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Versions: 00 01 02 03 04 05 06 07 08 09 RFC 6108

Internet Engineering Task Force                                 C. Chung
Internet-Draft                                               A. Kasyanov
Intended status: Informational                              J. Livingood
Expires: October 2, 2010                                         N. Mody
                                                                 Comcast
                                                             B. Van Lieu
                                                            Unaffiliated
                                                          March 31, 2010


               Example of an ISP Web Notification System
                  draft-livingood-web-notification-06

Abstract

   The objective of this document is to describe one method of providing
   notifications to web browsers that has been deployed by Comcast, an
   Internet Service Provider (ISP).  Such a notification system can be
   used by an ISP to provide near-immediate notifications to their
   users, such as to warn them that their traffic exhibits patterns that
   are indicative of malware or virus infection, for example.  There are
   other proprietary systems that can perform such notifications but
   these systems utilize Deep Packet Inspection (DPI) technology.  This
   document describes one example of a system that does not rely upon
   DPI, and is instead based in open standards and open source
   applications.  While the system described herein is in some ways
   specific to the Data-Over-Cable Service Interface Specifications
   (DOCSIS) networks used by most cable-based broadband ISPs, components
   and concepts described in this document could generally be applied to
   many different types of networks.

Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with the
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   Internet-Drafts are working documents of the Internet Engineering
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   The list of Internet-Draft Shadow Directories can be accessed at
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   This Internet-Draft will expire on October 2, 2010.

Copyright Notice

   Copyright (c) 2010 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   it for publication as an RFC or to translate it into languages other
   than English.




















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Table of Contents

   1.  Requirements Language  . . . . . . . . . . . . . . . . . . . .  4
   2.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  High-Level Design of the System  . . . . . . . . . . . . . . .  4
   4.  Design Requirements  . . . . . . . . . . . . . . . . . . . . .  5
     4.1.  General  . . . . . . . . . . . . . . . . . . . . . . . . .  5
     4.2.  Web Proxy  . . . . . . . . . . . . . . . . . . . . . . . .  6
     4.3.  ICAP Server  . . . . . . . . . . . . . . . . . . . . . . .  6
     4.4.  Messaging Service  . . . . . . . . . . . . . . . . . . . .  7
   5.  Functional Overview  . . . . . . . . . . . . . . . . . . . . .  7
     5.1.  Functional Components Described  . . . . . . . . . . . . .  7
     5.2.  Functional Diagram . . . . . . . . . . . . . . . . . . . .  9
   6.  High Level Communication Flow  . . . . . . . . . . . . . . . .  9
   7.  Communication Between Web Proxy and ICAP Server  . . . . . . . 11
   8.  End-to-End Web Notification Flow . . . . . . . . . . . . . . . 11
     8.1.  Step-by-Step Description of the End-to-End Web
           Notification Flow  . . . . . . . . . . . . . . . . . . . . 12
     8.2.  Diagram of the End-to-End Web Notification Flow  . . . . . 13
   9.  Example HTTP Headers and JavaScript for a Web Notification . . 14
   10. Deployment Considerations  . . . . . . . . . . . . . . . . . . 16
   11. Security Considerations  . . . . . . . . . . . . . . . . . . . 17
   12. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 17
   13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 17
   14. References . . . . . . . . . . . . . . . . . . . . . . . . . . 17
     14.1. Normative References . . . . . . . . . . . . . . . . . . . 17
     14.2. Informative References . . . . . . . . . . . . . . . . . . 19
   Appendix A.  Document Change Log . . . . . . . . . . . . . . . . . 19
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 20






















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1.  Requirements Language

   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 [RFC2119].


2.  Introduction

   Internet Service Providers (ISPs) have a need for a system that is
   capable of communicating with customers in a nearly immediate manner,
   to convey critical service notices such as warnings concerning likely
   malware infection.  Given the prevalence of the web browser as the
   predominant client software in use by Internet users, the web browser
   is an ideal vehicle for providing notifications.  This document
   describes a system that has been deployed by Comcast, a broadband
   ISP, to provide near-immediate notifications to web browsers.  This
   type of system is also designed to provide a non-intrusive, though
   obvious, notification to a user's web browser.

   In evaluating potential solutions, most commercially available
   systems were either proprietary and/or utilized inline-based Deep
   Packet Inspection (DPI) technology.  Other ISPs may also desire to
   use a system based on open standards, non-proprietary software, and
   which does not require the use of DPI, which is one of the
   motivations for producing this document.  While the system described
   herein is specific to the Data-Over-Cable Service Interface
   Specifications (DOCSIS, [CableLabs DOCSIS]) networks used by most
   cable-based broadband ISPs, components and concepts described in this
   document can generally be applied to many different types of
   networks.


3.  High-Level Design of the System

   The web notification system design is based on the use of the
   Internet Content Adaptation Protocol [RFC3507].  The design uses open
   source applications such as Squid Web Proxy, GreasySpoon ICAP server,
   and Apache Tomcat.  The ICAP protocol allows for message
   transformation or adaptation.  An ICAP client passes a HyperText
   Transport Protocol (HTTP, [RFC2616]) response to an ICAP server for
   content adaption.  The ICAP Server in turn responds back to the
   client with the HTTP response containing the notification message.

   Message modification itself may then be provided via either a HTTP
   request or HTTP response.  However, for the specific system described
   in this document, only the HTTP response is modified, by using the
   'respmod' method defined in Section 3.2 of [RFC3507].



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4.  Design Requirements

   This section describes all of the requirements taken into
   consideration for the design of this system.

4.1.  General

   REQ1:   TCP Port 80: The system should provide notifications via TCP
           port 80, the well-known port for HTTP traffic.

   REQ2:   Block Listing: It is possible that the HyperText Markup
           Language (HTML, [RFC1866]) or JavaScript [RFC4329] used for
           notifications may cause problems while accessing a particular
           website.  Therefore, such a system should be capable of using
           a block list of website Uniform Resource Indicators (URIs,
           [RFC2396]) or Fully Qualified Domain Named (FQDNs, Section
           5.1 of [RFC1035]) that conflict with the system, to instruct
           the system to not provide a notifications related to certain
           sites, in order to reduce any errors or unexpected results.

   REQ3:   Instant Messaging (IM): Some IM clients use TCP port 80 in
           their communications, often as an alternate port when
           standard, well-known ports do not work.  This system should
           not conflict with or cause unexpected results for IM clients
           (or any other client types).

   REQ4:   Handling of Active Sessions: To the extent that a web
           notification system must temporarily route TCP port 80
           traffic in order to provide a notification, previously
           established TCP port 80 sessions should not be disrupted and
           should be routed to the proxy layer.

   REQ5:   No TCP Resets: The use of TCP resets has been widely
           criticized, both in the Internet community generally as well
           as in [RFC3360].  As such, except for the case of
           unintentional errors, the use of TCP resets must be avoided.

   REQ6:   Non-Disruptive: The web notification system should not
           disrupt the end user experience, such as causing significant
           clients errors.

   REQ7:   Notification Acknowledgement: Once a user responds and
           acknowledges a notification, the notification should
           immediately stop.







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   REQ8:   Non-Modification of Content: Such a system should not
           significantly alter the content of the HTTP response from any
           website the user is accessing.

   REQ9:   Unexpected Content: The system should transparently handle
           traffic for which it cannot provide a web notification.
           Thus, widely varying content should be expected, and all such
           unexpected traffic should be able to be handled by the system
           without generating errors or unexpected results.

   REQ10:  No Caching: Web content must not be cached by the system.

   REQ11:  No Advertising Replacement or Insertion: The system must not
           be used to replace any advertising provided by a website, or
           insert advertising into websites where none was intended by
           the owner of a given website.

4.2.  Web Proxy

   REQ12:  Open-Source Software: The system should use an open source
           web proxy server, such as Squid.  (While it is possible to
           use any web proxy, the use of open source, and openly
           documented software is recommended.)

   REQ13:  ICAP Client: The web proxy server should have an integrated
           ICAP client.

   REQ14:  Access Control: Access to the proxy should be limited
           exclusively to the IP addresses of users for which
           notifications are intended, and only for limited periods of
           time.  Furthermore, if a Session Management Broker (SMB) is
           utilized, as described in Section 5.1 below, then the proxy
           should restrict access only to the address of the SMB.

4.3.  ICAP Server

   REQ15:  Request and Response Support: The system should support both
           request and response adaptation.

   REQ16:  Consistency: The system must be able to consistently provide
           a specific notification.

   REQ17:  Multiple Notification Types: The system must be able to
           provide many different types of notifications.







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   REQ18:  Simultaneous Differing Notifications: The system must be able
           to simultaneously serve multiple notifications, including
           notifications of varying types, to different users.  As a
           result, User A should be able to get the notification
           intended specifically for User A, at the same time that User
           B receives an entirely different notification, which was
           intended specifically for User B.

4.4.  Messaging Service

   REQ19:  Messaging Service: The Messaging Service, as described in
           Section 5.1 below caches the notifications for each specific
           user.  Thus, by caching the notification messages, the system
           may provide notifications without significantly affecting the
           web browsing experience of the user.

   REQ20:  Process Acknowledgements: The Messaging Service should
           process acknowledgements to properly remove entries from the
           cache and forward acknowledgements to the Messaging Service.

   REQ21:  Ensure Notification Targeting Accuracy: The Messaging Service
           must ensure that notifications are presented to the intended
           users.

   REQ22:  Keep Records for Customer Support: The Messaging Service
           should maintain some type of record that a notification has
           been presented and/or acknowledged, in case a user inquires
           with customer support personnel.


5.  Functional Overview

   This section defines the various core functional components of the
   system.  These components are then shown in a diagram to describe how
   the various components are linked and relate to one another.

5.1.  Functional Components Described

   Please note that when a specific software package is cited below, it
   is but one example of a possible selection for each component and
   should not be considered the only possible option.  Though this
   accurately list describes the initial software packages used by the
   system described herein, those selections are subject to change for a
   variety of reasons.







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   5.1.A.  Web Proxy: The system uses Squid Proxy, an open source web
           proxy application in wide use, and one which supports an
           integrated ICAP client.

   5.1.B.  ICAP Server: This should be an open source application
           capable of supporting content adaptation in both request and
           response modes.  The ICAP Server retrieves the notifications
           from the Messaging service cache when content adaption is
           needed.  The initial version of this system uses GreasySpoon,
           an open source application.

   5.1.C.  Customer Database: The Customer Database holds the user
           information including the notifications setup for each user.
           The database may also hold status of which users were
           notified and users pending notification.

   5.1.D.  Messaging Service: This is a process engine that retrieves
           specific web notification messages from a catalog of possible
           notifications.  When a notification for a specific user is
           not in cache, the process retrieves this information from the
           Customer Database and populates the cache for a specific
           period of time.  The initial version of this service uses
           Apache Tomcat, an open source application.

   5.1.E.  Session Management Broker: A Load Balancer (LB) with a
           customized layer 7 inspection policy is used to differentiate
           between HTTP and non-HTTP traffic on TCP port 80.  The SMB
           functions as a full stateful TCP proxy with the ability to
           forward packets from existing TCP sessions that do not exist
           in the internal session table.  New HTTP sessions are load
           balanced to the web proxy layer either transparently or using
           source Network Address Translation (NAT [RFC1631]) from the
           SMB, with additional layer 7 inspection as needed.  Non-HTTP
           traffic for established TCP sessions not in the SMB session
           table is simply forwarded to the destination transparently
           via the TCP proxy layer.















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5.2.  Functional Diagram


   +--------+        +------------+        +----------+
   |  ICAP  | <----> | Messaging  | <----> | Customer |
   | Server |        |  Service   |        | Database |
   +--------+        +------------+        +----------+
     ^
     |                +----------+
     |                |          |
     |      +-------> | Internet | <-------+
     |      |         |          |         |
     |      |         +----------+         |
     |      |              ^               |
     v      v              |               |
   +----------+            v               v
   |+--------+|        +-------+       +--------+
   ||  ICAP  || <----> |  SMB  | <---> | Access |
   || Client ||        +-------+       | Router |
   |+--------+|                        +--------+
   || SQUID  ||                            ^
   || Proxy  ||                            |
   |+--------+|                            v
   +----------+                       +----------+
                                      | Network  |
                                      | Element* |
                                      +----------+
                                          ^
                                          |
                                          v
                                       +------+
                                       |  PC  |
                                       +------+

    * An access network element, such as a Cable Modem Termination
     System (CMTS).



         Figure 1: Web Notification System - Functional Components


6.  High Level Communication Flow








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   6.A.  Setup Differentiated Services (DiffServ): Using DiffServe
         [RFC2474] [RFC2475] [RFC2597] [RFC3140] [RFC3246] [RFC3260]
         [RFC4594], set a policy to direct TCP port 80 traffic to the
         web notification system's web proxy.

   6.B.  Session Management: TCP port 80 packets are routed to a Session
         Management Broker which distinguishes between HTTP or non-HTTP
         traffic and between new and existing sessions.  HTTP packets
         are forwarded to the web proxy by the SMB.  Non-HTTP packets
         such as instant messaging (IM) traffic are forwarded to a TCP
         proxy layer for routing to destination or the SMB operates as
         the full TCP proxy and forwards the non-HTTP packets to the
         destination.  Pre-established TCP sessions on port 80 are
         identified by the SMB and forwarded with no impact.

   6.C.  Web Proxy Forwards Request: The web proxy forwards the HTTP
         request on to the destination site, a web server, as a web
         proxy normally would do.

   6.D.  On Response, Send Message to ICAP Server: When the HTTP
         response is received from the destination server, the web proxy
         sends a message to the ICAP server for the web notification.

   6.E.  Messaging Service: The Messaging Service should respond with
         appropriate notification content or null response if
         notification is not cached.

   6.F.  ICAP Server Responds: The ICAP server responds and furnishes
         the appropriate content for the web notification to the web
         proxy.

   6.G.  Web Proxy Sends Response: The web proxy then forwards the HTTP
         response to the client web browser containing the web
         notification.

   6.H.  User Response: The user observes the web notification, and
         clicks an appropriate option, such as: OK/acknowledged, snooze/
         remind me later, etc.

   6.I.  More Information: Depending upon the notification, the user may
         be provided with more information.  Using the example of a web
         notification to a user explaining that it is highly likely that
         they have been infected with a virus or malware, the user may
         click an acknowledgement that indicates that clicking that will
         take them to a page with information about virus/malware
         scanning and remediation.





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   6.J.  Turn Down DiffServ: Once the notification transaction has
         completed, remove any special DiffServ settings.


7.  Communication Between Web Proxy and ICAP Server

   +------------+
   |  www URI   |
   +------------+
      ^      |
   (2)|      |(3)
      |      v
     +--------+     (4)     +--------+     (4)     +--------+
     |        |------------>|        |------------>|        |
     |        |     (5)     |        |     (5)     |        |
     | Proxy  |<------------|  ICAP  |<------------|  ICAP  |
     | Module |     (6)     | Client |     (6)     | Server |
     |        |------------>|        |------------>|        |
     |        |     (7)     |        |     (7)     |        |
     |        |<------------|        |<------------|        |
     +--------+             +--------+             +--------+
      ^      |
   (1)|      |(8)
      |      v
   +------------+              (9)             +------------+
   |            |----------------------------->|            |
   |  Browser   |              (10)            | Web Server |
   |            |<-----------------------------|            |
   +------------+                              +------------+

   (1) - HTTP GET (TCP 80)
   (2) - Proxy HTTP GET (TCP 80)
   (3) - HTTP 200 OK w/ Response
   (4) - ICAP RESPMOD
   (5) - ICAP 200 OK
   (6) - TCP Stream - Encapsulate Header
   (7) - ICAP 200 OK Insert Message
   (8) - HTTP 200 OK w/ Response + Message Frame
   (9) - HTTP GET for Message
   (10) - HTTP 200 w/ Message Content

         Figure 2: Communication Between Web Proxy and ICAP Server


8.  End-to-End Web Notification Flow






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8.1.  Step-by-Step Description of the End-to-End Web Notification Flow

   8.1.1.  Policy-Based Routing

   1.  TCP port 80 packets from the user that needs to be notified may
       be routed to the Web Proxy via policy based routing.

   2.  Packets are forwarded to the Session Management Broker, which
       establishes a session with the Web Proxy and routes the packets
       to the Web Proxy.

   8.1.2.  Web Proxy

   1.   The user's HTTP request is directed to the Web Proxy.

   2.   The Web Proxy receives HTTP traffic and retrieves content from
        the requested web site.

   3.   The Web Proxy receives the response and forwards it to the ICAP
        Server for response adaptation.

   4.   The ICAP Server checks the HTTP content in order to determine
        whether notification message can be inserted.

   5.   The ICAP Server initiates a request to the Messaging Service
        cache process with the IP address of the user.

   6.   If a notification message for the user exists then the
        appropriate notification is cached on the Messaging Service.
        The Messaging Service then returns the appropriate notification
        content to the ICAP Server.

   7.   Once the notification message is retrieved from Messaging
        Service cache the ICAP server may insert the notification
        message in the HTTP response body without altering or modifying
        the original content of the HTTP response.

   8.   The ICAP Server then sends the response back to the Web Proxy,
        which in turn forwards the HTTP response back to the browser.

   9.   If the user's IP address is not found or provisioned for a
        notification message, then the ICAP Server should return a '204
        No Modifications Needed' response to the ICAP Client as defined
        in section 4.3.3 of [RFC3507].  As a result, the user will not
        receive any web notification message.

   10.  The user observes the web notification, and clicks an
        appropriate option, such as: OK/acknowledged, snooze/ remind me



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        later, etc.

8.2.  Diagram of the End-to-End Web Notification Flow

   The two figures below show the communications flow from the Web
   Browser, through the Web Notification System.

   The first figure below illustrates what occurs when a notification
   request cannot be inserted because the notification type for the
   user's IP address is not cached in the Messaging Service.

                            ICAP     ICAP    Message          Customer
         Browser   Proxy   Client   Server   Service  Internet    DB
           |  HTTP  |         |         |        |        |        |
           |  GET   | Proxy   |         |        |        |        |
           +------->| Request |         |        |        |        |
           |        +---------|---------|--------|------->|        |
           |        |         |         |        | 200 OK |        |
           |        |<--------|---------|--------|--------+        |
           |        | ICAP    |         |        |        |        |
           |        | RESPMOD | ICAP    |        |        |        |
           |        +-------->| RESPMOD | Check  |        |        |
           |        |         +-------->| Cache  |        |        |
           |        |         |         | for IP |        |        |
           |        |         |         | Match  |        |        |
           |        |         |         +------->|        |        |
           |        |         |         | Cache  |        |        |
           |        |         |         | Miss   |        |        |
           |        |         |         |<-------+ Request|        |
           |        |         | 204 No  |        | Type   |        |
           |        |         | Modif.  |        +--------|------->|
           |        |         | Needed  |        |        |        |
           |        | No      |<--------+        |        | Type   |
           |        | Insert  |         |        |        |Returned|
           | 200 OK |<--------+         |        |<-------|--------+
           | w/o    |         |         |        |        |        |
           | Insert |         |         |        |        |        |
           |<-------+         |         |        |        |        |
           |        |         |         |        |        |        |

       Figure 3: End-to-End Web Notification Flow - With Cache Miss

   The figure below illustrates what occurs when a notification request
   for the user's IP address is cached in the Messaging Service.







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                            ICAP     ICAP    Message          Customer
         Browser   Proxy   Client   Server   Service  Internet    DB
           |  HTTP  |         |         |        |        |        |
           |  GET   | Proxy   |         |        |        |        |
           +------->| Request |         |        |        |        |
           |        +---------|---------|--------|------->|        |
           |        |         |         |        | 200 OK |        |
           |        |<--------|---------|--------|--------+        |
           |        | ICAP    |         |        |        |        |
           |        | RESPMOD | ICAP    |        |        |        |
           |        +-------->| RESPMOD | Check  |        |        |
           |        |         +-------->| Cache  |        |        |
           |        |         |         | for IP |        |        |
           |        |         |         | Match  |        |        |
           |        |         |         +------->|        |        |
           |        |         |         | Cache  |        |        |
           |        |         |         | Hit    |        |        |
           |        |         | Insert  |<-------+        |        |
           |        | Return  | Type    |        |        |        |
           |        | 200 OK  |<--------+        |        |        |
           |        | with    |         |        |        |        |
           |        | Insert  |         |        |        |        |
           | 200 OK |<--------+         |        |        |        |
           | w/     |         |         |        |        |        |
           | Notify |         |         |        |        |        |
           |<-------+         |         |        |        |        |
           |        |         |         |        |        |        |

        Figure 4: End-to-End Web Notification Flow - With Cache Hit


9.  Example HTTP Headers and JavaScript for a Web Notification

   The figure below shows an example of a normal HTTP GET request from
   the user's web browser to www.example.com, a web server on the
   Internet.















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------------------------------------------------------------------------
1.  HTTP Get Request to www.example.com
------------------------------------------------------------------------
http://www.example.com/

GET / HTTP/1.1
Host: www.example.com
User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.1.14)
        Gecko/20080404 Firefox/2.0.0.14
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: en-us,en;q=0.5
Accept-Encoding: gzip,deflate
Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7
Keep-Alive: 300
Connection: keep-alive
Pragma: no-cache
------------------------------------------------------------------------

     Figure 5: Example HTTP Headers for a Web Notification - HTTP Get

   In the figure below, the traffic is routed via the Web Proxy, which
   communicates with the ICAP Server and returns the response from
   www.example.com.  In this case that response is a 200 OK, with the
   desired notification message inserted.

------------------------------------------------------------------------
2.  Response from www.example.com via PROXY
------------------------------------------------------------------------
HTTP/1.x 200 OK
Date: Thu, 08 May 2008 16:26:29 GMT
Server: Apache/2.2.3 (CentOS)
Last-Modified: Tue, 15 Nov 2005 13:24:10 GMT
Etag: "b80f4-1b6-80bfd280"
Accept-Ranges: bytes
Content-Length: 438
Connection: close
Content-Type: text/html; charset=UTF-8
Age: 18
X-Cache: HIT from localhost.localdomain
Via: 1.0 localhost.localdomain (squid/3.0.STABLE5)
Proxy-Connection: keep-alive
------------------------------------------------------------------------

   Figure 6: Example HTTP Headers for a Web Notification - HTTP Response

   The figure below shows an example of the web notification content
   inserted in the 200 OK response, in this example JavaScript code.




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------------------------------------------------------------------------
3.  Example of JavaScript containing Notification Insertion
------------------------------------------------------------------------
<!--all elements used in a notification should have css properties
defined to avoid unwanted inheritance from parent page-->
<style type="text/css">
#example {
  position: absolute; left: 100px; top: 50px;
  z-index: 9999999; height: auto; width: 550px;
  padding: 10px;
  border: solid 2px black;
  background-color:#FDD017;
  opacity: 0.8; filter: alpha(opacity = 80);
}
</style>

<script language="javascript" type="text/javascript">
// ensure that content is not part of an iframe
if (self.location == top.location) {
  // this is a floating div with 80% transparency
  document.write('<div id="example" name="example">');
  document.write('<h2>IMPORTANT MESSAGE</h2>');
  document.write('<p>Lorem ipsum dolor sit amet, consecteteur ');
  document.write('adipisicing elit, sed do eiusmod tempor ');
  document.write('incididunt ut labore et dolore magna aliqua. ');
  document.write('Ut enim ad minim veniam, quis nostrud ');
  document.write('exercitation ullamco laboris nisi ut aliquip ex ');
  document.write('ea commodo consequat.');
  document.write('</div>');
}</script>
------------------------------------------------------------------------

          Figure 7: Example JavaScript Used in a Web Notification


10.  Deployment Considerations

   The components of the web notification system should be distributed
   throughout the network and close to end users.  This ensures that the
   routing performance and the user's web browsing experience remains
   acceptable.  It is also recommended that a HTTP-aware load balancer
   is used in each datacenter where servers are located, so that traffic
   can be spread across N+1 servers and the system can be easily scaled
   out.







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11.  Security Considerations

   This web notification system was conceived in order to provide an
   additional method of notifying ISP customers that their computer was
   infected with malware.  Depending upon the nature of the alert
   contained in the web notification, such as the malware alert, users
   could fear that it is some kind of phishing attack.  As a result,
   care should be taken with the text and any links contained in the web
   notification itself.  For example, the ISP may find it best to
   provide a general URI or a telephone number.  In contrast to that,
   the ISP should NOT ask for login credentials or for someone to follow
   a link in the web notification in order to change their password
   since these are common phishing techniques.  Finally, care should be
   taken to provide confidence that the web notification is valid and
   from a trusted party, and/or that the user has an alternate method of
   checking the validity of the web notification.


12.  IANA Considerations

   There are no IANA considerations in this document.

   NOTE TO RFC EDITOR: PLEASE REMOVE THIS NULL SECTION PRIOR TO
   PUBLICATION.


13.  Acknowledgements

   The authors wish to thank Alissa Cooper for her review of and
   comments on the document, as well as others who reviewed the
   document.


14.  References

14.1.  Normative References

   [RFC1035]  Mockapetris, P., "Domain names - implementation and
              specification", STD 13, RFC 1035, November 1987.

   [RFC1631]  Egevang, K. and P. Francis, "The IP Network Address
              Translator (NAT)", RFC 1631, May 1994.

   [RFC1866]  Berners-Lee, T. and D. Connolly, "Hypertext Markup
              Language - 2.0", RFC 1866, November 1995.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.



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   [RFC2396]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifiers (URI): Generic Syntax", RFC 2396,
              August 1998.

   [RFC2434]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 2434,
              October 1998.

   [RFC2474]  Nichols, K., Blake, S., Baker, F., and D. Black,
              "Definition of the Differentiated Services Field (DS
              Field) in the IPv4 and IPv6 Headers", RFC 2474,
              December 1998.

   [RFC2475]  Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z.,
              and W. Weiss, "An Architecture for Differentiated
              Services", RFC 2475, December 1998.

   [RFC2597]  Heinanen, J., Baker, F., Weiss, W., and J. Wroclawski,
              "Assured Forwarding PHB Group", RFC 2597, June 1999.

   [RFC2616]  Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
              Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
              Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.

   [RFC2782]  Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS RR for
              specifying the location of services (DNS SRV)", RFC 2782,
              February 2000.

   [RFC2915]  Mealling, M. and R. Daniel, "The Naming Authority Pointer
              (NAPTR) DNS Resource Record", RFC 2915, September 2000.

   [RFC3140]  Black, D., Brim, S., Carpenter, B., and F. Le Faucheur,
              "Per Hop Behavior Identification Codes", RFC 3140,
              June 2001.

   [RFC3246]  Davie, B., Charny, A., Bennet, J., Benson, K., Le Boudec,
              J., Courtney, W., Davari, S., Firoiu, V., and D.
              Stiliadis, "An Expedited Forwarding PHB (Per-Hop
              Behavior)", RFC 3246, March 2002.

   [RFC3260]  Grossman, D., "New Terminology and Clarifications for
              Diffserv", RFC 3260, April 2002.

   [RFC3261]  Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
              A., Peterson, J., Sparks, R., Handley, M., and E.
              Schooler, "SIP: Session Initiation Protocol", RFC 3261,
              June 2002.




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   [RFC3263]  Rosenberg, J. and H. Schulzrinne, "Session Initiation
              Protocol (SIP): Locating SIP Servers", RFC 3263,
              June 2002.

   [RFC3507]  Elson, J. and A. Cerpa, "Internet Content Adaptation
              Protocol (ICAP)", RFC 3507, April 2003.

   [RFC4329]  Hoehrmann, B., "Scripting Media Types", RFC 4329,
              April 2006.

   [RFC4594]  Babiarz, J., Chan, K., and F. Baker, "Configuration
              Guidelines for DiffServ Service Classes", RFC 4594,
              August 2006.

14.2.  Informative References

   [CableLabs DOCSIS]
              CableLabs, "Data-Over-Cable Service Interface
              Specifications", CableLabs Specifications Various DOCSIS
              Reference Documents, <http://www.cablelabs.com/
              specifications/archives/docsis.html>.

   [RFC3360]  Floyd, S., "Inappropriate TCP Resets Considered Harmful",
              BCP 60, RFC 3360, August 2002.


Appendix A.  Document Change Log

   [RFC Editor: This section is to be removed before publication]

   o  -06 - Corrected WL/BL error

   o  -05 - fixed odd spacing in 8.1

   o  -04 - corrections and tweaks by Jason

   o  -03 - corrections and clarifications from Nirmal and BVL

   o  -02 - updated BVL's contact info, clearing one open issue.  Also
      added content to Security Considerations.

   o  -01 - updated doc to reflect that this system is deployed and not
      in development, closing out two open issues.  Added reference for
      JavaScript, closing an open issue.

   o  -00 - first version published





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Authors' Addresses

   Chae Chung
   Comcast Cable Communications
   One Comcast Center
   1701 John F. Kennedy Boulevard
   Philadelphia, PA  19103
   US

   Email: chae_chung@cable.comcast.com
   URI:   http://www.comcast.com


   Alex Kasyanov
   Comcast Cable Communications
   One Comcast Center
   1701 John F. Kennedy Boulevard
   Philadelphia, PA  19103
   US

   Email: alexander_kasyanov@cable.comcast.com
   URI:   http://www.comcast.com


   Jason Livingood
   Comcast Cable Communications
   One Comcast Center
   1701 John F. Kennedy Boulevard
   Philadelphia, PA  19103
   US

   Email: jason_livingood@cable.comcast.com
   URI:   http://www.comcast.com


   Nirmal Mody
   Comcast Cable Communications
   One Comcast Center
   1701 John F. Kennedy Boulevard
   Philadelphia, PA  19103
   US

   Email: nirmal_mody@cable.comcast.com
   URI:   http://www.comcast.com







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   Brian Van Lieu
   Unaffiliated
   Bethlehem, PA  18018
   US

   Email: brian@vanlieu.net













































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