A flow might be partially switched instead of completely switched in these situations: • If the switch is configured as a member of the IP multicast group on the RPF interface of the multicast source (using the ip igmp join-group command). • During the registering state, if the switch is the first-hop router to the source in PIM sparse mode (in this case, the switch must send PIM-register messages to the rendezvous point [RP]). • If the multicast TTL threshold is ..
Movement of Regionals onto Commercial Providers
The NSFNETregional and mid-level networks that previously provided the distribution layer of the network needed a new core. However, more than one core existed in the new architecture, and these commercial core providers were connected to the four Internet NAPs. Each regional network then had two connection choices: Connect directly to a NAP, establish peering relationships with other regionals, and establish a customer relationship with one or more of the commercial core p..
A primary function of access-edge policies is to establish and enforce trust boundaries. A trust boundary is the point within the network where markings (such as CoS or DSCP) begin to be accepted. Previously set markings are overridden (as required) at the trust boundary. The design objective relating to trust boundaries is to enforce these as close to the endpoints as technically and administratively possible. This is illustrated in Figure 12-3. Figure 12-3. Establishing T..
Cisco Implementations of Frame Relay Fragmentation
This section discusses the few fragmentation schemes supported by Cisco. Cisco has developed three different methods of performing fragmentation with Frame Relay: FRF.12 Fragmentation, Frame Relay Fragmentation using FRF.11 Annex C, and the Cisco Proprietary Fragmentation. Each fragmentation scheme uses a different data format or encapsulation. Frame Relay frames are fragmented based on one of the three formats, depending on how the Frame Relay PVC was set up. It is importan..
The Origins of Frame Relay: X.25
v\:* {behavior:url(#default#VML);} o\:* {behavior:url(#default#VML);} w\:* {behavior:url(#default#VML);} .shape {behavior:url(#default#VML);} Frame Relay has its roots in the X.25 protocol, a robust packet-switched WAN protocol widely deployed in the early 1970s to connect geographically dispersed LANs and WANs. The X.25 protocol works well on noisy transmission mediums, which observe a high rate of errors and packet drops. X.25's windowing, flow, and error control fe..
