RFC 2225 AND 2226

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RFC 2225 AND 2226

• Jehanzeb Khan
• Sagar Tamhane
• CSE 5346

2
RFC 2225 2226

• RFC 2225 states specifications to implement
  transmission of IP datagrams and ATMARP/InATMARP
  requests/responses over ATM networks.
• RFC 2225 is intended to provide alternative to
  legacy LANs and backbone networks.
• RFC 2226 is intended to introduce mechanism of IP
  Broadcasting in ATM networks .

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Running IP over ATM Two approaches

• LANE Provides interoperability between Legacy LAN
  and ATM hosts.
• Used for extension of legacy LANS.
• Special purpose bridges/switches translated MAC
  addresses into ATM addresses and vice versa.

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Classical IP over ATM RFC 2225

• IP treats ATM as a separate technology.
• IP gets access to all ATM functions such as QoS.
• IP hosts are connected to ATM network in form of
  LIS.

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Minimum Requirements for LIS configuration

• All hosts must have same IP prefix and subnet
  mask, Example 192.10.8.X, with address mask of
  255.255.255.192 will give two subnets,
  192.10.8.64 and 192.10.8.128.
• All members in an LIS must be directly connected
  to ATM network.
• All members must register to ATMARP server SVC
  .
• All members must register to InATMARP server
  PVC.
• In an LIS there must be fully-meshed virtual
  connection topology.
• Inter LIS communication must happen through
  routers .

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Minimum ATM specific Requirements

• ATM hardware Address atmha, either E.164 or
  NSAP ATM addressing scheme , NSAP is used for
  private networks and it is 20 bytes long.
• ATMARP Request Address List atmarp-req-list, a
  list containing hardware addresses of one or more
  ATMARP servers.
• A LIS must have at least one ATMARP server
  configured, and all clients must have its entry
  in their ATMARP request address List.

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MAXIMUM TRANSMISSION UNIT OPTIONS

• The default IP MTU for use with ATM AAL 5 is 9180
  octets.
• PVCs do not implement any ATM signalling
  protocols, therefore they must use this default
  value unless both parties have agreed in advance
  to use other MTU value when connection is
  established.
• SWC first must attempt to negotiate this value
  during connection establishment.
• Two AAL5 controlling parameters are used
• Forward maximum CS-SDU
• Backward maximum CS-SDU

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AAL5 CS-SDU NEGOTIATION PROCESS

• Calling party sends MTU value in FM CS-SDU Field
  during VC set up process.
• If the called party is able to accept this value,
  it will in response send BM CS SDU value that
  matches FM CS-SDU value.
• If the called party wants smaller value then it
  will set the desired value in both of the
  parameters in its response.
• All routers if any must implement Path MTU
  Discovery.

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IP PACKET ENCAPSULATION

• VC MULTIPLEXING
• Binds one protocol with each Virtual circuit.
• This approach reduces payload.
• Increases number of open VC connections.

• LLC/SNAP
• Number of protocols can be multiplexed on same
  VC.
• IP packets will be encapsulated into IEEE 802.2
  SNAP header.

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ADDRESS RESOLUTION PVC

• InATMARP is used for address resolution.
• Requesting station formats a request containing
  following fields.
• For every InATMARP request 0.0.0.0, source
  reply its IP address and both sides update their
  table.

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ADRESS RESOLUTION SWC

• A host sends ATMARP to ATMARP server.
• ATMARP server maintains a table with following
  fields.
• ATMARP server either sends positive reply or NAK.

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ATMARP CLIENT REQUIREMENTS

• Each client should establish a VC to ATMARP
  server for the purpose of transmitting and
  receiving ATMARP packets.
• Once connection is established, a client will
  send ATM ARP packet to the server with its own IP
  address as the source and target address to
  resolve the ATM address .
• Each client must refresh its ATMARP information
  at least once every 15 minutes.

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ATMARP/INATMARP PACKET FORMAT

• 16 bits hardware type.
• 16 bits protocols type IP is 0x0800.
• Type and length of source ATM number and
  subaddress.
• Operation
• 1 ATM_REQUEST
• 2 ATM_REPLY
• 8 InARP_REQUEST
• 9 InARP_REPLY
• 10 NAK

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ATMARP EXAMPLE

• ATMARP EXAMPLE

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IP Broadcast over ATM RFC 2226

• Aim To emulate IP broadcast within Logical IP
  Subnets (LIS).
• Challenges
• Diskless clients
• Multicast servers (MCS)

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Using ARP

• Host issues ARP request for every member in LIS.
  Then setup point-to-point connections with all
  members.
• Disadvantages
• Load on ARP server is very large.
• Diskless clients will not work.

17
Multicast Address Resolution Server (MARS)

• Centralized registry and distribution mechanism
  for mappings between IP multicast addresses and
  groups of ATM unicast addresses.
• Contains an architecture for dealing with
  scalability issues - Supports VC mesh and MCS.
• 1 MARS per LIS.

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VC Mesh

• Each source establishes its own independent point
  to multipoint VC.

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Multicast servers (MCS)

• Source establishes VC to an intermediate node
  (MCS).
• MCS establishes a point to multipoint VC to
  desired destinations.

20
Using MARS for broadcasts

• Host joins the MARS by sending MARS_JOIN message
  to 255.255.255.255.
• To broadcast, host issues MARS_REQUEST.
• MARS returns ATM addresses of all destinations in
  a single MARS_MULTI message or a MARS_NAK.
• Host creates VC mesh or uses MCS to perform the
  broadcast.
• To leave the broadcast group, host issues
  MARS_LEAVE.
• Group membership changes are broadcasted to all
  members.

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Creating point to multipoint VC

• L_MULTI_RQ Establish multicast VC to a specific
  endpoint.
• L_MULTI_ADD Add new leaf node to the previously
  established VC.
• L_MULTI_DROP Remove specific leaf node from VC.
• L_RELEASE Release all leaves of multicast VC.
• Quality of service unavailable, temporary failure
  while creating new multicast VC reissue
  L_MULTI_RQ or L_MULTI_ADD after random delay of 5
  to 10 seconds.

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References

• Christoph L. Schuba, Berry Kercheval, and Eugene
  H. Spafford. Classical IP and ARP over ATM.
  Technical Report 95-024, Purdue University, March
  1995.
• G. Armitage. RFC 2022 Support for Multicast over
  UNI 3.0/3.1 based ATM Networks. November 1996.
  http//rfc.net/rfc2022.html
• Performance of TCP/IP Over ATM Networks, by
  Hassan, Mahbub. Atiquzzaman, Mohammed
• IP over ATM http//www.cisco.com/en/US/tech/tk39/t
  k371/tsd_technology_support_protocol_home.html

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CONCLUSION

• These two RFCs provides scalable solution for
  implementing IP over ATM.
• The major drawback requirement of router for
  inter-LIS communications can be removed
  through.
• VLANS
• NHRP Next hop resolution protocol, RFC 2332

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QA SESSION