Use at least one condition to match packets. router(config-cmap)# match any match not match-criteria ▪ Use descriptions in large and complex configurations. The description has no operational meaning. router(config-cmap)# description description BIT - NET 4007 Slide 144  Classifying Traffic with ACLs ◼ Standard ACL router(config)# access-list access-list-number {permit | deny | remark} source [mask] ▪ Extended ACL router(config)# access-list access-list-number {permit | deny} protocol source source-wildcard [operator port] destination destination-wildcard [operator port] [established] [log] ▪ Use an ACL as a match criterion router(config-cmap)# match access-group access-list-number BIT - NET 4007 Slide 145  Step 2: Policy Maps: “What Will Be Done to This Traffic?” ◼ A policy map defines a traffic policy, which configures the QoS features associated with a traffic class that was previously identified using a class map. ◼ A traffic policy contains three major elements: A case-sensitive name A traffic class The QoS policy that is associated with that traffic class ◼ Up to 256 traffic classes can be associated with a single traffic policy. ◼ Multiple policy maps can be nested to influence the sequence of QoS actions. BIT - NET 4007 Slide 146  Configuring Policy Maps ◼ Enter policy-map configuration mode. Policy maps are identified by a case-sensitive name. router(config)# policy-map policy-map-name ▪ Enter the per-class policy configuration mode by using the name of a previously configured class map. Use the class-default name to configure the policy for the default class. router(config-pmap)# class {class-name | class-default} ▪ Optionally, you can define a new class map by entering the condition after the name of the new class map. Uses the match-any strategy. router(config-pmap)# class class-name condition BIT - NET 4007 Slide 147  Step 3: Attaching Service Policies: “Where Will This Policy Be Implemented?” ▪ Attach the specified service policy map to the input or output interface router(config-if)# service-policy {input | output} policy-map-name class-map HTTP match protocol http ! policy-map PM Service policies class HTTP bandwidth 2000 can be applied to class class-default an interface for bandwidth 6000 inbound or ! outbound interface Serial0/0 service-policy output PM packets BIT - NET 4007 Slide 148  Modular QoS CLI Configuration Example router(config)# class-map match-any business-critical-traffic 1 router(config-cmap)# match protocol http url “*customer*” router(config-cmap)# match protocol http url citrix router(config)# policy-map myqos policy 2 router(config-pm am)# class business-critical-traffic router(config-pm am-c)# bandwidth 1000 3 router(config)# interface serial 0/0 router(config-if)# service-policy output myqos policy BIT - NET 4007 Slide 149  MQC Example ◼ Voice traffic needs priority, low delay, and constant bandwidth. ◼ Interactive traffic needs bandwidth and low delay. BIT - NET 4007 Slide 150  MQC Configuration hostname Office ! class-map VoIP match access-group 100 Classification class-map Application match access-group 101 ! policy-map QoS-Policy class VoIP priority 100 QoS Policy class Application bandwidth 25 class class-default fair-queue ! interface Serial0/0 QoS Policy on Interface service-policy output QoS-Policy ! access-list 100 permit ip any any precedence 5 access-list 100 permit ip any any dscp ef access-list 101 permit tcp any host 10.1.10.20 Classification access-list 101 permit tcp any host 10.1.10.40 BIT - NET 4007 Slide 151  Basic Verification Commands ◼ Display the class maps router# show class-map ▪ Display the policy maps router# show policy-map ▪ Display the applied policy map on the interface router# show policy-map interface type number BIT - NET 4007 Slide 152  NET 4007 Multimedia Networking Implement the DiffServ QoS Model BIT - NET 4007 Slide 153 Classification and Marking  Classification ◼ Classification is the process of identifying and categorizing traffic into classes, typically based upon: Incoming interface IP precedence DSCP Source or destination address Application ◼ Without classification, all packets are treated the same. ◼ Classification should take place as close to the source as possible.  Marking ◼ Marking is the QoS feature component that “colors” a packet (frame) so it can be identified and distinguished from other packets (frames) in QoS treatment. ◼ Commonly used markers: Link layer: CoS (ISL, 802.1p) MPLS EXP bits Frame Relay Network layer: DSCP IP precedence  DiffServ Model ◼ Describes services associated with traffic classes, rather than traffic flows. ◼ Complex traffic classification and conditioning is performed at the network edge. ◼ No per-flow state in the core. ◼ The goal of the DiffServ model is scalability. ◼ Interoperability with non-DiffServ-compliant nodes. ◼ Incremental deployment.  Classification Tools IP Precedence and DiffServ Code Points Version ToS Len ID Offset TTL Proto FCS IP SA IP DA Data Length Byte IPv4 Packet 7 6 5 4 3 2 1 0 Standard IPv4 IP Precedence Unused DiffServ Code Point (DSCP) IP ECN DiffServ Extensions ◼ IPv4: three most significant bits of ToS byte are called IP Precedence (IPP)—other bits unused ◼ DiffServ: six most significant bits of ToS byte are called DiffServ Code Point (DSCP)—remaining two bits used for flow control ◼ DSCP is backward-compatible with IP precedence IP ToS Byte and DS Field Inside the IP Header  IP Precedence and DSCP Compatibility ◼ Compatibility with current IP precedence usage (RFC 1812) ◼ Differentiates probability of timely forwarding: (xyz000) >= (abc000) if xyz > abc ◼ That is, if a packet has DSCP value of 011000, it has a greater probability of timely forwarding than a packet with DSCP value of 001000. Queuing