Abstract:
In a network communication system involving a client and a server, communications are separated and forwarded into multiple subsystems for processing independently and concurrently. A protocol offloading system for processing information transmitted between a client and a server is provided. The protocol offloading system includes a first subsystem for processing protocol information and a second subsystem, independent of the first subsystem, for processing the actual data.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application claims the benefits under 35 U.S.C. §119(e) of U.S. provisional patent application Ser. No. 60/347,246 filed Jan. 14, 2002. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to web servers configured to process information requests from clients in client-server type applications. 
   2. Description of Related Art 
   Current web server architecture utilizes one system to process HTTP data (both requests and responses) and Ethernet, IP, TCP, and HTTP protocols. However, such an architecture does not scale because as the packet data is passed up the stack and processed, and each level of the stack is required to parse out the data that it needs from the original packet. 
   Conventional computer network architecture consists of three main sections. The first of these is the client software. Common examples are Microsoft Internet Explorer™ and Netscape Mozilla™ browsers for the HTTP protocol. The client software is the interface that is used to present the data or information to the user and is therefore under the full control of the user. Normally the client software issues requests to the Web server via the neck of communication mechanism for the data that the user desires to see. However, before the HTTP session can be established, low level protocols are used to establish the communication channel thereby providing HTTP with the reliable protocol transport that it requires. 
   The second main section is a communication mechanism in place to provide a reliable transport of information and data between the client software and server software. Fault-tolerant protocols are used to transfer the requests and responses, normally as part of a session between the client and server software. The network is made up of a physical communication mechanism that today is constructed from either copper or fiber cables. The cables carry the signals that are generated by the network connection equipment. The network connection equipment converts the protocols in use today to the low level signals that are needed to transfer the data across the physical connection. 
   The third main section of network architecture is the server software. There are many examples of server software in use today; however, for HTTP, Microsoft&#39;s™ IIS Web server and the open software foundations&#39; Apache Web™ server are the dominant solutions in use today. The application-specific server software generally resides on top of a general-purpose operating system that is capable of doing many things in a acceptable manner. However, it is generally not capable of providing the most efficient and high performance environment that would be optimal for the application. It is a trade-off between being able to do many things and being extremely efficient at a single task, or a number of smaller tasks. Because of these trade-offs, Web servers in use today are inefficient and do not provide the most cost-effective solution or even the best utilization of the computing resources that they consume. 
   The procedure and handshaking process is very well-defined and followed by all the vendors that make use of the Internet today, because most systems in use follow the same set of rules, and interoperability, at least at the protocol level, is assured. 
   With reference to  FIG. 1 , the client follows what is referred to as a three-way TCP (Transmission Control Protocol) handshake procedure. The client sends (at  200 ) a SYN packet to the glistening port on the server. The server is required to acknowledge receipt of the SYN packet and acknowledges receipt by replying (at  202 ) with a SYN-ACK. When the client successfully receives the SYN-ACK it acknowledges that the server is ready to accept a connection and sets up a connection on the client. When the connection is successfully initialized it will send an ACK ( 204 ) back to the server indicating to the server that the client is now ready to request data  204 . Once the three-way handshake is complete and a TCP connection has been established, the connection is ready to transfer application data, which in this example is an HTTP connection. The HTTP client will now send ( 206 ) a valid HTTP request for the data that is needed by the client. The server will reply ( 208 ) with the requested data. This sequence of events will continue until the client has all the data that was requested. To terminate the connection the server sends ( 210 ) a FIN packet to the client. The client acknowledges receipt of the FIN packet and the fact that the connection with the server needs to be terminated, by replying ( 212 ) to the server with a FIN-ACK acknowledgment packet. When the server receives the FIN-ACK it will terminate the connection with the client, and it can now release all the resources that were being used for the communication to the client, and reply ( 214 ) back to the client with an acknowledgment packet. 
   Although the above procedure is a very simple handshaking and simple request and response mechanism that is used to transfer the data, it is possible for the client to have multiple connections to multiple servers. As a result, the servers are forced to manage each of these connections in a very reliable fashion. The server is required to maintain the status of 14 fields in the case of IP (RFC 791) and 18 fields in the case of TCP (RFC 793), for each connection. This connection management function that the server is required to perform places a significant drain on the computing resources that could have been otherwise used for data management functions. 
   The present invention therefore seeks to free up the computing resources of servers by facilitating connection management. 
   BRIEF SUMMARY OF THE INVENTION 
   In accordance with the invention, a protocol offloading system for processing information transmitted between a client and a server is provided. The protocol offloading system includes a first subsystem for processing protocol information and a second subsystem, independent of the first subsystem, for processing the actual data. 
   Further in accordance with the invention, a method is provided for performing protocol offloading associated with communication of information between a client and a server, the method including identifying the protocol information for processing in a first subsystem, and processing the actual data in a second subsystem, independent of the first subsystem. 
   The invention may provide numerous benefits, including: 
   Reliability. Each of the handlers or brokers ensures that the data is valid and therefore only valid data is passed on to the next handler. 
   Flexibility. Because the system is event driven and fully pluggable, additional handlers can be written to handle new protocols or process existing protocols in a different manner. 
   Scalability Systems using this architecture are significantly more scalable. Not only are they able to process more data in less time but also with significantly less latency. This is achieved because the data does not have to be parsed to remove, modify or insert specific data. Rather, the data is passed to each handler as a data structure that does not need to be searched because it can be referenced by name or offset. 
   Efficiency. The invention allows the computer CPU and associated components to operate much more efficiently because it does not cause the CPU to context switch, makes full use of the CPU, interrupt controller and bus pipelining mechanisms. 
   Reduced Latency. Because the data is not required to be parsed, the data server can simply perform a lookup against the data in the data structure and therefore be able to process the data without delay. 
   Predictability. Because data parsing requires expensive lookups, when large amounts of data are being used, conventional systems become unpredictable. According to the invention, because the data server does not have to parse the content, it allows for the data server to have predictable data processing times, thereby allowing for excellent capacity planning and computer requirement forecasting. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S) 
     Many advantages of the present invention will be apparent to those skilled in the art with a reading of this specification in conjunction with the attached drawings, wherein like reference numerals are applied to like elements and wherein: 
       FIG. 1  is a diagram of an HTTP connection flow; 
       FIG. 2  is a schematic illustration of a system for application protocol offloading in accordance with the invention; 
       FIG. 3  is a flow diagram of an application protocol offloading system in accordance with the invention; 
       FIG. 4  is a flow diagram of the operation of an HTTP application protocol handler in accordance with the invention; 
       FIG. 5  is a flow diagram of the operation of a TCP protocol broker/handler in accordance with the invention; and 
       FIG. 6  is a flow diagram of the operation of a data system in accordance with the invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  is a schematic illustration of a system for application protocol offloading in accordance with the invention. Such a system provides the solution of separating the HTTP (Hypertext Transfer Protocol) processing (requests and responses) into multiple subsystems for processing independently and concurrently. While described in terms of HTTP, it is to be understood that the invention is applicable to other application level protocols, such as FTP, SMTP, XML, streaming media, and so forth. 
   A request  12  for information originates with a client  10 , and is sent, via a network such as Internet  14 , to a protocol offloading system  18 . The protocol offloading system  18 , which can be a combination of other protocol subsystems (not shown) in which one or multiple protocols are processed, processes the Ethernet, IP, TCP and HTTP protocols of the request. The processed request is then forwarded, as a pre-processed request, to separate data system  24 , via communication channel  22 . Examples of possible bus architectures used as communication channels are PCIX, InfiniBand, and Hypertransport. Examples of networks are internal networks, such as Ethernets, ATMs and so forth. 
   The data system  24  processes the actual data—that is, the request and the subsequent response. The data system  24  then sends a response, without any protocol information, back to the protocol offloading system  18 , via communication channel  22 . The protocol offloading system  18  appends the protocol information to the response it receives from the data system  24 , and sends its response ( 28 ) to the client  10 , via network  14 . Information transferred between the protocol offloading system  18  and the data system  24  may be encrypted. Further, the information may be grouped—for example multiple requests or responses being sent in a single packet or stream. Alternatively, the information may be sent in packets or streams each corresponding to a single request or response. It is also contemplated that multiple protocol offloading systems  18  can be connected with multiple data systems  24 . 
   The mechanism to improve the scalability of the current network architecture in accordance with the invention is the offloading of the protocol-specific processing mechanisms. The protocol offloading system  18  needs only to communicate the required data to the data system  24 , and thereby provide the scalability that is needed by the higher processing needs of today&#39;s enterprise customers. 
   No changes are required on the client end, and therefore the solution of the invention can be easily implemented without any changes to the current installed base. The client  10  issues a simple HTTP request for data via existing communication mechanisms that will transfer the request to the protocol offloading system  18 . The protocol offloading system  18  provides all the protocol-specific mechanisms that are required to communicate with the client  10  over the existing network. 
     FIG. 3  schematically shows the protocol offloading system, comprising a protocol event engine  32 , which is the entry point for all client requests. The event engine  32  is responsible for directing requests from the client to a relevant protocol broker or handler, for example TCP Protocol broker/handler  40 , IP Protocol broker/handler  42 , or UDP Protocol broker/handler  44 . Other protocols are also possible, and appropriate brokers/handlers are provided therefor. In the case that the protocol is unknown, the protocol event engine  32  sends the packet to a forwarding agent  34  without any modification, and direct communication with the server is established. 
   To provide a scalable and flexible architecture, each protocol will make use of its own protocol broker/handler ( 40 ,  42 ,  44 ) that has specific knowledge required for that protocol. Each broker/handler can then simply register with the protocol event engine  32 , and as part of the registration process, provide the protocol engine with the specific details that it needs to provide the event services and guarantee that all packets that conform to a prescribed rule set will be directed to that protocol broker/handler, thereby ensuring that the correct protocol packets are all sent to the correct broker. To ensure that data integrity is maintained, client requests are validated against the registered protocol brokers or handlers in protocol event engine  32 . In the case of a client request using an unregistered protocol, the request will simply be forwarded directly to the application server  34 . An important function of the broker/handler is to populate the data structures with the protocol-specific information. 
   When the lower-level protocol issues have been addressed by the protocol broker/handlers  40 ,  42 ,  44 , the relevant data is passed on to application protocol brokers, such as for example HTTP Application Protocol Broker  50 , IP-based Application Protocol Broker  52 , and UDP-based Application Protocol Broker  54 . It is the responsibility of the application protocol broker  50 ,  52 ,  54  to take the data structure as populated by the protocol broker/handler  40 ,  42 ,  44  and add to it the HTTP protocol-specific data, and then to place it on the queue or generate the event so that the data system  60  can access the data. The process is then reversed, and the response to the client request is sent, at process  70 . 
   Each application protocol broker is required to understand the application protocol nuances and specifics. Therefore, although the architecture its modular and provides a simple interface for new application brokers to be written and registered, an HTTP application protocol handler will be discussed for this invention. 
   Referring to  FIG. 4 , to maintain a high level of data integrity, the packet data is verified at  140  to ascertain compliance with the strict HTTP rules as defined with the RFC. If a data service has registered with the HTTP application handler  142 , it is determined at  157  if this valid HTTP packet is a request or response. Otherwise direct communication with the server is established ( 156 ). If it is a request the protocol handler determines if this is a new or existing session (at  144 ), and if it is a new session, any application specific and checking is completed at  146 . Various security specific functions, such as authentication mechanisms, are activated here. The session status is verified  148  before the packet is parsed to gather HTTP data at  150  so that the data structure can be populated with the HTTP data ( 152 ) in order for an event to be generated ( 154 ) to wake up the data system. The data is placed on a queue for processing by the data system  154 . If the data is a response, the data structure is populated at  158 , and the event generated at  160 . 
     FIG. 5  shows the operation of the TCP protocol broker/handler mechanism. The broker/handler is responsible for the protocol-specific error and validity checking ( 200 ), and data structure population ( 214 ). If a determination at  206  of an existing session is made, then a status check  210  is performed. Otherwise a session is established first, at  208 . Parsing is performed at  212 , data structure population at  214 , and an event generated at  216 . Packet generation is also performed at  204 . It will be appreciated that TCP is discussed here, but as shown in the application protocol offloading system flow diagram ( FIG. 3 ), other protocols such as IP  42  and UDP  44  can easily be accommodated simply by creating the appropriate protocol handler and registering with the application protocol offloading system. 
   The application protocol offloading system ensures that only valid requests are received directly to the protocol event engine  32 . Even so, the TCP protocol broker is required to perform, at  200 , protocol specific checks to ensure the data integrity and validity of the packet received. It is then determined if the data structure needs to be populated from the packet contents or if the packet needs to be grated from the data structure. In the case of a client request having been received from the client, it needs to be determined if any protocol specific actions need to be taken. In the case of TCP a three-way handshake needs to be completed as discussed above, so the TCP broker checks to see if this is an existing session (at  206 ), and if it is not, completes the TCP handshake (at  208 ) as defined in the RFC. If this is a new session, or an existing session, the status of the session is verified by the session status check function  210 . TCP packet is parsed  212  and data that was gathered is used to populate the data structure  214 . An event is generated for the correct application broker at  216 . 
   The operation of the data system is discussed with reference to  FIG. 6 . The data system is an application-specific processing solution that is focused on solving the business issues on hand without the distractions of the low level protocol functions. Its operation is thus performed in a cost-effective, scalable manner with low latency, thereby providing the consumer of the business data logic the best possible experience. The data system, depending on its event registration data, will retrieve (at  300 ) any lower protocol data and ascertain, at  302 , that the data contained in the data structure is in fact the data that the service can process. Depending on the application needs, it is possible that it requires an existing session with possible authentication and security verification that was completed by the HTTP protocol handler  148 , and the state and associated data would be retrieved from the data structure. If necessary, as determined at  306 , a new session is established ( 308 ) using the new session data from the data structure as created by the HTTP protocol handler. The data system verifies ( 310 ) that all the session data collected is valid and can be used for processing. The business logic uses the data from the data structure  312  to complete its desired tasks and to deliver the business logic. The business logic response is populated into the data structure  314  and then an event is generated (at  316 ) so that the response data can be processed by the HTTP protocol handler. Information can be place in queue for correct data server to generate event at  304 . 
   Tables 1–13 below illustrate various data structures for reference. 
   
     
       
             
           
             
             
             
             
             
           
         
             
               TABLE 1 
             
           
           
             
                 
             
             
               Registration data structure 
             
           
        
         
             
                 
               Field name 
               Data Type 
               Data Size 
               Mandatory 
             
             
                 
                 
             
             
                 
               Timestamp 
               time_t 
                 
               Y 
             
             
                 
               Flow 
               small integer 
               Boolean 
               Y 
             
             
                 
               Low-Protocol 
               Small integer 
               Boolean 
               Y 
             
             
                 
               Application Protocol 
               Small integer 
               Boolean 
               Y 
             
             
                 
               Access 
               Small Integer 
               Boolean 
               Y 
             
             
                 
               Protocol Handler ID 
               Int 
               — 
               Y 
             
             
                 
               Application Handler 
               Int 
               — 
               Y 
             
             
                 
               Application Data 
               Int 
               — 
               Y 
             
             
                 
                 
             
           
        
       
     
   
   
     
       
             
           
             
             
             
             
             
           
         
             
               TABLE 2 
             
           
           
             
                 
             
             
               HTTP Common Data Structure 
             
           
        
         
             
                 
               Field Name 
               Data Type 
               Size 
               Mandatory 
             
             
                 
                 
             
             
                 
               Hash 
               String 
               64 
               Y 
             
             
                 
               Source IP 
               Integer 
               32 
               Y 
             
             
                 
               Destination IP 
               Integer 
               32 
               Y 
             
             
                 
               Cache-control 
               Structure 
               — 
               N 
             
             
                 
               Date 
               Date 
               — 
               N 
             
             
                 
               Pragma 
               String 
               128  
               N 
             
             
                 
               Trailer 
               String 
               128  
               N 
             
             
                 
               Transfer-encoding 
               String 
               48 
               N 
             
             
                 
               Upgrade 
               String 
               128  
               N 
             
             
                 
               Via 
               Structure[16] 
               — 
               N 
             
             
                 
               Warning 
               Structure 
               — 
               N 
             
             
                 
                 
             
           
        
       
     
   
   
     
       
             
           
             
             
             
             
             
           
         
             
               TABLE 3 
             
           
           
             
                 
             
             
               HTTP Request Data Structure 
             
           
        
         
             
                 
                 
               Data 
                 
                 
             
             
                 
               Field Name 
               Type 
               Size 
               Mandatory 
             
             
                 
                 
             
             
                 
               Hash 
               String 
                64 
               Y 
             
             
                 
               HTTP Method 
               Small 
                1 
               Y 
             
             
                 
                 
               Integer 
             
             
                 
               URL 
               String 
               256 
               Y 
             
             
                 
               Accept 
               String 
               128 
               N 
             
             
                 
               Accept-charset 
               String 
                48 
               N 
             
             
                 
               Accept-encoding 
               String 
               128 
               N 
             
             
                 
               Accept-Language- 
               String 
                8 
               N 
             
             
                 
               Primary 
             
             
                 
               Accept-Language- 
               String 
                8 
               N 
             
             
                 
               Secondary 
             
             
                 
               Authorization 
               String 
               256 
               N 
             
             
                 
               Expect 
               String 
               256 
               N 
             
             
                 
               From 
               String 
               128 
               N 
             
             
                 
               Host 
               String 
               128 
               N 
             
             
                 
               If-match 
               String 
               128 
               N 
             
             
                 
               If-Modified-since 
               Date 
               — 
               N 
             
             
                 
               If-none-match 
               String 
               128 
               N 
             
             
                 
               If-Range 
               String 
               128 
               N 
             
             
                 
               If-Unmodified-since 
               Date 
               — 
               N 
             
             
                 
               Max-forwards 
               Int 
                1 
               N 
             
             
                 
               Proxy-authorization 
               String 
               256 
               N 
             
             
                 
               Range 
               Structure 
               — 
               N 
             
             
                 
               Referrer 
               String 
               256 
               N 
             
             
                 
               TE 
               String 
               128 
               N 
             
             
                 
               User-agent 
               String 
               128 
               Y 
             
             
                 
               Data Length 
               Int 
               — 
               Y 
             
             
                 
               Data 
               String 
               Variable 
               N 
             
             
                 
                 
             
           
        
       
     
   
   
     
       
             
           
             
             
             
             
             
           
         
             
               TABLE 4 
             
           
           
             
                 
             
             
               HTTP Response Data Structure 
             
           
        
         
             
                 
                 
               Data 
                 
                 
             
             
                 
               Field Name 
               Type 
               Size 
               Mandatory 
             
             
                 
                 
             
             
                 
               Status Line 
               String 
               128 
               Y 
             
             
                 
               Accept-Ranges 
               Int 
               Boolean 
               N 
             
             
                 
                 
                 
               Flag 
             
             
                 
               Age 
               Long Int 
               — 
               N 
             
             
                 
               Etag 
               String 
               128 
               N 
             
             
                 
               Location 
               String 
               128 
               N 
             
             
                 
               Proxy-Authenticate 
               String 
               256 
               N 
             
             
                 
               Retry-After 
               String 
                48 
               N 
             
             
                 
               Server 
               String 
               128 
               N 
             
             
                 
               Vary 
               String 
               128 
               N 
             
             
                 
               WWW-Authenticate 
               String 
               128 
               N 
             
             
                 
               Allow 
               Int 
               Boolean 
               N 
             
             
                 
                 
                 
               Flag 
             
             
                 
               Content-encoding 
               String 
               128 
               N 
             
             
                 
               Content-Language 
               String 
                48 
               N 
             
             
                 
               Content-Length 
               Long Int 
               — 
               N 
             
             
                 
               Content-Location 
               String 
               256 
               N 
             
             
                 
               Content-MD5 
               String 
               128 
               N 
             
             
                 
               Content-Range 
               Structure 
               — 
               N 
             
             
                 
               Content-Type 
               String 
                48 
               N 
             
             
                 
               Expires 
               Date 
               — 
               N 
             
             
                 
               Last-Modified 
               Date 
               — 
               N 
             
             
                 
               Extension header 
               String 
               Variable 
               N 
             
             
                 
               Data Length 
               int 
               — 
               Y 
             
             
                 
               Data 
               String 
               Variable 
               N 
             
             
                 
                 
             
           
        
       
     
   
   
     
       
             
           
             
             
             
           
         
             
               TABLE 5 
             
             
                 
             
             
               Flow Values 
             
             
                 
             
           
           
             
                 
             
           
        
         
             
                 
               Request 
               1 
             
             
                 
               Response 
               2 
             
             
                 
               Bi-directional 
               3 
             
             
                 
                 
             
           
        
       
     
   
   
     
       
             
           
             
             
             
           
         
             
               TABLE 6 
             
             
                 
             
             
               Access Values 
             
             
                 
             
           
           
             
                 
             
           
        
         
             
                 
               Event 
               0 
             
             
                 
               Queue 
               1 
             
             
                 
                 
             
           
        
       
     
   
   
     
       
             
           
             
             
             
           
         
             
               TABLE 7 
             
             
                 
             
             
               Protocol Values B 
             
             
               Boolean 
             
             
                 
             
           
           
             
                 
             
           
        
         
             
                 
               IP 
               1 
             
             
                 
               TCP 
               2 
             
             
                 
               UDP 
               3 
             
             
                 
               Multi-cast UDP 
               4 
             
             
                 
               HTTP 
               5 
             
             
                 
                 
             
           
        
       
     
   
   
     
       
             
           
             
             
             
           
         
             
               TABLE 8 
             
             
                 
             
             
               HTTP Method Values 
             
             
               Boolean 
             
             
                 
             
           
           
             
                 
             
           
        
         
             
                 
               GET 
               1 
             
             
                 
               HEAD 
               2 
             
             
                 
               POST 
               3 
             
             
                 
               CONNECT 
               4 
             
             
                 
               PUT 
               5 
             
             
                 
               DELETE 
               6 
             
             
                 
               TRACE 
               7 
             
             
                 
               OPTIONS 
               8 
             
             
                 
                 
             
           
        
       
     
   
   
     
       
             
           
             
             
             
             
           
         
             
               TABLE 9 
             
           
           
             
                 
             
             
               Cache-Control Request 
             
           
        
         
             
                 
               Field Name 
               Type 
               Size 
             
             
                 
                 
             
             
                 
               No-cache 
               Boolean 
               — 
             
             
                 
               No-store 
               Boolean 
               — 
             
             
                 
               Max-age 
               Long Int 
               — 
             
             
                 
               Max-stale 
               Long Int 
               — 
             
             
                 
               Min-fresh 
               Long Int 
               — 
             
             
                 
               No-transform 
               Boolean 
               — 
             
             
                 
               Only-if-cached 
               Boolean 
               — 
             
             
                 
               Cache-extension 
               String 
               128 
             
             
                 
                 
             
           
        
       
     
   
   
     
       
             
           
             
             
             
             
           
         
             
               TABLE 10 
             
           
           
             
                 
             
             
               Cache-Control Response 
             
           
        
         
             
                 
               Field Name 
               Type 
               Size 
             
             
                 
                 
             
             
                 
               Public 
               Boolean 
               — 
             
             
                 
               Private 
               Boolean 
               — 
             
             
                 
               No-cache 
               Boolean 
               — 
             
             
                 
               No-store 
               Boolean 
               — 
             
             
                 
               No-transform 
               Boolean 
               — 
             
             
                 
               Must-validate 
               Boolean 
               — 
             
             
                 
               Proxy-revalidate 
               Boolean 
               — 
             
             
                 
               Max-age 
               Long Int 
               — 
             
             
                 
               s-maxage 
               Long Int 
               — 
             
             
                 
               Cache-extension 
               String 
               128 
             
             
                 
                 
             
           
        
       
     
   
   
     
       
             
           
             
             
             
             
           
         
             
               TABLE 11 
             
           
           
             
                 
             
             
               Content MD5 
             
           
        
         
             
                 
               Field Name 
               Type 
               Size 
             
             
                 
                 
             
             
                 
               Byte-content-unit 
               String 
               16 
             
             
                 
               Byte-content-range-resp 
               Long Int 
               — 
             
             
                 
               Byte-content-range-length 
               Long Int 
               — 
             
             
                 
               Byte-range-first-byte 
               Long Int 
               — 
             
             
                 
               Byte-range-last-byte 
               Long Int 
               — 
             
             
                 
               Instance-Length 
               Int 
               — 
             
             
                 
                 
             
           
        
       
     
   
   
     
       
             
           
             
             
             
             
           
         
             
               TABLE 12 
             
           
           
             
                 
             
             
               Via 
             
           
        
         
             
                 
               Field Name 
               Type 
               Size 
             
             
                 
                 
             
             
                 
               Received Protocol 
               String 
               8 
             
             
                 
               Received Protocol-Version-Maj 
               String 
               2 
             
             
                 
               Received Protocol-Version-Min 
               String 
               2 
             
             
                 
               Received By 
               String 
               48  
             
             
                 
               Pseudonym 
               String 
               256  
             
             
                 
                 
             
           
        
       
     
   
   
     
       
             
           
             
             
             
             
           
         
             
               TABLE 13 
             
           
           
             
                 
             
             
               Warning 
             
           
        
         
             
                 
               Field Name 
               Type 
               Size 
             
             
                 
                 
             
             
                 
               Warn-code 
               String 
                3 
             
             
                 
               W-agent 
               String 
               128 
             
             
                 
               Warn-text 
               String 
               128 
             
             
                 
               Warn-Date 
               Date 
               —