All cloud registered Webex apps and Cisco Video devices initiate outbound connections only. Cisco’s Webex Cloud never initiates outbound connections to cloud registered Webex apps and Cisco Video devices, but can make outbound calls to SIP devices.

Webex services for meetings and messaging are hosted in globally distributed data centers that are either Cisco owned (e.g. Webex data centers for identity services, meeting services, and media servers) or hosted in a Cisco Virtual Private Cloud (VPC) on the Amazon AWS platform (e.g. Webex messaging micro-services, messaging storage services). Webex services also reside in Microsoft Azure data centers for Video Interop with Microsoft Teams (VIMT).

트래픽 유형:

Webex app and Cisco Video devices establish signaling and media connections to the Webex cloud.

Signaling traffic
Webex app and Cisco Video devices use HTTP as HTTP over TLS (HTTPS) and Secure Web Sockets (WSS) over TLS for REST based signaling to the Webex cloud. Signaling connections are outbound only and use URLs for session establishment to Webex services.

TLS signaling connections to Webex services use TLS version 1.2 or 1.3. The cipher selection is based on the Webex server TLS preference.

Using either TLS 1.2 or 1.3, Webex prefers ciphers suites using:

• ECDHE for key negotiation
• RSA-based certificates (3072-bit key size)
• SHA2 authentication (SHA384 or SHA256)
• Strong encryption ciphers using 128 or 256 bits (for example, AES_256_GCM)

Webex supports cipher suites in the following preference order for TLS version 1.2 connections*:

TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384
TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256
TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305_SHA256
TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384
TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256

Note - CBC mode encryption is supported for older browsers without more secure GCM mode encryption.
   
Webex supports cipher suites in the following preference order for TLS version 1.3 connections*:

TLS_AES_256_GCM_SHA384
TLS_CHACHA_POLY1305_SHA256
TLS_AES_128_GCM_SHA256

Note – With TLS 1.3, ECDHE key negotiation and RSA-based certificates are a mandatory part of the specification and this detail is therefore omitted in the cipher suite description.
 
*The cipher suites and cipher suite preference order may vary for some Webex services
 
Establishing signaling connections to Webex services using URLs
If you have deployed proxies, or firewalls to filter traffic leaving your enterprise network, the list of destination URLs that need to be allowed to access the Webex service can be found in the section "Domains and URLs that need to be accessed for Webex Services".

Webex strongly recommends that you do not alter or delete HTTP header values as they pass through your proxy/ firewall unless permitted in these guidelines https://www.w3.org/TR/ct-guidelines/#sec-altering-header-values. Modification or deleting of HTTP headers outside of these guidelines can impact access to Webex Services, including loss of access to Webex services by Webex apps and Cisco Video devices.

Webex에서 사용하는 IP 주소는 동적이고 언제든지 변경될 수 있기 때문에 IP 주소별 Webex 시그널링 트래픽 필터링은 지원되지 않습니다.

Media traffic
The Webex app and Cisco Video devices encrypt real-time media for audio, video, and content sharing streams using the following encryption ciphers:

• AES-256-GCM 암호
• AES-CM-128-HMAC-SHA1-80 암호

AES-256-GCM is the preferred encryption cipher by the Webex app and Cisco Video devices to encrypt real time media.     

AES-CM-128-HMAC-SHA1 is a mature cipher that has proven interoperability between vendors. AES-CM-128-HMAC-SHA1 is typically used to encrypt media to Webex services from endpoints using SRTP with SIP signaling (e.g. Cisco and 3rd party SIP devices).

In preference order, Webex apps and Cisco Video devices support UDP, TCP and TLS as media transport protocols. If UDP ports are blocked by your firewall, Webex apps and Cisco Video devices will fall back to TCP. If TCP ports are blocked Webex apps and Cisco Video devices will fall back to TLS.

UDP – Cisco recommended media transport protocol
In line with RFC 3550 RTP – A Transport Protocol for Real-Time Applications, Cisco prefers and strongly recommends UDP as the transport protocol for all Webex voice and video media streams.
 
Disadvantages of using TCP as a media transport protocol
Webex apps and Cisco Video devices also support TCP as a fall-back media transport protocol. 하지만 Cisco는 음성 및 비디오 미디어 스트림에 대한 전송 프로토콜로 TCP를 권장하지 않습니다. TCP는 연결 지향성이고, 확실하게 전달하도록 디자인되었으며, 올바르게 주문된 데이터를 더 높은 계층의 프로토콜로 전송하는 데 중점을 두기 때문입니다. TCP를 사용하면 발신자는 유실된 패킷이 인식될 때까지 해당 패킷을 다시 전송하며, 수신인은 유실된 패킷이 복구될 때까지 패킷 스트림을 버퍼합니다. 미디어 스트림에 대해 이 작동은 증가된 대기 시간/지터로 나타나며, 이는 통화의 참가자가 경험하는 미디어 품질에 영향을 미칩니다.

Disadvantages of using TLS as a media transport protocol
Encrypted TCP connections (TLS) can suffer from a further degradation in media quality due to potential Proxy server bottlenecks. If TLS is used as the media transport protocol by Webex apps and Cisco Video devices with a configured proxy server, this media traffic will be routed through your proxy server which can create bandwidth bottlenecks and subsequent packet loss.  Cisco strongly recommends that TLS is not used to transport media in production environments.

Webex 미디어는 내부에서 시작하는 대칭적인 5-튜플(소스 IP 주소, 대상 IP 주소, 소스 포트, 대상 포트, 프로토콜) 스트림을 사용하여 양방향으로 흐르고 Webex 클라우드로 아웃바운드합니다.
 
The Webex app and Cisco Video devices also use STUN (RFC 5389) for firewall traversal and media node reachability testing. 자세한 내용은 Webex 방화벽 기술 문서를 참조하십시오.
 
Webex  – Destination IP address ranges for media
To reach Webex media servers that process media traffic leaving your enterprise network, you must allow the IP subnets that host these media services to be reachable via your Enterprise firewall. Webex 미디어 노드로 발송된 미디어 트래픽에 대한 대상 IP 주소 범위는 "Webex 미디어 서비스용 IP 서브넷” 섹션에서 찾을 수 있습니다.