Specifications

56 IBM Voice Over Frame Relay Perform Guide
4.0.1 IP
Understanding the difference between UDP and TCP is very important in
understanding VoFR and VoIP concepts and design issues.
.
Figure 23. TCP and UDP
4.0.1.1 UDP
UDP is a connectionless protocol. UDP is basically an application interface to IP.
It adds no reliability, flow-control or error recovery to IP. It simply serves as a
multiplexer/demultiplexer for sending and receiving datagram, using ports to
direct the datagrams applications using UDP. UDP includes:
• Trivial File Transfer Protocol (TFTP)
• Domain Name System (DNS) name server
• Remote Procedure Call (RPC), used by the Network File System (NFS)
• Simple Network Management Protocol (SNMP)
• Lightweight Directory Access Protocol (LDAP)
• RTP (Real-time transport protocol) (one of VoIP application)
UDP traffic is difficult to compare with TCP because UDP does not have
flow-control.
4.0.1.2 TCP
TCP provides considerably more facilities for applications than UDP, notably error
recovery, flow control and reliability. The primary purpose of TCP is to provide
reliable logical circuit or connection service between pairs of processes. TCP is a
connection-oriented protocol. It does not assume reliability from the lower-level
protocols (such as IP), so TCP must guarantee this itself. TCP can be
characterized by the following facilities it provides for the applications using it.
Frame Relay CIR Monitoring
Congestion
Monitoring
DE bits
FRF.11
FRF.12
CIR Monitoring
Congestion
Monitoring
DE bits
FRF.11
FRF.12
CIR Monitoring
Congestion
Monitoring
DE bits
FRF.11
FRF.12
Voice SNA IP
TCP UDP
M ultim edia
M ission-critical
Ap plication
ACK
ACK
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App lication