Specifications

73
Release Notes for Cisco 7000 Family for Cisco IOS Release 12.1 T
78-10811-05
New and Changed Information
• SVCs with ingress and egress (AAL5) common part convergence sublayer (CPCS) service data unit
(SDU) maximum size of at least 1506 bytes when supporting LLC/SNAP encapsulation, and 1502
bytes when supporting virtual circuit multiplexed encapsulation.
• Maximum Transmission Unit (MTU) negotiation as described in RFC-1626, “Default IP MTU size
for use over ATM AAL5”.
• Shaping of each egress PVC and SVC (up to the maximum number supported for the interface) to
no more than the PCR specified during connection establishment.
• Egress traffic shaping on a per-ATM service category basis.
• Link Control Protocol (LCP) configuration options
• Internet Protocol Control Protocol (IPCP) configuration options
• Network Control Program (NCP) types including IP.
• PPP idle timeout and absolute timeout.
• Forwarding Information Base (FIB) switching and fast-switching.
• RADIUS
• RADIUS attributes to identify the session-user as an SVC user. Attributes 30 and 31,
(Called-Station-Id and Calling-Station-Id) identify Called Party Address and Calling Party Address
of SVC calls. NAS Port Type identifies the SVC virtual path identifier (VPI)/virtual channel
identifier (VCI) and the ATM interface.
• Same ATM address on multiple ports. This feature enables ATM switches to balance sessions
across interfaces with same ATM address.
• Configuration of maximum number of SVCs of each ATM service category type.
• Configuration of maximum amount of equivalent bandwidth allowed to all SVCs. SVC calls are
rejected when bandwidth taken exceeds specified maximum amount of allocated bandwidth.
• Configuration of maximum amount of equivalent bandwidth allowed for each ATM service
category. SVC calls are be rejected when bandwidth taken would exceeds specified maximum
amount of bandwidth allocated for the specified ATM service category, such as ubr and vbr-nrt.
• 2000 PPP over ATM SVC sessions on a Cisco 7200 series router with an NPE-200 with 128MB
DRAM.
RSVP Support for Low Latency Queuing
Platforms: Cisco 7200 series and Cisco 7500 series routers
RSVP is a network-control protocol that provides a means for reserving network resources—primarily
bandwidth—to guarantee that applications transmitting end-to-end across networks achieve the desired
quality of service (QoS).
RSVP enables real-time traffic (which includes voice flows) to reserve resources necessary for low
latency and bandwidth guarantees.
Voice traffic has stringent delay and jitter requirements. It must have very low delay and minimal jitter
per hop to avoid degradation of end-to-end QoS. This calls for an efficient queuing implementation that
can service voice traffic at almost strict priority in order to minimize delay and jitter.
RSVP uses weighted fair queuing (WFQ) to provide fairness among flows and to assign a low weight
to a packet to attain priority. However, the preferential treatment provided by RSVP is insufficient to
minimize the jitter because of the nature of the queuing algorithm itself. As a result, the low latency and
jitter requirements of voice flows might not be met in the prior implementation of RSVP and WFQ.