[Docs] [txt|pdf] [Tracker] [WG] [Email] [Nits]

Versions: 00

INTERNET-DRAFT                                         M Cieslak
<draft-ietf-wrec-web-pro-00.txt>                       D Forster
                                                       Cisco Systems
                                                       1 June 1999
                                                       Expires December 1999

                  Web Cache Coordination Protocol V1.0

Status of this Memo

   This document is an Internet-Draft and is in  full  conformance  with
   all provisions of Section 10 of RFC2026.

   Internet-Drafts are working documents  of  the  Internet  Engineering
   Task Force (IETF), its areas, and its working groups. Note that other
   groups may also distribute working documents as Internet-Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
   and  may be updated, replaced, or obsoleted by other documents at any
   time.  It  is  inappropriate  to  use  Internet-Drafts  as  reference
   material or to cite them other than as "work in progress".

   The  list   of   current   Internet-Drafts   can   be   accessed   at
   http://www.ietf.org/ietf/lid-abstracts.txt

   The list of Internet-Draft Shadow  Directories  can  be  accessed  at
   http://www.ietf.org/shadow.html

   Cisco has a patent pending that may  relate  to  WCCP  V1.0.  If  any
   patents  issue  to  Cisco  or  its  subsidiaries with claims that are
   necessary for practicing WCCP V1.0, then any party will  be  able  to
   obtain  a  license  from  Cisco  to  use any such patent claims under
   openly specified, reasonable, non-discriminatory terms  to  implement
   WCCP V1.0. No license is required for nonprofit institutions.

Abstract

   This draft documents the Web Cache Coordination Protocol (WCCP) V1.0.
   This  protocol  is  used (a) to associate a single router with one or
   more web-caches for the purposes of transparent redirection  of  HTTP
   traffic,  and  (b)  to allow one of the web-caches to dictate how the
   router  distributes  transparently-redirected  traffic   across   the
   associated web-caches.

   This draft describes the interactions between a  router  and  one  or
   more  web-caches.  It  does  not  describe the interactions between a
   group of associated web-caches or those between  a  web-cache  and  a
   web-server.



                                                               [Page 1]


Definitions

   Transparent Redirection.

      Transparent redirection is a technique used to deploy  web-caching
      without  the  need for reconfiguration of web-clients. It involves
      the interception and redirection of HTTP traffic to  one  or  more
      web-caches by a router or switch, transparently to the web-client.

   Web-Cache Farm.

      One or more web-caches associated with a router.

   Designated Web-Cache.

      The web-cache in a web-cache farm responsible for dictating to the
      router  how  redirected  traffic  should be distributed across the
      members of the farm.

   Redirection Hash Table.

      A 256-bucket hash table maintained by the router. This table  maps
      the  IP  destination address of a packet for redirection to the IP
      address of a web-cache in the farm

Description of Protocol

   WCCP has two main functions. The first is to allow a  router  enabled
   for  transparent  redirection  to  discover,  verify,  and  advertise
   connectivity to one or more web-caches.

   The second function is to allow one of the web-caches, the designated
   web-cache,  to  dictate how the router distributes redirected traffic
   across the web-cache farm.

   It is recommended that the web-cache with the lowest  IP  address  is
   elected as designated web-cache for a farm.

Discovery

   WCCP V1.0 allows a single router to be associated with  one  or  more
   web-caches.  A  group  of  web-caches  associated  with  a  router is
   referred to as a web-cache farm. A web-cache may be directly attached
   to the router or some hops distant.

Joining a web-cache farm

   A web-cache joins a  web-cache  farm  by  periodically  unicasting  a



                                                               [Page 2]


WCCP_HERE_I_AM  packet  to  the  router  associated  with the farm at
   intervals of HERE_I_AM_T (10) seconds. The source IP address  of  the
   WCCP_HERE_I_AM uniquely identifies the web-cache. The router unicasts
   a WCCP_I_SEE_YOU packet back to the web-cache  in  response  to  each
   WCCP_HERE_I_AM it receives.

Verifying connectivity

   The Received_ID  fields  in  the  WCCP_HERE_I_AM  and  WCCP_I_SEE_YOU
   packets  are  used  to verify two-way connectivity between the router
   and web-cache. The router increments the  value  of  the  Received_ID
   field  each time it sends a WCCP_I_SEE_YOU to a web-cache and expects
   to receive the same value back in the Received_ID field of  the  next
   WCCP_HERE_I_AM  from that cache. WCCP_HERE_I_AM packets containing an
   invalid Received_ID are ignored.

   The Received_ID in the initial WCCP_HERE_I_AM sent from  a  web-cache
   is ignored. The router will only consider a web-cache to be reachable
   when it has received  a  subsequent  WCCP_HERE_I_AM  with  a  correct
   Received_ID.  Note  that a useable web-cache is merely reachable; the
   router will not redirect traffic to  a  newly-acquired  useable  web-
   cache  until instructed to do so in a WCCP_ASSIGN_BUCKETS packet from
   the designated web-cache.

Advertising connectivity

   The router includes a list of  the  web-caches  it  considers  to  be
   usable  in each WCCP_I_SEE_YOU packet it transmits. Each entry in the
   list includes the IP address of the  web-cache  and  indicates  which
   buckets  in the Redirection Hash Table are currently assigned to that
   web-cache. This information  is  provided  for  the  benefit  of  the
   designated web-cache.

   A Change ID in the WCCP_I_SEE_YOU packet is incremented whenever  the
   web-cache  list  changes or the bucket allocation for an entry in the
   list is modified.

Timing-out a web-cache

   If the router does  not  receive  a  valid  WCCP_HERE_I_AM  for  3  *
   HERE_I_AM_T  seconds  it  will  no  longer consider a web-cache to be
   useable. In this case the web-cache is no longer  advertised  in  the
   WCCP_I_SEE_YOU  packet  and  all  buckets  previously assigned to the
   web-cache in the  router's  Redirection  Hash  Table  are  marked  as
   unassigned.

Assignment




                                                               [Page 3]


The router associated with a web-cache  farm  distributes  redirected
   traffic  by  destination IP address across the members of the farm as
   directed by the  designated  web-cache  via  the  WCCP_ASSIGN_BUCKETS
   packet.

   How the designated web-cache  arrives  at  the  traffic  distribution
   described  by  the WCCP_ASSIGN_BUCKETS packet is outside the scope of
   this draft.

   Since the  router  has  no  knowledge  of  the  designated  web-cache
   election process it will accept a WCCP_ASSIGN_BUCKETS packet from any
   member of the web-cache farm.

   The value of the Received_ID in the WCCP_ASSIGN_BUCKETS  packet  must
   match  that  in  the  last WCCP_I_SEE_YOU sent to the designated web-
   cache. If the Received_ID is not valid the  router  will  ignore  the
   WCCP_ASSIGN_BUCKETS packet.

   On receipt of a valid WCCP_ASSIGN_BUCKETS packet the router will  set
   its  Redirection Hash Table from information contained in the packet.
   This information comprises a list of web-caches followed  by  a  256-
   bucket  hash  table.  The  position of a web-cache in the list is its
   index number, the index number of the first entry  being  zero.  Each
   bucket  in  the  hash table may contain the value 0xFF, indicating no
   web-cache has been assigned to that bucket, or the index number of  a
   web-cache.

   The  router  does  not  generate  a  packet  in   response   to   the
   WCCP_ASSIGN_BUCKET.  However the change in the Redirection Hash Table
   will be reflected in subsequent WCCP_I_SEE_YOU packets  generated  by
   the router.

Packet Redirection

Detection

   The router detects HTTP packets (TCP packets with a destination  port
   number  of  80)  and  redirects  them to a web-cache in the web-cache
   farm.

   The destination IP address of a candidate packet is hashed  to  yield
   an  index  into  the  256-bucket  Redirection Hash Table. The indexed
   bucket indicates to which web-cache the packet should be  redirected.
   If  the bucket in the Redirection Hash Table is unassigned the packet
   cannot be redirected and should be forwarded normally.

Encapsulation




                                                               [Page 4]


Each redirected packet  is  encapsulated  in  a  GRE  packet[1].  The
   encapsulation  uses the base four-octet GRE header with the two Flags
   and version octets set to zero and a Protocol Type of 0x883E.

   An encapsulated packet may be fragmented if  it  exceeds  the  output
   interface's MTU.

Returned packets

   The router must ensure that HTTP  traffic  passing  through  it  from
   members  of  the  web-cache  farm  en-route  to  a  web-server is not
   redirected.

   The router will  not  redirect  any  packet  with  a  source  address
   belonging to a member of the web-cache farm.




































                                                               [Page 5]


Format of Protocol Packets

   This section defines the format of the WCCP packets.

   Each WCCP  protocol  packet  is  carried  in  a  UDP  packet  with  a
   destination port of 2048

Here I Am

   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              Type                             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                         Protocol Version                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Hash Revision                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        Hash Information (0)                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                            .                                  |
   |                            .                                  |
   |                            .                                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        Hash Information (7)                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |U|                         Reserved                            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Received ID                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Type

      WCCP_HERE_I_AM (7)

   Protocol Version

      4

   Hash Revision

      0

   Hash Information

      A  256-element  bit-vector.  A  set   bit   indicates   that   the
      corresponding        bucket  in  the  Redirection  Hash  Table  is
      assigned to this  web-cache.   Normally  the  value  of  the  Hash



                                                               [Page 6]


Information present in the last WCCP_I_SEE_YOU message received by
      this cache. In the initial WCCP_HERE_I_AM sent to  the  router  it
      may  be  zero  or  the  value  assigned to the cache in a previous
      membership of this web-cache farm. This information may be used by
      the designated web-cache to re-assign buckets to the cache.

   U

      Normally  the  value  of  the  U  flag   present   in   the   last
      WCCP_I_SEE_YOU  message  received  by  this  cache.  Set  in first
      WCCP_HERE_I_AM to indicate that Hash Information is historical.

   Received ID

      The value of the Received ID present in  the  last  WCCP_I_SEE_YOU
      received by this web-cache.



































                                                               [Page 7]


I See You

   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                            Type                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                         Protocol Version                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                         Change Number                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                         Received ID                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Number of WCs                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                    Web-Cache List Entry(0)                    |
   |                            .                                  |
   |                            .                                  |
   |                            .                                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                    Web-Cache List Entry(n)                    |
   |                            .                                  |
   |                            .                                  |
   |                            .                                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Type

      WCCP_I_SEE_YOU (8)

   Protocol Version

      4

   Change Number

      Incremented if a Web-Cache List Entry has been added,  removed  or
      its   hash   information   has   been   modified  since  the  last
      WCCP_I_SEE_YOU sent by the router.

   Received ID

      Incremented each time the router generates a WCCP_I_SEE_YOU.  Will
      never be zero.

   Number of WCs

      Number of Web-Cache List Entry elements in the packet.



                                                               [Page 8]


Web-Cache List Entry

   The Web-Cache List Entry describes a  Web-Cache  by  IP  Address  and
   lists the redirection hash table entries assigned to it.

   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                         IP Address                            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Hash Revision                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        Hash Information (0)                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                            .                                  |
   |                            .                                  |
   |                            .                                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        Hash Information (7)                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |U|                         Reserved                            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   IP Address

      Web-cache IP Address

   Hash Revision

      0

   Hash Information

      A  256-element  bit-vector.  A  set   bit   indicates   that   the
      corresponding        bucket  in  the  Redirection  Hash  Table  is
      assigned to this web-cache.

   U

      If set indicates web-cache is not assigned in the Redirection Hash
      Table  and that the web-cache hash information is historical. This
      information may be used by the designated  web-cache  to  reassign
      buckets to a web-cache which has rejoined the farm.








                                                               [Page 9]


Assign Bucket

   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                            Type                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                         Received ID                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Number of Web Caches                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Web-Cache 0 IP Address                    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             .                                 |
   |                             .                                 |
   |                             .                                 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Web-Cache n IP Address                    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Bucket 0    |   Bucket 1    |   Bucket 2    |   Bucket 3    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             .                                 |
   |                             .                                 |
   |                             .                                 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Bucket 252  |   Bucket 253  |   Bucket 254  |   Bucket 255  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Type

      WCCP_ASSIGN_BUCKET (9)

   Received ID

      Value of Received ID in last WCCP_I_SEE_YOU received from router.

   Number of Web Caches

      Number of Web Caches to which redirect traffic can be sent.

   Web-Cache IP Address, 0-n

      IP Addresses of Web-Caches to which redirect traffic can be  sent.
      The  position of a Web-Cache's IP Address in this list is the Web-
      Cache's index number. The first entry in the  list  has  an  index
      number of zero.

   Bucket 0-255



                                                              [Page 10]


These 256 buckets represent the redirection hash table. The  value
      of  each  bucket  may  be  0xFF  (Unassigned) or a Web-Cache index
      number (0-31).

References

   [1] Hanks, Li, Farinacci &  Traina,  "Generic  Routing  Encapsulation
   (GRE)", RFC 1701, October 1994

Authors' Addresses

   Martin Cieslak
   Cisco Systems
   170 Tasman Drive
   San Jose, CA 95143

   David Forster
   Cisco Systems
   170 Tasman Drive
   San Jose, CA 95143

   Phone: +44-181-7568967
   Email: dforster@cisco.com


   Expires December 1999

























                                                              [Page 11]


Html markup produced by rfcmarkup 1.124, available from https://tools.ietf.org/tools/rfcmarkup/