RFC: CS.485/585

CS 485/585 Fall 2015 UNM Layer 7 Transport Protocol: UNML7TP

PREFACE ........................................................ iii

1. INTRODUCTION ................................................   1

   1.1. REQUIREMENTS TERMINOLOGY ...............................   2
   
   1.2. MOTIVATION .............................................   3

   1.3. INTERFACES .............................................   4
   
   1.4. PROTOCOL OVERVIEW ......................................   5

2. FUNCTIONAL SPECIFICATION ....................................   5

   2.1. MESSAGE FORMATS ........................................   6
   
   2.1.2. CLIENT HELLO .........................................   6
   
   2.1.3. SERVER HELLO .........................................   6
   
   2.1.4. CHUNK ................................................   6
   
   2.1.5. ERROR ................................................   6
   
3. GLOSSARY ....................................................   7

PREFACE

This document describes the application layer transport control
protocol as specified in class 14 Oct. 2015. All code examples,
format strings, and coding related examples in this RFC will be 
in C.

1. INTRODUCTION

1.1. REQUIREMENTS TERMINOLOGY
     
   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in 
   this document are to be interpreted as described in RFC 2119 [REQ].

1.2. MOTIVATION

  This lab is intended to get you familiar with reading RFCs, 
  defining, interperating, and implementing communications protocols 
  for a computer network.
  
1.3. PROTOCOL OVERVIEW

  This RFC describes the UNM layer 7 transport protocol hereafter 
  refered to as UNML7TP as defined in class on 14 Oct. 2015 for 
  CS485/545. This protocol is built on top of the transmission control
  protocol hereafter refered to as TCP. TCP is an interprocess 
  communication (IPC) mechanism that allows two  applications running 
  on different (or the same) machine to transfer data between 
  eachother
  reliably and in full-duplex. Because of this fact, UNML7TP is 
  lightweight in the sense that very little state information about 
  the connection and data transfer will be maintained by UNML7TP.

  There are two components to this protocol, client messages and
  server messages. The server MUST listen on port 1049. It must 
  wait indefinitely for a client to connect to it. The server MUST 
  be able to handle mutliple conncurrent connection. Once a client 
  has connected, the client MUST then send the CLIENT HELLO as defined
  in section 2.1.1.
  
  After the server receives this message from the client, it MUST 
  reply with the SERVER HELLO as defined in section 2.1.2.
  
  The server MUST then send 1 CHUNK of data as defined in section 
  2.1.3. The server MUST continue to send 1 CHUNK until N chunks 
  have been sent to the client. N is the number of chunks that the
  client asked for in the original CLIENT HELLO message.
 
  If the server OR the client sends an invalid CLIENT HELLO or 
  SERVER HELLO or CHUNK, the reciever of the invalid message MUST 
  send the ERROR message as defined in section 2.1.5 and terminate th
  connection.

2. FUNCTIONAL SPECIFICATION

2.1. MESSAGE FORMATS

  2.1.1. CLIENT HELLO

  The CLIENT HELLO is a message from the client to the server. It 
  tells the server the the client wants an arbitrary number of chunks.
  in the range [1, UINT_MAX). Where UINT_MAX = 4294967295. UINT_MAX
  specifies the largest possible value for a 32 bit unsigned integer.
  
  The exact message format MUST conform to the following format 
  string:
  
      "HELLO I'M THE CLIENT GIVE ME %u CHUNKS\n"

  The meaning of '%u' MUST be interperated as the format specifier 
  for 4 byte (32 bit) unsigned integers. The '\n' character MUST be 
  interperated as the newline character. All other characters MUST be 
  either uppercase ALPHBETIC, or the space character.

  If client sends a CLIENT HELLO to the server that does not conform 
  to this format, the server MUST responed with an ERROR message and 
  terminate the connection.

  2.1.2. SERVER HELLO

      "HELLO I'M THE SERVER HERE ARE %u CHUNKS\n"

  The meaning of '%u' MUST be interperated as the format specifier 
  for 4 byte (32 bit) unsigned integers. The '\n' character MUST be 
  interperated as the newline character. All other characters MUST be 
  either uppercase ALPHBETIC, or the space character.
  
  The server MUST specify that it is sending N CHUNKs of data, where 
  N is the number of CHUNKs the client requested in the original 
  CLIENT HELLO message.  The server MUST then send N chunks of data
  to the client.
  
  If the server sends a SERVER HELLO to the client that does not 
  conform to this format, the client MUST responed with an ERROR 
  message and terminate the connection.

  2.1.3. CHUNK
  
  A chunck is defined to be 74 bytes of characters. The server SHOULD
  return a string of *uniformlly distributed* random printable 8 bit
  ascii characters. The behavior is undefined for data sent in other
  formats. The only hard requirement is that the server MUST terminate
  the CHUNK with a '\n' character. Therefore, the total length of the 
  message is 74 bytes random data + 1 byte newline character.
  
  CHUNK ::= <74 bytes > , '\n'
  
  If the servers sends a data buffer that does not have a '\n' 
  character terminating the buffer, the client MUST send an ERROR 
  message and terminate the connection.
  
  2.1.4. ERROR
  
  The error message has the form:
  
  "ERROR\n"
  
  It is used for transport control and tells one of the two 
  communicating parties that an error occurred and that the 
  connectin MUST be terminated. 
  
  Upon sending an ERROR message, the sender MUST then terminate the 
  connection.
  
  Upon receiving an ERROR message, the receiver MUST then terminate 
  the connection.

3. GLOSSARY

3.1. Making a stream socket in C:

     int socket = socket(AF_INET, SOCK_STREAM, 0);

3.2. Server port to listen on: 1049

3.3. CLIENT HELLO: "HELLO I'M THE CLIENT GIVE ME %u CHUNKS\n"

3.4. SERVER HELLO: "HELLO I'M THE SERVER HERE ARE %u CHUNKS\n"

3.5. CHUNK:        <74 bytes of random data> + '\n' == 75 bytes total.