1 Network Architecture and Design Internet QoS Differentiated Services (DiffServ) Multiprotocol Label Switching (MPLS) Reference Zheng Wang, Internet QoS, Architectures and Mechanisms for QoS, ISBN , 2001.

2 Network Architecture and Design DiffServ - Overview Integrated services provides QoS; but Problem of scalability The routers have to maintain state on every flow passing through them. Heterogeneous networks may not be able to provide particular QoS controls or even RSVP. Differentiated service (DiffServ) aims to offer QoS to aggregated flows.

3 Network Architecture and Design DiffServ - Overview DiffServ defines Differentiated Service Code Point (DSCP) in IPv4 TOS field, IPv6 Traffic Class field. All traffic in one DSCP is treated the same. Per hop behaviour (PHB) is determined by DSCP of packet. Service Level Agreements concern aggregate traffic not individual flows.

4 Network Architecture and Design DiffServ - Operation Per Hop Behaviour (PHB) Assured Forwarding provides low loss probability for compliant traffic. Guarantees ordering of packets in a given AF class. Expedited Forwarding: near constant delay/throughput Virtual Wire aggregate

5 Network Architecture and Design DiffServ - Operation Resource allocation BB: Bandwidth Broker: global view of resources Static provisioning: may give poor service to flows Signalling: use of RSVP to allocate resources

6 Network Architecture and Design DiffServ - Operation

7 Network Architecture and Design DiffServ - Operation classifiermarker meter Shaper/ dropper To interior nodes Input

8 Network Architecture and Design DiffServ - Operation Classification: marks packets according to classification rules to be specified Metering: checks whether the traffic falls within the negotiated profile Marking: marks traffic that falls within profile Conditioning: delays and then forwards, discards, or remarks other traffic

9 Network Architecture and Design DiffServ - Operation 2-Bit Differentiated Services Architecture for the Internet Premium service Premium service levels are specified as a desired peak bit rate for a specific flow Assured service Best-effort service

10 Network Architecture and Design DiffServ - Operation In-profile traffic is marked: A-bit is set in every packet Out-of-profile (excess) traffic is unmarked A-bit is cleared (if it was previously set) in every packet; this traffic treated as best-effort r bps b bits metering in-profile traffic out-of-profile traffic user profile (token bucket) set A-bit clear A-bit assured traffic

11 Network Architecture and Design DiffServ - Operation In-profile traffic marked: Set P-bit in each packet Out-of-profile traffic is delayed, and when buffer overflows it is dropped r bps b bits Metering/ Shaper/ Set P-bit in-profile traffic out-of-profile traffic (delayed and dropped) premium traffic user profile (token bucket)

12 Network Architecture and Design IntServ Vs DiffServ Integrated Services Differentiated Services QoS guaranteePer data streamAggregated data streams ConfigurationPer session end- to end Between domains Duration of guarantee Short-livedLong-term SignalingRSVPNot yet defined

13 Network Architecture and Design IntServ Vs DiffServ IntServ provides fine grain control and handles dynamic allocation of resources to flows DiffServ provides course grain control of flows through their aggregates The two together can be combined to provide scalable end to end Integrated service, using a DiffServ region as a single element Controlled Load can be implemented over Assured Forwarding PHB Guaranteed can be implemented over Expedited Forwarding PHB

14 Network Architecture and Design IntServ & DiffServ

15 Network Architecture and Design Internet QoS Differentiated Services (DiffServ) Multiprotocol Label Switching (MPLS)

16 Network Architecture and Design Current Situation Geographically dispersed enterprise networks need to be connected for transparent and secure private IP interconnection. Full (n^2) mesh of virtual-circuits needs for desired guaranteed performance, or partial meshing for low cost. IP uses 64K size packets whereas ATM uses 53 byte-cells. IP and circuit-switching (e.g., ATM) technologies use different addressing scheme.

17 Network Architecture and Design MPLS Overview MPLS (Multiprotocol Label Switching) Improves the forwarding speed of a router. Introduces new capabilities for large IP networks Introduction of many of the qualities and attributes of switched networks to IP networks Integrates Layers 2 and 3.

18 Network Architecture and Design MPLS Operation MPLS Components Edge-LSR: Edge-Label Switching Router Assigns a label in an incoming IP packet Removes the label of an incoming IP packet LSP: Label Switching Path The path that a packet follows in an MPLS network LSR: Label Switching Router Makes forwarding decisions based SOLELY on the contents of the label (basic advantage) Strips off the existing label and applies a new label which tells the next hop how to forward the packet

19 Network Architecture and Design MPLS – Traditional IP Routing IP

20 Network Architecture and Design MPLS – MPLS Routing IP

21 Network Architecture and Design MPLS - Example 1a. Existing routing protocols (e.g. OSPF, ISIS) establish reachability to destination networks 1b. Label Distribution Protocol (LDP) establishes label to destination network mappings. 3. Label Switches switch label packets using label swapping 4. Label Edge Router at egress removes label and delivers packet 2. Ingress Label Edge Router receives packet, performs Layer 3 value-added services, and “label” packets

22 Network Architecture and Design MPLS Label Format IP packet is encapsulated in MPLS header and sent down LSP IP packet is restored at end of LSP by egress router TTL is adjusted also … IP Packet 32-bit MPLS Header

23 Network Architecture and Design MPLS Label format TTLLabelCoSS Label Class of service Stacking bit Time to live Decrement at each LSR, or Pass through unchanged

24 Network Architecture and Design Label Distribution Protocols CR-LDP RSVP-TE

25 Network Architecture and Design MPLS Fast forwarding speed Traffic Engineering constraint-based routing explicit routing ability to compute a path at the source ability to reserve network resources and to modify link attributes Voice/Video on IP delay variation + QoS constraints Virtual Private Networks controllable tunneling mechanism equivalent to a Frame Relay or ATM VC

26 Network Architecture and Design MPLS Benefits 14 IP over ATM Integration Shared backbone for economies of scale Keep up with Internet growth Reduced complexity for lower operational cost Faster time to market for IP services => more revenue Traffic Engineering Traffic eng. for lower trunk costs; Hierarchical routing for improve reliability of core Shared IP/Frame backbone for economies of scale VPNs New revenue opportunity for SPs Scalability for lower operational costs and faster rollout L2 privacy and performance for IP

27 Network Architecture and Design Second Intermediate Report Integrated and Differentiated Services I. Stergiou Group Communication, MBONE, MPLS A. Sgora Deadline: 11/02/03

28 Network Architecture and Design Second Intermediate Report Structure Overview of examined technology Focus on open research points Related to open points works - State of the art behind open points Your own interests - Ideas Conclusions References

29 Network Architecture and Design Second Intermediate Report Report (soft and hard copy) A related presentation (about twenty minutes).

30 Network Architecture and Design End of Fourth Lecture