Introduction to WAN Protocols

Transcription

1 2001, Cisco Systems, Inc. All rights reserved. 1 Introduction to WAN Protocols Session: 2 1

2 Technology Assumptions Basic Understanding of the OSI Reference Model Basic understanding of routing and switching. Basic Understanding of Networking Terms & Acronyms 3 Definition of a Wide Area Network A WAN is a network that covers a broad geographic area and often uses transmission facilities provided by common carriers. WAN technologies function at the lower three layers of the OSI reference model: Physical Layer (L1) Data Link Layer (L2) Network Layer (L3) 4 2

3 Layer 2 Encapsulation OSI Reference Module Application Presentation Session Transport Network Link Physical CPE A Network Link Physical Router / WAN Switch X Application Presentation Session Transport Network Link Physical CPE B Layer 2 Frames: Transport for L3 across L1 Error Detection & Possible Correction Establish peering across links Different Characteristics L2 Encapsulation Time Division Multiplexing (TDM) HDLC PPP FR / Frame Switching ATM / Cell Switching 5 Why Understanding Protocols Matters? Availability Scalability Efficiency Security Life Cycle Cost Data Only Multiservice 6 3

4 Making The Grade Scalability Efficiency Security Cost Life Cycle Data Data Only Only Overall Overall Multiservice Multiservice Protocol Look at the technology in terms of individual Availability requirements. Think of long term requirements ( 18mos - 3 years ) Consider if protocol overhead or protocol delay is of more importance? 7 Do You Remember? What are the important characteristics to consider in evaluating WAN protocols? What are the 3 HDLC Frame Formats? What are two applications of the Multilink Protocol in PPP? What equivalent FRF specs exist in Frame Relay? In Frame Relay, what is the purpose of the FECN and BECN bits in the Frame Header? What is one of the primary functions of the ATM Adaption Layer? 8 4

5 Agenda Introduction Time Division Multiplexing (TDM) High Level Datalink Control (HDLC) Point to Point Protocol (PPP) Frame Relay (FR) Asynchronous Transfer Mode (ATM) Summary 9 Time Division Multiplexing (TDM) D D D MUX MUX D D D D D D D E E E E E E E E 8 bits per timeslot TS1 TS2 TS22 TS3 TS23 TS24 F Framing (1 bit) 193 bits per frame (24*8 + 1) 125 µsec T1 (1.54Mbps) = 24 DSO s or Channels of 64kbps each Timeslots are always present regardless if data is being sent. Bandwidth is statically allocated to the applications Protocol Independent (HDLC, PPP, etc.) 10 5

6 TDM - Application / ISDN To Corporate Network 64Kbps PSTN / ISDN ISDN BRIs Switch Switch 64Kbps T1 = 24 DS0 s Call Oriented Setup (Q.931) Fixed Bandwidth (No More / No Less) LAP D Frame Format (similar to HDLC) 11 Making The Grade Protocol Availability Scalability Efficiency Security Cost Life Cycle Data Data Only Only Overall Overall Multiservice Multiservice A A A C C C D C D+ A A A D D D C C C Definite Support for Multiservice Applications. Predictable Delay Bandwidth likely to be under-utilized. Secure, L1 End-to-End Will be around for a while, but likely usurped by converged networks. Costs can be prohibitive in a tariffed environment. 12 6

7 Agenda Introduction Time Division Multiplexing (TDM) High Level Datalink Control (HDLC) Point to Point Protocol (PPP) Frame Relay (FR) Asynchronous Transfer Mode (ATM) IP-VPNs Summary 13 HDLC HDLC supports 16 or 32 bit Checksums HDLC supports 3 modes; NRM, ARM, and ABM HDLC LAP B is the WAN relevant application HDLC is sequenced and can perform Flow and Error control 14 7

8 HDLC - Frame Format L3 Datagram 1 1 or 2 1 or 2 Variable 2 1 Flag Address Control L3 Datagram (Data) FCS Flag N(R) P N(S) 0 I-Frames 0x0F 0x00 0x0800 Cisco Frame OR 3 Frame Types: Information, Supervisory, & Unnumbered Point-to-Point configuration typically employed Cisco HDLC (proprietary) Point-to-Point Configuration 15 HDLC - Application Internet Point-to-Point Applications (Leased Line) L2 QoS Doesn t Matter / Data Throughput Matters No Multiservice L2 Intelligence / L3 Queuing can partially assist Under-utilized links makes Multiservice possible on High Speed links (DS3+), but unpredictable. 16 8

9 Making The Grade Protocol Availability Scalability Efficiency Security Cost Life Cycle Data Data Only Only A B - Overall Overall Multiservice Multiservice - A B A D B A A A C F D Data Only = Excellent Currently supported up to DS3 links, with rate limiting for sub. Light Overhead, ideal for applications where maximum throughput matters. 17 Agenda Introduction Time Division Multiplexing (TDM) High Level Datalink Control (HDLC) Point to Point Protocol (PPP) Frame Relay (FR) Asynchronous Transfer Mode (ATM) Summary 18 9

10 PPP Point-to-Point Protocol. Used in Dial, xdsl, ISDN, Serial applications PPP can Multiplex multiple Network Protocols over a single link (Protocol Agnostic) Options for IP address assignment and management Link Configuration, Quality, and Error Detection Can negotiate additional options for Authentication, Compression, Multilink Support, etc. PPP uses an HDLC Frame for Encapsulation 19 PPP - Frame Format Flag 0xFF 0x03 0x0800 L3 Datagram FCS Flag PPP doesn t assign individual station address therefore using the broadcast address Indicates the NLPID of the CRC Error Checking L3 Datagram in the payload of the frame Maximum Transmission Unit (minus overhead) Indicates transmission of user data in an nonsequenced frame (connectionless) Protocol ID s Novell 0x8137 Appletalk 0x809B NetBIOS 0x00F0 Banyan 0x00BC More.. 0x

11 PPP - Operation Se2/0:7 PPP: Phase is ESTABLISHING, Passive Open [0 sess, 0 load] Se2/0:7 LCP: State is Listen Se2/0:7 LCP: I CONFREQ [Listen] id 230 len 27 Se2/0:7 LCP: AuthProto CHAP (0x0305C22305) Se2/0:7 LCP: MagicNumber 0x4CDA0A5B (0x05064CDA0A5B) Se2/0:7 LCP: MRRU 1524 (0x110405F4) Se2/0:7 LCP: EndpointDisc a (0x ) Se2/0:7 LCP: O CONFREQ [Listen] id 76 len 30 Se2/0:7 LCP: AuthProto CHAP (0x0305C22305) Se2/0:7 LCP: MagicNumber 0xCC96D7E6 (0x0506CC96D7E6) Se2/0:7 LCP: MRRU 1524 (0x110405F4) Se2/0:7 LCP: EndpointDisc _PE1 (0x130B F504531) Se2/0:7 LCP: O CONFACK [Listen] id 230 len 27 Se2/0:7 LCP: AuthProto CHAP (0x0305C22305) Se2/0:7 LCP: MagicNumber (0x05064CDA0A5B) Se2/0:7 LCP: MRRU 1524 (0x110405F4) Se2/0:7 LCP: EndpointDisc a (0x ) Se2/0:7 LCP: I CONFACK [ACKsent] id 76 len 30 Se2/0:7 LCP: AuthProto CHAP (0x0305C22305) Se2/0:7 LCP: MagicNumber 0xCC96D7E6 (0x0506CC96D7E6) Se2/0:7 LCP: MRRU 1524 (0x110405F4) Se2/0:7 LCP: EndpointDisc _PE1 (0x130B F504531) Se2/0:7 LCP: State is Open LCP: LCP Listen Option Negotiation Link Quality is determined (Optional) Network Layer Configuration Begins (IPCP, IPXCP, ATCP) Link Establishment (LCP Open) LCP Termination 21 PPP - Authentication (CHAP) 1720a 3640a Both Peers Challenging (Debug): Se2/0:7 PPP: Phase is AUTHENTICATING, by both [0 sess, 0 load] Se2/0:7 CHAP: O CHALLENGE id 76 len 29 from "3640a" Se2/0:7 CHAP: I CHALLENGE id 69 len 26 from "1720a" Se2/0:7 CHAP: Waiting for peer to authenticate first Se2/0:7 CHAP: I RESPONSE id 76 len 26 from "1720a" Se2/0:7 PPP: Phase is FORWARDING [0 sess, 0 load] Se2/0:7 PPP: Phase is AUTHENTICATING [0 sess, 0 load] CHAP Characteristics: 3-Way Handshake on link establishment. Authenticator sends a Challenge Peer responds with a value based on a oneway hash Authenticator validates against its own calculation. Se2/0:7 CHAP: O SUCCESS id 76 len 4 Se2/0:7 CHAP: Processing saved Challenge, id 69 Se2/0:7 CHAP: O RESPONSE id 69 len 29 from "3640a" Se2/0:7 CHAP: I SUCCESS id 69 len

12 e: e: Need Need debug debug output, output, but but lab lab is is tore tore down down until until June June 4th. 4th. PPP - NCP Negotiation 3640a 1720a Both Peers Challenging (Debug): Holder Holder Holder Holder Holder NCP Characteristics: Responsible for configuring, enabling and disabling the L3 protocol. Uses L2 protocol field 0x8021 to identify the payload as IPCP Address Assignment (DHCP) NetBios Name Servers Domain Name System 23 PPP - Multilink LCP Negotiated Option Member Links Identified through Endpoint Discriminator and / or Authenticated name. Bundles Multiple Physical Links into a logical bundle Bandwidth on Demand Multiservice support through fragmentation 24 12

13 PPP - Fragmentation & Interleaving MP Fragmentation Breaks up Large Data Packets in smaller sequenced fragments. Fragment-Delay is used to stipulate the maximum time a fragment can be on an individual link MP creates opportunities for non-mp encapsulated traffic (I.e, RTP) used in Voice applications to be interleaved. MP fragmentation and interleaving ideal in low speed (< 1.2Mbps) where delay is priority over throughput. 25 Making The Grade Scalability Efficiency Security Cost Life Cycle Data Data Only Only Multiservice Multiservice Overall Overall Protocol Primarily used in Data applications, however, can be used from Availability A B- B Multiservice A A B - B- B B B+ - B - - A A A Mature Protocol with new life in Broadband Aggregation applications HDLC style header is efficient for Data, MP is efficient for Multiservice BW Aggregation

14 Agenda Introduction Time Division Multiplexing (TDM) High Level Datalink Control (HDLC) Point to Point Protocol (PPP) Frame Relay (FR) Asynchronous Transfer Mode (ATM) Summary 27 Frame Relay - Overview N * (N-1) / 2 = Full Mesh Chicago 5 Sites = 10 LL 10 Sites = 45 LL San Francisco New York Dallas Miami What is the purpose / advantage of a Virtual Circuit? 28 14

15 Frame Relay SP Network Branch Packet Switched (Compared to Circuit Switched) Statistical Multiplexing Alleviates Wasted silence Uses a Virtual Circuit (VC) or Path through the network BW is not Allocated Until Needed Buffering and Congestion Control mechanisms Relies on Upper Layer Protocols (ex. TCP) for error recovery Frame Relay supported up to 45Mbps HQ 29 Frame Relay - Frame Format Bytes 1 2 Variable ( 0 ~ 4096) 2 1 Flag Header L3 Datagram (Data) FCS Flag Bits DLCI C/R EA DLCI FECN BECN DE EA DLCI - 10 Bit field (1024 Possible connections), Locally Significant C / R - Undefined Field EA - Extended Address ( 1 = End, 0 = More DLCI in 2nd Octet) FECN - Forward Explicit Congestion Notification ( --> Direction) BECN - Backward Explicit Congestion Notification ( <-- Direction) DE - Discard Eligibility: Set by end node allows frames to be dropped in a congested network or when CIR is being exceeded 30 15

16 Frame Relay - LMI Which DLCI s are active? DTE DCE Status_Enquiry Status Frame Switch DLCI 19, 23, 58 = Active DLCI 21, 29, 5 = Inactive LMI - Local Management Interface VC Discovery (DLCI) Multicasting Global Addressing LMI is used to check the Status of PVCs on the network LMI Uses reserved DLCI ( 0 = ITU, ANSI or 1023 = Cisco) Enquiry Types: Short Long Asynchronous 31 Frame Relay - UNI / NNI Site B Site A DLCI 100 DLCI 120 Frame UNI Switch NNI Service Provider Cloud Frame Switch UNI UNI DLCI 80 DLCI 60 Site C The Service Provider s cloud could be non-fr (I.e. ATM, etc.) Inverse ARP allows Network Layer address discovery (RFC 1293) Static Mapping required without use of iarp (not manageable) DLCI s are Locally significant. DLCI swapping is job of FR the Switch. The SP network will set FECN & BECN bits based on Congestion The SP will set DE bits based on Service Contracts

17 Frame Relay - FRF.12 DTE - DTE Fragmentation PHY I/F DLCI 120 V V V V DLCI 100 Data Data D V D V D V D V D PHY I/F V V V DLCI 54 V DLCI 147 Data Data Fragment Large frames into a sequence of shorter frames Control Delay critical for Multiservice applications (Voice, etc.) Fragmentation occurs on a per-vc basis 2 Byte Sequence Header keeps packets ordered (10 bits seq.) Large Frames hog time on wire, create delay problems 33 Frame Relay - FRF.16 MFR PHY I/F Data 1 PHY I/F MFR Data 1 Data 2 PHY I/F PHY I/F Data 2 Data 1 Data 2 Bundle Bundle Links FRF16 = Multilink Frame Relay Same encapsulation as FRF12 - UNI / NNI Fragmentation Increase Bandwidth where there are service offering gaps (T1 x N) Eliminate single points of failure with Physical interfaces. Inverse MUX ing several Physical Interfaces into 1 Logical Interface 34 17

18 Frame Relay - Application Chicago Sales / Remote Offices Reduces Interfaces Simplify Configuration Partial Mesh or Hub and Spoke design Reduce LL costs San Francisco Dallas DLCI 32 DLCI 31 DLCI 33 DLCI 3 DLCI 2 DLCI 4 DLCI 1 Head Quarters New York DLCI Pros Frame Relay - Characterization Dynamic Allocation of Bandwidth Bandwidth is not wasted. The hungry mouth gets it. Statistical Multiplexing allows idle VC s to share bandwidth with active VC s Can Be Used for Multiservice Applications Frame Switches Are Used for Multiservice Applications (DVV) (Less s over Subscription and Reasonable Speed Links) Technology is still being enhanced (FRF.12, FRF.16, etc.) Bandwidth is expandable (FRF.16) Cons Unable to Guarantee Performance (in FIFO Mode) Frame Switches Typically Operate in FIFO (First in-first out) Mode, so One Application Can Impact the Performance of Others Medium Delay and Variability in Delay Each Switch Has to Receive an Entire Frame before Forwarding It to the Next Switch; Therefore Transit Delay Increases with Number of Switches s in the Path The FIFO Mode of Each Switch Causes a Variability at Each Switch 36 18

19 Frame Relay: Report Card Protocol Availability Scalability Efficiency Security Cost Life Cycle Data Data Only Only Multiservice Multiservice Overall Overall A B B+ B - B A B B+ L2 - B B+ - B+ B- B+ B Fits into a Multiservice Application. Speeds up to DS3 and MFR scales (NxT1). Light Protocol Overhead (2 Bytes) and LFI make it efficient for Data and Multiservice. 37 Agenda Introduction Time Division Multiplexing (TDM) High Level Datalink Control (HDLC) Point to Point Protocol (PPP) Frame Relay (FR) Asynchronous Transfer Mode (ATM) Summary 38 19

20 ATM - Overview Connection Oriented transport (VC s pre-established) known as Cell Switching Hybrid of Circuit Switching and Packet Switching Fixed Cell size 5byte Header + 48byte Payload reduces latency typical to large data packets ATM Supports Multiple Qualities of Service Virtual Path + Virtual Channel = Virtual Circuit ATM supports Permanent VC s and Switched VC s ATM speeds up to OC-48 (2.5Gbps) 39 ATM - Functional Layers Segmentation & Reassembly Payload Error Control End-to-End Timing OSI RM Network Layer Data Link Layer B-ISDN RM AAL ATM Layer VPI / VCI Switching Cell MUX / DEMUX Flow Control / HEC QoS Support Physical Layer Physical Layer 1 Bitstream Conversion ATM Cell Boundaries 40 20

21 ATM - Cell Format Transmission Path H P H P H P H P H P Header Payload GFC VPI VCI PT CLP HEC GFC - Generic Flow Control VCI - Virtual Channel Identifier CLP - Cell Loss Priority VPI - Virtual Path Identifier PT - Payload Type HEC - Header Error Check 41 ATM - Operation IP Datagram LLC Segmentation IP Data ATM Adaption Layer VPI / VCI Assignment VC MUXing Serialization ATM Layer PHY Layer 42 21

22 ATM - Traffic Definitions CBR - Constant Bit Rate, Connection Oriented w / end-to-end timing required, utilizes AAL1 (Leased Line Emulation) ABR - Available Bit Rate UBR - Unspecified Bit Rate, connectionless packet data, best-effort transport. No guarantees to loss, delay, or bandwidth available, utilizes AAL5 Others, VBR-NRT, VBR-RT, etc. 43 ATM - Application Enterprise WAN Core Define Multiple Traffic Contracts Predictable Delays for Multiservice Applications No under-utilized bandwidth (like TDM) Scale VC s by application. San Francisco Data - AAL5 UBR Voice - AAL1 CBR Head Quarters New York 44 22

23 ATM I-LMII Site B Site A End-System IME UNI IME ATM Switch Private / Public Switch ATM Switch IME Private / Public Switch IME IME End-System Site C Public ATM Switch Public ATM Switch Integrated local management interface-ilmi Use SNMP across UNI and NNI for ILMI MIB Uses AAL 5 encapsulation Used for ATM end system address (AESA) formerly NSAP addressing for svc s Automatic recognition of UNI or NNI interface protocol 45 Making The Grade Protocol Availability Scalability Efficiency Security Cost Life Cycle Data Data Only Only Overall Overall Multiservice Multiservice B B B A A A B- A B C+ D - B B B ATM is great for multiservice applications, data-only pays a cell tax Bandwidth is scalable up to 2.5Gbps Delay is predictable and bandwidth use is efficient, more applications coming 46 23

24 Pros ATM - Characterization Dynamic Allocation of Bandwidth Available Bandwidth Is Allocated Dynamically to Any Application that Needs It One Application Can Use Bandwidth Allocated to the other if that Traffic Is Not Present Guaranteed performance Cell Switches with Efficient Traffic and Bandwidth Management Schemes Can Ensure that Each Application Receives Guaranteed Performance (TM, QoS Queuing, CAC, PNNI/UNI Etc.) Low Delay (Controlled and Bounded) and Low Variability in Delay Using Fixed Length Cells Ensures that Network Transit Delay and Variability in Delay Is Minimized Switches Use QoS-Based Queuing and Scheduling Such as CBR, VBR, ABR Typically Multiservice Cons As a Result of Low Delay, Low Variability in Delay and the Ability to Guarantee Performance, Cell Switches Are Ideally Suited to Support Multiple Services Concurrently Overhead However the Bandwidth Efficiency and Ability to Provide Low Delay y and Low Variability in Delay in Cell Switching Easily Overcomes the Small Incremental Overhead 47 All Together Now VPDN Internet DS-3 Chicago Boston San Francisco OC-3 384K 256K New York ATM Frame-Relay HDLC PPPoX Ft. Worth Dallas 256K 128K Austin 48 24

25 Agenda Introduction Time Division Multiplexing (TDM) High Level Datalink Control (HDLC) Point to Point Protocol (PPP) Frame Relay (FR) Asynchronous Transfer Mode (ATM) Summary 49 Summary There is no universally correct WAN technology to choose. Understanding your requirements and predicting growth will be essential elements to cost-effective, scalable, efficient network implementation

26 WAN - Futures PPPoX xdsl IP-VPNs MPLS-VPNs 51 Do You Remember? What are the important characteristics to consider in evaluating WAN protocols? What are the 3 HDLC Frame Formats? What are two applications of the Multilink Protocol in PPP? What equivalent FRF specs exist for Frame Relay? In Frame Relay, what is the purpose of the FECN and BECN bits in the Frame Header? What is one of the primary functions of the ATM Adaption Layer? 52 26

27 Follow On Presentations WMS-201 WMS-301 WMS-210 VVT-213 Deploying WAN Protocols Troubleshooting WAN Protocols Deploying Multiservice Networks Deploying QoS for Voice & Video 53 Q & A 54 27

28 Please Complete Your Evaluation Form 55 Presentation_ID 2001, Cisco Systems, Inc. All rights reserved