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-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]
-\f
-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]
-\f
- 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]
-\f
- 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]
-\f
- 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.
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- [Page 5]
-\f
-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]
-\f
- 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.
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- [Page 7]
-\f
-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]
-\f
-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.
-
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- [Page 9]
-\f
-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]
-\f
- 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
-
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- Expires December 1999
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projects / thirdparty / squid.git / commitdiff
