6/2/2016
`
`draft-bressler-sigtran-ipss7l2-00 - SS7 Level Two over IP
`
`Internet Engineering Task Force William Bressler
`Internet Draft NORTEL Networks
`
`Expires in Six Months January 1999
`
` SS7 Level Two over IP
` <draft-bressler-sigtran-ipss7l2-00.txt>
`
`Status of this Memo
`
`This document is an Internet Draft. 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.
`Internet Drafts may be updated, replaced, or obsoleted by other
`documents at any time. It is not appropriate to use Internet Drafts as
`reference material or to cite them other than as a "working draft" or
`"work in progress".
`
`To learn the current status of any Internet-Draft, please check the
`1id-abstracts.txt listing contained in the Internet-Drafts Shadow
`Directories on ds.internic.net, nic.nordu.net, ftp.isi.edu, or
`munnari.oz.au.
`
`1 Abstract
`
`This document proposes the use of TCP/IP as the transport protocol for
`common channel signaling, Signaling System #7 (SS7).
`
`The migration from the current 56k/64k physical layer to an IP based
`transport will reduce the cost associated with dedicated trunk based
`link. Also, the current signaling point (SP) network using quasi-
`associated architecture will be maintained to make the transition as
`seamless as possible.
`
`2 Scope
`
`This draft defines the encapsulation of SS7 signal units (SU) in a TCP
`packet. The concept of a physical link will be maintained, which will
`emulate the current SS7 links and link control mechanisms.
`
`2.1 Quasi-associated Network Architecture
`
`The scope of network architecture in this recommendation is limited to
`the use of quasi-associated SP's. It is assumed that the current SS7
`network will be intact with IPlink phased in as the technology proves
`https://tools.ietf.org/html/draft-bressler-sigtran-ipss7l2-00
`
`1/12
`
`Ex. 1004
`YMax Corporation
`Page 1 of 12
`
`

`
`draft-bressler-sigtran-ipss7l2-00 - SS7 Level Two over IP
`6/2/2016
`itself as a cost effective, reliable alternative. Using the current
`quasi-associated SS7 networks also decreases the number of hops between
`SP's and the number of endpoints to a minimum. Each SP would have two
`IP addresss (two IPlinks) in addition to its current point code(s).
`
`Bressler 1
`
`https://tools.ietf.org/html/draft-bressler-sigtran-ipss7l2-00
`
`2/12
`
`Ex. 1004
`YMax Corporation
`Page 2 of 12
`
`

`
`draft-bressler-sigtran-ipss7l2-00 - SS7 Level Two over IP
`6/2/2016
`2.2 IP Signaling Link (IPlink)
`
`The scope of IP signaling link, IPlink, in this Recommendation includes
`the following:
`
`- A link will be identified by an IP address
`- The link alignment procedure.
`- The emergency link alignment procedure.
`- The link Basic Error Rate (BER) monitor.
`- The link Alignment Error Rate (AER) monitor.
`- Either software or hardware shall calculate SU CRC-16 checksums.
`- Preventative Cyclic Retransmission (PCR) shall be the default
` forward error correction.
`- Signaling message handling.
`- MSU load sharing.
`
`3 Quasi-associated Network
`
`A quasi-associated network between a signaling service point (SSP) and
`a signaling transfer point (STP) is shown below. Currently, SS7
`messaging traverse from SSP through the STP to another SSP using T1
`trunking, which is very reliable, and is configured for redundancy
`(not shown). If the IP network is to be a viable alternative to T1
`trunking, it must be able to demonstrate at least equal reliability and
`alternate routing capabilty.
`
` SS7 Messaging
`
` T1 trunk
` ------------------------------------------------------
` | | |
` V V V
` ------- -------------- ------- -------------- -------
` | SSP |<->| IP Network |<->| STP |<->| IP Network |<->| SSP |
` ------- -------------- ------- -------------- -------
`
`3.1 Network Nodes
`
`Current network topology should be unchanged. SSP, STP, signaling
`control point (SCP), authentication centers (AC), customer service
`centers (CSC), home location register (HLR), visiting location register
`(VLR), etc., will all be accessible.
`
`3.2 Signaling Link
`
`Each link will have it's own IP address and processor. This will
`maintain the current link concepts intact for reliability,
`redundency, alignment, changeover/changeback, load sharing, etc.
`
`IPlinks should have the same behaviour as the current SS7 links to
`gain acceptance into the existing network architecture. SS7 <-> IP-SS7
`interworking should be as transparent as possible.
`
`https://tools.ietf.org/html/draft-bressler-sigtran-ipss7l2-00
`
`3/12
`
`Ex. 1004
`YMax Corporation
`Page 3 of 12
`
`

`
`draft-bressler-sigtran-ipss7l2-00 - SS7 Level Two over IP
`6/2/2016
`Bressler 2
`
`https://tools.ietf.org/html/draft-bressler-sigtran-ipss7l2-00
`
`4/12
`
`Ex. 1004
`YMax Corporation
`Page 4 of 12
`
`

`
`6/2/2016
`4 TCP encapsulation
`
`draft-bressler-sigtran-ipss7l2-00 - SS7 Level Two over IP
`
`The current SS7 protocol is to be used as is. It provides a high
`reliability transport for telephony information. TCP packets will be
`used to carry the current SS7 messaging. This greatly reduces the risk
`of IP-SS7 by eliminating the need for new protocols. Telephony vendors
`already offer IP connectivity on their STP products. The largest MSU
`allowed, 272 octets, easily fits in a TCP packet.
`
`-------------------------------
`| TCP Header | SS7 SU |
`-------------------------------
`
`5 SS7 CRC-16 Checksum
`
`The reliability of the SS7 network is due in large part to the use of a
`CRC-16 checksum, calculated by hardware. This same reliability must be
`used in IPlink. Currently, existing hardware will most likely not
`support the encapsulation of the SS7 packet after the checksum has been
`calculated. The CRC-16, while cumbersome, will have to be performed in
`software. This can be speeded up greatly by the use of table driven
`calculations.
`
`6 L2 Timers
`
`Since the CRC-16 is computed in software, the L2 timers for IPlink have
`been extended.
`
`T1 (aligned/ready) 20 Sec
`T2 (not aligned) 30 Sec
`T3 (aligned) 20 Sec
`T4 (Pn) 5 Sec
`T4 (Pe) 2 Sec
`T5 (SIB) 500 ms
`T6 (remote congestion) 6 Sec
`T7 (ACK delay) 2 Sec
`
`7 FISU Transmitting
`
`Currently, SS7 links will send fill-in SUs (FISU) continuously,
`separated only by an HDLC flag (value 7E hex). To reduce processing
`overhead in IPlink, FISU's will be transmitted under the following
`conditions:
`
`- A FISU will be transmitted every 20 ms (Tfs) while the links are
` aligned.
`- A FISU may be sent at any time to ACK/NACK MSU's.
`
`The FISU transmit timer is reset to Tfs after the transmission of any
`SU (FISU, LSSU, MSU).
`
`https://tools.ietf.org/html/draft-bressler-sigtran-ipss7l2-00
`
`5/12
`
`Ex. 1004
`YMax Corporation
`Page 5 of 12
`
`

`
`draft-bressler-sigtran-ipss7l2-00 - SS7 Level Two over IP
`6/2/2016
`Bressler 3
`
`https://tools.ietf.org/html/draft-bressler-sigtran-ipss7l2-00
`
`6/12
`
`Ex. 1004
`YMax Corporation
`Page 6 of 12
`
`

`
`6/2/2016
`8 IPlink Error Detection
`
`draft-bressler-sigtran-ipss7l2-00 - SS7 Level Two over IP
`
`Since L2 no longer has any knowledge of the physical media over which
`it is carried, detectable errors such as framing bit errors, abort
`sequences etc., no longer apply. Error detection will be based on
`either the expiry of a timer or the detection of CRC-16 checksum
`errors.
`
`8.1 IPlink Receive Timeout
`
`A timer to detect IPlink receive failure will be set to 200ms (Tipr).
`This timer will be reset after the receipt of any type SU. IPlink timer
`expiry will force the IPlink to the out of service state.
`
`8.2 IPlink Transmit Timeout
`
`A timer to detect IPlink transmit failure will be set to 1 Sec (Tipt).
`This timer will be reset after the the successful transmission of any
`type SU. IPlink timer expiry will force the IPlink to the out of
`service state.
`
`8.3 IPlink Excessive Delay
`
`Ping (or other similar tool) will be used to measure IPlink delay. The
`rate at which the delay is to be measured will be set to 5 Secs (Tipd).
`This timer will be reset after the receipt of the ping response. The
`IP address of the ping will be the other end of the IPlink. Excessive
`link delay will trigger either congestion or PCR.
`
`9 IPlink Loading
`
`Current link engineering guidelines are set to have a maximum load of
`0.4 erlang per link. This allows a link to take the load of a failed
`link (0.8 erlang total) and still have abundant overhead for
`processing. The processor(s) used for IPlink applications should follow
`similar guidelines.
`
`9.1 IPlink CPU Utilization
`
`CPU percent utilization could be monitored for 60% idle time as the
`minimum recommended for reliable operation if the changeover procedure
`is invoked.
`
`10 IPlink PCR
`
`At this time, network delays are expected to be between the current T1
`and satellite delays. These delays are also expected to vary widely
`from minimum to maximum (allowed) with time. PCR dictates re-
`transmitting MSU's when:
`
`https://tools.ietf.org/html/draft-bressler-sigtran-ipss7l2-00
`
`7/12
`
`Ex. 1004
`YMax Corporation
`Page 7 of 12
`
`

`
`draft-bressler-sigtran-ipss7l2-00 - SS7 Level Two over IP
`6/2/2016
`Bressler 4
`
`https://tools.ietf.org/html/draft-bressler-sigtran-ipss7l2-00
`
`8/12
`
`Ex. 1004
`YMax Corporation
`Page 8 of 12
`
`

`
`draft-bressler-sigtran-ipss7l2-00 - SS7 Level Two over IP
`6/2/2016
`- There is no new MSU to be transmitted.
`- There is no LSSU to be transmitted.
`
`Since IPlink delays are being monitored, PCR is enabled/disabled by the
`threshold times Tpcrst (PCR start) and Tpcrsp (PCR stop), with initial
`values of 400ms and 200ms respectively.
`
`11 IPlink Signal Unit Error Rate Monitor
`
`This procedure is unchanged from the current procedure.
`
`12 IPlink Alignment Error Rate Monitor
`
`This procedure is unchanged from the current procedure.
`
`13 IPlink L2 Flow Control
`
`This procedure is unchanged from the current procedure.
`
`14 IPlink Processor Outage
`
`This procedure is unchanged from the current procedure.
`
`15 IPlink ACK/NACK
`
`This procedure is unchanged from the current procedure
`
`16 IPlink Busy
`
`This procedure is unchanged from the current procedure
`
`17 IPlink BER
`
`This procedure will not be used as the physical media is unknown.
`
`18 IPlink Retransmission
`
`This procedure is unchanged from the current procedure
`
`19 IPlink Message Sequencing
`
`This procedure is unchanged from the current procedure
`
`20 IPlink Identification
`
`The the IPlink is identified by an IP address. Most SSPs are small and
`require only two IPlinks, other SPs will require more.
`
`https://tools.ietf.org/html/draft-bressler-sigtran-ipss7l2-00
`
`9/12
`
`Ex. 1004
`YMax Corporation
`Page 9 of 12
`
`

`
`draft-bressler-sigtran-ipss7l2-00 - SS7 Level Two over IP
`6/2/2016
`Bressler 5
`
`https://tools.ietf.org/html/draft-bressler-sigtran-ipss7l2-00
`
`10/12
`
`Ex. 1004
`YMax Corporation
`Page 10 of 12
`
`

`
`6/2/2016
`Authors' Addresses
`
`draft-bressler-sigtran-ipss7l2-00 - SS7 Level Two over IP
`
` William Bressler
` Nortel Networks
` 2201 Lakeside Blvd.
` Richardson, TX 75082
` bressler@nortelnetworks.com
`
`Full Copyright Statement
`
` Copyright (C) The Internet Society (1998). All Rights Reserved.
`
` This document and translations of it may be copied and furnished to
` others, and derivative works that comment on or otherwise explain it
` or assist in its implementation may be prepared, copied, published
` and distributed, in whole or in part, without restriction of any
` kind, provided that the above copyright notice and this paragraph
` are included on all such copies and derivative works. However, this
` document itself may not be modified in any way, such as by removing
` the copyright notice or references to the Internet Society or other
` Internet organizations, except as needed for the purpose of
` developing Internet standards in which case the procedures for
` copyrights defined in the Internet Standards process must be
` followed, or as required to translate it into languages other than
` English.
`
` The limited permissions granted above are perpetual and will not be
` revoked by the Internet Society or its successors or assigns.
`
` This document and the information contained herein is provided on an
` "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
` TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
` BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
` HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
` MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
`
`Expires in Six Months January 1999
`https://tools.ietf.org/html/draft-bressler-sigtran-ipss7l2-00
`
`11/12
`
`Ex. 1004
`YMax Corporation
`Page 11 of 12
`
`

`
`draft-bressler-sigtran-ipss7l2-00 - SS7 Level Two over IP
`6/2/2016
`Bressler 6
`
`https://tools.ietf.org/html/draft-bressler-sigtran-ipss7l2-00
`
`12/12
`
`Ex. 1004
`YMax Corporation
`Page 12 of 12