Cisco Cisco 1800 2800 3800 Series AP-AG 802.11a b g High-Speed WIC

Page 3 of 26

Today’s 4G LTE technology was designed to support single-user devices such as cell phones and tablets. LTE

QoS is based on a traffic flow template pushed to the LTE modem from the network. Historically, the flow template

was based on a 5-tuple (source and destination IP addresses, protocol, source and destination port numbers). A

use case was streaming of pay-per-view video content. This method of classification by the modem is not scalable

for network-based multi-user deployment.

Verizon and Cisco have partnered to leverage LTE technology for use as a last mile Widea Area Network access

with Private Network Traffic Management. The extensions are deployment options, network enhancements, and

ISR enhancements, which meet today’s LTE open 3GPP standards. Below are the key characteristics:

Verizon offers two bearer channels across an LTE Private Network connection. Both bearers are part of a

single logical connection via a single ISR interface and IP address. The service rate options are 512Kbps

or 2Mbps for the bearer supporting Mission Critical Class-of-Service (CoS).

Traffic is classified and placed onto the appropriate LTE bearer based on the ToS byte of an IP packet

(e.g. DSCP value). This allows integration with an organization’s existing QoS model per generally

accepted practices (mark DSCP close to the source and treat traffic across the network based on DSCP

in each packet). Multiple classes can be mapped to the bearer offering enhanced QoS.

The PNTM bearers include the dedicated bearer (supports all packets marked DSCP CS3, AF3x, CS4,

AF4x, CS5, EF), and the default bearer (supports all other packets). The default bearer is provided best

effort service, while the dedicated bearer is provided prefential treatment (Mission Critical CoS) up to the

service rate (512Kbps or 2Mbps). Note that traffic above the service rate in the dedicated bearer is

dropped by the network`.

Today’s LTE cellular modems do not provide the granularity in congestion feedback that wireline

interfaces offer. QoS traffic congestion control and prioritization mechanisms are engaged when there is

congestion notification (too many packets in a queue). The current lack of quick and granular notification

from the LTE modem to the device (e.g. an ISR interface) requires deploying a method to artificially

generate the congestion notification, allowing the QoS mechanisms to be engaged. A configuration

method to enable this has been developed by Cisco and Verizon, and is explained next.

Traffic shaping is a method of rate limiting traffic without dropping the excess packets. Packets that would exceed

a particular bit-per-second rate are momentarily queued. This provides traffic smoothing, with TCP-based flows

adapting to a lower throughput rate, so those applications can operate without retransmitting packets and

exacerbating the congestion. Traffic shaping also self-induces congestion notification.

The configuration guidelines in this document are based on traffic shaping and multi-level traffic treatment. The

configurations are constructed in a way that allow for simple modification when current limitations of LTE modem

congestion notification are mitigated (by removing the top level shaper). The QoS configuration includes 3 levels of

traffic treatment, and are described below.

First level: all traffic sent over an LTE connection is shaped. Recommendations regarding determining

the shaped rate are included in the subsequent deployment section. If the traffic sent is below the shaped

rate, the overall traffic is not conditioned. If the traffic to be sent will exceed the shaped rate, the traffic is

temporarly queued to smooth bursts. The traffic is also then prioritized based on the second level.

Second level: if congestion for overall traffic has occurred, any traffic marked with DSCP CS5 or EF is

provided strict priority over all other traffic up to a defined bit rate. Any traffic marked with CS3, CS4,