Endtoend resource management in Diff Serv Networks Diff
- Slides: 10
• End-to-end resource management in Diff. Serv Networks – – Diff. Serv focuses on singal domain Users want end-to-end services No consensus at this time Two proposals: • Integrated Services over Differentiated Services • Bandwidth Broker
• Integrated Services over Differentiated Services – Apply integrated services model end to end across a network with one or more Diff. Serv domains. – Diff. Serv networks are treated as a link layer medium – Integrated Service requests are mapped to diffserv capability • Services to PHB – Two tier resource allocation • Diff. Serv distributes aggregated resources at core • Int. Serv allocates the resources to indivudual users – Example: Figure 3. 8 – Do we have end-to-end Qo. S guarantees in this model?
• Bandwidth Broker (BB) – Resource allocation between different backbone service providers, as well as support Qo. S on local LAN. – Each network is associated with one or model BB, which keep track on local network usage • Admission control, policy control, reservation aggregation – BB needs the knowledge of routing – Example, Figure 3. 9 – Per flow end-to-end Qo. S guarantee?
Multiprotocol Label Switching • Virtual circuit at IP level – A short, fixed length label is used forwarding. – Similar too other circuit switched technology: ATM, Frame Relay, WDM • Convergence of datagram and virtual circuit. – How virtual circuit/datagram works? – Fundamental trade-off: complexity at routing and signaling.
• Motivation: IP over ATM integration. – Without MPLS: • Overlay model (classical IP over ATM) – ATM is treated like another subnet technology. – When ATM is treated as a subnet, it is different from both point-to-point or shared media network: » multiple neighbors, but no broadcast capability (ARP) » ATM may contain multiple logical IP subnets (LIS) – ATM ARP: need to emulate ARP. – Next. Hop Resolution Protocol (NHRP) • Problems: – Have scaling problems. Need VC to connect hosts in a logical subnet. O(N^2) connections and O(N) neighbors. – Going through IP layer in an ATM cloud is not efficient. – Lose Qo. S capability
• Motivation: IP over ATM integration. – With MPLS: • IP routing and signaling protocols take over the control path. • ATM switches are used only to data transmission. • ATM switches are now in the IP routing domain. • NHRP and on demand SVCs are no longer needed • MPLS matches ATM’s capability – Labels are SVC circuit IDs – Switching is done by ATM switches – Qo. S can be preserved in a LSP.
• Some advantages for MPLS: – Simpler packet classification and table lookup • Trade off between simple forwarding and complexity in signaling. – Protocol independent forwarding • Even IP has many protocols. (CIDR, v 4, v 6, etc) – Finer forwarding granularity • Can treat different customers differently. – Traffic Engineering • MPLS can setup explicit route between two nodes. • key application
• IP packet forwarding (Figure 4. 2): – Control path: making routing decisions. • unicast routing protocols and multicast routing protocols – Data path: move packet from input ports to output ports. • unicast forwarding table, unicast forwarding engine, multicast forwarding table, multicast forwarding engine • Forwarding is done by longest match between dst address and entries in the forwarding table.
• MPLS packet forwarding (Figure 4. 4): – Control path: making routing decisions. • unicast routing protocols and multicast routing protocols • Other control protocols (ATM, FR) – Data path: move packet from input ports to output ports. • Label-switching table • Label-based forwarding engine
– IP centric control: • IP is here to stay. • IP control protocols are more mature and scalable than other alternative protocols. • IP control protocols for everything (ATM, FR, optical WDM) – A unified control plane integrated IP with different link layer technologies and simplify the management.
