IP Class of Service (CoS)
Sprint created a Frequently Asked Questions (FAQ) document to assist customers with terminology used in the Sprint IP Class of Service Policy and Guidelines document For further information on Class of Service router configurations, please visit Ciscos website at www.cisco.com.
What is Class of Service (CoS)?
Class of Service is traffic differentiation or the ability to treat packets differently based on the packet’s importance. Class of Service works with both IPv4 and IPv6 protocols.
When is Class of Service needed?
When there is congestion or when there is more traffic sent over an access link than that of the link’s capacity. Class of Service ensures that the highest priority packets, e.g. voice and video are delivered first.
Where is Class of Service needed?
Class of Service is most often used on the customer access links as these links are frequently low-bandwidth connections.
What is Sprint’s Class of Service Product?
Sprint’s IP Class of Service offering allows Dedicated IP and CPE-based IP VPN customers to make efficient use of existing bandwidth by ensuring the delivery of time-sensitive or mission-critical applications over non-critical applications during periods of congestion on the customer access link. IP Class of Service maps IP applications into 4 priority classes based on the customer’s business requirements.
How many classes does the Sprint IP Class of Service product offer?
Class A Premium Traffic: This class is configured as a Priority Queue reserved for latency-sensitive applications only. During congestion conditions, the Priority Queue is guaranteed bandwidth based on the customer’s bandwidth allocation. The priority command implements a maximum bandwidth guarantee. The priority queue is reserved only for Voice over IP (VoIP) or Video over IP traffic. Customers who use both VoIP and video traffic, the video traffic will be placed into Class B.
Class B Critical Traffic: This class is the highest class for data applications, e.g. financial transactions.
Class C Business Traffic: This class is the second class for data applications, e.g. database applications.
Class D Standard Traffic: This class is the default class, all traffic not prioritized in the above queues will be serviced in this class. Typical traffic for this queue is web browsing.
What are Sprint’s Bandwidth Allocation recommendations?
Sprint recommends that IP Class of Service should be deployed on 768kbps links or greater when deploying Voice over IP (VoIP) or Video over IP applications. In addition to overall port speed recommendation, below are bandwidth allocations per class recommendations.

Class A Premium Traffic:

This priority class is reserved only for VoIP or video traffic. Sprint recommends 35% of customer’s bandwidth be assigned to Class A when the customer is using VoIP. This may vary depending on the CODEC used by the customer. Please go to Cisco’s website for more information on CODEC recommendations. Sprint recommends 17% of customer’s bandwidth be assigned to Class A when the customer is using video.

Class B Critical Traffic:

Sprint recommends that 25% of the customer’s bandwidth is allocated to this class.

Class C Business Traffic:

Sprint recommends that 15% of the customer’s bandwidth is allocated to this class.

Class D Standard Traffic:

Sprint recommends that 25% of the customer’s bandwidth is allocated to this class.
It is important to note that the above allocations are simply Sprint’s overall recommendations, as each customer’s business needs vary each customer’s CoS policies will vary.
What is a Virtual Private Network (VPN)?
A virtual private network, or VPN, employs logical separation or encapsulation of customer traffic over a shared network to emulate the characteristics of a private network. Increasingly, the term IP VPN is used interchangeably with VPN, although an IP VPN typically refers to a network that is aware of the TPC/IP protocol and provides routing or traffic differentiation based on IP addresses or packet header information. An IP VPN is a specific implementation of an VPN that uses the public Internet backbone as the transport network.
What is IPSec?
IPsec (Internet Protocol Security) is a technology standard for security at the network layer. IPsec is predominantly used for implementing virtual private network(VPN) and for remote user access through dial-up connection to private networks. IPSec uses encryption protocols such as DES for data integrity.
What is encrypted traffic?
Encryption is the conversion of data into a form that cannot be easily understood by unauthorized people. Data Encryption Standard (DES) is a widely-used method of data encryption.
What is a port type?
A port is the physical transport connection. Dedicated port speeds can range from Fractional T1 (64kbps), T1 (1.54mbps), Multimegabit T1 (3mbps to 9mbps), Fractional T3 (12mbps), T3 (45mbps), OC3 (155mbps), OC12 (622mbps), OC48 (2.488gbps), Fast Ethernet (100M, Gigabit Ethernet (1000M) and 10 Gigabit (10,000m) interfaces.
What are the IP Precedence bits?
The Type of Service (ToS) byte is found in the Layer 3 IPv4 packet header. The IP precedence bits are the first 3 bits of the ToS byte, for example {XXX}XXXXX. The IP precedence bits define the packet priority as specified in Internet Engineering Task (IETF) Request for Comment (RFC) number 791.
What is network control traffic?
The Network Control precedence designation is intended to be used within a network only. The actual use and control of that designation is up to each network. The Internetwork Control designation is intended for use by gateway control originators only. If the actual use of these precedence designations is of concern to a particular network, it is the responsibility of that network to control the access to, and use of, those precedence designations.
What is the Network Control Queue?
The network control queue is reserved for network control traffic only. When the customer send network control traffic, it will be prioritized above all other traffic.
What are Sprint's Voice over IP recommendations?
Sprint’s overall recommendation for VoIP customers is that customers allocate up to 35% of their bandwidth for the Priority Queue. This will vary depending on the customer’s CODEC and number of Public Switch Telephone Network (PSTN) voice channels.
What is a CODEC?
Short for compressor/decompressor, a codec is any technology for compressing and decompressing data. Codecs impact bandwidth because they determine the payload size of the packets transferred over the IP leg of a call. Voice over IP traffic is usually compressed for transmission. For more information on the various codecs, please visit Cisco’s website at www.cisco.com.
What is Class Based Weighted Fair Queuing (CBWFQ)?
Class Based Weighted Fair Queuing (CBWFQ) allows a customer to define traffic classes and then assign characteristics to that class. For example, the minimum bandwidth delivered to the class during congestion can be designated.
What is Low Latency Queuing (LLQ)?
Low Latency Queuing adds strict priority queuing to CBWFQ.
Strict priority
queuing allows delay-sensitive applications, such as voice and video, to be sent first.
What is Tail Drop?
Tail drop treats all traffic equally and does not differentiate between classes of service. Queues fill during periods of congestion. When the output queue is full and tail drop is in effect, packets are dropped until the congestion is eliminated and the queue is no longer full.
What is Weighted RED (WRED)
WRED generally drops packets selectively based on IP precedence. Packets with a higher IP precedence are less likely to be dropped than packets with a lower precedence. Thus, higher priority traffic is delivered with a higher probability than lower priority traffic. However, you can also configure WRED to ignore IP precedence when making drop decisions so that non-weighted RED behavior is achieved.
WRED is useful on any output interface where you expect to have congestion. However, WRED is usually used in the core routers of a network, rather than the edge. Edge routers assign IP precedence to packets as they enter the network. WRED uses these precedences to determine how it treats different types of traffic.
What is MultiMegabit?
Multi-Megabit T1 service (a NxT1 configuration) is Sprint’s NxT1 service offering. Sprint has only certified Multi-Megabit T1 for customers using Cisco routers. Multi-Megabit T1 provisions multiple T1’s with static routes to a single customer router. The switching mechanism in the router determines whether the data is sent on a per-packet or per-destination basis. Multi-Megabit T1 can work for up to 6 T1s (an aggregate of 9Mbps).
What are the Guidelines for Use of Cisco Express Forwarding (CEF) For Load Balancing across Multiple Paths?
Sprint recommends for those customers running Voice Over IP and Video Over IP applications where packet reordering of such applications could adversely affect the fidelity of the original voice payload, that only Per-Destination CEF load-balancing be configured for those customers utilizing Sprint's Multi-MegaBit service.
Sprint has developed Class of Service guidelines and recommendations for providing Class of Service on dedicated IP and IP VPN networks. These are guidelines and recommendations only. As each customer’s requirements will vary, Sprint cannot guarantee that the recommendations will be optimal or applicable to a particular’s customer’s requirements. Sprint can assist customers with Class of Service policies through a managed service or professional service. Please contact your account team for more information on these services.
Sprint makes no representations or warranties regarding the below information, or with regard to these guidelines, and Sprint will not be responsible for any claims, damage, loss or harm, including consequential damages, caused to an entity’s equipment or services based on the use of information provided on this website.