telecom • networking • design

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DHCP: Dynamic Host Configuration Protocol

Dynamic Host Configuration Protocol (DHCP) is used to dynamically provide IP addresses and configuration information to client nodes. DHCP provides greater flexibility by leasing out IP addresses to host nodes. DHCP supports mechanisms that can be used by hosts to renew their lease.
This sequence diagram describes the DHCP interactions between a Laptop and the DHCP servers in the intranet. Four different cases are covered.
  1.    Laptop boots up for the first time and requests an IP address.
  2.    Laptop’s IP address lease is renewed.
  3.    Laptop reboots and confirms the IP address settings
  4.    Laptop is disconnected from Subnet 1 and reconnected in Subnet 3.

DHCP sequence diagram

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BGP peering and route updates

BGP peering and route update messaging is explored in detail in this flow.

This message flow shows how two BGP routers:

  1. Peer by establishing a TCP connection and exchanging BGP OPEN messages.
  2. Exchange Keep Alive messages to ensure that the routers are reachable.
  3. Exchange routes using BGP UPDATE messages.
  4. Release the BGP connection on operator command.
All messages in this sequence diagram may be clicked to see complete field level details of every BGP message.

BGP peering and route update


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Generate sequence diagrams from PCAP files that carry tunneled GTP traffic

VisualEther 6.1.103 now supports generating sequence diagrams from tunneled messages in PCAP files. You can create filters that will ignore the outer GTP message and extract the fields from the inner message.
Capture inner and outer messages is GTP


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SIP call setup with authentication

This call flow shows the SIP call setup between a SIP client (192.168.0.10) and a SIP server (216.234.64.8). The flow also shows the RTP message flow between the SIP client and the Media Gateway (216.234.64.16).
The example covers the following:

  1. SIP invite from the client.
  2. The SIP server challenges the client to authenticate.
  3. The client responds to the authentication challenge.
  4. The call is connected.
  5. The call enters the conversation phase with RTP traffic.
  6. The SIP call is cleared.

SIP call flow with authentication


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HTTPS SSL/TLS Session for SPDY Sequence Diagram

This sequence diagram covers the establishment of a SSL/TLS connection for sending Google SPDY data. The protocol flow covers:

  1. SSL/TLS initial cryptographic parameter negotiation.
  2. X.509 Certificate exchange and encryption start with elliptic curve Diffie Hellman key exchange.
  3. Master key generation and encrypted data transfer.
  4. SSL/TLS session release.
    SSL TLS Sequence Diagram for SPDY


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Voice Over LTE (VoLTE) Originating Call

Voice over LTE (VoLTE) is the standard for voice call setup in LTE networks. When VoLTE is deployed, phones will not need to fallback to 3G for voice calls.

VoLTE uses IMS SIP signaling to set up voice calls. The following VoLTE call flow describes the IMS call setup and release. An example of sending an SMS over IMS is also included. Sample RTP and RTCP messages are also shown in the flow.
Voice over LTE Call Flow


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BGP Router Startup

The Border Gateway Protocol (BGP) is an inter-autonomous system routing protocol. An autonomous system is a group of networks under common administrative control and routing policies.

This sequence diagram describes the sequence of messages exchanged when a new BGP router is made operational. The steps involved are:

  1. Establish TCP connections
  2. Exchange BGP Open messages.
  3. Start periodic exchange of Keepalive messages.
  4. Exchange routing information with the BGP Update message.

BGP Router Startup