Connecting the WAN
We have so far concentrated on scenarios with
If the provider has an mVPN service, you can connect your
Figure 9-16. mVPN Service
It is more likelyat least at the time of this writingthat multicast traffic will need to be tunneled across the WAN. Figure 9-17 shows this simpler scenario. The WAN edge routers have a LAN-facing MTI interface for MDT connectivity, a WAN-
Figure 9-17. Single-Domain-per-Branch Site
If the remote site is also virtualized, mVPN runs on all sites, as shown in Figure 9-18. The WAN edge routers use a different GRE tunnel for each virtual network. The remote site in Figure 9-18 uses
Figure 9-18. Multiple-Domains-per-Branch Site
The final scenario, in Figure 9-19, shows each site as a different mVPN domain, where the CE of one domain is the PE of another. The tunnels are regular GRE and transport native multicast traffic across the WAN.
Figure 9-19. Multiple-Domains-per-Branch Site
In all cases, remember that RPF requires a unicast route to the multicast source (or RP). Routers in each site must have appropriate unicast routing information in every VRF;
This chapter discussed three main topics: basic multicast, managing multicast source and receivers across VRFs, and transport architectures.
A virtualized enterprise network is fully capable of carrying multicast traffic. The simplest case has source and recipients in the same VRF, in which case the design decision is whether to use p2p transport or mVPN.
The mVPN extranet solution addresses the case where source and receiver are not in the same VRF.
Standards work continues in this area. The references sections in Appendices C and D include
Chapter 10. Quality of Service in a Virtualized Environment
The protocols used to
This chapter attempts to cover both effects and starts by demystifying certain technologies, such as differentiated services-aware traffic engineering (DS-TE), before looking at which mechanisms can be applied (and how) in Virtualized Network.
QoS Models and Mechanisms: A Review
QoS is a continuation of network policy. Policy information is set at certain points, carried in protocol headers, and enforced throughout the network. The result should provide a predefined level of service for different types of traffic.
You can also use QoS can to protect the network against certain types of security attacks, but that is beyond the scope of this discussion.
Many of the protocols used to
On the device itself, the mechanisms used to effect policy should be familiar to readers of this book. In the interest of having standard definitions, the following list summarizes them:
QoS mechanisms detailed are deployed in support of a particular model or architecture. The initial Internet model was, of course,
(p2p) best effort. Other models include
(IntServ), which uses the
Resource Reservation Protocol
(RSVP) to reserve bandwidth for flows of application traffic, and DiffServ. We review DiffServ in the
The DiffServ model is an architecture that allows scalable differentiation between data flows. With DiffServ, the majority of the labor-
Traffic admitted to the network core is
DiffServ does not require state information or signaling of resource requirements, either on a flow or aggregate basis. Instead, each device is configured with certain administratively determined limits on the amount of resource per class. DiffServ is defined in RFC 2474 ( Definition of the Differentiated Services Field [DS Field] in the IPv4 and IPv6 Headers ) and RFC 2475 ( An Architecture for Differentiated Services ).
DiffServ introduces an important concept, namely per-hop behavior (PHB). PHB is the observable behavior of a device as it processes traffic. An end-to-end QoS service can be provided as long as the PHB is consistent across the network.
RFC 2474 defines two PHBs:
The two most significant PHBs that use DiffServ are Assured Forwarding (AF) and Expedited Forwarding (EF), which are both defined in separate RFC documents.
RFC 2597 defines AF, and RFC 2598 defines EF:
It is important to apply the correct DSCP value to a packet. In a switched environment, there are typically two QoS domains (Layer 2 and Layer 3), and policy classifications must be correctly
In a typical campus network, the access switch classifies traffic based on either the incoming interface or ToS settings (the latter is common when a PC is connected to a switch through an IP phone) and marks this information in the 802.1p bits on the VLAN trunks that connect to the distribution layer. On the distribution switch, these ToS settings are copied to IP DSCP bits.
Cisco provides guidelines for which Layer 2 and 3 values to use in an enterprise network. Table 10-1 gives the complete 11 DSCP values and corresponding PHB
Table 10-1. Guidelines for 802.1p, IP Precedence, DSCP, and PHB Values in Enterprise Networks
The first settings column of the table lists the settings (limited to 7 classes) for IP Precedence rather than DSCP. Similarly, the last settings column shows the Layer 2 equivalence for each class.
The baseline QoS model is extremely granular, and it is often necessary to
However, the VPN protocols