B2B Expressway-E

Business to Business Calling through Expressway

Business to Business (B2B) video communication is a core feature of the Expressway product. You will configure it in this lab as a stepping stone to enabling external B2B calls to Microsoft Skype for Business, which is basically a more complex version of a B2B call. B2B allows users to place video calls inbound and outbound from the enterprise to and from external video services or customers over the Internet, while traversing the corporate firewalls in a secure fashion.

At the heart of B2B calling is the Expressway's call routing capability. While it can perform domain-based routing like Unified CM and most other SIP call control entities, it also has the notion of a DNS zone. This is basically a wildcard destination and is configured on the Expressway-E, the component closest to the edge of the network. You do not need to explicitly define a remote destination. Instead, Expressway uses DNS to find the destination. This DNS Zone is already set up for you.

The DNS zone first performs a variety of DNS SRV lookups attempting to find the destination for the domain that is being called. For SIP, it looks for _sips._tcp.domain and/or _sip.tcp.domain depending on the security and encryption settings. If any of those SRV lookups fail, Expressway can be configured to also perform standard A record queries to find the destination. For the purposes of this lab, you will only be using SIP over TCP and leveraging SRV records in DNS to facilitate the connectivity. These lookups allow the Expressway to route calls to destinations that are not explicitly defined. The customer or video service can simply register these DNS SRV records in a public DNS and then automatically be able receive calls from external customers or clients. This is often referred to as an open federation.

A Traversal Zone which accepts a connection from the Expressway-C has already been set up for you, as well.

Configure Dial Plan on Expressway-E

Now you can focus on configuring the dial plan on the Expressway-E. The dial plan will consist of only two rules. One rule will match anything destined to the local domain (pod2.cms.lab) or the CMS domain (conf.pod2.cms.lab) and send those calls to the Traversal Zone, as these calls are destined to the enterprise. The other rule will match anything else that did not match those two domains and route them to the DNS zone to find the destination on the Internet.

  1. Open the browser to the Expressway-E at https://expe1a.pod2.cms.lab:445
    Note: If you skipped the External WebRTC section, then you'll need to use https://expe1a.pod2.cms.lab, as the admin port has not yet been changed.
  2. Log in with username admin and password c1sco123
  3. Navigate to Configuration > Dial plan > Search rules
  4. Click New
  5. Configure the following:

    Parameter Value
    Rule Name Local Domains Inbound
    Priority 10

    Note: Remember that the lower the number the higher the priority in the Expressway product
    Protocol SIP
    Mode Alias pattern match
    Pattern type Regex
    Pattern string .*@(conf\.)?pod2\.cms\.lab.*

    Note: This regular expression matches any URI that is either the Jabber / Unified CM domain, pod2.cms.lab or the CMS domain, conf.pod2.cms.lab. The Expressway has good regular expression support. There is also a tool within the GUI, under Maintenance > Tools > Check pattern that allows you to test your expressions and has links to the relevant help sections.
    Pattern behavior Leave
    On successful match Stop
    Target Traversal Zone

  6. Click Create search rule.

Next, add a rule for the DNS zone. Instead of matching a wildcard, you will define the rule that matches any domain that does NOT match the local domains. Additionally we specify that the source of the call must be the Traversal Zone. We don't want external calls to be hairpinned back out via this zone.

  1. Navigate to Configuration > Dial plan > Search rules.
  2. Click New
  3. Configure the following:

    Parameter Value
    Rule Name DNS Zone Outbound
    Priority 20
    Protocol SIP
    Source Named
    Source name Traversal Zone

    Note: This is to limit this rule to requests coming from the inside/traversal zone. This avoids routing loops.
    Mode Alias pattern match
    Pattern type Regex
    Pattern string (?!.*@(conf\.)?pod2\.cms\.lab).*

    Note: Notice this is the previous regular expression, enclosed in a negation to indicate a match of anything that is NOT the old expression (?! old expression).
    Pattern behavior Leave
    On successful match Stop
    Target DNS Zone

  4. Click Create search rule.

Now we can move on to the Expressway-C configuration.