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Network Protocol Software: Design and Implementation

Network Protocol Software: Design and Implementation. An Industrial Perspective. Overview: Network Protocols MPLS with RSVP-TE Practical Considerations on Protocol Software Implementation The requirements for protocol software The design for protocol software

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Network Protocol Software: Design and Implementation

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  1. Network Protocol Software:Design and Implementation An Industrial Perspective Edward Qian

  2. Overview: Network Protocols MPLS with RSVP-TE Practical Considerations on Protocol Software Implementation The requirements for protocol software The design for protocol software The implementation for protocol software The verification for protocol software Discussions Edward Qian

  3. Overview • Network Protocols: the communication language that network devices talk to each other at a specific layer • One example: Even since the Internet was developed, two camps of religious debates over “datagram” vs. “virtual circuit” • Connectionless IP carries a transmission connection (TCP) • Connected-oriented ATM or MPLS needs its connectionless routing to guide the way in setting up a connection. • Industry actually accepted both. • No matter which way network devices communicate, they communicate with protocols. • We take MPLS technology and its protocols as the example for this lecture Edward Qian

  4. Overview • Typically a router would be equipped with most of these protocol stacks in it. RSVP-TE Edward Qian

  5. Overview • Almost all network protocols are implemented as software (stacks) • Software design and implementation of network protocols play a crucial roles in developing network systems/devices • The early buggy implementation of OSI protocol stacks burned its users, so it stuck even though it’s got later improvement • Relatively compare with the TCP/IP as part of free Berkeley UNIX, it gained user acceptance quickly, got better improvement, then wider user acceptance Edward Qian

  6. Overview: Network Protocols • MPLS with RSVP-TE Practical Considerations on Protocol SoftwareImplementation The requirements for protocol software The design for protocol software The implementation for protocol software The verification for protocol software Discussions Edward Qian

  7. MPLS with RSVP-TE • What is MPLS? • Multi-protocol Label Switching – a network technology defined within IETF body • IP-based routing but connect-oriented label-based switching of packet. • MPLS borrows concepts from other networking protocols such as ATM and IP – which makes it well suited for a lot of today’s networks need. • Why uses MPLS? • ATM to IP core network evolution (one common MPLS core for multi-service accesses) • Next-Gen Convergence Network (voice, video and data) • Stringent SLA delivery in an IP network (QoS offering with DiffServ)Control of: end-to-end delay, jitter, packet loss, packet order, etc. • Traffic engineering with path protection and fast re-route to provide carrier-grade services (especially important for Voice in convergence IP network) • Value-added services (MPLS enabled VPNs, Voice over MPLS, …) Edward Qian

  8. MPLS with RSVP-TE • MPLS is a hybrid model adopted by IETF to make use of the best properties in both packet routing and circuit switching. MPLS IP ATM IP Routing Software IP Routing Software ATM Control Plan Label Distribution Signaling Packet Forwarding Label Switching Label Switching Edward Qian

  9. What is a Label? MPLS with RSVP-TE Edward Qian

  10. MPLS with RSVP-TE • MPLS Key Concepts • FEC (Forwarding Equivalence Class) • A group of IP packets which are forwarded in the same manner (e.g., over the same path, with the same priority and the same label) • Label • A short fixed length identifier which is used to identify a FEC • Label Stacking – Tunneling • Label Swapping – Looking up the incoming label to determine the outgoing label, encapsulation and port. • Label Switching Router (LSR) – An MPLS capable router. • Label Edge Router (LER) – An MPLS capable router at the endpoint of LSP. • Label Switched Path (LSP) – Path through one or more LSRs for a particular FEC • Data Forwarding • Label encapsulation • Label operations: PUSH, SWAP and POP, Penultimate-hop Popping Edward Qian

  11. MPLS with RSVP-TE • MPLS Key Concepts (cont’d) • Label Distribution/Signaling • Label Distribution Protocol • Provide procedures by which one LSR informs another for the label/FEC binding • LDP, CR-LDP/RSVP-TE, MPLS-BGP • Path Protection • Protection Switching (Head-End Repair) • Fast Re-Routing (Local Repair) • Crankback of Setup failure • Traffic Engineering • L-LSPs and E-LSPs • Routing Protocols Traffic Engineering Extensions • Extensions to Routing Protocols – Existing routing protocols can be extended to distribute traffic engineering information Edward Qian

  12. RSVP (RFC2205) RSVP for IntServ (RFC2210/11/12) RSVP Ext for IP Tunnel (RFC2746) RSVP Ext for Security (RFC2747/3097) RSVP Ext for Refresh Reduction (RFC2961) RSVP-TE (RFC3209) More RSVP Ext for IntServ … … MPLS with RSVP-TE • RSVP-TE • What is RSVP-TE • Use of RSVP protocol with certain traffic engineering extensions to setup MPLS LSP. • The relationship between RSVP-TE and RSVPRSVP-TE (RFC3209), RSVP(RFC2205) • Syntactically, RSVP-TE as a protocol is an extension to RSVP • Semantically, RSVP-TE is used for MPLS LSP setup as a label distribution protocol which is very differently from the original RSVP as mainly for resource reservation for IntServ. GMPLS Extensions (draft-ietf-mpls-generalized-rsvp-te-##) Edward Qian

  13. MPLS with RSVP-TE • RSVP-TE • Main Functions • Signaling for path (with explicit route, crankback, refresh, auto-restart) • Label Request and Distribution • Resource Reservation (with Traffic Engineering) • Keep Alive (RSVP Hello) • Label Distribution/Signaling • How to use RSVP-TE? • Signaling a path for LSP. Along the path peer nodes are expected to be RSVP-TE capable • Explicit source routing as path selection (ERO extension) • Request and Distribute labels (LRO and LO extension) • More traffic engineering parameters (SAO extension) • Fast peer failure detection (HELLO extension) • And more …… Edward Qian

  14. MPLS with RSVP-TE • PATH Message <Path Message> ::= <Common Header> [ <INTEGRITY> ] <SESSION> <RSVP_HOP> <TIME_VALUES> [ <EXPLICIT_ROUTE> ]<LABEL_REQUEST> [ <SESSION_ATTRIBUTE> ] [ <NOTIFY_REQUEST> ] [ <POLICY_DATA> ... ]<sender descriptor> <sender descriptor> ::= <SENDER_TEMPLATE> <SENDER_TSPEC> [ <ADSPEC> ] [ <RECORD_ROUTE> ] • RESV Message <Resv Message> ::=<Common Header> [ <INTEGRITY> ] <SESSION> <RSVP_HOP> <TIME_VALUES> [ <RESV_CONFIRM> ] [ <SCOPE> ] [ <NOTIFY_REQUEST> ] [ <POLICY_DATA> ... ] <STYLE><flow descriptor list> <flow descriptor list> ::= <FF flow descriptor list>| <SE flow descriptor> <FF flow descriptor list> ::= <FLOWSPEC> <FILTER_SPEC> <LABEL>[ <RECORD_ROUTE>] | <FF flow descriptor list> <FF flow descriptor> <FF flow descriptor> ::= [ <FLOWSPEC> ] <FILTER_SPEC><LABEL> [ <RECORD_ROUTE> ] <SE flow descriptor> ::= <FLOWSPEC> <SE filter spec list> <SE filter spec list> ::= <SE filter spec>| <SE filter spec list> <SE filter spec> <SE filter spec> ::= <FILTER_SPEC><LABEL> [ <RECORD_ROUTE> ] In Backus and Naur Form (BNF) Edward Qian

  15. LSP PATH (Label Request) PATH (Label Request) PATH (Label Request) RESV (Label 40) RESV (Label 53) RESV (Label 81) RESVCONF RESVCONF RESVCONF MPLS with RSVP-TE • LSP Setup (RSVP-TE Signaling) • Label distribution with RSVP-TE signaling • Uni-Directional • Downstream-on-Demand R6 40 40 53 53 81 81 10.60.0.0/16 R1 (Ingress) R2 R3 R4 (Egress) R5 Edward Qian

  16. LO: LO: LO: 40 53 81 RRO: RRO: RRO: R2 R3 R3 R4 R4 R4 ERO: ERO: ERO: R2 R3 R3 R4 R4 R4 PATH (Label Request) PATH (Label Request) PATH (Label Request) RESV (Label 40) RESV (Label 53) RESV (Label 81) MPLS with RSVP-TE Note: At each node, ERO list is popped till the bottom; RSVP uses NH IP address to query routing table for NH interface; and then encap to IP packet destined to Egress with router alert option • LSP Setup (RSVP-TE Signaling) With more details SO: IPd=10.60.0.0/16, Tunnel ID=12 ERO: R1-R2-R3-R4 LRO: L3PID SAO: setup/holding priorities, flag for local protect STO: sender address, LSP ID RRO: R1 ERO: R2-R3-R4 RRO: R1-R2 ERO: R3-R4 RRO: R1-R2-R3 ERO: R4 RRO: R1-R2-R3-R4 40 40 53 53 81 81 10.60.0.0/16 R1 (Ingress) R2 R3 R4 (Egress) RRO: R1-R2-R3-R4 40-53-81 LO: Label 40 RRO: R2-R3-R4 40-53-81 LO: Label 53 RRO: R3-R4 53-81 LO: Label 81 RRO: R4 81 SO: Session Obj ERO: Explicit Route Obj LRO: Label Request Obj LO: Label Obj SAO: Session Attribute Obj STO: Sender Template Obj RRO: Record Route Obj R6 R5 Edward Qian

  17. 40 53 81 81 MPLS with RSVP-TE • LSP Setup (RSVP-TE Signaling) With more details Tunnel (ID=12) 10.60.0.0/16 R1 (Ingress) R2 R3 R4 (Egress) R6 R5 Edward Qian

  18. POP 81 PUSH SWAP SWAP 40 53 81 81 40 IP L2 header Label MPLS with RSVP-TE • Data Forwarding Edge LSR (Ingress) LSR LSR Edge LSR (Egress) 40 40 53 53 81 81 Edward Qian

  19. MPLS with RSVP-TE • Path Protection Setup Primary Tunnel PATH for Primary LSP PLR (Point of Local Repair) MP (Merge Point) Primary LSP Ingress Avoid Node Egress Setup Detour Tunnel RESV for Primary LSP RESV for Primary LSP PATHd for Detour LSP RESVd for Detour LSP Detour LSP Edward Qian

  20. MPLS with RSVP-TE • Path Protection PLR (Point of Local Repair) MP (Merge Point) Primary LSP Ingress Avoid Node Egress Detour LSP Edward Qian

  21. MPLS with RSVP-TE • Path Protection PLR (Point of Local Repair) MP (Merge Point) Primary LSP Ingress Avoid Node Egress Detour LSP Edward Qian

  22. Overview: Network Protocols MPLS with RSVP-TE Practical Considerations on Protocol SoftwareImplementation • The requirements for protocol software The design for protocol software The implementation for protocol software The verification for protocol software Discussions Edward Qian

  23. Requirements for Protocols • General Considerations • Communication needs for inter-networking … • As “signaling”, for connected-oriented networks • As “routing”, for connectionless networks • Layered, so we call a protocol stack • Peer-to-peer, client-server, end-to-end … • control or data (layers, stacks, planes…) • Scalability • Third-party protocol stack purchasing; In-house development vs. outsourcing • Our Example • Label switched router • RSVP-TE as the signaling protocol for label distribution and managing LSPs/Tunnels • Perform label pushing/swapping/popping operation in data forwarding (switching) • Connection-oriented traffic engineered tunnels for voice/video streams • Carrier-grade high availability with MPLS path level protection • Taking advantage of third-party protocol stack to improve time-to-market and development cost Edward Qian

  24. Overview: Network Protocols MPLS with RSVP-TE Practical Considerations on Protocol SoftwareImplementation The requirements for protocol software • The design for protocol software The implementation for protocol software The verification for protocol software Discussions Edward Qian

  25. Design for Protocols • General Considerations • Modular Design, Separation of Concerns • Distributed vs. Centralized • Redundancy • Certain extensions to the protocol (BNF as notation for protocol message) • Evaluation and selection of the third-party protocol stack, stack porting and integration to your system as a part of your design • Our Example • (see a generic reference design, next …) Edward Qian

  26. Design for Protocols • A generic reference design Configuration Management Routing Protocols (OSPF/IS-IS/BGP) with Routing Table Manager (RTM) MPLS Label Manager (LM) Traffic Engineering Database (TED) Embedded control software running on RTOS RSVP-TE Forwarding Information Base (FIB) IP Stack Device Drivers Control • MPLS Switch HW • label operation • control flow Data Data Edward Qian

  27. Overview: Network Protocols MPLS with RSVP-TE Practical Considerations on Protocol SoftwareImplementation The requirements for protocol software The design for protocol software • The implementation for protocol software The verification for protocol software Discussions Edward Qian

  28. Implementation for Protocols • General Considerations • Real-time • Protocol stack outsourcing, third-party stack source code evaluation • Porting • Integrating • OS dependency • Multi-tasking, preemption, critical region, priority inversion, starvation, dead-lock • Memory management (not too frequent dynamic allocation…buffer ownership) • Performance issues • Timer services • Flexibility for PDU framing and manipulations • Extensibility • APIs (loosely or tightly coupled) • Network Order (Big Endian) Edward Qian

  29. Overview: Network Protocols MPLS with RSVP-TE Practical Considerations on Protocol Software Implementation The requirements for protocol software The design for protocol software The implementation for protocol software • The verification for protocol software Discussions Edward Qian

  30. Verification for Protocols • General Considerations • Functional behavior • Protocol conformance and compliance • Interoperability with other vendor devices in the networks • Performance test and the room for improvement • Stress test in extreme situation • Our Example • Follow RFCs and I-Ds for all functional specs that you claim to be conformed with for those MPLS/RSVP-TE related features • For configuration, certain MIBs to be supported and extended, able to set/get and provide required traps. • People often quote that functioning first, then performance…you will find that you have to pay a high price to alter your design due to some key performance issues. • You will also learn some painful lessons that your “free-style” coding habit caused the system failed at extreme large connections…you may have memory leak. • … … Edward Qian

  31. Overview: Network Protocols MPLS with RSVP-TE Practical Considerations on Protocol Software Implementation The requirements for protocol software The design for protocol software The implementation for protocol software The verification for protocol software • Discussions Edward Qian

  32. Discussions • Qualification as a Protocol Designer and Software Engineer • General software engineering principle and practice • Working knowledge of network architecture and protocols • Real-time embedded software design skill (RTOS, concurrent programming …) • In-depth understanding of modern network devices (routers, switches, multiplexers, as well as the state-of-art network processors), and their management. • C/C++ • Recommended Courses • Computer Networks (like this course) • Distributed Systems • Operating Systems (better yet Real-Time OS) • Data Structures and Algorithms • Concurrent Programming • Software Engineering/Processes Edward Qian

  33. Discussions • Loose the other end • Protocols are evolving • As in computing, IBM’s PL/I as the language of the future  DoD’s Ada  …?…  now we are enjoying (or suffering) with C/C++  now here comes a cup of Java… • ISDN once was believed as the “telecom GUT” the way people (with such end devices) communicate through the whole world  ATM (B-ISDN)  IP  Converged+MPLS  …future? (or back to future with the good old Ethernet and SONET?)… • Follow the money or the technology? • Engineers facing the challenges and even paradigm shift • Sharpening your skills (not only the technical side…) • Be brave to lead or at least to adaptively follow • … … be flexible Edward Qian

  34. The Dao of Design Edward Qian

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