TCP构成RFC793，1323,1122,2018,2581

RFC1122 - Requirements for Internet Hosts - Communication Layers Network Working Group Internet Engineering Task Force Request for Comments: 1122 R. Braden, Editor October 1989 Requirements for Internet Hosts -- Communication Layers Status of This Memo This RFC is an official specification for the Internet community. It incorporates by reference, amends, corrects, and supplements the primary protocol standards documents relating to hosts. Distribution of this document is unlimited. Summary This is one RFC of a pair that defines and discusses the requirements for Internet host software. This RFC covers the communications protocol layers: link layer, IP layer, and transport layer; its companion RFC-1123 covers the application and support protocols. Table of Contents 1. INTRODUCTION ............................................... 5 1.1 The Internet Architecture .............................. 6 1.1.1 Internet Hosts .................................... 6 1.1.2 Architectural Assumptions ......................... 7 1.1.3 Internet Protocol Suite ........................... 8 1.1.4 Embedded Gateway Code ............................. 10 1.2 General Considerations ................................. 12 1.2.1 Continuing Internet Evolution ..................... 12 1.2.2 Robustness Principle .............................. 12 1.2.3 Error Logging ..................................... 13 1.2.4 Configuration ..................................... 14 1.3 Reading this Document .................................. 15 1.3.1 Organization ...................................... 15 1.3.2 Requirements ...................................... 16 1.3.3 Terminology ....................................... 17 1.4 Acknowledgments ........................................ 20 2. LINK LAYER .................................................. 21 2.1 INTRODUCTION ........................................... 21 RFC1122 INTRODUCTION October 1989 2.2 PROTOCOL WALK-THROUGH .................................. 21 2.3 SPECIFIC ISSUES ........................................ 21 2.3.1 Trailer Protocol Negotiation ...................... 21 2.3.2 Address Resolution Protocol -- ARP ................ 22 2.3.2.1 ARP Cache Validation ......................... 22 2.3.2.2 ARP Packet Queue ............................. 24 2.3.3 Ethernet and IEEE 802 Encapsulation ............... 24 2.4 LINK/INTERNET LAYER INTERFACE .......................... 25 2.5 LINK LAYER REQUIREMENTS SUMMARY ........................ 26 3. INTERNET LAYER PROTOCOLS .................................... 27 3.1 INTRODUCTION ............................................ 27 3.2 PROTOCOL WALK-THROUGH .................................. 29 3.2.1 Internet Protocol -- IP ............................ 29 3.2.1.1 Version Number ............................... 29 3.2.1.2 Checksum ..................................... 29 3.2.1.3 Addressing ................................... 29 3.2.1.4 Fragmentation and Reassembly ................. 32 3.2.1.5 Identification ............................... 32 3.2.1.6 Type-of-Service .............................. 33 3.2.1.7 Time-to-Live ................................. 34 3.2.1.8 Options ...................................... 35 3.2.2 Internet Control Message Protocol -- ICMP .......... 38 3.2.2.1 Destination Unreachable ...................... 39 3.2.2.2 Redirect ..................................... 40 3.2.2.3 Source Quench ................................ 41 3.2.2.4 Time Exceeded ................................ 41 3.2.2.5 Parameter Problem ............................ 42 3.2.2.6 Echo Request/Reply ........................... 42 3.2.2.7 Information Request/Reply .................... 43 3.2.2.8 Timestamp and Timestamp Reply ................ 43 3.2.2.9 Address Mask Request/Reply ................... 45 3.2.3 Internet Group Management Protocol IGMP ........... 47 3.3 SPECIFIC ISSUES ........................................ 47 3.3.1 Routing Outbound Datagrams ........................ 47 3.3.1.1 Local/Remote Decision ........................ 47 3.3.1.2 Gateway Selection ............................ 48 3.3.1.3 Route Cache .................................. 49 3.3.1.4 Dead Gateway Detection ....................... 51 3.3.1.5 New Gateway Selection ........................ 55 3.3.1.6 Initialization ............................... 56 3.3.2 Reassembly ........................................ 56 3.3.3 Fragmentation ..................................... 58 3.3.4 Local Multihoming ................................. 60 3.3.4.1 Introduction ................................. 60 3.3.4.2 Multihoming Requirements ..................... 61 3.3.4.3 Choosing a Source Address .................... 64 3.3.5 Source Route Forwarding ........................... 65 RFC1122 INTRODUCTION October 1989 3.3.6 Broadcasts ........................................ 66 3.3.7 IP Multicasting ................................... 67 3.3.8 Error Reporting ................................... 69 3.4 INTERNET/TRANSPORT LAYER INTERFACE ..................... 69 3.5 INTERNET LAYER REQUIREMENTS SUMMARY .................... 72 4. TRANSPORT PROTOCOLS ......................................... 77 4.1 USER DATAGRAM PROTOCOL -- UDP .......................... 77 4.1.1 INTRODUCTION ...................................... 77 4.1.2 PROTOCOL WALK-THROUGH ............................. 77 4.1.3 SPECIFIC ISSUES ................................... 77 4.1.3.1 Ports ........................................ 77 4.1.3.2 IP Options ................................... 77 4.1.3.3 ICMP Messages ................................ 78 4.1.3.4 UDP Checksums ................................ 78 4.1.3.5 UDP Multihoming .............................. 79 4.1.3.6 Invalid Addresses ............................ 79 4.1.4 UDP/APPLICATION LAYER INTERFACE ................... 79 4.1.5 UDP REQUIREMENTS SUMMARY .......................... 80 4.2 TRANSMISSION CONTROL PROTOCOL -- TCP ................... 82 4.2.1 INTRODUCTION ...................................... 82 4.2.2 PROTOCOL WALK-THROUGH ............................. 82 4.2.2.1 Well-Known Ports ............................. 82 4.2.2.2 Use of Push .................................. 82 4.2.2.3 Window Size .................................. 83 4.2.2.4 Urgent Pointer ............................... 84 4.2.2.5 TCP Options .................................. 85 4.2.2.6 Maximum Segment Size Option .................. 85 4.2.2.7 TCP Checksum .....................