






                            Terrestrial Wideband Network


            _A_d_d_r_e_s_s:
            Terrestrial Wideband Network
            c/o BBN Systems and Technologies Corp.
            10 Moulton St.
            Cambridge, MA 02138
            Attn: Karen Seo

            _E-_m_a_i_l: wbhelp@bbn.com

            _P_h_o_n_e: (617) 873-3427 (Terrestrial Wideband Network hotline)


            _D_e_s_c_r_i_p_t_i_o_n

            The Terrestrial Wideband Network was built and  deployed  by
            BBN  STC  as  a  part  of  the  initial phase of the Defense
            Research Internet (DRI).  In May 1989, this network replaced
            the  Satellite Wideband Network, which had been in operation
            for the previous 8 years.   The  Satellite  Wideband  was  a
            domestic  3 Mbit/sec network that had been used for research
            into the use of packet satellite technology  to  efficiently
            support  applications  with  varying  delay, throughput, and
            reliability requirements, e.g., interconnection  of  distri-
            buted  operating  system clusters, development of end-to-end
            bulk transfer protocols, multimedia conferencing,  intercon-
            nection  real-time  interactive simulation/training systems.
            The Terrestrial Wideband continues this tradition  by  using
            one  of  the cross-country T1 trunks from the DARPA National
            Networking Testbed (NNT) to support research in  high  speed
            networking,  to  provide  connectivity  among  academic  and
            government sites, and to support a testbed for Internet pro-
            tocol  development  and  experimentation  with applications.
            Currently this network is  carrying  cross-country  Internet
            datagram  traffic associated with DARPA-funded projects.  It
            also supports a research  environment  for  multimedia  con-
            ferencing  and voice/video conferencing using gateways which
            use a real-time connection oriented protocol over a  connec-
            tionless network.

            _________________________
            The information in this section is provided  in  accor-
            dance  with the copyright notice appearing at the front
            of this guide.




            September 27, 1989          NNSC       Section 5.21,  Page 1








            _N_e_t_w_o_r_k _A_c_c_e_s_s

            Access to the Terrestrial Wideband is typically via an IP or
            ST  gateway.  Connection of such a host is at the discretion
            of DARPA.  The current network includes the following  Wide-
            band  Packet  Switches (WPS) and user sites -- BBN (BBN), NY
            (RADC), Washington (DARPA, NRL), Chicago (NCSA),  LA  (ISI),
            SRI  (SRI,  Stanford).   This fall, Ft Monmouth will be con-
            nected to the NY WPS and CMU will be connected to a  WPS  to
            be installed in Pittsburgh.

            _W_h_o _C_a_n _U_s_e _t_h_e _N_e_t_w_o_r_k

            The Terrestrial Wideband Network is to be  used  for  DARPA-
            funded  research  and development activities of the Internet
            community.  Users typically access the network via  gateways
            which have Internet connectivity to the Terrestrial Wideband
            Network.  Applications which might  benefit  most  from  the
            Terrestrial  Wideband  Network  are those which require high
            bandwidth and/or low delay  between  geographically  distant
            sites,  such  as bulk file transfer, remote procedure calls,
            conferencing, graphic simulations, and distributed operating
            systems.

            _M_i_s_c_e_l_l_a_n_e_o_u_s _I_n_f_o_r_m_a_t_i_o_n

            a) System and Network Architecture
                 The  Terrestrial  Wideband  is   currently   a   trans-
                 continental network built on T1 trunks belonging to the
                 National Networking Testbed (NNT).  The Wideband packet
                 switch  nodes  (WPSs)  are  located  at  unattended NNT
                 Points of Presence (POPs).  They are based on Butterfly
                 multiprocessor  hardware  and  are connected via the T1
                 fiberoptic trunks into a backbone  configuration.   The
                 WPSs  pass  network traffic using the Dual Bus Protocol
                 reservation scheme.  Local area networks at user sites,
                 e.g.,  ethernets,  are connected to the backbone packet
                 switches via Internet IP and ST gateways  and  T1  tail
                 circuits.

                 The current topology of  the  network,  which  resulted
                 from  external  constraints,  is  a  series  of  packet
                 switches connected in a line by T1  trunks.   This  can
                 result in partitioning of the network in the event of a
                 packet switch failure.  To minimize outages,  the  Ter-
                 restrial   Wideband   Network   includes  a  number  of
                 features.  The  multiprocessor  hardware  configuration
                 used  for the packet switch provides redundancy in case



            September 27, 1989          NNSC       Section 5.21,  Page 2








                 a processor node fails.  Also, a failsafe box  isolates
                 the WPS upon detection of an outage while continuing to
                 maintain connectivity between the T1 trunks in and  out
                 of the failed WPS, thus maintaining network continuity.
                 The network also allows remote  dial-in  access  for  a
                 number of emergency functions that would otherwise have
                 to be performed by on-site staff.

            b) Operations
                 A remote monitoring  center  provides  network  control
                 capabilities,  and  a dialup capability provides backup
                 monitoring and control when necessary.  The Terrestrial
                 Wideband  Network packet switch software can be updated
                 via remote downloading.  Network operations support  is
                 provided between 8AM and 8PM Eastern time.

            c) Protocols

                 - TCP/IP traffic is supported by the Terrestrial  Wide-
                 band  Network.   This is accomplished by using standard
                 Internet gateways.

                 - Stream Protocol (ST) protocol (based on IEN  119)  is
                 used   between   gateways   which  support  voice/video
                 traffic.  This is a connection-oriented protocol  which
                 operates  over  the connectionless Terrestrial Wideband
                 Network, and allows the gateways  to  send  packets  to
                 other  destinations  with minimal delay, as is required
                 for voice/video conferencing.

                 - Gateways communicate with  the  Terrestrial  Wideband
                 Network  packet  switches   (WPSs)  via the Host Access
                 Protocol (HAP), specified in RFC 907-A.  This is a pro-
                 tocol  by  which  a  host can send datagrams across the
                 network, and can request and manage network bandwidth.

                 -  The  WPS  software  provides  an  echo  host   which
                 responds  to  ICMP ping  packets.

                 - Dual Bus Protocol  provides  a  link-level  transport
                 protocol  which uses a reservation mechanism to provide
                 access fairness for each WPS.  This is a type  of  Dis-
                 tributed  Queue Dual Bus (DQDB) protocol similar to the
                 IEEE 802.6 Metropolitan Area  Network  (MAN)  protocol,
                 but with features that support wide area networking and
                 multimedia conferencing.  Whereas  conventional  packet
                 store  and forwarding would involve per packet forward-
                 ing processing  and  buffering  at  every  intermediate



            September 27, 1989          NNSC       Section 5.21,  Page 3








                 node, a DQDB protocol performs processing and buffering
                 only at the entry point and  minimizes  the  processing
                 and buffering at subsequent nodes along the trunk until
                 the exit point.

                 - Wideband Monitoring Protocol (IP protocol number  78)
                 is used between the WPSs and the monitoring center.












































            September 27, 1989          NNSC       Section 5.21,  Page 4


